Lombok @Builder和JPA Default构造函数

Question

我正在使用项目Lombok和Spring Data JPA.有没有办法将Lombok @Builder与JPA默认构造函数连接？

码:

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

据我所知,JPA需要默认构造函数,它被@Builder注释覆盖.那有什么解决方法吗？

这段代码给了我错误: org.hibernate.InstantiationException: No default constructor for entity: : app.domain.model.Person

Answer 1

更新

基于反馈和John的回答,我已经更新了不再使用的答案,@Tolerate或者@Data我们通过创建访问器和mutator,@Getter并@Setter创建默认构造函数@NoArgsConstructor,最后我们创建构建器所需的所有args构造函数@AllArgsConstructor.

既然你想使用构建器模式,我想你想要限制构造函数和mutators方法的可见性.为实现此目的,我们package private通过注释上的属性和注释上的access属性设置可见性.@NoArgsConstructor@AllArgsConstructorvalue@Setter

重要

记住要正确重写toString,equals和hashCode.有关详细信息,请参阅Vlad Mihalcea的以下帖子:

• 该条最佳方式对实施-等于-哈希码和-的toString与 - JPA-和休眠
• 如何对实现-等于-和哈希码 - 使用最JPA实体标识符
• 休眠-事实,等于和 - 哈希码

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());
    }
}

旧版本使用@Tolerate和@Data:

使用@Tolerate工作允许添加noarg构造函数.

由于您想要使用构建器模式,我想您想要控制setter方法的可见性.

该@Data注解使得生成的制定者public,应用@Setter(value = AccessLevel.PROTECTED)的领域,因此他们protected.

记住要正确重写toString,equals和hashCode.有关详细信息,请参阅Vlad Mihalcea的以下帖子:

• 该条最佳方式对实施-等于-哈希码和-的toString与 - JPA-和休眠
• 如何对实现-等于-和哈希码 - 使用最JPA实体标识符
• 休眠-事实,等于和 - 哈希码

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

您还可以@Data @Builder @NoArgsConstructor @AllArgsConstructor结合使用类定义来明确解决它.

Answer 3

如果同时使用构造函数上的lombok.Tolerate和某些属性上的javax.validation.constraints.NotNull注释，sonarqube 会将其标记为严重错误：PROPERTY 标记为“javax.validation.constraints.NotNull”但不是在此构造函数中初始化。

如果项目使用带有JPA的SpringData，可以使用org.springframework.data.annotation.PersistenceConstructor解决（Spring注解，不是JPA！）

然后，结合 Lombok，注解会是这样的：

@RequiredArgsConstructor(onConstructor = @__(@PersistenceConstructor))

对于 Lombok builder，您还需要添加：

@Builder
@AllArgsConstructor

Answer 4

注释的顺序在这里似乎很重要，使用相同的注释，但是使用不同的顺序，可以使代码正常运行，也可以不正常运行。

这是一个无效的示例：

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

这是一个有效的示例：

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

因此，请确保将@Builder批注放在最高位置，在我的情况下，我会遇到此错误，因为我想按字母顺序对批注进行排序。

Answer 5

使用@NoArgsConstructorand@AllArgsContructor将有助于解决使用默认构造函数的问题@Builder。

例如

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

这是因为@Builder需要所有参数构造函数并且仅指定默认构造函数会导致问题。

这里没有解释：https://github.com/rzwitserloot/lombok/issues/1389#issuecomment-369404719

Answer 6

使用以下组合

• 龙目岛
• 日本PA
  • 增删改查
  • 恰当的@EqualsAndHashCode
• 不变性 - 公共最终字段
• 无吸气剂
• 没有二传手
• 通过@Builder和进行更改@With

我用了：

//Lombok & JPA
///sf/ask/2396920291/

//Mandatory in conjunction with JPA: an equal based on fields is not desired
@lombok.EqualsAndHashCode(onlyExplicitlyIncluded = true)
//Mandatory in conjunction with JPA: force is needed to generate default values for final fields, that will be overriden by JPA
@lombok.NoArgsConstructor(access = AccessLevel.PRIVATE, force = true)
//Hides the constructor to force usage of the Builder.
@lombok.AllArgsConstructor(access = AccessLevel.PRIVATE)
@lombok.ToString
//Good to just modify some values
@lombok.With
//Mandatory in conjunction with JPA: Some suggest that the Builder should be above Entity - /sf/answers/3643378721/
//Good to be used to modify all values
@lombok.Builder(toBuilder = true)
//final fields needed for imutability, the default access to public - since are final is safe 
@lombok.experimental.FieldDefaults(makeFinal = true, level = AccessLevel.PUBLIC)
//no getters and setters
@lombok.Getter(value = AccessLevel.NONE)
@lombok.Setter(value = AccessLevel.NONE)

//JPA
@javax.persistence.Entity
@javax.persistence.Table(name = "PERSON_WITH_MOTTO")
//jpa should use field access 
@javax.persistence.Access(AccessType.FIELD)
public class Person {
  @javax.persistence.Id
  @javax.persistence.GeneratedValue
  //Used also automatically as JPA
  @lombok.EqualsAndHashCode.Include
  Long id;
  String name;
  String motto;
}