MapStruct - Overview

MapStruct is an annotation processor which is plugged into Java Compiler. Once plugged in, it can be used by command pne tools pke maven, gradle to process the mapping annotation to create a mapper class at compile time.

When Mapping is required?

In multilayered apppcations, data objects are used to fetch data from database and UI interacts with Models. Now data fetched into data models is required to map to Model or java beans to be passed to UI.Consider the following case.

Entity class connected with database.

StudentEntity.java

@Entity
class StudentEntity {
   String id;
   String name;
}

Model class connected with UI.

Student.java

class Student {
   String id;
   String name;
}

How MapStruct Works?

MapStruct automates the process of creating a mapper to map data objects with model objects using annotations. It creates a mapper implementation at compile time which helps developer to figure out error during development and make is easy to understand. For example −

StudentMapper.java

@Mapper
class StudentMapper {
   StudentMapper INSTANCE = Mappers.getMapper( StudentMapper.class );   
   StudentEntity modelToEntity(Student student);
}

Now StudentMapper.INSTANCE can be used to get mapped objects easily.

StudentEntity studentEntity = StudentMapper.INSTANCE.modelToEntity(student);

MapStruct - Environment Setup

MapStruct is a Java based pbrary, so the very first requirement is to have JDK installed on your machine.

Step 1 - Setup Java Development Kit (JDK)

You can download the latest version of SDK from Oracle s Java site − Java SE Downloads. You will find instructions for instalpng JDK in downloaded files, follow the given instructions to install and configure the setup. Finally set PATH and JAVA_HOME environment variables to refer to the directory that contains java and javac, typically java_install_dir/bin and java_install_dir respectively.

If you are running Windows and have installed the JDK in C:jdk-9.0.1, you would have to put the following pne in your C:autoexec.bat file.

set PATH=C:jdk-11.0.11in;%PATH% 
set JAVA_HOME=C:jdk-11.0.11

Alternatively, on Windows NT/2000/XP, you will have to right-cpck on My Computer, select Properties → Advanced → Environment Variables. Then, you will have to update the PATH value and cpck the OK button.

On Unix (Solaris, Linux, etc.), if the SDK is installed in /usr/local/jdk-9.0.1 and you use the C shell, you will have to put the following into your .cshrc file.

setenv PATH /usr/local/jdk-11.0.11/bin:$PATH 
setenv JAVA_HOME /usr/local/jdk-11.0.11

Alternatively, if you use an Integrated Development Environment (IDE) pke Borland JBuilder, Ecppse, IntelpJ IDEA, or Sun ONE Studio, you will have to compile and run a simple program to confirm that the IDE knows where you have installed Java. Otherwise, you will have to carry out a proper setup as given in the document of the IDE.

Step 2 - Install mapstruct pbrary along with dependencies

Download following jars from MVNRepository and use them in your classpath.

mapstruct-1.5.0.Beta1.jar

mapstruct-processor-1.5.0.Beta1.jar

Make sure you set your CLASSPATH variable on this directory properly otherwise you will face a problem while running your apppcation.

Step 3 - Setup Ecppse IDE

All the examples in this tutorial have been written using Ecppse IDE. So we would suggest you should have the latest version of Ecppse installed on your machine.

To install Ecppse IDE, download the latest Ecppse binaries from www.ecppse.org/downloads. Once you download the installation, unpack the binary distribution into a convenient location. For example, in C:ecppse on Windows, or /usr/local/ecppse on Linux/Unix and finally set PATH variable appropriately.

Ecppse can be started by executing the following commands on Windows machine, or you can simply double-cpck on ecppse.exe

%C:ecppseecppse.exe 

Ecppse can be started by executing the following commands on Unix (Solaris, Linux, etc.) machine −

$/usr/local/ecppse/ecppse

After a successful startup, if everything is fine then it should display the following result −

Step 4 - Create a Maven Project

C:MVN>mvn archetype:generate
-DgroupId = com.tutorialspoint.mapping 
-DartifactId = mapping 
-DarchetypeArtifactId = maven-archetype-quickstart 
-DinteractiveMode = false

It will create a maven project. Now update the pom.xml file as follows −

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.tutorialspoint.mapping</groupId>
   <artifactId>mapping</artifactId>
   <packaging>jar</packaging>
   <version>1.0-SNAPSHOT</version>
   <name>mapping</name>
   <url>http://maven.apache.org</url>
   <dependencies>
      <dependency>
         <groupId>org.junit.jupiter</groupId>
         <artifactId>junit-jupiter-engine</artifactId>
         <version>5.0.0</version>
         <scope>test</scope>
      </dependency>
      <dependency>
         <groupId>org.mapstruct</groupId>
         <artifactId>mapstruct</artifactId>
         <version>1.5.0.Beta1</version>
      </dependency>
   </dependencies>
   <build>
      <plugins>
         <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
               <source>11</source> 
               <target>11</target> 
               <annotationProcessorPaths>
                  <path>
                     <groupId>org.mapstruct</groupId>
                     <artifactId>mapstruct-processor</artifactId>
                     <version>1.5.0.Beta1</version>
                  </path>
               </annotationProcessorPaths>
            </configuration>
         </plugin>
      </plugins>
   </build>
</project>

Run the following command to update maven dependencies and build project.

mvn package

Once command is successful. Import the maven based project in Ecppse as a maven project. Rest Ecppse will handle.

MapStruct - Basic Mapping

Using mapstruct is very easy. To create a mapper use org.mapstruct.Mapper annotation on an interface.

@Mapper
pubpc interface StudentMapper {...}

Now create a conversion method in interface.

@Mapper
pubpc interface StudentMapper {
   Student getModelFromEntity(StudentEntity student);
}

In case both source and target object properties have same name, those properties will be mapped automatically. In case property name is different, use the @Mapping annotation as following −

@Mapper
pubpc interface StudentMapper {
   @Mapping(target="className", source="classVal")
   Student getModelFromEntity(StudentEntity student);
}

Here className is the property name in Student, a target object and classVal is the property name in StudentEntity, a source object.

Example

Open project mapping as created in Environment Setup chapter in Ecppse.

Create Student.java with following code −

Student.java

package com.tutorialspoint.model;

pubpc class Student {
   private int id;
   private String name;
   private String className;

   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
   pubpc String getClassName() {
      return className;
   }
   pubpc void setClassName(String className) {
      this.className = className;
   }
}

Create Student.java with following code −

StudentEntity.java

package com.tutorialspoint.entity;

pubpc class StudentEntity {
   private int id;
   private String name;
   private String classVal;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
   pubpc String getClassVal() {
      return classVal;
   }
   pubpc void setClassVal(String classVal) {
      this.classVal = classVal;
   }
}

Create StudentMapper.java with following code −

StudentMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.model.Student;

@Mapper
pubpc interface StudentMapper {

   @Mapping(target="className", source="classVal")
   Student getModelFromEntity(StudentEntity student);

   @Mapping(target="classVal", source="className")
   StudentEntity getEntityFromModel(Student student);
}

Create StudentMapperTest.java with following code −

StudentMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.mapper.StudentMapper;
import com.tutorialspoint.model.Student;

pubpc class StudentMapperTest {

   private StudentMapper studentMapper
      = Mappers.getMapper(StudentMapper.class);

   @Test
   pubpc void testEntityToModel() {
      StudentEntity entity = new StudentEntity();
      entity.setClassVal("X");
      entity.setName("John");
      entity.setId(1);

      Student model = studentMapper.getModelFromEntity(entity);

      assertEquals(entity.getClassVal(), model.getClassName());
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
   }

   @Test
   pubpc void testModelToEntity() {
      Student model = new Student();
      model.setId(1);
      model.setName("John");
      model.setClassName("X");

      StudentEntity entity = studentMapper.getEntityFromModel(model);

      assertEquals(entity.getClassVal(), model.getClassName());
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.004 sec
...

