Spring can not only inject beans (components, services, entities, however you want to call them), it can also inject them according to a certain scope. This is great if you have state-full objects which belongs (for example) to a dedicated user and not to the whole application. To do that, Spring introduced the @Scope annotation.
The usage of @Scope is straight forward: just annotate your bean with it and specify the scope to use:
@Component
@Scope(value="session")
public class MyComponent {
// ...
}
The value of @Scope can be one of singleton (one single instance for the whole app), prototype (a new instance for every injection), request (an instance per web request) or session (an instance per web session). See here.
The last two scopes (request and session) are only available in Spring web applications where the current session is exposed. To do so, you need to add a listener to the web.xml which makes the context available:
org.springframework.web.context.request.RequestContextListener
If you got both, your annotated bean and the listener in your web.xml, you will typically have another problem: how to use a session scoped bean in a normal (not session scoped) service?
To solve this problem, Spring provides a proxy mechanism. This means Spring can wire a proxy with the same interface as your actual bean instead of the bean itself. The proxy will not be session scoped (it will be a singleton), but it will fetch the according session scoped bean for each request. This means you can wire your session scoped bean in a not session scoped service and the proxy will do the rest behind the scenes.
To use such a proxy, you can just add it to the @Scope annotation like that:
@Component
@Scope(value="session", proxyMode = ScopedProxyMode.TARGET\_CLASS)
public class MyComponent {
// ...
}
If you do so, you will discover the next problem soon: what about your integration tests you made which probably will fail now as they got no session? The easiest fix for this, is to add the following bean configuration, which adds a session context for each thread (see the post of Tarun Sapra for the original description):
Best regards, Thomas