Dependency Injection inside of HttpSessionListener implementation

Question

Problem: This injected dependency will always return 0 from SimpleController

1. Why does the context get lost for this bean when try

Answer 1

This is an answer here that shows the actual solution.

You should modify SessionCountListener like this, and the above example will work:

public class SessionCounterListener implements HttpSessionListener {

  @Autowired
  private SessionService sessionService;

  @Override
  public void sessionCreated(HttpSessionEvent arg0) {
    getSessionService(se).addOne();
  }

  @Override
  public void sessionDestroyed(HttpSessionEvent arg0) {
    getSessionService(se).removeOne();
  }

  private SessionService getSessionService(HttpSessionEvent se) {
    WebApplicationContext context = 
      WebApplicationContextUtils.getWebApplicationContext(
        se.getSession().getServletContext());
    return (SessionService) context.getBean("sessionService");
  } 
}

Answer 2

When you declare a <listener> in web.xml like so

<listener>
    <listener-class>com.stuff.morestuff.SessionCounterListener</listener-class>
</listener>

you are telling your Servlet container to instantiate the class specified in the listener-class element. In other words, this instance will not be managed by Spring and it will therefore not be able to inject anything and the field will remain null.

There are workarounds to this. And some more.

Note that this

<!-- Scan for my SessionService & assume it has been setup correctly by spring-->
<context:component-scan base-package="com.stuff"/>

is not a valid entry in web.xml. I don't know if that was a copy mistake on your part.