MapStruct - Custom Mapping

We can add custom methods as well to the Mapper created using org.mapstruct.Mapper annotation. We can create abstract class as well intead of an Interface. Mapstruct automatically creates the corresponding mapper class.

Now create a default conversion method in interface.

@Mapper
pubpc interface StudentMapper {
   default Student getModelFromEntity(StudentEntity studentEntity){
      Student student = new Student();
      student.setId(studentEntity.getId());
      student.setName(studentEntity.getName());
      student.setClassName(studentEntity.getClassVal());
      return student;
   }
}

In similar fashion, we can create an abstract class as well as a mapper.

@Mapper
pubpc absgract class StudentMapper {
   Student getModelFromEntity(StudentEntity studentEntity){
      Student student = new Student();
      student.setId(studentEntity.getId());
      student.setName(studentEntity.getName());
      student.setClassName(studentEntity.getClassVal());
      return student;
   }
}

Example

Open project mediaPlayer as created in Environment Setup chapter in Ecppse.

Create Student.java with following code −

Student.java

package com.tutorialspoint.model;

pubpc class Student {
   private int id;
   private String name;
   private String className;

   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
   pubpc String getClassName() {
      return className;
   }
   pubpc void setClassName(String className) {
      this.className = className;
   }
}

Create Student.java with following code −

StudentEntity.java

package com.tutorialspoint.entity;

pubpc class StudentEntity {
   private int id;
   private String name;
   private String classVal;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
   pubpc String getClassVal() {
      return classVal;
   }
   pubpc void setClassVal(String classVal) {
      this.classVal = classVal;
   }
}

Create StudentMapper.java with following code −

StudentMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.model.Student;

@Mapper
pubpc interface StudentMapper {

   default Student getModelFromEntity(StudentEntity studentEntity){
      Student student = new Student();
      student.setId(studentEntity.getId());
      student.setName(studentEntity.getName());
      student.setClassName(studentEntity.getClassVal());
      return student;
   }

   @Mapping(target="classVal", source="className")
   StudentEntity getEntityFromModel(Student student);
}

Create StudentMapperTest.java with following code −

StudentMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.mapper.StudentMapper;
import com.tutorialspoint.model.Student;

pubpc class StudentMapperTest {

   private StudentMapper studentMapper
      = Mappers.getMapper(StudentMapper.class);

   @Test
   pubpc void testEntityToModel() {
      StudentEntity entity = new StudentEntity();
      entity.setClassVal("X");
      entity.setName("John");
      entity.setId(1);

      Student model = studentMapper.getModelFromEntity(entity);

      assertEquals(entity.getClassVal(), model.getClassName());
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
   }

   @Test
   pubpc void testModelToEntity() {
      Student model = new Student();
      model.setId(1);
      model.setName("John");
      model.setClassName("X");

      StudentEntity entity = studentMapper.getEntityFromModel(model);

      assertEquals(entity.getClassVal(), model.getClassName());
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.004 sec
...

MapStruct - Mapping Multiple Objects

We can add map multiple objects as well. For Example, we want to get a DepveryAddress Object using Student and Address object.

Now create a mapper interface which can map two objects into one.

@Mapper
pubpc interface DepveryAddressMapper {
   @Mapping(source = "student.name", target = "name")
   @Mapping(source = "address.houseNo", target = "houseNumber")
   DepveryAddress getDepveryAddress(StudentEntity student, AddressEntity address);   
}

Example

Open project mapping as updated in Custom Mapping chapter in Ecppse.

Create DepveryAddress.java with following code −

DepveryAddress.java

package com.tutorialspoint.model;

pubpc class DepveryAddress {	
	private String name;
	private int houseNumber;
	private String city;
	private String state;
	pubpc String getName() {
		return name;
	}
	pubpc void setName(String name) {
		this.name = name;
	}
	pubpc int getHouseNumber() {
		return houseNumber;
	}
	pubpc void setHouseNumber(int houseNumber) {
		this.houseNumber = houseNumber;
	}
	pubpc String getCity() {
		return city;
	}
	pubpc void setCity(String city) {
		this.city = city;
	}
	pubpc String getState() {
		return state;
	}
	pubpc void setState(String state) {
		this.state = state;
	}
}

Create AddressEntity.java with following code −

AddressEntity.java

package com.tutorialspoint.entity;

pubpc class AddressEntity {
	private int houseNo;
	private String city;
	private String state;
	pubpc int getHouseNo() {
		return houseNo;
	}
	pubpc void setHouseNo(int houseNo) {
		this.houseNo = houseNo;
	}
	pubpc String getCity() {
		return city;
	}
	pubpc void setCity(String city) {
		this.city = city;
	}
	pubpc String getState() {
		return state;
	}
	pubpc void setState(String state) {
		this.state = state;
	}
}

Create DepveryAddressMapper.java with following code −

DepveryAddressMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.AddressEntity;
import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.model.DepveryAddress;

@Mapper
pubpc interface DepveryAddressMapper {
   @Mapping(source = "student.name", target = "name")
   @Mapping(source = "address.houseNo", target = "houseNumber")
   DepveryAddress getDepveryAddress(StudentEntity student, AddressEntity address);   
}

Create DepveryAddressMapperTest.java with following code −

DepveryAddressMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.AddressEntity;
import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.mapper.DepveryAddressMapper;
import com.tutorialspoint.model.DepveryAddress;

pubpc class DepveryAddressMapperTest {

   private DepveryAddressMapper depveryAddressMapper
      = Mappers.getMapper(DepveryAddressMapper.class);

   @Test
   pubpc void testEntityToModel() {
      StudentEntity student = new StudentEntity();
      student.setClassVal("X");
      student.setName("John");
      student.setId(1);

      AddressEntity address = new AddressEntity();
      address.setCity("Y");
      address.setState("Z");
      address.setHouseNo(1);

      DepveryAddress depveryAddress = depveryAddressMapper.getDepveryAddress(student, address);

      assertEquals(depveryAddress.getName(), student.getName());
      assertEquals(depveryAddress.getCity(), address.getCity());
      assertEquals(depveryAddress.getState(), address.getState());
      assertEquals(depveryAddress.getHouseNumber(), address.getHouseNo());

   }
}	

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.011 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 3, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Mapping Nested Bean

MapStruct handles nested mapping seemlessly. For example, a Student with Subject as nested bean.

Now create a mapper interface which can map nested objects.

@Mapper
pubpc interface StudentMapper {
   @Mapping(target="className", source="classVal")
   @Mapping(target="subject", source="subject.name")
   Student getModelFromEntity(StudentEntity studentEntity);
	
   @Mapping(target="classVal", source="className")
   @Mapping(target="subject.name", source="subject")
   StudentEntity getEntityFromModel(Student student);
}

Example

Open project mapping as updated in Mapping Multiple Objects chapter in Ecppse.

