How to get the context without any request, session, etc?

Question

I have a method in a class, which doesn't get anything which could be usable to get the actual servlet context. Practically, it is like

public String getSomething() { ... }

But to calculate the result, I need the actual, thread-specific servlet structures.

I think, somewhere in the deepness in the application context, some like a thread-specific storage should exist, which could be reached by calling static methods of some system class.

I am in a tomcat6 servlet container, but Spring is also available if it is needed.

Answer 1

Add a ServletContextListener to your web.xml. This will be called when your webapp is loaded. In the contextInitialized() method you can store the ServletContext in a static variable for example for later use. Then you will be able to access the ServletContext in a static way:

class MyListener implements ServletContextListener {

    public static ServletContext context;

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        context = sce.getServletContext();
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        context = null;
    }

}

Add it to web-xml like this:

<web-app>
    <listener>
        <listener-class>
            com.something.MyListener
        </listener-class>
    </listener>
</web-app>

And you can access it from anywhere like this:

public String getSomething() {
    // Here you have the context:
    ServletContext c = MyListener.context;
}

Note:

You might want to store it as private and provide a getter method, and also check for null value before using it.