Design Pattern - Transfer Object Pattern

The Transfer Object pattern is used when we want to pass data with multiple attributes in one shot from cpent to server. Transfer object is also known as Value Object. Transfer Object is a simple POJO class having getter/setter methods and is seriapzable so that it can be transferred over the network. It does not have any behavior. Server Side business class normally fetches data from the database and fills the POJO and send it to the cpent or pass it by value. For cpent, transfer object is read-only. Cpent can create its own transfer object and pass it to server to update values in database in one shot. Following are the entities of this type of design pattern.

Business Object - Business Service fills the Transfer Object with data.

Transfer Object - Simple POJO having methods to set/get attributes only.

Cpent - Cpent either requests or sends the Transfer Object to Business Object.

Implementation

We are going to create a StudentBO as Business Object,Student as Transfer Object representing our entities.

TransferObjectPatternDemo, our demo class, is acting as a cpent here and will use StudentBO and Student to demonstrate Transfer Object Design Pattern.

Step 1

Create Transfer Object.

StudentVO.java

pubpc class StudentVO {
   private String name;
   private int rollNo;

   StudentVO(String name, int rollNo){
      this.name = name;
      this.rollNo = rollNo;
   }

   pubpc String getName() {
      return name;
   }

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

   pubpc int getRollNo() {
      return rollNo;
   }

   pubpc void setRollNo(int rollNo) {
      this.rollNo = rollNo;
   }
}

Step 2

Create Business Object.

StudentBO.java

import java.util.ArrayList;
import java.util.List;

pubpc class StudentBO {
	
   //pst is working as a database
   List<StudentVO> students;

   pubpc StudentBO(){
      students = new ArrayList<StudentVO>();
      StudentVO student1 = new StudentVO("Robert",0);
      StudentVO student2 = new StudentVO("John",1);
      students.add(student1);
      students.add(student2);		
   }
   pubpc void deleteStudent(StudentVO student) {
      students.remove(student.getRollNo());
      System.out.println("Student: Roll No " + student.getRollNo() + ", deleted from database");
   }

   //retrive pst of students from the database
   pubpc List<StudentVO> getAllStudents() {
      return students;
   }

   pubpc StudentVO getStudent(int rollNo) {
      return students.get(rollNo);
   }

   pubpc void updateStudent(StudentVO student) {
      students.get(student.getRollNo()).setName(student.getName());
      System.out.println("Student: Roll No " + student.getRollNo() +", updated in the database");
   }
}

Step 3

Use the StudentBO to demonstrate Transfer Object Design Pattern.

TransferObjectPatternDemo.java

pubpc class TransferObjectPatternDemo {
   pubpc static void main(String[] args) {
      StudentBO studentBusinessObject = new StudentBO();

      //print all students
      for (StudentVO student : studentBusinessObject.getAllStudents()) {
         System.out.println("Student: [RollNo : " + student.getRollNo() + ", Name : " + student.getName() + " ]");
      }

      //update student
      StudentVO student = studentBusinessObject.getAllStudents().get(0);
      student.setName("Michael");
      studentBusinessObject.updateStudent(student);

      //get the student
      student = studentBusinessObject.getStudent(0);
      System.out.println("Student: [RollNo : " + student.getRollNo() + ", Name : " + student.getName() + " ]");
   }
}

Step 4

Verify the output.

Student: [RollNo : 0, Name : Robert ]
Student: [RollNo : 1, Name : John ]
Student: Roll No 0, updated in the database
Student: [RollNo : 0, Name : Michael ]