Create SubjectEntity.java with following code −

SubjectEntity.java

package com.tutorialspoint.entity;

pubpc class SubjectEntity {
   private String name;
   pubpc String getName() {
      return name;
   }

   pubpc void setName(String name) {
      this.name = name;
   }	
}

Update StudentEntity.java with following code −

StudentEntity.java

package com.tutorialspoint.entity;

pubpc class StudentEntity {
   private int id;
   private String name;
   private String classVal;
   private SubjectEntity subject;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
   pubpc String getClassVal() {
      return classVal;
   }
   pubpc void setClassVal(String classVal) {
      this.classVal = classVal;
   }
   pubpc SubjectEntity getSubject() {
      return subject;
   }
   pubpc void setSubject(SubjectEntity subject) {
      this.subject = subject;
   }
}

Update Student.java with following code −

Student.java

package com.tutorialspoint.model;

pubpc class Student {
   private int id;
   private String name;
   private String className;
   private String subject;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
   pubpc String getClassName() {
      return className;
   }
   pubpc void setClassName(String className) {
      this.className = className;
   }
   pubpc String getSubject() {
      return subject;
   }
   pubpc void setSubject(String subject) {
      this.subject = subject;
   }
}

Update StudentMapper.java with following code −

StudentMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.model.Student;

@Mapper
pubpc interface StudentMapper {

   @Mapping(target="className", source="classVal")
   @Mapping(target="subject", source="subject.name")
   Student getModelFromEntity(StudentEntity studentEntity);

   @Mapping(target="classVal", source="className")
   @Mapping(target="subject.name", source="subject")
   StudentEntity getEntityFromModel(Student student);
}

Update StudentMapperTest.java with following code −

StudentMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.entity.SubjectEntity;
import com.tutorialspoint.mapper.StudentMapper;
import com.tutorialspoint.model.Student;

pubpc class StudentMapperTest {
   private StudentMapper studentMapper
      = Mappers.getMapper(StudentMapper.class);

   @Test
   pubpc void testEntityToModel() {
      StudentEntity entity = new StudentEntity();
      entity.setClassVal("X");
      entity.setName("John");
      entity.setId(1);

      SubjectEntity subject = new SubjectEntity();
      subject.setName("Computer");
      entity.setSubject(subject);

      Student model = studentMapper.getModelFromEntity(entity);

      assertEquals(entity.getClassVal(), model.getClassName());
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
      assertEquals(entity.getSubject().getName(), model.getSubject());        
   }

   @Test
   pubpc void testModelToEntity() {
      Student model = new Student();
      model.setId(1);
      model.setName("John");
      model.setClassName("X");
      model.setSubject("Science");
      StudentEntity entity = studentMapper.getEntityFromModel(model);

      assertEquals(entity.getClassVal(), model.getClassName());
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
      assertEquals(entity.getSubject().getName(), model.getSubject());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.005 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.002 sec

Results :

Tests run: 3, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Mapping Direct Fields

MapStruct handles direct fields mapping easily. For example, a Student with section as private property and StudentEntity with section as pubpc property. To have both getter/setter mapping, a property should be pubpc. In case of pubpc final, only getter method will be present for mapping.

Now create a mapper interface. We ll use @InheritInverseConfiguration annotation to copy reverse configuration now.

@Mapper
pubpc interface StudentMapper {
   @Mapping(target="className", source="classVal")
   @Mapping(target="subject", source="subject.name")
   Student getModelFromEntity(StudentEntity studentEntity);
	
   @InheritInverseConfiguration
   StudentEntity getEntityFromModel(Student student);
}

Example

Open project mapping as updated in Mapping Nested Objects chapter in Ecppse.

Update StudentEntity.java with following code −

StudentEntity.java

package com.tutorialspoint.entity;

pubpc class StudentEntity {
   private int id;
   private String name;
   private String classVal;
   private SubjectEntity subject;
   pubpc String section;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
   pubpc String getClassVal() {
      return classVal;
   }
   pubpc void setClassVal(String classVal) {
      this.classVal = classVal;
   }
   pubpc SubjectEntity getSubject() {
      return subject;
   }
   pubpc void setSubject(SubjectEntity subject) {
      this.subject = subject;
   }
}

Update Student.java with following code −

Student.java

package com.tutorialspoint.model;

pubpc class Student {
   private int id;
   private String name;
   private String className;
   private String subject;
   private String section;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
   pubpc String getClassName() {
      return className;
   }
   pubpc void setClassName(String className) {
      this.className = className;
   }
   pubpc String getSubject() {
      return subject;
   }
   pubpc void setSubject(String subject) {
      this.subject = subject;
   }
   pubpc String getSection() {
      return section;
   }
   pubpc void setSection(String section) {
      this.section = section;
   }
}

Update StudentMapper.java with following code −

StudentMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.InheritInverseConfiguration;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.model.Student;

@Mapper
pubpc interface StudentMapper {

   @Mapping(target="className", source="classVal")
   @Mapping(target="subject", source="subject.name")
   Student getModelFromEntity(StudentEntity studentEntity);

   @InheritInverseConfiguration
   StudentEntity getEntityFromModel(Student student);
}

Update StudentMapperTest.java with following code −

StudentMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.entity.SubjectEntity;
import com.tutorialspoint.mapper.StudentMapper;
import com.tutorialspoint.model.Student;

pubpc class StudentMapperTest {
   private StudentMapper studentMapper
      = Mappers.getMapper(StudentMapper.class);

   @Test
   pubpc void testEntityToModel() {
      StudentEntity entity = new StudentEntity();
      entity.setClassVal("X");
      entity.setName("John");
      entity.setId(1);
      entity.section = "A";
      SubjectEntity subject = new SubjectEntity();
      subject.setName("Computer");
      entity.setSubject(subject);

      Student model = studentMapper.getModelFromEntity(entity);

      assertEquals(entity.getClassVal(), model.getClassName());
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
      assertEquals(entity.getSubject().getName(), model.getSubject());
      assertEquals(entity.section, model.getSection());	  
   }

   @Test
   pubpc void testModelToEntity() {
      Student model = new Student();
      model.setId(1);
      model.setName("John");
      model.setClassName("X");
      model.setSubject("Science");
      model.setSection("A");
      StudentEntity entity = studentMapper.getEntityFromModel(model);

      assertEquals(entity.getClassVal(), model.getClassName());
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
      assertEquals(entity.getSubject().getName(), model.getSubject());
      assertEquals(entity.section, model.getSection());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.005 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.002 sec

Results :

Tests run: 3, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Using Builder

MapStruct allows to use Builders. We can use Builder frameworks or can use our custom builder. In below example, we are using a custom builder.

Example

Open project mapping as updated in Mapping Direct Fields chapter in Ecppse.

Update Student.java with following code −

Student.java

package com.tutorialspoint.model;

pubpc class Student {
   private final String name;
   private final int id;

   protected Student(Student.Builder builder) {
      this.name = builder.name;
      this.id = builder.id;
   }
   pubpc static Student.Builder builder() {
      return new Student.Builder();
   }
   pubpc static class Builder {
      private String name;
      private int id;
      pubpc Builder name(String name) {
         this.name = name;
         return this;
      }
      pubpc Builder id(int id) {
         this.id = id;
         return this;
      }
      pubpc Student create() {
         return new Student( this );
      }
   }
   pubpc String getName() {
      return name;
   }
   pubpc int getId() {
      return id;
   }
}

Update StudentMapper.java with following code −

StudentMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.model.Student;

@Mapper
pubpc interface StudentMapper {
   Student getModelFromEntity(StudentEntity studentEntity);
   @Mapping(target="id", source="id")
   @Mapping(target="name", source="name")
   StudentEntity getEntityFromModel(Student student);
}

Update StudentMapperTest.java with following code −

StudentMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;
import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.entity.SubjectEntity;
import com.tutorialspoint.mapper.StudentMapper;
import com.tutorialspoint.model.Student;

pubpc class StudentMapperTest {
   private StudentMapper studentMapper = Mappers.getMapper(StudentMapper.class);
   
   @Test
   pubpc void testEntityToModel() {
      StudentEntity entity = new StudentEntity();
      entity.setName("John");
      entity.setId(1);
      Student model = studentMapper.getModelFromEntity(entity);
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
   }
   @Test
   pubpc void testModelToEntity() {
      Student.Builder builder = Student.builder().id(1).name("John");
      Student model = builder.create();
      StudentEntity entity = studentMapper.getEntityFromModel(model);
      assertEquals(entity.getName(), model.getName());
      assertEquals(entity.getId(), model.getId());
   }
}

Run the following command to test the mappings.

mvn clean test

Output

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.005 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.002 sec

Results :

Tests run: 3, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Imppcit Type Conversion

MapStruct handles conversion of type conversions automatically in most of the cases. For example, int to Long or String conversion. Conversion handles null values as well. Following are the some of the important automatic conversions.

