Lombok @Builder and JPA Default constructor

Question

I'm using project Lombok together with Spring Data JPA. Is there any way to connect Lombok @Builder with JPA default constructor?

Code:

@Entity 
@Builder
class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
}

As far as I know JPA needs default constructor which is overriden by @Builder annotation. Is there any workaround for that?

This code gives me error: org.hibernate.InstantiationException: No default constructor for entity: : app.domain.model.Person

Answer 1

Updated

Based on the feedback and John's answer I have updated the answer to no longer use @Tolerate or @Data and instead we create accessors and mutators via @Getter and @Setter, create the default constructor via @NoArgsConstructor, and finally we create the all args constructor that the builder requires via @AllArgsConstructor.

Since you want to use the builder pattern I imagine you want to restrict visibility of the constructor and mutators methods. To achieve this we set the visibility to package private via the access attribute on the @NoArgsConstructor and @AllArgsConstructor annotations and the value attribute on the @Setterannotation.

Important

Remember to properly override toString, equals, and hashCode. See the following posts by Vlad Mihalcea for details:

• the-best-way-to-implement-equals-hashcode-and-tostring-with-jpa-and-hibernate
• how-to-implement-equals-and-hashcode-using-the-jpa-entity-identifier
• hibernate-facts-equals-and-hashcode

package com.stackoverflow.SO34299054;

import static org.junit.Assert.*;

import java.util.Random;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

import org.junit.Test;

import lombok.AccessLevel;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

@SuppressWarnings("javadoc")
public class Answer {

    @Entity
    @Builder(toBuilder = true)
    @AllArgsConstructor(access = AccessLevel.PACKAGE)
    @NoArgsConstructor(access = AccessLevel.PACKAGE)
    @Setter(value = AccessLevel.PACKAGE)
    @Getter
    public static class Person {

        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        private Long id;

        /*
         * IMPORTANT:
         * Set toString, equals, and hashCode as described in these
         * documents:
         * - https://vladmihalcea.com/the-best-way-to-implement-equals-hashcode-and-tostring-with-jpa-and-hibernate/
         * - https://vladmihalcea.com/how-to-implement-equals-and-hashcode-using-the-jpa-entity-identifier/
         * - https://vladmihalcea.com/hibernate-facts-equals-and-hashcode/
         */
    }

    /**
     * Test person builder.
     */
    @Test
    public void testPersonBuilder() {

        final Long expectedId = new Random().nextLong();
        final Person fromBuilder = Person.builder()
            .id(expectedId)
            .build();
        assertEquals(expectedId, fromBuilder.getId());

    }

    /**
     * Test person constructor.
     */
    @Test
    public void testPersonConstructor() {

        final Long expectedId = new Random().nextLong();
        final Person fromNoArgConstructor = new Person();
        fromNoArgConstructor.setId(expectedId);
        assertEquals(expectedId, fromNoArgConstructor.getId());
    }
}

Old Version using @Tolerate and @Data:

Using @Tolerate worked to allow adding a noarg constructor.

Since you want to use the builder pattern I imagine you want to control visibility of the setter methods.

The @Data annotation makes the generated setters public, applying @Setter(value = AccessLevel.PROTECTED) to the fields makes them protected.

Remember to properly override toString, equals, and hashCode. See the following posts by Vlad Mihalcea for details:

• the-best-way-to-implement-equals-hashcode-and-tostring-with-jpa-and-hibernate
• how-to-implement-equals-and-hashcode-using-the-jpa-entity-identifier
• hibernate-facts-equals-and-hashcode

package lombok.javac.handlers.stackoverflow;

import static org.junit.Assert.*;

import java.util.Random;

import javax.persistence.GenerationType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

import lombok.AccessLevel;
import lombok.Builder;
import lombok.Data;
import lombok.Setter;
import lombok.experimental.Tolerate;

import org.junit.Test;

public class So34241718 {

    @Builder
    @Data
    public static class Person {

        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        @Setter(value = AccessLevel.PROTECTED)
        Long id;

        @Tolerate
        Person() {}

       /* IMPORTANT:
          Override toString, equals, and hashCode as described in these 
          documents:
          - https://vladmihalcea.com/the-best-way-to-implement-equals-hashcode-and-tostring-with-jpa-and-hibernate/
          - https://vladmihalcea.com/how-to-implement-equals-and-hashcode-using-the-jpa-entity-identifier/
          - https://vladmihalcea.com/hibernate-facts-equals-and-hashcode/
          */
    }

    @Test
    public void testPersonBuilder() {

        Long expectedId = new Random().nextLong();
        final Person fromBuilder = Person.builder()
            .id(expectedId)
            .build();
        assertEquals(expectedId, fromBuilder.getId());

    }

    @Test
    public void testPersonConstructor() {

        Long expectedId = new Random().nextLong();
        final Person fromNoArgConstructor = new Person();
        fromNoArgConstructor .setId(expectedId);
        assertEquals(expectedId, fromNoArgConstructor.getId());
    }
}

Answer 2

You can also solve it explicitly with @Data @Builder @NoArgsConstructor @AllArgsConstructor combined on the class definition.

Answer 3

It seems that the annotations order is important here, using the same annotations, but different orders, you can have the code working, or not.

Here is a non working example:

@AllArgsConstructor
@Builder
@Data
@Entity
@EqualsAndHashCode
@NoArgsConstructor
@RequiredArgsConstructor
@Table
@ToString
public class Person implements Serializable {
  private String name;
}

And this is a working example:

@Builder
@Data
@Entity
@EqualsAndHashCode
@AllArgsConstructor
@NoArgsConstructor
@RequiredArgsConstructor
@Table
@ToString
public class Person implements Serializable {
  private String name;
}

So be sure to have the @Builder annotation at the very top position, in my case I encountered this error because I wanted to sort annotations alphabetically.