Spring Framework - Application Context - three ways to get to the application context

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This article shows you three different ways how to get to the Spring Framework Application Context in your code.

Summary

(This is a repost of an older article I wrote in 2010). In searching Google for “Spring ApplicationContextAware ”, you will come across a lot of recommendations and I also see a lot of folks continuing to complain saying that their setApplicationContext method does not get invoked. So to help clarify, I’m blogging a few notes in hope that it helps clarify how the context works.

Method-1

In your class you implement ApplicationContextAware class like this:

public class MyClass implements ApplicationContextAware {

    static final long serialVersionUID = 02L;

    ApplicationContext applicationContext = null;

    public void doSomething(){
        if (applicationContext != null && applicationContext.containsBean("accessKeys")){
            MyBean beanA = (MyBean) applicationContext.getBean("mybean");
            //Do something with this AccessBean
        }

        return null;
    }

    @Override
    public void setApplicationContext(final ApplicationContext applicationContext) throws BeansException {
        System.out.println("setting context");
        this.applicationContext = applicationContext;
    }

}

Method-2

If you are in a Java Servlet, you can do the following:

public class gzservlet extends HttpServlet {
    static final long serialVersionUID = 02L;

    ApplicationContext applicationContext = null;

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        if (applicationContext == null){
            System.out.println("setting context in get");
            applicationContext = WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());
        }
        if (applicationContext != null && applicationContext.containsBean("accessKeys")){
            AccessBean thisAccessBean = (AccessBean) applicationContext.getBean("accessKeys");
            req.setAttribute("keys", thisAccessBean.toString());
            System.out.println("setting keys");
        }

        req.getRequestDispatcher("/index2.jsp").include(req,resp);
    }

}

So the question one would ask is when to use what? And the answer is. Depends on how you are invoking Spring.

What works for Method #1: when you invoke Spring you are using the DispatcherServlet link this. Then Method #1 will resolve the implementation of ApplicationContextAware and call the setApplicationContext() method to set the context.

In web.xml:

If you are not using the DispatcherServlet and you are initializing Spring using a Listener and you have your own Servlet that’s driving the Request\Response scope then use Method #2. Below is an example of how the web.xml will look like in this case.

I hope this clarifies why sometimes even though you have implemented the ApplicationContextAware interface, your setter does not get invoked.

[09/12/2010] Here is a third way to get your context:

Create the following class with a static method to get your context:


import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

public class ApplicationContextProvider implements ApplicationContextAware{
	private static ApplicationContext ctx = null;
 	public static ApplicationContext getApplicationContext() {
		return ctx;
 	}
 	public void setApplicationContext(ApplicationContext ctx) throws BeansException {
		this.ctx = ctx;
 	}
}

and in your spring bean configuration xml file add the following:

And now in your classes, you can do the following:

    
ApplicationContext ctx = ApplicationContextProvider.getApplicationContext();

That’s it!!!

Cheers.

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