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Struts example source code file (PerThreadTagHandlerPool.java)

This example Struts source code file (PerThreadTagHandlerPool.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Struts tags/keywords

enumeration, exception, http, jsp, jspexception, object, option_maxsize, perthreaddata, perthreaddata, perthreadtaghandlerpool, perthreadtaghandlerpool, servlet, tag, tag, threadlocal, threadlocal, util, vector

The Struts PerThreadTagHandlerPool.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.struts2.jasper.runtime;

import java.util.Enumeration;
import java.util.Vector;

import javax.servlet.ServletConfig;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.Tag;

import org.apache.struts2.jasper.Constants;

/**
 * Thread-local based pool of tag handlers that can be reused.
 *
 * @author Jan Luehe
 * @author Costin Manolache
 */
public class PerThreadTagHandlerPool extends TagHandlerPool {

    private int maxSize;

    // For cleanup
    private Vector perThreadDataVector;

    private ThreadLocal perThread;

    private static class PerThreadData {
        Tag handlers[];
        int current;
    }

    /**
     * Constructs a tag handler pool with the default capacity.
     */
    public PerThreadTagHandlerPool() {
        super();
        perThreadDataVector = new Vector();
    }

    protected void init(ServletConfig config) {
        maxSize = Constants.MAX_POOL_SIZE;
        String maxSizeS = getOption(config, OPTION_MAXSIZE, null);
        if (maxSizeS != null) {
            maxSize = Integer.parseInt(maxSizeS);
            if (maxSize < 0) {
                maxSize = Constants.MAX_POOL_SIZE;
            }
        }

        perThread = new ThreadLocal() {
            protected Object initialValue() {
                PerThreadData ptd = new PerThreadData();
                ptd.handlers = new Tag[maxSize];
                ptd.current = -1;
                perThreadDataVector.addElement(ptd);
                return ptd;
            }
        };
    }

    /**
     * Gets the next available tag handler from this tag handler pool,
     * instantiating one if this tag handler pool is empty.
     *
     * @param handlerClass Tag handler class
     *
     * @return Reused or newly instantiated tag handler
     *
     * @throws JspException if a tag handler cannot be instantiated
     */
    public Tag get(Class handlerClass) throws JspException {
        PerThreadData ptd = (PerThreadData)perThread.get();
        if(ptd.current >=0 ) {
            return ptd.handlers[ptd.current--];
        } else {
	    try {
		return (Tag) handlerClass.newInstance();
	    } catch (Exception e) {
		throw new JspException(e.getMessage(), e);
	    }
	}
    }

    /**
     * Adds the given tag handler to this tag handler pool, unless this tag
     * handler pool has already reached its capacity, in which case the tag
     * handler's release() method is called.
     *
     * @param handler Tag handler to add to this tag handler pool
     */
    public void reuse(Tag handler) {
        PerThreadData ptd=(PerThreadData)perThread.get();
	if (ptd.current < (ptd.handlers.length - 1)) {
	    ptd.handlers[++ptd.current] = handler;
        } else {
            handler.release();
        }
    }

    /**
     * Calls the release() method of all tag handlers in this tag handler pool.
     */
    public void release() {        
        Enumeration enumeration = perThreadDataVector.elements();
        while (enumeration.hasMoreElements()) {
	    PerThreadData ptd = (PerThreadData)enumeration.nextElement();
            if (ptd.handlers != null) {
                for (int i=ptd.current; i>=0; i--) {
                    if (ptd.handlers[i] != null) {
                        ptd.handlers[i].release();
		    }
                }
            }
        }
    }
}

Other Struts examples (source code examples)

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