假设我有一些像下面这样的
Message
课程。 (为了简单起见,这是一个虚构的课程。)
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,并且可能想要对这种发送能力进行单元测试,我认为我应该在 MessageSender
的 Message
方法中注入 send()
。但我该怎么做呢?
我见过的和我理解的所有 Guice 示例似乎都是在构造函数中进行注入:
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
Message
类在其构造函数中接受了 text
参数,我不想注入该参数。那我该怎么办呢?
(注:我是一个十足的 Google Guice 菜鸟。我想我理解依赖注入,但我不明白如何用 Guice 实际实现它。)
您可以使用辅助注入通过工厂提供文本,以及由 Guice 实例化的消息发送者:
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));
}
}
用途:
@Inject MessageFactory messageFactory;
void test(Recipient recipient){
Message message = messageFactory.buildMessage("hey there");
message.send(recipient);
}