Why does Autowiring not function in a thread?

I've made a maven project in Spring 3.0, I've made some DAO, services and controllers, in one of mine controller I call a service in which I start a thread, the problem is that in the thread I declare a "service variable" that should be initialized with Autowired annotiation, but it doesn't work and the variable isn't initilized and has the value null.

this is the thread class

package com.project.tasks;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.task.TaskExecutor;
import org.springframework.stereotype.Component;

import com.project.entities.user.User;
import com.project.services.IUserService;

@Component
public class AddFriendInMyFriendListTaskExecutor {
private class AddFriendInMyFriendListTask implements Runnable {


     // HERE IS THE PROBLEM
    @Autowired
    private IUserService uService;

    private User a;
    private User b;

    public AddFriendInMyFriendListTask() {
        ;
    }

    public AddFriendInMyFriendListTask(User aA, User bB) {
        a = aA;
        b = bB;
    }

    public User getA() {
        return a;
    }
    public void setA(User a) {
        this.a = a;
    }
    public User getB() {
        return b;
    }
    public void setB(User b) {
        this.b = b;
    }


    public void run() {
                    // FROM HERE IT PRINTS THE VALUE OF uService THAT IS NULL
        System.out.println("uService:" + uService);
        uService.insertRightUserIntoLeftUserListOfFriends(a, b);
    }
}

private TaskExecutor taskExecutor;

  public AddFriendInMyFriendListTaskExecutor(TaskExecutor taskExecutor) {
    this.taskExecutor = taskExecutor;
  }

  public void doIt(User a, User b) {
      taskExecutor.execute(new AddFriendInMyFriendListTask(a, b));
  }
}

this is the piece of code that calls the thread

    User a = uDao.getUser(hrA.getMyIdApp());
    User b = uDao.getUser(hrA.getOtherIdApp());
    SimpleAsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor();
    AddFriendInMyFriendListTaskExecutor tmp = new AddFriendInMyFriendListTaskExecutor(taskExecutor);
    tmp.doIt(a, b);

I'd like to highlight that in all the other tests in which I don't call any threads, the Autowired of a UserService instance functions corre开发者_JAVA百科ctly! The method I call: insertRightUserIntoLeftUserListOfFriends(User a, User b), works correctly.

For a bean to be autowired by Spring, the bean must be a Spring bean (i.e. be declared in the context.xml file or be annotated with a Spring annotation (@Service, @Component, etc.).

And of course, it must be instantiated by Spring, and not by your code. If you instantiate a Spring bean yourself with new, Spring doesn't know about the bean, and doesn't inject anything into it.

Spring just autowires beans of the context, no instances created by new. But why do you have declared uService in AddFriendInMyFriendListTask and not as a bean property of the outer (bean) class AddFriendInMyFriendListTaskExecutor, that should simply work:

@Component
public class AddFriendInMyFriendListTaskExecutor {

  private class AddFriendInMyFriendListTask implements Runnable {

    private final User a;
    private final User b;

    public AddFriendInMyFriendListTask(User aA, User bB) {
      a = aA;
      b = bB;
    }

    public void run() {
      AddFriendInMyFriendListTaskExecutor.this.uService.insertRightUserIntoLeftUserListOfFriends(a, b);
    }
  }

  @Autowired
  private IUserService uService;

  @Autowired
  private TaskExecutor taskExecutor;

  public void doIt(User a, User b) {
    taskExecutor.execute(new AddFriendInMyFriendListTask(a, b));
  }
}

(removed some unused getter/setter and made taskExecutor also a bean property)

If you need to autowire a newly created instance (without container support) invoke

ctx.getAutowireCapableBeanFactory().autowireBean(instance)

where ctx is your ApplicationContext and instance the newly created instance.

I asked a similar question here

Another solution would be to inject the user IUserService in a spring managed component (service, component, etc.) and pass the injected value to the constructor of the class AddFriendInMyFriendListTask.

Thus, the constructor becomes something like this

public AddFriendInMyFriendListTask(User aA, User bB, IUserService userService) {
    a = aA;
    b = bB;
    this.userService = userService;
}

and remove the @Autowired from the AddFriendInMyFriendListTask class.

Had a similar issue had to Autowire in the service and pass to the method that implements runnable through the constructor.