MapStruct - 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 Eclipse.

Update Student.java with following code −

Student.java

package com.tutorialspoint.model;

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

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

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;

public class StudentMapperTest {
   private StudentMapper studentMapper = Mappers.getMapper(StudentMapper.class);
   
   @Test
   public 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
   public 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] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running com.tutorialspoint.test.[1mDeliveryAddressMapperTest[m
[INFO] [1;32mTests run: [0;1;32m1[m, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.035 s -- in com.tutorialspoint.test.[1mDeliveryAddressMapperTest[m
[INFO] Running com.tutorialspoint.test.[1mStudentMapperTest[m
[INFO] [1;32mTests run: [0;1;32m2[m, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.009 s -- in com.tutorialspoint.test.[1mStudentMapperTest[m
[INFO] 
[INFO] Results:
[INFO] 
[INFO] [1;32mTests run: 3, Failures: 0, Errors: 0, Skipped: 0[m
[INFO] 
[INFO] [1m------------------------------------------------------------------------[m
[INFO] [1;32mBUILD SUCCESS[m
[INFO] [1m------------------------------------------------------------------------[m
[INFO] Total time:  3.665 s
[INFO] Finished at: 2025-09-13T17:07:08+05:30
[INFO] [1m------------------------------------------------------------------------[m