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 Eclipse.

Update StudentEntity.java with following code −

StudentEntity.java

package com.tutorialspoint.entity;

public class StudentEntity {
   private String id;
   private String name;
   private String classVal;
   private SubjectEntity subject;
   public String section;
   public String getId() {
      return id;
   }
   public void setId(String 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;
   }
}

Student.java is unchanged 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() {
      ret+urn id;
   }
}

Update DeliveryAddressMapperTest.java with following code −

DeliveryAddressMapperTest.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.DeliveryAddressMapper;
import com.tutorialspoint.model.DeliveryAddress;

public class DeliveryAddressMapperTest {
   private DeliveryAddressMapper deliveryAddressMapper = Mappers.getMapper(DeliveryAddressMapper.class);

   @Test
   public 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);

      DeliveryAddress deliveryAddress = deliveryAddressMapper.getDeliveryAddress(student, address);

      assertEquals(deliveryAddress.getName(), student.getName());
      assertEquals(deliveryAddress.getCity(), address.getCity());
      assertEquals(deliveryAddress.getState(), address.getState());
      assertEquals(deliveryAddress.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;

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(Integer.parseInt(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(Integer.parseInt(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: mvnmappingtargetsurefire-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
...