在运行时

Question

假设我定义了以下服务接口（以及实现）：

interface Service1 { /* Methods omitted for brevity */ }
interface Service2 { /* Methods omitted for brevity */ }

我也有这个无法修改的界面（它不在我的手中）：

interface YouAreNotAllowedToModifyMe {
  Object createSomething();
}

进一步假设我有一个实现YouAreNotAllowedToModifyMe接口的类，并接受这些服务的实现以及当前的HttpServletRequest。请注意，请求是实现细节，而不是接口的一部分。

class Demo implements YouAreNotAllowedToModifyMe {

  private final HttpServletRequest request;
  private final Service1 service1;
  private final Service2 service2;

  @Inject
  public Demo(HttpServletRequest request, Service1 service1, Service2 service2) {
    this.request = request;
    this.service1 = service1;
    this.service2 = service2;
  }

  public Object createSomething() {
    // Use the request, service1, and service2 in order to create the object.
  }
}

Demo直到运行时才能实例化，因为它需要当前的HttpServletRequest，但是我希望CDI注入能够注入其他参数。我怎么能这样做？

基本上，我希望这是可能的（它不是）：

class Foo {

  @Inject
  private final Instance<Demo> demoInstance;

  public void doSomething(HttpServletRequest request) {

    // This is pretend. This won't really work, though I wish it would.
    // Essentially, I pass in the request and CDI takes care of everything else.
    Demo demo = demoInstance.get(request);
  }
}

Answer 1

你不能使用注入了一半参数的构造函数和一半手工提供的构造函数。但是你有其他选择：

• 为HttpServletRequest创建一个制作人。更好的是，使用Delta Spike。那么你实际上可以注入 HttpServletRequest！

• 将Demo修改为YouAreNotAllowedToModifyMe的实例 factory ，而不是实现它：

  @ApplicationScoped //probably-but not necessarily???
  public class Demo {
      @Inject
      private final Service1 service1;
      @Inject
      private final Service2 service2;
  
      public YouAreNotAllowedToModifyMe makeYouAreNotAllowedToModifyMe(HttpServletRequest request) {
          return new YouAreNotAllowedToModifyMeImpl(request);
      }
  
      private class YouAreNotAllowedToModifyMeImpl implements YouAreNotAllowedToModifyMe {
          YouAreNotAllowedToModifyMeImpl(HttpServletRequest request) {
              // do what you must...
          }
  
          // implement it!
          // remember, you can actually use service1 &
          // service 2 from the enclosing instance
      }
  }