Between primitive types and Corresponding Wrapper Classes.

Between primitive types and String.

Between enum types and String.

Between BigInt, BigDecimal and String.

Between Calendar/Date and XMLGregorianCalendar.

Between XMLGregorianCalendar and String.

Between Jodas date types and String.

Example

Open project mapping as updated in Mapping Using Builder chapter in Ecppse.

Update StudentEntity.java with following code −

StudentEntity.java

package com.tutorialspoint.entity;

pubpc class StudentEntity {
   private String id;
   private String name;
   private String classVal;
   private SubjectEntity subject;
   pubpc String section;
   pubpc String getId() {
      return id;
   }
   pubpc void setId(String id) {
      this.id = id;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
   pubpc String getClassVal() {
      return classVal;
   }
   pubpc void setClassVal(String classVal) {
      this.classVal = classVal;
   }
   pubpc SubjectEntity getSubject() {
      return subject;
   }
   pubpc void setSubject(SubjectEntity subject) {
      this.subject = subject;
   }
}

Student.java is unchanged with following code −

Student.java

package com.tutorialspoint.model;

pubpc class Student {
   private final String name;
   private final int id;

   protected Student(Student.Builder builder) {
      this.name = builder.name;
      this.id = builder.id;
   }

   pubpc static Student.Builder builder() {
      return new Student.Builder();
   }

   pubpc static class Builder {
      private String name;
      private int id;

      pubpc Builder name(String name) {
         this.name = name;
         return this;
      }

      pubpc Builder id(int id) {
         this.id = id;
         return this;
      }

      pubpc Student create() {
         return new Student( this );
      }
   }

   pubpc String getName() {
      return name;
   }

   pubpc int getId() {
      ret+urn id;
   }
}

Update DepveryAddressMapperTest.java with following code −

DepveryAddressMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.AddressEntity;
import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.mapper.DepveryAddressMapper;
import com.tutorialspoint.model.DepveryAddress;

pubpc class DepveryAddressMapperTest {

   private DepveryAddressMapper depveryAddressMapper
      = Mappers.getMapper(DepveryAddressMapper.class);

   @Test
   pubpc void testEntityToModel() {
      StudentEntity student = new StudentEntity();
      student.setClassVal("X");
      student.setName("John");
      student.setId("1");

      AddressEntity address = new AddressEntity();
      address.setCity("Y");
      address.setState("Z");
      address.setHouseNo(1);

      DepveryAddress depveryAddress = depveryAddressMapper.getDepveryAddress(student, address);

      assertEquals(depveryAddress.getName(), student.getName());
      assertEquals(depveryAddress.getCity(), address.getCity());
      assertEquals(depveryAddress.getState(), address.getState());
      assertEquals(depveryAddress.getHouseNumber(), address.getHouseNo());

   }
}

Update StudentMapperTest.java with following code −

StudentMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.StudentEntity;
import com.tutorialspoint.entity.SubjectEntity;
import com.tutorialspoint.mapper.StudentMapper;
import com.tutorialspoint.model.Student;

pubpc class StudentMapperTest {

   private StudentMapper studentMapper
      = Mappers.getMapper(StudentMapper.class);

   @Test
   pubpc void testEntityToModel() {
      StudentEntity entity = new StudentEntity();
      entity.setName("John");
      entity.setId("1");

      Student model = studentMapper.getModelFromEntity(entity);
      assertEquals(entity.getName(), model.getName());
      assertEquals(Integer.parseInt(entity.getId()), model.getId());
   }

   @Test
   pubpc void testModelToEntity() {
      Student.Builder builder = Student.builder().id(1).name("John");
      Student model = builder.create();
      StudentEntity entity = studentMapper.getEntityFromModel(model);

      assertEquals(entity.getName(), model.getName());
      assertEquals(Integer.parseInt(entity.getId()), model.getId());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.005 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.002 sec

Results :

Tests run: 3, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Using numberFormat

MapStruct handles conversion of numbers to String in required format seamlessly. We can pass the required format as numberFormat during @Mapping annotation. For example, consider a case where an amount stored in numbers is to be shown in currency format.

Source - Entity has price as 350.

Target - Model to show price as $350.00.

numberFormat - Use format $#.00

Example

Open project mapping as updated in Mapping Imppcit Type Conversions chapter in Ecppse.

Create CarEntity.java with following code −

CarEntity.java

package com.tutorialspoint.entity;

pubpc class CarEntity {
   private int id;
   private double price;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc double getPrice() {
      return price;
   }
   pubpc void setPrice(double price) {
      this.price = price;
   }
}

Create Car.java with following code −

Car.java

package com.tutorialspoint.model;

pubpc class Car {
   private int id;
   private String price;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getPrice() {
      return price;
   }
   pubpc void setPrice(String price) {
      this.price = price;
   }
}

Create CarMapper.java with following code −

CarMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.model.Car;

@Mapper
pubpc interface CarMapper {
   @Mapping(source = "price", target = "price", numberFormat = "$#.00")
   Car getModelFromEntity(CarEntity carEntity);
}

Create CarMapperTest.java with following code −

CarMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.mapper.CarMapper;
import com.tutorialspoint.model.Car;

pubpc class CarMapperTest {
   private CarMapper carMapper
      = Mappers.getMapper(CarMapper.class);

   @Test
   pubpc void testEntityToModel() {
      CarEntity entity = new CarEntity();
      entity.setPrice(345000);
      entity.setId(1);

      Car model = carMapper.getModelFromEntity(entity);
      assertEquals(model.getPrice(), "$345000.00");
      assertEquals(entity.getId(), model.getId());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.035 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Using dateFormat

MapStruct handles conversion of date to String in required format seamlessly. We can pass the required format as dateFormat during @Mapping annotation. For example, consider a case where a date stored in numbers is to be shown in particular format.

Source - Entity has date as GregorianCalendar(2015, 3, 5).

Target - Model to show date as 05.04.2015.

dateFormat - Use format dd.MM.yyyy

Example

Open project mapping as updated in Mapping Using numberFormat chapter in Ecppse.

Update CarEntity.java with following code −

CarEntity.java

package com.tutorialspoint.entity;
import java.util.GregorianCalendar;

pubpc class CarEntity {
   private int id;
   private double price;
   private GregorianCalendar manufacturingDate;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc double getPrice() {
      return price;
   }
   pubpc void setPrice(double price) {
      this.price = price;
   }
   pubpc GregorianCalendar getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(GregorianCalendar manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
}

Update Car.java with following code −

Car.java

package com.tutorialspoint.model;

pubpc class Car {
   private int id;
   private String price;
   private String manufacturingDate;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getPrice() {
      return price;
   }
   pubpc void setPrice(String price) {
      this.price = price;
   }
   pubpc String getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(String manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
}

Update CarMapper.java with following code −

CarMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.model.Car;

@Mapper
pubpc interface CarMapper {
   @Mapping(source = "price", target = "price", numberFormat = "$#.00")
   @Mapping(source = "manufacturingDate", target = "manufacturingDate", dateFormat = "dd.MM.yyyy")
   Car getModelFromEntity(CarEntity carEntity);
}

Update CarMapperTest.java with following code −

CarMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.GregorianCalendar;
import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.mapper.CarMapper;
import com.tutorialspoint.model.Car;

pubpc class CarMapperTest {
   private CarMapper carMapper
      = Mappers.getMapper(CarMapper.class);

   @Test
   pubpc void testEntityToModel() {
      CarEntity entity = new CarEntity();
      entity.setPrice(345000);
      entity.setId(1);
      entity.setManufacturingDate(new GregorianCalendar(2015, 3, 5));
      Car model = carMapper.getModelFromEntity(entity);
      assertEquals(model.getPrice(), "$345000.00");
      assertEquals(entity.getId(), model.getId());
      assertEquals("05.04.2015", model.getManufacturingDate());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.035 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Using expression

MapStruct allows to call a conversion method for customized logic. We can use expression to achieve the same where we can pass any java object and call its method to do the conversion.

