/*
* $Header: /home/cvspublic/jakarta-tomcat/src/share/org/apache/jasper/runtime/TagHandlerPoolImpl.java,v 1.2 2001/05/11 18:43:18 clucas Exp $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 1999 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Group.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package org.apache.jasper.runtime;
import javax.servlet.jsp.tagext.Tag;
import java.util.Stack;
import java.util.EmptyStackException;
import java.util.Enumeration;
import org.apache.tomcat.util.log.Log;
/**
* This class provides a basic implementation of TagHandlerPool.
* Its pooling strategy is to grow the pool so that a caller
* never has to wait for a tag handler. Therefore in the worst
* case, the pool size will be equal to the total number of
* concurently used tags (that are at the same reuse scope.) This
* implementation does not shrink the pool.
*
* @author Casey Lucas <clucas@armassolutions.com>
* @see TagPoolManagerImpl
*/
public class TagHandlerPoolImpl implements TagHandlerPool {
/**
* the class of tag handler that we store
*/
Class myHandlerClass = null;
/**
* the collection of available handlers
*/
Stack myHandlers = new Stack();
/**
* Tomcat logging mechanism
*/
Log myLog = null;
/**
* Unique name for this pool
*
* @see TagPoolGenerator
*/
String myPoolName = null;
/**
* Keep this constructor private because we need to know what type
* of handlers to create.
*/
private TagHandlerPoolImpl() {
}
/**
* Create a TagHandlerPoolImpl that will store objects of the given
* class type
*
* @param handlerClass
* tag handler class
*/
public TagHandlerPoolImpl(Class handlerClass, String poolName) {
if (! Tag.class.isAssignableFrom(handlerClass)) {
throw new IllegalArgumentException
("TagHandlerPoolImpl should only be used with Tag objects");
}
myHandlerClass = handlerClass;
myPoolName = poolName;
myLog = Log.getLog(TagPoolManagerImpl.LOG_NAME, this);
if (myLog.getLevel() >= Log.INFORMATION) {
myLog.log("New tag pool named '" + myPoolName + "' created to handle " +
handlerClass.getName(), Log.INFORMATION);
}
}
/**
* Obtain a tag handler. This implementation allocates one if one
* is not available. So the collection will grow with concurent
* tag handler use.
*
* @return tag handler
*/
public Tag getHandler() {
Tag returnValue = null;
try {
synchronized (myHandlers) {
if (myHandlers.empty()) {
if (myLog.getLevel() >= Log.DEBUG) {
myLog.log("Allocating new tag of type " +
myHandlerClass.getName(), Log.DEBUG);
}
returnValue = (Tag) myHandlerClass.newInstance();
} else {
if (myLog.getLevel() >= Log.DEBUG) {
myLog.log("Obtaining cached tag of type " +
myHandlerClass.getName(), Log.DEBUG);
}
returnValue = (Tag) myHandlers.pop();
}
}
}
// Ignore these two errors. The jsp page should get the same error
// if it tries to allocate a tag handler.
catch (InstantiationException exception) {
if (myLog.getLevel() >= Log.WARNING) {
myLog.log("Failed to allocate tag of type " + myHandlerClass.getName() +
": " + exception.toString(), Log.WARNING);
}
}
catch (IllegalAccessException exception) {
if (myLog.getLevel() >= Log.WARNING) {
myLog.log("Failed to allocate tag of type " + myHandlerClass.getName() +
": " + exception.toString(), Log.WARNING);
}
}
return returnValue;
}
/**
* This method releases a tag handler obtained from getHandler.
* The JSP shouls always call this method after finished using a
* tag handler.
*
* @param usedTag tag previously obtained from getHandler
* @param removeFromPool
* Set to true to remove handler from pool. One reason for this
* is an exception during tag processing.
*/
public void releaseHandler(Tag usedTag, boolean removeFromPool) {
if (myLog.getLevel() >= Log.DEBUG) {
String message = null;
if (removeFromPool) {
message = "Removing tag of type " + myHandlerClass.getName() + " from cache";
} else {
message = "Returning tag of type " + myHandlerClass.getName() + " to cache";
}
myLog.log(message, Log.DEBUG);
}
if (removeFromPool) {
usedTag.release();
} else {
synchronized (myHandlers) {
myHandlers.push(usedTag);
}
}
}
/**
* This method performs pool shutdown. It will call Tag.release
* for all of its tag handlers.
*/
public void shutdown() {
synchronized (myHandlers) {
if (myLog.getLevel() >= Log.INFORMATION) {
myLog.log("Shutting down pool '" + myPoolName + "', pool contained " +
myHandlers.size() + " tags", Log.INFORMATION);
}
Enumeration handlers = myHandlers.elements();
while (handlers.hasMoreElements()) {
((Tag) handlers.nextElement()).release();
}
myHandlers.removeAllElements();
}
}
}