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 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: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec

Results :

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