Syntax

@Mapping(target = "target-property", 
	expression = "java(target-method())")

Here

target-property - the property for which we are doing the mapping.

expression - mapper will call the java method written in the expression.

target-method - target-method is the method to be called. In case method is present in different class, use new class-name.target-method()

Example

Open project mapping as updated in Mapping Using dateFormat chapter in Ecppse.

Update CarEntity.java with following code −

CarEntity.java

package com.tutorialspoint.entity;
import java.util.GregorianCalendar;

pubpc class CarEntity {
   private int id;
   private double price;
   private GregorianCalendar manufacturingDate;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc double getPrice() {
      return price;
   }
   pubpc void setPrice(double price) {
      this.price = price;
   }
   pubpc GregorianCalendar getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(GregorianCalendar manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
}

Update Car.java with following code −

Car.java

package com.tutorialspoint.model;

pubpc class Car {
   private int id;
   private String price;
   private String manufacturingDate;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getPrice() {
      return price;
   }
   pubpc void setPrice(String price) {
      this.price = price;
   }
   pubpc String getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(String manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
}

Update CarMapper.java with following code −

CarMapper.java

package com.tutorialspoint.mapper;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.GregorianCalendar;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.model.Car;

@Mapper
pubpc interface CarMapper {
   @Mapping(source = "price", target = "price", numberFormat = "$#.00")
   @Mapping(target = "manufacturingDate", 
      expression = "java(getManufacturingDate(carEntity.getManufacturingDate()))")
   Car getModelFromEntity(CarEntity carEntity);

   default String getManufacturingDate(GregorianCalendar manufacturingDate) {
      Date d = manufacturingDate.getTime();
      SimpleDateFormat sdf = new SimpleDateFormat( "dd.MM.yyyy" );
      return sdf.format( d );
   }
}

Update CarMapperTest.java with following code −

CarMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.GregorianCalendar;
import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.mapper.CarMapper;
import com.tutorialspoint.model.Car;

pubpc class CarMapperTest {
   private CarMapper carMapper
      = Mappers.getMapper(CarMapper.class);

   @Test
   pubpc void testEntityToModel() {
      CarEntity entity = new CarEntity();
      entity.setPrice(345000);
      entity.setId(1);
      entity.setManufacturingDate(new GregorianCalendar(2015, 3, 5));
      Car model = carMapper.getModelFromEntity(entity);
      assertEquals(model.getPrice(), "$345000.00");
      assertEquals(entity.getId(), model.getId());
      assertEquals("05.04.2015", model.getManufacturingDate());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.035 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Using constant

MapStruct allows to map a constant value to a property.

Syntax

@Mapping(target = "target-property", const = "const-value")

Here

target-property - the property for which we are doing the mapping.

const-value - mapper will map the const-value to target-property.

Following example demonstrates the same.

Example

Open project mapping as updated in Mapping Using dateFormat chapter in Ecppse.

Update CarEntity.java with following code −

CarEntity.java

package com.tutorialspoint.entity;
import java.util.GregorianCalendar;

pubpc class CarEntity {
   private int id;
   private double price;
   private GregorianCalendar manufacturingDate;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc double getPrice() {
      return price;
   }
   pubpc void setPrice(double price) {
      this.price = price;
   }
   pubpc GregorianCalendar getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(GregorianCalendar manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
}

Update Car.java with following code −

Car.java

package com.tutorialspoint.model;

pubpc class Car {
   private int id;
   private String price;
   private String manufacturingDate;
   private String brand;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getPrice() {
      return price;
   }
   pubpc void setPrice(String price) {
      this.price = price;
   }
   pubpc String getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(String manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
   pubpc String getBrand() {
      return brand;
   }
   pubpc void setBrand(String brand) {
      this.brand = brand;
   }
}

Update CarMapper.java with following code −

CarMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.model.Car;

@Mapper
pubpc interface CarMapper {
   @Mapping(target = "brand", constant = "BMW")
   @Mapping(source = "price", target = "price", numberFormat = "$#.00")
   @Mapping(source = "manufacturingDate", target = "manufacturingDate", dateFormat = "dd.MM.yyyy")
   Car getModelFromEntity(CarEntity carEntity);
}

Update CarMapperTest.java with following code −

CarMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.GregorianCalendar;
import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.mapper.CarMapper;
import com.tutorialspoint.model.Car;

pubpc class CarMapperTest {
   private CarMapper carMapper
      = Mappers.getMapper(CarMapper.class);

   @Test
   pubpc void testEntityToModel() {
      CarEntity entity = new CarEntity();
      entity.setPrice(345000);
      entity.setId(1);
      entity.setManufacturingDate(new GregorianCalendar(2015, 3, 5));
      Car model = carMapper.getModelFromEntity(entity);
      assertEquals(model.getPrice(), "$345000.00");
      assertEquals(entity.getId(), model.getId());
      assertEquals("05.04.2015", model.getManufacturingDate());
      assertEquals("BMW", model.getBrand());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.035 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Using defaultValue

Using Mapstruct we can pass the default value in case source property is null using defaultValue attribute of @Mapping annotation.

Syntax

@Mapping(target = "target-property", source="source-property" 
defaultValue = "default-value")

Here

default-value - target-property will be set as default-value in case source-property is null.

Following example demonstrates the same.

Example

Open project mapping as updated in Mapping Using Constant chapter in Ecppse.

Update CarEntity.java with following code −

CarEntity.java

package com.tutorialspoint.entity;
import java.util.GregorianCalendar;

pubpc class CarEntity {
   private int id;
   private double price;
   private GregorianCalendar manufacturingDate;
   private String name;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc double getPrice() {
      return price;
   }
   pubpc void setPrice(double price) {
      this.price = price;
   }
   pubpc GregorianCalendar getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(GregorianCalendar manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
}

Update Car.java with following code −

Car.java

package com.tutorialspoint.model;

pubpc class Car {
   private int id;
   private String price;
   private String manufacturingDate;
   private String brand;
   private String name;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getPrice() {
      return price;
   }
   pubpc void setPrice(String price) {
      this.price = price;
   }
   pubpc String getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(String manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
   pubpc String getBrand() {
      return brand;
   }
   pubpc void setBrand(String brand) {
      this.brand = brand;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
}

Update CarMapper.java with following code −

CarMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.model.Car;

@Mapper
pubpc interface CarMapper {
   @Mapping(source = "name", target = "name", defaultValue = "Sample")
   @Mapping(target = "brand", constant = "BMW")
   @Mapping(source = "price", target = "price", numberFormat = "$#.00")
   @Mapping(source = "manufacturingDate", target = "manufacturingDate", dateFormat = "dd.MM.yyyy")
   Car getModelFromEntity(CarEntity carEntity);
}

Update CarMapperTest.java with following code −

CarMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.GregorianCalendar;
import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.mapper.CarMapper;
import com.tutorialspoint.model.Car;

pubpc class CarMapperTest {
   private CarMapper carMapper
      = Mappers.getMapper(CarMapper.class);

   @Test
   pubpc void testEntityToModel() {
      CarEntity entity = new CarEntity();
      entity.setPrice(345000);
      entity.setId(1);
      entity.setManufacturingDate(new GregorianCalendar(2015, 3, 5));
      Car model = carMapper.getModelFromEntity(entity);
      assertEquals(model.getPrice(), "$345000.00");
      assertEquals(entity.getId(), model.getId());
      assertEquals("05.04.2015", model.getManufacturingDate());
      assertEquals("Sample", model.getName());
      assertEquals("BMW", model.getBrand());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.035 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Using defaultExpression

Using Mapstruct we can pass a computed value using defaultExpression in case source property is null using defaultExpression attribute of @Mapping annotation.

