Spring - Injecting a dependency into a ServletContextListener

Question

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?

Community · Accepted Answer · 2017-05-23 11:54:47Z

31

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 ... }

edited May 23, 2017 at 11:54

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answered Jun 28, 2012 at 22:22

a.b.d

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4 Comments

christopher Over a year ago

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?

Wouter Lievens Over a year ago

Chris: I get the same problem!

asgs Over a year ago

@christopher @Wouter You'll have to include the Spring's ContextLoaderListener to fix it as detailed in this post.

Gunnar Over a year ago

Very nice, helped me to build an image cache on Liferay JSF portlet deployment (instead of waiting one minute when doing this in a @PostConstruct).

dogbane · Accepted Answer · 2011-01-21 08:40:33Z

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"); }

The way beans are instantiated make testing difficult, see my answer.

RicoZ · Accepted Answer · 2011-01-20 11:29:17Z

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

answered Jan 20, 2011 at 11:29

RicoZ

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2 Comments

dogbane Over a year ago

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.

RicoZ Over a year ago

if you use the listener, you cannot inject spring dependencies, so the ServletContextAware is an alternative

Community · Accepted Answer · 2017-05-23 12:18:17Z

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?

@dogbane see the edited post. Added a new link that may be useful for your case as well

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