Guice只注入一些构造函数 [英] Guice injecting only some of the constructor

问题描述

假设我有一些消息类，如下所示。 （这是一个简单的组合类。）

Suppose I have some Message class like the following. (This is a made-up class for simplicity.)

public class Message {
  private String text;

  public Message(String text) {
    this.text = text;
  }

  public void send(Person recipient) {
    // I think I should be Guice-injecting the sender.
    MessageSender sender = new EmailBasedMessageSender();
    sender.send(recipient, this.text);
  }
}

由于我有不同的 MessageSender 实现，可能想单位测试这个发送能力，我想我应该在消息中注入 MessageSender code>的 send（）方法。但是我该怎么做？

Since I have different MessageSender implementations, and might want to unit test this sending ability, I think I should be injecting the MessageSender in Message's send() method. But how do I do this?

我看到的所有的Guice示例，我理解似乎在构造函数中注入：

All the Guice examples I've seen and that I understand seem to do the injection in the constructor:

public class Message {
  private String text;
  private MessageSender sender;

  // ??? I don't know what to do here, since the `text` argument shouldn't be injected.
  @Inject
  public Message(String text, MessageSender sender) {
    this.text = text;
    this.sender = sender;
  }

  public void send(Person recipient) {
    this.sender.send(recipient, this.text);
  }
}

public class MessageSenderModule extends AbstractModule {
  @Override 
  protected void configure() {
    bind(MessageSender.class).to(EmailBasedMessageSender.class);
  }
}

但是我的 code>类在其构造函数中接收一个 text 参数，我不想注入。所以我应该做什么？

But my Message class takes in a text argument in its constructor, which I don't want to inject. So what am I supposed to do instead?

（注意：我是一个完整的Google Guice noob，我认为我了解依赖注入，但是我不明白您可以使用辅助注射来通过工厂提供文本以及消息。

(Note: I'm a complete Google Guice noob. I think I understand dependency injection, but I don't understand how to actually implement it with Guice.)

推荐答案

发件人由Guice实例化：

You could use assisted injection to provide the text through a factory, along with the message sender instantiated by Guice:

public class Message {
  private String text;
  private MessageSender sender;

  @Inject
  public Message(@Assisted String text, MessageSender sender) {
    this.text = text;
    this.sender = sender;
  }

  public void send(Person recipient) {
    this.sender.send(recipient, this.text);
  }
}

工厂：

public interface MessageFactory{
    Message buildMessage(String text);
}

模块：

public class MessageSenderModule extends AbstractModule {
  @Override 
  protected void configure() {
    bind(MessageSender.class).to(EmailBasedMessageSender.class);
    FactoryModuleBuilder factoryModuleBuilder = new FactoryModuleBuilder();
    install(factoryModuleBuilder.build(MessageFactory.class));
  }
}

用法：

@Inject MessageFactory messageFactory;

void test(Recipient recipient){
  Message message = messageFactory.buildMessage("hey there");
  message.send(recipient);
}

辅助注册维基

这篇关于Guice只注入一些构造函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！