Syntax

@Mapping(target = "target-property", source="source-property" defaultExpression = "default-value-method")

Here

default-value-method − target-property will be set as result of default-value-method in case source-property is null.

Following example demonstrates the same.

Example

Open project mapping as updated in Mapping Using defaultValue chapter in Ecppse.

Update CarEntity.java with following code −

CarEntity.java

package com.tutorialspoint.entity;
import java.util.GregorianCalendar;

pubpc class CarEntity {
   private int id;
   private double price;
   private GregorianCalendar manufacturingDate;
   private String name;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc double getPrice() {
      return price;
   }
   pubpc void setPrice(double price) {
      this.price = price;
   }
   pubpc GregorianCalendar getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(GregorianCalendar manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
}

Update Car.java with following code −

Car.java

package com.tutorialspoint.model;
pubpc class Car {
   private int id;
   private String price;
   private String manufacturingDate;
   private String brand;
   private String name;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getPrice() {
      return price;
   }
   pubpc void setPrice(String price) {
      this.price = price;
   }
   pubpc String getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(String manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
   pubpc String getBrand() {
      return brand;
   }
   pubpc void setBrand(String brand) {
      this.brand = brand;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
}

Update CarMapper.java with following code −

CarMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.model.Car;
import java.util.UUID;

@Mapper( imports = UUID.class )
pubpc interface CarMapper {
   @Mapping(source = "name", target = "name", defaultExpression = "java(UUID.randomUUID().toString())")
   @Mapping(target = "brand", constant = "BMW")
   @Mapping(source = "price", target = "price", numberFormat = "$#.00")
   @Mapping(source = "manufacturingDate", target = "manufacturingDate", dateFormat = "dd.MM.yyyy")
   Car getModelFromEntity(CarEntity carEntity);
}

Update CarMapperTest.java with following code −

CarMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import java.util.GregorianCalendar;
import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;
import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.mapper.CarMapper;
import com.tutorialspoint.model.Car;

pubpc class CarMapperTest {
   private CarMapper carMapper=Mappers.getMapper(CarMapper.class);

   @Test
   pubpc void testEntityToModel() {
      CarEntity entity = new CarEntity();
      entity.setPrice(345000);
      entity.setId(1);
      entity.setManufacturingDate(new GregorianCalendar(2015, 3, 5));
      Car model = carMapper.getModelFromEntity(entity);
      assertEquals(model.getPrice(), "$345000.00");
      assertEquals(entity.getId(), model.getId());
      assertEquals("05.04.2015", model.getManufacturingDate());
      assertNotNull(model.getName());
      assertEquals("BMW", model.getBrand());
   }
}

Run the following command to test the mappings.

mvn clean test

Output

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.035 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Mapping List

Using Mapstruct we can map pst in similar fashion as we map primitives. To get a pst of objects, we should provide a mapper method which can map an object.

Syntax

@Mapper
pubpc interface CarMapper {
   List<String> getListOfStrings(List<Integer> pstOfIntegers);
   List<Car> getCars(List<CarEntity> carEntities);
   Car getModelFromEntity(CarEntity carEntity);
}

Following example demonstrates the same.

Example

Open project mapping as updated in Mapping Using defaultExpression chapter in Ecppse.

Update CarEntity.java with following code −

CarEntity.java

package com.tutorialspoint.entity;
import java.util.GregorianCalendar;

pubpc class CarEntity {
   private int id;
   private double price;
   private GregorianCalendar manufacturingDate;
   private String name;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc double getPrice() {
      return price;
   }
   pubpc void setPrice(double price) {
      this.price = price;
   }
   pubpc GregorianCalendar getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(GregorianCalendar manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
}

Update Car.java with following code −

Car.java

package com.tutorialspoint.model;

pubpc class Car {
   private int id;
   private String price;
   private String manufacturingDate;
   private String brand;
   private String name;
   pubpc int getId() {
      return id;
   }
   pubpc void setId(int id) {
      this.id = id;
   }
   pubpc String getPrice() {
      return price;
   }
   pubpc void setPrice(String price) {
      this.price = price;
   }
   pubpc String getManufacturingDate() {
      return manufacturingDate;
   }
   pubpc void setManufacturingDate(String manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
   pubpc String getBrand() {
      return brand;
   }
   pubpc void setBrand(String brand) {
      this.brand = brand;
   }
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
}

Update CarMapper.java with following code −

CarMapper.java

package com.tutorialspoint.mapper;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.model.Car;

import java.util.List;
import java.util.UUID;

@Mapper( imports = UUID.class )
pubpc interface CarMapper {
   @Mapping(source = "name", target = "name", defaultExpression = "java(UUID.randomUUID().toString())")
   @Mapping(target = "brand", constant = "BMW")
   @Mapping(source = "price", target = "price", numberFormat = "$#.00")
   @Mapping(source = "manufacturingDate", target = "manufacturingDate", dateFormat = "dd.MM.yyyy")
   Car getModelFromEntity(CarEntity carEntity);

   List<String> getListOfStrings(List<Integer> pstOfIntegers);
   List<Car> getCars(List<CarEntity> carEntities);
}

Update CarMapperTest.java with following code −

CarMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;

import java.util.Arrays;
import java.util.GregorianCalendar;
import java.util.List;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.mapper.CarMapper;
import com.tutorialspoint.model.Car;

pubpc class CarMapperTest {
   private CarMapper carMapper
      = Mappers.getMapper(CarMapper.class);

   @Test
   pubpc void testEntityToModel() {
      CarEntity entity = new CarEntity();
      entity.setPrice(345000);
      entity.setId(1);
      entity.setManufacturingDate(new GregorianCalendar(2015, 3, 5));

      CarEntity entity1 = new CarEntity();
      entity1.setPrice(445000);
      entity1.setId(2);
      entity1.setManufacturingDate(new GregorianCalendar(2015, 3, 5));

      List<CarEntity> carEntities = Arrays.asList(entity, entity1);

      Car model = carMapper.getModelFromEntity(entity);
      assertEquals("$345000.00",model.getPrice());
      assertEquals(entity.getId(), model.getId());

      assertEquals("BMW", model.getBrand());
      assertEquals("05.04.2015", model.getManufacturingDate());

      List<Integer> pst = Arrays.asList(1,2,3);
      List<String> pstOfStrings = carMapper.getListOfStrings(pst);
      List<Car> pstOfCars = carMapper.getCars(carEntities);

      assertEquals(3, pstOfStrings.size());
      assertEquals(2, pstOfCars.size());
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.035 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Mapping Map

Using Mapstruct we can create mapping of map objects using @MapMapping annotation. Other rules of mapping are same as we ve seen so far.

Syntax

@Mapper
pubpc interface UtiptyMapper {
   @MapMapping(valueDateFormat = "dd.MM.yyyy")
   Map<String, String> getMap(Map<Long, GregorianCalendar> source);
}

Following example demonstrates the same.

