In searching Google for “Spring ApplicationContextAware“, you 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 a few things.
Two Ways to Get Application Context:
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.
<servlet>
<servlet-name>dispatchservlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatchservlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
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.
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
<servlet-name>MyOwnServlet</servlet-name>
<servlet-class>com.something.myservlet</servlet-class>
<load-on-startup>2</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>MyOwnServlet</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
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:
<bean id="applicationContextProvider" class="ApplicationContextProvider"></bean>
And now in your classes, you can do the following:
ApplicationContext ctx = ApplicationContextProvider.getApplicationContext();
That’s it!!!
Cheers.
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