如何通过Lombok与Guice为不同调用类注入命名Provider？

要实现为CallerA和CallerB分别注入绑定不同Client的Strategy，你可以通过Guice的命名绑定配合Lombok构造器注解来实现，具体步骤如下：

1. 调整Strategy类（不硬编码Client绑定） #

不需要在Strategy的Client字段上固定命名注解，让Guice通过模块配置控制注入的Client实例：

@RequiredArgsConstructor(onConstructor = @__(@Inject))
class Strategy {
    private final Client client;

    public void runMe() {
        // 原有业务逻辑
        client.doThings();
    }
}

2. 完善Guice模块配置 #

在模块中新增两个命名的Strategy提供者，分别关联对应的Client实例：

public class ClientModule extends AbstractModule {
    @Override
    protected void configure() {}

    // 提供ClientA实例
    @Provides
    @Named("ClientA")
    public Client providesClientA() {
        return ClientA.builder().build();
    }

    // 提供ClientB实例
    @Provides
    @Named("ClientB")
    public Client providesClientB() {
        return new ClientB(); // 替换为你的ClientB构造逻辑
    }

    // 绑定使用ClientA的Strategy实例
    @Provides
    @Named("StrategyWithClientA")
    public Strategy providesStrategyWithClientA(@Named("ClientA") Client client) {
        return new Strategy(client);
    }

    // 绑定使用ClientB的Strategy实例
    @Provides
    @Named("StrategyWithClientB")
    public Strategy providesStrategyWithClientB(@Named("ClientB") Client client) {
        return new Strategy(client);
    }
}

3. 修改Caller类，注入对应命名的Strategy #

CallerA（使用ClientA的Strategy） #

@RequiredArgsConstructor(onConstructor = @__(@Inject))
class CallerA {
    @Named("StrategyWithClientA")
    private final Strategy strategy;

    public void run() {
        strategy.runMe();
    }
}

CallerB（使用ClientB的Strategy） #

@RequiredArgsConstructor(onConstructor = @__(@Inject))
class CallerB {
    @Named("StrategyWithClientB")
    private final Strategy strategy;

    public void run() {
        strategy.runMe();
    }
}

可选优化：用自定义绑定注解替代@Named #

如果想避免字符串魔法值，可创建自定义绑定注解让代码更健壮：

1. 创建两个自定义注解：

@BindingAnnotation
@Target({FIELD, PARAMETER, METHOD})
@Retention(RUNTIME)
public @interface ForClientA {}

@BindingAnnotation
@Target({FIELD, PARAMETER, METHOD})
@Retention(RUNTIME)
public @interface ForClientB {}

2. 调整模块中的提供者注解：

@Provides
@ForClientA
public Client providesClientA() {
    return ClientA.builder().build();
}

@Provides
@ForClientB
public Client providesClientB() {
    return new ClientB();
}

@Provides
@ForClientA
public Strategy providesStrategyForClientA(@ForClientA Client client) {
    return new Strategy(client);
}

@Provides
@ForClientB
public Strategy providesStrategyForClientB(@ForClientB Client client) {
    return new Strategy(client);
}

3. 修改Caller类的字段注解：

// CallerA
@RequiredArgsConstructor(onConstructor = @__(@Inject))
class CallerA {
    @ForClientA
    private final Strategy strategy;
    // ...
}

// CallerB
@RequiredArgsConstructor(onConstructor = @__(@Inject))
class CallerB {
    @ForClientB
    private final Strategy strategy;
    // ...
}

内容的提问来源于stack exchange，提问作者ikmckenz