27

I would like to inject a dependency into a ServletContextListener. However, my approach is not working. I can see that Spring is calling my setter method, but later on when contextInitialized is called, the property is null.

Here is my set up:

The ServletContextListener:

public class MyListener implements ServletContextListener{

    private String prop;

    /* (non-Javadoc)
     * @see javax.servlet.ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)
     */
    @Override
    public void contextInitialized(ServletContextEvent event) {
        System.out.println("Initialising listener...");
        System.out.println(prop);
    }

    @Override
    public void contextDestroyed(ServletContextEvent event) {
    }

    public void setProp(String val) {
        System.out.println("set prop to " + prop);
        prop = val;
    }
}

web.xml: (this is the last listener in the file)

<listener>
  <listener-class>MyListener</listener-class>
</listener>

applicationContext.xml:

<bean id="listener" class="MyListener">
  <property name="prop" value="HELLO" />
</bean>

Output:

set prop to HELLO
Initialising listener...
null

What is the correct way to achieve this?

dogbane
  • 266,786
  • 75
  • 396
  • 414

4 Answers4

30

The dogbane's answer (accepted) works but it makes testing difficult because of the way beans are instantiated. I prefere the approach suggested in this question :

@Autowired private Properties props;

@Override
public void contextInitialized(ServletContextEvent sce) {
    WebApplicationContextUtils
        .getRequiredWebApplicationContext(sce.getServletContext())
        .getAutowireCapableBeanFactory()
        .autowireBean(this);

    //Do something with props
    ...
}
Community
  • 1
  • 1
a.b.d
  • 2,190
  • 3
  • 26
  • 26
  • 3
    I know this is old,but for future readers, when I attempt this I get an `IllegalStateException` with the message *No WebApplicationContext found: no ContextLoaderListener registered?* – christopher Aug 22 '13 at 14:33
  • Chris: I get the same problem! – Wouter Lievens Aug 31 '13 at 11:57
  • @christopher @Wouter You'll have to include the Spring's `ContextLoaderListener` to fix it [as detailed in this post](http://stackoverflow.com/questions/5511152/dependency-inject-servlet-listener#answer-5511255). – asgs Jun 12 '15 at 21:19
17

I resolved this by removing the listener bean and creating a new bean for my properties. I then used the following in my listener, to get the properties bean:

@Override
public void contextInitialized(ServletContextEvent event) {

    final WebApplicationContext springContext = WebApplicationContextUtils.getWebApplicationContext(event.getServletContext());
    final Properties props = (Properties)springContext.getBean("myProps");
}
dogbane
  • 266,786
  • 75
  • 396
  • 414
5

As mentioned before the ServletContextListener is created by the server and so it is not managed by spring.

If you wish to be notified of the ServletContext, you can implement the interface:

org.springframework.web.context.ServletContextAware
RicoZ
  • 835
  • 5
  • 16
  • Sorry, I don't understand why I need to implement `ServletContextAware`? My listener already has a reference to the `ServletContext` because it is present in the `ServletContextEvent`. – dogbane Jan 20 '11 at 12:16
  • if you use the listener, you cannot inject spring dependencies, so the ServletContextAware is an alternative – RicoZ Jan 20 '11 at 15:18
1

You cant have spring to do that, as already stated that is created by the server. If you need to pass params to your listener, you can define it in your web xml as a context-param

<context-param> 
        <param-name>parameterName</param-name>
        <param-value>parameterValue</param-value>
    </context-param>

And in the Listener you can retrieve it like below;

 event.getServletContext().getInitParameter("parameterName")

Edit 1:

See the link below for another possible solution:

How to inject dependencies into HttpSessionListener, using Spring?

Community
  • 1
  • 1
fmucar
  • 14,361
  • 2
  • 45
  • 50