Java 如何在方法上使用 Lombok @Builder 注释

How to use Lombok @Builder annotation on Methods

提问by user3139545

I want to have an easy way to construct test data and have found the Builder pattern to be a good fit as described here. However to reduce boilerplate codes in the component tests, even more, I have found @Builderfrom Project Lombok to be a nice candidate to try. However, I can't find any documentation or online examples on how to use it on a method. I want to use @Builderon some sort of factory method since I can't make any changes to the implementation.

我想有一种简单的方法来构建测试数据，并且发现 Builder 模式非常适合此处所述。然而，为了减少组件测试中的样板代码，我发现Project Lombok 中的@Builder是一个不错的选择。但是，我找不到有关如何在方法上使用它的任何文档或在线示例。我想使用@Builder某种工厂方法，因为我无法对实现进行任何更改。

Can someone give an example on how to actually use @Builderon a method?

有人可以举例说明如何实际使用@Builder方法吗？

采纳答案by Jeff

import static org.junit.Assert.*;
import lombok.Builder;
import lombok.Value;

import org.junit.Test;

@SuppressWarnings("javadoc")
public class ImmutableAnimals {

    @Builder(builderMethodName = "dogBuilder")
    public static Dog newDog(String color, String barkSound) {
        return new Dog(color, barkSound);
    }

    @Builder(builderMethodName = "catBuilder")
    public static Cat newCat(String color, String meowSound) {
        return new Cat(color, meowSound);
    }

    public static interface Animal {
        String getColor();
    }

    @Value
    public static class Cat implements Animal {
        String color;
        String meowSound;
    }

    @Value
    public static class Dog implements Animal {
        String color;
        String barkSound;
    }

    @Test
    public void testDog() {
        final String expectedBarkSound = "woof";
        final String expectedColor = "brown";

        final Dog dog = Animals.dogBuilder()
            .barkSound(expectedBarkSound)
            .color(expectedColor)
            .build();

        assertEquals(expectedBarkSound, dog.getBarkSound());
        assertEquals(expectedColor, dog.getColor());
    }

    @Test
    public void testCat() {
        final String expectedMeowSound = "purr";
        final String expectedColor = "white";

        final Cat cat = Animals.catBuilder()
            .meowSound(expectedMeowSound)
            .color(expectedColor)
            .build();

        assertEquals(expectedMeowSound, cat.getMeowSound());
        assertEquals(expectedColor, cat.getColor());
    }
}

import static org.junit.Assert.*;
import lombok.Builder;
import lombok.Data;

import org.junit.Test;

@SuppressWarnings("javadoc")
public class MutableAnimals {

    @Builder(builderMethodName = "dogBuilder")
    public static Dog newDog(String color, String barkSound) {
        final Dog dog = new Dog();
        dog.setBarkSound(barkSound);
        dog.setColor(color);
        return dog;
    }

    @Builder(builderMethodName = "catBuilder")
    public static Cat newCat(String color, String meowSound) {
        final Cat cat = new Cat();
        cat.setMeowSound(meowSound);
        cat.setColor(color);
        return cat;
    }

    public static interface Animal {
        String getColor();
    }

    @Data
    public static class Cat implements Animal {
        String color;
        String meowSound;
    }

    @Data
    public static class Dog implements Animal {
        String color;
        String barkSound;
    }

    @Test
    public void testDog() {
        final String expectedBarkSound = "woof";
        final String expectedColor = "brown";

        final Dog dog = MutableAnimals.dogBuilder()
            .barkSound(expectedBarkSound)
            .color(expectedColor)
            .build();

        assertEquals(expectedBarkSound, dog.getBarkSound());
        assertEquals(expectedColor, dog.getColor());
    }

    @Test
    public void testCat() {
        final String expectedMeowSound = "purr";
        final String expectedColor = "white";

        final Cat cat = MutableAnimals.catBuilder()
            .meowSound(expectedMeowSound)
            .color(expectedColor)
            .build();

        assertEquals(expectedMeowSound, cat.getMeowSound());
        assertEquals(expectedColor, cat.getColor());
    }
}

回答by Deendayal Garg

This is how you use @Builder.

这就是你如何使用@Builder。

//Employee.Java
import lombok.Builder;
import lombok.ToString;

@Builder
@ToString
public class Employee {
   private final String empName;
   private final int salary;
}

//   Main.java

public class Main {

public static void main(String[] args) {
    Employee emp = Employee.builder().empName("Deendaya").salary(100).build();
    System.out.println(emp);
  }
}