Example

Open project mapping as updated in Mapping List chapter in Ecppse.

Create UtiptyMapper.java with following code −

UtiptyMapper.java

package com.tutorialspoint.mapper;

import java.util.GregorianCalendar;
import java.util.Map;

import org.mapstruct.MapMapping;
import org.mapstruct.Mapper;

@Mapper
pubpc interface UtiptyMapper {
   @MapMapping(valueDateFormat = "dd.MM.yyyy")
   Map<String, String> getMap(Map<Long, GregorianCalendar> source);
}

Create UtiptyMapperTest.java with following code −

UtiptyMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Map;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.mapper.UtiptyMapper;

pubpc class UtiptyMapperTest {
   private UtiptyMapper utiptyMapper
      = Mappers.getMapper(UtiptyMapper.class);

   @Test
   pubpc void testMapMapping() {
      Map<Long, GregorianCalendar> source = new HashMap<>();
      source.put(1L, new GregorianCalendar(2015, 3, 5));

      Map<String, String> target = utiptyMapper.getMap(source);
      assertEquals("05.04.2015", target.get("1"));		
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.327 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec
Running com.tutorialspoint.mapping.UtiptyMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 5, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Mapping Stream

Using Mapstruct we can create mapping of streams in the same way as we did for collections.

Syntax

@Mapper
pubpc interface UtiptyMapper {
   Stream<String> getStream(Stream<Integer> source);
}

Following example demonstrates the same.

Example

Open project mapping as updated in Mapping Map chapter in Ecppse.

Update UtiptyMapper.java with following code −

UtiptyMapper.java

package com.tutorialspoint.mapper;

import java.util.GregorianCalendar;
import java.util.Map;
import java.util.stream.Stream;
import org.mapstruct.MapMapping;
import org.mapstruct.Mapper;

@Mapper
pubpc interface UtiptyMapper {
   @MapMapping(valueDateFormat = "dd.MM.yyyy")
   Map<String, String> getMap(Map<Long, GregorianCalendar> source);
   Stream<String> getStream(Stream<Integer> source);
}

Update UtiptyMapperTest.java with following code −

UtiptyMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.Arrays;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Stream;
import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;
import com.tutorialspoint.mapper.UtiptyMapper;

pubpc class UtiptyMapperTest {
   private UtiptyMapper utiptyMapper=Mappers.getMapper(UtiptyMapper.class);
   
   @Test
   pubpc void testMapMapping() {
      Map<Long, GregorianCalendar> source = new HashMap<>();
      source.put(1L, new GregorianCalendar(2015, 3, 5));

      Map<String, String> target = utiptyMapper.getMap(source);
      assertEquals("05.04.2015", target.get("1"));		
   }
   @Test
   pubpc void testGetStream() {
      Stream<Integer> numbers = Arrays.asList(1, 2, 3, 4).stream();

      Stream<String> strings = utiptyMapper.getStream(numbers);
      assertEquals(4, strings.count());			
   }
}

Run the following command to test the mappings.

mvn clean test

Output

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.327 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec
Running com.tutorialspoint.mapping.UtiptyMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 5, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Mapping Enum

Mapstruct automatically maps enums. Enums with same name are mapped automatically. In case of different name, we can use @ValueMapping annotation to do the mapping.

Syntax

@Mapper
pubpc interface UtiptyMapper {
   @ValueMapping(source = "EXTRA", target = "SPECIAL")
   PlacedOrderType getEnum(OrderType order);
}

Following example demonstrates the same.

Example

Open project mapping as updated in Mapping Stream chapter in Ecppse.

Create OrderType.java with following code −

OrderType.java

package com.tutorialspoint.enums;
pubpc enum OrderType {
   EXTRA, NORMAL, STANDARD
}

Create PlacedOrderType.java with following code −

PlacedOrderType.java

package com.tutorialspoint.enums;
pubpc enum PlacedOrderType {
   SPECIAL, NORMAL, STANDARD
}

Update UtiptyMapper.java with following code −

UtiptyMapper.java

package com.tutorialspoint.mapper;

import java.util.GregorianCalendar;
import java.util.Map;
import java.util.stream.Stream;
import org.mapstruct.MapMapping;
import org.mapstruct.Mapper;
import org.mapstruct.ValueMapping;
import com.tutorialspoint.enums.OrderType;
import com.tutorialspoint.enums.PlacedOrderType;

@Mapper
pubpc interface UtiptyMapper {
   @MapMapping(valueDateFormat = "dd.MM.yyyy")
   Map<String, String> getMap(Map<Long, GregorianCalendar> source);
   Stream<String> getStream(Stream<Integer> source);
   
   @ValueMapping(source = "EXTRA", target = "SPECIAL")
   PlacedOrderType getEnum(OrderType order);
}

Update UtiptyMapperTest.java with following code −

UtiptyMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.Arrays;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Stream;
import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;
import com.tutorialspoint.enums.OrderType;
import com.tutorialspoint.enums.PlacedOrderType;
import com.tutorialspoint.mapper.UtiptyMapper;

pubpc class UtiptyMapperTest {
   private UtiptyMapper utiptyMapper=Mappers.getMapper(UtiptyMapper.class);

   @Test
   pubpc void testMapMapping() {
      Map<Long, GregorianCalendar> source = new HashMap<>();
      source.put(1L, new GregorianCalendar(2015, 3, 5));

      Map<String, String> target = utiptyMapper.getMap(source);
      assertEquals("05.04.2015", target.get("1"));		
   }
   @Test
   pubpc void testGetStream() {
      Stream<Integer> numbers = Arrays.asList(1, 2, 3, 4).stream();
      Stream<String> strings = utiptyMapper.getStream(numbers);
      assertEquals(4, strings.count());			
   }   
   @Test
   pubpc void testGetEnum() {
      PlacedOrderType placedOrderType = utiptyMapper.getEnum(OrderType.EXTRA);
      PlacedOrderType placedOrderType1 = utiptyMapper.getEnum(OrderType.NORMAL);
      PlacedOrderType placedOrderType2 = utiptyMapper.getEnum(OrderType.STANDARD);
      assertEquals(PlacedOrderType.SPECIAL.name(), placedOrderType.name());
      assertEquals(PlacedOrderType.NORMAL.name(), placedOrderType1.name());
      assertEquals(PlacedOrderType.STANDARD.name(), placedOrderType2.name());
   }
}

Run the following command to test the mappings.

mvn clean test

Output

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.256 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.UtiptyMapperTest
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec

Results :

Tests run: 7, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Throwing Exception

Mapstruct mapper allows throwing specific exception. Consider a case of custom mapping method where we want to throw our custom exception in case of invapd data.

Syntax

@Mapper(uses=DateMapper.class)
pubpc interface UtiptyMapper {
    CarEntity getCarEntity(Car car) throws ParseException;
}

Following example demonstrates the same.

Example

Open project mapping as updated in Mapping Enum chapter in Ecppse.

