当我们使用龙目岛建造者建立继承关系时，如何构建对象？

@Builder无法确定您希望公开哪些字段。Parent

当 放置在类上时，只有在该类上显式声明的字段才会添加到 .@Builder*Builder

当放置在静态方法或构造函数上时，结果将具有每个参数的方法。@Builder*Builder

另外，如果您正在使用，那么是否可以安全地假设至少意味着是不可变的？@BuilderChild

我举了两个例子，一个是可变的和不可变的，另一个是两者都是不可变的。ParentChildParentChild

不可变的父项和子项

import static org.junit.Assert.*;
import lombok.Builder;
import lombok.EqualsAndHashCode;
import lombok.ToString;
import lombok.Value;
import lombok.experimental.NonFinal;

import org.junit.Test;

public class So32989562ValueTest {

    @Value
    @NonFinal
    public static class Parent {

        protected final String nationality;

    }

    @Value
    @ToString(callSuper = true)
    @EqualsAndHashCode(callSuper = true)
    public static class Child extends Parent {

        private final String firstName;

        private final String lastName;

        @Builder(toBuilder = true)
        private Child(String nationality, String firstName, String lastName) {
            super(nationality);
            this.firstName = firstName;
            this.lastName = lastName;
        }
    }

    @Test
    public void testChildBuilder() {

        String expectedFirstName = "Jeff";
        String expectedLastName = "Maxwell";
        String expectedNationality = "USA";

        Child result = Child.builder()
            .firstName(expectedFirstName)
            .lastName(expectedLastName)
            .nationality(expectedNationality)
            .build();

        assertEquals(result.toString(), expectedFirstName, result.getFirstName());
        assertEquals(result.toString(), expectedLastName, result.getLastName());
        assertEquals(result.toString(), expectedNationality, result.getNationality());
    }
}

可变父项，不可变子项：

import static org.junit.Assert.*;
import lombok.Builder;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.ToString;
import lombok.Value;

import org.junit.Test;

public class So32989562DataTest {

    @Data
    public static class Parent {

        protected String nationality;

    }

    @Value
    @ToString(callSuper = true)
    @EqualsAndHashCode(callSuper = true)
    public static class Child extends Parent {

        private final String firstName;

        private final String lastName;

        @Builder(toBuilder = true)
        private Child(String nationality, String firstName, String lastName) {
            this.setNationality(nationality);
            this.firstName = firstName;
            this.lastName = lastName;
        }
    }

    @Test
    public void testChildBuilder() {

        String expectedFirstName = "Jeff";
        String expectedLastName = "Maxwell";
        String expectedNationality = "USA";

        Child result = Child.builder()
            .firstName(expectedFirstName)
            .lastName(expectedLastName)
            .nationality(expectedNationality)
            .build();

        assertEquals(result.toString(), expectedFirstName, result.getFirstName());
        assertEquals(result.toString(), expectedLastName, result.getLastName());
        assertEquals(result.toString(), expectedNationality, result.getNationality());
    }
}

上述解决方案有效，但是这需要太多的解决方法。此外，子类和父类中的任何更改都需要在任何地方更改构造函数参数。

龙目岛在版本1.18.2中引入了实验性功能，用于解决Builder注释面临的继承问题，并且可以通过@SuperBuilder注释解决，如下所示。

@SuperBuilder
public class ParentClass {
    private final String a;
    private final String b;
}

@SuperBuilder
public class ChildClass extends ParentClass{
    private final String c;
}

现在，可以使用如下所示的Builder类（这在@Builder注释中是不可能的）

ChildClass.builder().a("testA").b("testB").c("testC").build();