org.jasig.cas.web.init

Class SafeContextLoaderListener

java.lang.Object

org.jasig.cas.web.init.SafeContextLoaderListener

All Implemented Interfaces:

EventListener, javax.servlet.ServletContextListener

public final class SafeContextLoaderListener
extends Object
implements javax.servlet.ServletContextListener

A ServletContextListener which wraps Spring's ContextLoaderListener and catches anything that delegate throws so as to prevent its having thrown a Throwable from aborting the initialization of our entire web application context. Use of this ContextListener will not be appropriate for all deployments of a web application. Sometimes, a context listener's aborting context initialization is exactly the desired behavior. This might be because the resulting application inavailability is acceptable or because another layer (Apache, a proxy, a balancer, etc.) detects the inavailability of the context and provides an appropriate user experience. Or because a root context handles all requests that aren't otherwise handled. There are many fine alternatives to this approach. However, when using the bare Tomcat container with CAS as the root context, if your desired behavior is that a failure at context initialization results in a dummy CAS context that presents a user-friendly "CAS is unavailable at this time" message, using this ContextListener in place of Spring's ContextLoaderListener should do the trick. The error page associated with this deployment failure is configured in the web.xml via the standard error handling mechanism. Rather than being a generic ContextListener wrapper that will make safe any ContextListener, instead this implementation specifically wraps and delegates to a Spring ContextLoaderListener. As such, mapping this listener in web.xml is a one for one replacement for ContextLoaderListener.

The exception thrown is exposed in the Servlet Context under the key "exceptionCaughtByListener".

Author:

Andrew Petro

See Also:

ContextLoaderListener

Field Summary

Fields

Modifier and Type	Field and Description
static String	CAUGHT_THROWABLE_KEY The name of the ServletContext attribute whereat we will place a List of Throwables that we caught from our delegate context listeners.

Constructor Summary

Constructors

Constructor and Description
SafeContextLoaderListener()

Method Summary

Methods

Modifier and Type	Method and Description
void	contextDestroyed(javax.servlet.ServletContextEvent sce)
void	contextInitialized(javax.servlet.ServletContextEvent sce)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CAUGHT_THROWABLE_KEY

public static final String CAUGHT_THROWABLE_KEY

The name of the ServletContext attribute whereat we will place a List of Throwables that we caught from our delegate context listeners.

See Also:

Constant Field Values

Constructor Detail

SafeContextLoaderListener

public SafeContextLoaderListener()

Method Detail

contextInitialized

public void contextInitialized(javax.servlet.ServletContextEvent sce)

Specified by:

contextInitialized in interface javax.servlet.ServletContextListener

contextDestroyed

public void contextDestroyed(javax.servlet.ServletContextEvent sce)

Specified by:

contextDestroyed in interface javax.servlet.ServletContextListener