为什么我不能在我的控制器内的新线程中使用@In(使用jboss seam)注入依赖项？

Question

我有依赖注入的麻烦,因为我对Seam很新,我可能会以错误的方式做某事!

我需要在一个从控制器内触发的新线程上注入依赖项 - 我没有例外,但它们只是来了null.首先,我尝试d1在线程中重复使用(见下文),但是null我有了这个想法,再次注释这个对象@In...不幸的是同样的事情发生了(得到了空)!

@Scope(ScopeType.CONVERSATION)
@Name("myController")
public class MyController{
    @In(create = true)
    private Dependency1 d1; //ok, gets injected with no problems!

    public void importantMethod(){
        //this part of the method is important and is fast
        //but below comes an expensive part that takes some minutes

        new Thread(new Runnable(){
            @In(create = true)
            private Dependency1 anotherD1;  //I still need d1 here!!!       

            @Override
            public void run(){
                //I want to run expensive code here.
                //A new thread is required in order to leave
                //the visitor free to go else where on the web site

                //First trial was to make d1 final and simply use it here!
                //d1.doExpensiveStuff();
            };
        }).start();
    }
}

有没有人知道为什么会这样？使用DI/Seam/Threading时有什么好的做法吗？

Answer 1

注射仅发生:

1. 在Seam组件中(在您的示例中,MyController是一个组件,Runnable您在其中创建的匿名不是组件).
2. 在Seam生命周期内.生命周期由JSF请求启动,异步执行或由您自己手动启动.

所以,你不能@In在你的线程中使用,因为它不是一个组件,Seam不会拦截对它的调用.要掌握异步线程中的组件,您需要使用Seam API来启动生命周期并获取所需的组件:

@Scope(ScopeType.CONVERSATION)
@Name("myController")
public class MyController {

    @In(create = true)
    private transient Dependency1 d1;

    public void importantMethod() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                LifeCycle.beginCall(); // Start the Seam lifecycle
                Dependency1 d1 = (Dependency1) Component.getInstance("dependency1");
                d1.doExpensiveStuff();
                LifeCycle.endCall();   // Dispose the lifecycle
            }
        }).start();
    }
}

Seam提供的@Asynchronous注释可以满足您的需求.如果在Seam组件的方法中使用此批注,则该方法将在后台线程中执行(取自Seam拥有的线程池).请注意,异步方法将能够使用注入的依赖项,就像它是正常的Seam调用一样:

@Name("myBackgroundWork")
public class MyBackgroundWork {
    @In private transient Dependency1 d1;

    @Asynchronous
    public void runInBackground() {
         d1.doExpensiveStuff();
    }
}

然后在MyController你可以调用异步方法,它将启动后台工作并立即返回:

@Scope(ScopeType.CONVERSATION)
@Name("myController")
public class MyController {
    @In(create = true)
    private MyBackgroundWork myBackgroundWork;

    public void importantMethod() {
        // Execution will return immediately and thread will start
        myBackgroundWork.runInBackground();
    }
}

更多信息:

http://docs.jboss.org/seam/2.2.2.Final/reference/en-US/html/jms.html#d0e21609