MapStruct - Mapping Nested Bean


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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
public 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 Eclipse.

Create SubjectEntity.java with following code −

SubjectEntity.java

package com.tutorialspoint.entity;

public class SubjectEntity {
   private String name;
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }	
}

Update StudentEntity.java with following code −

StudentEntity.java

package com.tutorialspoint.entity;

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

Update Student.java with following code −

Student.java

package com.tutorialspoint.model;

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

public class StudentMapperTest {
   private StudentMapper studentMapper = Mappers.getMapper(StudentMapper.class);
   @Test
   public 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
   public 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 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: \mvn\mapping\target\surefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.DeliveryAddressMapperTest
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
...
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