Lombok @builder在一个扩展另一个类的类上

Question

我有两个课程Child延伸Parent.我需要在类上放置@Builder注释,这样我就不需要自己创建构建器了.

package jerry;// Internal compiler error: java.lang.NullPointerException

import lombok.AllArgsConstructor;
import lombok.Builder;

@AllArgsConstructor(onConstructor=@__(@Builder))
public class Child extends Parent { 
//Multiple markers at this line
//  - Implicit super constructor Parent() is undefined. Must explicitly invoke another constructor
//  - overrides java.lang.Object.toString

   private String a;
   private int b;
   private boolean c;

}


@Builder
public class Parent {
    private double d;
    private float e;
}

我需要能够构建这样的子实例

Child child = Child.builder().a("aVal").b(1000).c(true).d(10.1).e(20.0F).build();

但到目前为止,我收到了代码注释中提到的错误.任何人都可以指出我正确的方向如何使用lombok或任何其他类似的库实现它？

子问题

为什么@AllArgsConstructor(onConstructor=@__(@Autowired))编译但@AllArgsConstructor(onConstructor=@__(@Builder))不是？

Answer 1

见https://blog.codecentric.de/en/2016/05/reducing-boilerplate-code-project-lombok/(@Builder和继承的部分)

调整到你的课程

@AllArgsConstructor
public class Parent {
  private double d;
  private float e;
}

public class Child extends Parent {
  private String a;
  private int b;
  private boolean c;

  @Builder
  public Child(String a, int b, boolean c, double d, float e) {
    super(d, e);
    this.a = a;
    this.b = b;
    this.c = c;
  }
}

有了这个设置

Child child = Child.builder().a("aVal").b(1000).c(true).d(10.1).e(20.0F).build();

工作正常

Answer 2

最新的lombok版本1.18.2包括新的实验@SuperBuilder.它支持超类(也是抽象类)的字段.有了它,解决方案就像这样简单:

@SuperBuilder
public class Child extends Parent {
   private String a;
   private int b;
   private boolean c;
}

@SuperBuilder
public class Parent {
    private double d;
    private float e;
}

Child instance = Child.builder().b(7).e(6.3).build();

PS:@SuperBuilder不起作用,因为@AllArgsConstructor(onConstructor=@__(@Builder))是一个注释处理注释,lombok在编译期间转换为代码.生成,然后转换新的龙目岛标注需要注释处理的几个迭代,以及龙目不支持.@Builder相反,它是运行时可用的常规Java注释.

Answer 3

您需要@SuperBuilder(toBuilder = true)在每个对象中使用。

@Data
@SuperBuilder(toBuilder = true)
public class Parent extends Child {
}

@Data
@SuperBuilder(toBuilder = true)
public class Child {
}