java - Lombok @Builder 和 JPA 默认构造函数

Question

我将 Lombok 项目与 Spring Data JPA 一起使用。 有没有办法将 Lombok @Builder 与 JPA 默认构造函数连接起来？

代码:

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

据我所知，JPA 需要由 @Builder 注释覆盖的默认构造函数。有什么解决办法吗？

这段代码给了我错误: org.hibernate.InstantiationException:没有实体的默认构造函数::app.domain.model.Person

Answer 1

更新

基于反馈和 John 的 answer我已经更新了不再使用 @Tolerate 或 @Data 的答案，而是通过 @Getter 和 @ 创建访问器和修改器Setter，通过@NoArgsConstructor创建默认构造函数，最后我们通过@AllArgsConstructor创建builder需要的all args构造函数。 p>

由于您想使用构建器模式，我想您想限制构造函数和修改器方法的可见性。 为了实现这一点，我们通过 @NoArgsConstructor 和 @AllArgsConstructor 注释上的 access 属性将可见性设置为 package private以及 @Setter 注释上的 value 属性。

重要

请记住正确覆盖 toString、equals 和 hashCode。 有关详细信息，请参阅 Vlad Mihalcea 的以下帖子:

• 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());
    }
}

使用 @Tolerate 和 @Data 的旧版本:

使用 @Tolerate 可以允许添加 noarg 构造函数。

由于您想使用构建器模式，我想您想控制 setter 方法的可见性。

@Data 注释使生成的 setter public，将 @Setter(value = AccessLevel.PROTECTED) 应用于字段使它们 protected 。

请记住正确覆盖 toString、equals 和 hashCode。 有关详细信息，请参阅 Vlad Mihalcea 的以下帖子:

• 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());
    }
}