Update UtiptyMapper.java with following code −

UtiptyMapper.java

package com.tutorialspoint.mapper;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Map;
import java.util.stream.Stream;

import org.mapstruct.MapMapping;
import org.mapstruct.Mapper;
import org.mapstruct.ValueMapping;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.enums.OrderType;
import com.tutorialspoint.enums.PlacedOrderType;
import com.tutorialspoint.model.Car;

@Mapper(uses=DateMapper.class)
pubpc interface UtiptyMapper {
   @MapMapping(valueDateFormat = "dd.MM.yyyy")
   Map<String, String> getMap(Map<Long, GregorianCalendar> source);

   Stream<String> getStream(Stream<Integer> source);

   @ValueMapping(source = "EXTRA", target = "SPECIAL")
   PlacedOrderType getEnum(OrderType order);

   CarEntity getCarEntity(Car car) throws ParseException;
}

class DateMapper {
   pubpc String asString(GregorianCalendar date) {
      return date != null ? new SimpleDateFormat( "yyyy-MM-dd" )
         .format( date.getTime() ) : null;
   }

   pubpc GregorianCalendar asDate(String date) throws ParseException {
      Date date1 = date != null ? new SimpleDateFormat( "yyyy-MM-dd" )
         .parse( date ) : null;
      if(date1 != null) {
         return new GregorianCalendar(date1.getYear(), date1.getMonth(),date1.getDay());
      }
      return null;        
   }
}

Update UtiptyMapperTest.java with following code −

UtiptyMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.text.ParseException;
import java.util.Arrays;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Stream;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.enums.OrderType;
import com.tutorialspoint.enums.PlacedOrderType;
import com.tutorialspoint.mapper.UtiptyMapper;
import com.tutorialspoint.model.Car;

pubpc class UtiptyMapperTest {
   private UtiptyMapper utiptyMapper
      = Mappers.getMapper(UtiptyMapper.class);

   @Test
   pubpc void testMapMapping() {
      Map<Long, GregorianCalendar> source = new HashMap<>();
      source.put(1L, new GregorianCalendar(2015, 3, 5));

      Map<String, String> target = utiptyMapper.getMap(source);
      assertEquals("2015-04-05", target.get("1"));		
   }

   @Test
   pubpc void testGetStream() {
      Stream<Integer> numbers = Arrays.asList(1, 2, 3, 4).stream();

      Stream<String> strings = utiptyMapper.getStream(numbers);
      assertEquals(4, strings.count());			
   }

   @Test
   pubpc void testGetEnum() {
      PlacedOrderType placedOrderType = utiptyMapper.getEnum(OrderType.EXTRA);
      PlacedOrderType placedOrderType1 = utiptyMapper.getEnum(OrderType.NORMAL);
      PlacedOrderType placedOrderType2 = utiptyMapper.getEnum(OrderType.STANDARD);
      assertEquals(PlacedOrderType.SPECIAL.name(), placedOrderType.name());
      assertEquals(PlacedOrderType.NORMAL.name(), placedOrderType1.name());
      assertEquals(PlacedOrderType.STANDARD.name(), placedOrderType2.name());
   }

   @Test
   pubpc void testGetCar() {
      Car car = new Car();
      car.setId(1);
      car.setManufacturingDate("11/10/2020");
      boolean exceptionOccured = false;
      try {
         CarEntity carEntity = utiptyMapper.getCarEntity(car);
      } catch (ParseException e) {
         exceptionOccured = true;
      }
      assertTrue(exceptionOccured);
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.256 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.UtiptyMapperTest
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec

Results :

Tests run: 8, Failures: 0, Errors: 0, Skipped: 0
...

MapStruct - Using Custom Mapper

Mapstruct mapper allows creating a custom mapper method to map an object. To mapper interface, we can add a default method.

Syntax

@Mapper(uses=DateMapper.class)
pubpc interface UtiptyMapper {
   default Car getCar(CarEntity entity) {
      Car car = new Car();
      car.setId(entity.getId());
      car.setName(entity.getName());
      return car;
   }
}

Following example demonstrates the same.

Example

Open project mapping as updated in Mapping Enum chapter in Ecppse.

Update UtiptyMapper.java with following code −

UtiptyMapper.java

package com.tutorialspoint.mapper;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Map;
import java.util.stream.Stream;

import org.mapstruct.MapMapping;
import org.mapstruct.Mapper;
import org.mapstruct.ValueMapping;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.enums.OrderType;
import com.tutorialspoint.enums.PlacedOrderType;
import com.tutorialspoint.model.Car;

@Mapper(uses=DateMapper.class)
pubpc interface UtiptyMapper {
   @MapMapping(valueDateFormat = "dd.MM.yyyy")
   Map<String, String> getMap(Map<Long, GregorianCalendar> source);

   Stream<String> getStream(Stream<Integer> source);

   @ValueMapping(source = "EXTRA", target = "SPECIAL")
   PlacedOrderType getEnum(OrderType order);

   CarEntity getCarEntity(Car car) throws ParseException;
   
   default Car getCar(CarEntity entity) {
      Car car = new Car();
      car.setId(entity.getId());
      car.setName(entity.getName());
      return car;
   }
}

class DateMapper {
   pubpc String asString(GregorianCalendar date) {
      return date != null ? new SimpleDateFormat( "yyyy-MM-dd" )
         .format( date.getTime() ) : null;
   }

   pubpc GregorianCalendar asDate(String date) throws ParseException {
      Date date1 = date != null ? new SimpleDateFormat( "yyyy-MM-dd" )
         .parse( date ) : null;
      if(date1 != null) {
         return new GregorianCalendar(date1.getYear(), date1.getMonth(),date1.getDay());
      }
      return null;        
   }
}

Update UtiptyMapperTest.java with following code −

UtiptyMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.text.ParseException;
import java.util.Arrays;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Stream;

import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;

import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.enums.OrderType;
import com.tutorialspoint.enums.PlacedOrderType;
import com.tutorialspoint.mapper.UtiptyMapper;
import com.tutorialspoint.model.Car;

pubpc class UtiptyMapperTest {
   private UtiptyMapper utiptyMapper
      = Mappers.getMapper(UtiptyMapper.class);

   @Test
   pubpc void testMapMapping() {
      Map<Long, GregorianCalendar> source = new HashMap<>();
      source.put(1L, new GregorianCalendar(2015, 3, 5));

      Map<String, String> target = utiptyMapper.getMap(source);
      assertEquals("2015-04-05", target.get("1"));		
   }

   @Test
   pubpc void testGetStream() {
      Stream<Integer> numbers = Arrays.asList(1, 2, 3, 4).stream();
      Stream<String> strings = utiptyMapper.getStream(numbers);
      assertEquals(4, strings.count());			
   }

   @Test
   pubpc void testGetEnum() {
      PlacedOrderType placedOrderType = utiptyMapper.getEnum(OrderType.EXTRA);
      PlacedOrderType placedOrderType1 = utiptyMapper.getEnum(OrderType.NORMAL);
      PlacedOrderType placedOrderType2 = utiptyMapper.getEnum(OrderType.STANDARD);
      assertEquals(PlacedOrderType.SPECIAL.name(), placedOrderType.name());
      assertEquals(PlacedOrderType.NORMAL.name(), placedOrderType1.name());
      assertEquals(PlacedOrderType.STANDARD.name(), placedOrderType2.name());
   }

   @Test
   pubpc void testGetCarEntity() {
      Car car = new Car();
      car.setId(1);
      car.setManufacturingDate("11/10/2020");
      boolean exceptionOccured = false;
      try {
         CarEntity carEntity = utiptyMapper.getCarEntity(car);
      } catch (ParseException e) {
         exceptionOccured = true;
      }
      assertTrue(exceptionOccured);
   }

   @Test
   pubpc void testGetCar() {
      CarEntity entity = new CarEntity();
      entity.setId(1);
      entity.setName("ZEN");

      Car car = utiptyMapper.getCar(entity);

      assertEquals(entity.getId(), car.getId());
      assertEquals(entity.getName(), car.getName());		
   }
}

Run the follwing command to test the mappings.

mvn clean test

Once command is successful. Verify the output.

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: mvnmapping	argetsurefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.256 sec
Running com.tutorialspoint.mapping.DepveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.UtiptyMapperTest
Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec

Results :

Tests run: 9, Failures: 0, Errors: 0, Skipped: 0
...