/
ListenerHolder.java
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/
ListenerHolder.java
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//
// ========================================================================
// Copyright (c) 1995-2020 Mort Bay Consulting Pty Ltd and others.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package org.eclipse.jetty.servlet;
import java.util.EventListener;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import org.eclipse.jetty.server.handler.ContextHandler;
/**
* ListenerHolder
*
* Specialization of BaseHolder for servlet listeners. This
* allows us to record where the listener originated - web.xml,
* annotation, api etc.
*/
public class ListenerHolder extends BaseHolder<EventListener>
{
private EventListener _listener;
public ListenerHolder()
{
this(Source.EMBEDDED);
}
public ListenerHolder(Source source)
{
super(source);
}
public ListenerHolder(Class<? extends EventListener> listenerClass)
{
super(Source.EMBEDDED);
setHeldClass(listenerClass);
}
public EventListener getListener()
{
return _listener;
}
/**
* Set an explicit instance. In this case,
* just like ServletHolder and FilterHolder,
* the listener will not be introspected for
* annotations like Resource etc.
*/
public void setListener(EventListener listener)
{
setInstance(listener);
}
@Override
public void doStart() throws Exception
{
super.doStart();
if (!java.util.EventListener.class.isAssignableFrom(getHeldClass()))
{
String msg = getHeldClass() + " is not a java.util.EventListener";
super.stop();
throw new IllegalStateException(msg);
}
ContextHandler contextHandler = ContextHandler.getCurrentContext().getContextHandler();
if (contextHandler != null)
{
_listener = getInstance();
if (_listener == null)
{
//create an instance of the listener and decorate it
try
{
ServletContext context = contextHandler.getServletContext();
_listener = (context != null)
? context.createListener(getHeldClass())
: getHeldClass().getDeclaredConstructor().newInstance();
}
catch (ServletException ex)
{
Throwable cause = ex.getRootCause();
if (cause instanceof InstantiationException)
throw (InstantiationException)cause;
if (cause instanceof IllegalAccessException)
throw (IllegalAccessException)cause;
throw ex;
}
}
_listener = wrap(_listener);
contextHandler.addEventListener(_listener);
}
}
@Override
public void doStop() throws Exception
{
super.doStop();
if (_listener != null)
{
try
{
ContextHandler contextHandler = ContextHandler.getCurrentContext().getContextHandler();
if (contextHandler != null)
contextHandler.removeEventListener(_listener);
getServletHandler().destroyListener(unwrap(_listener));
}
finally
{
_listener = null;
}
}
}
private EventListener wrap(final EventListener listener)
{
EventListener ret = listener;
ServletContextHandler contextHandler = getServletHandler().getServletContextHandler();
if (contextHandler != null)
{
for (ListenerHolder.WrapperFunction wrapperFunction : contextHandler.getBeans(ListenerHolder.WrapperFunction.class))
{
ret = wrapperFunction.wrapEventListener(ret);
}
}
return ret;
}
private static EventListener unwrap(EventListener listener)
{
EventListener unwrapped = listener;
while (ListenerHolder.WrapperEventListener.class.isAssignableFrom(unwrapped.getClass()))
{
unwrapped = ((ListenerHolder.WrapperEventListener)unwrapped).getWrappedListener();
}
return unwrapped;
}
@Override
public String toString()
{
return super.toString() + ": " + getClassName();
}
/**
* Experimental Wrapper mechanism for Servlet Listeners.
* <p>
* Beans in ServletContextHandler or WebAppContext that implement this interface
* will be called to optionally wrap any newly created ServletListeners before
* they are used for the first time.
* </p>
*/
public interface WrapperFunction
{
EventListener wrapEventListener(EventListener listener);
}
public static class WrapperEventListener implements EventListener
{
final EventListener _listener;
public WrapperEventListener(EventListener listener)
{
_listener = listener;
}
public EventListener getWrappedListener()
{
return _listener;
}
@Override
public String toString()
{
return String.format("%s:%s", this.getClass().getSimpleName(), _listener.toString());
}
}
}