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package org.apache.jasper.runtime;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.ServletConfig;
import org.apache.jasper.Constants;
/**
* Pool of tag handlers that can be reused.
*
* @author Jan Luehe
*/
public class TagHandlerPool {
public static final String OPTION_TAGPOOL="tagpoolClassName";
public static final String OPTION_MAXSIZE="tagpoolMaxSize";
private Tag[] handlers;
private ResourceInjector resourceInjector;
// index of next available tag handler
private int current;
public static TagHandlerPool getTagHandlerPool( ServletConfig config) {
TagHandlerPool result=null;
String tpClassName=getOption( config, OPTION_TAGPOOL, null);
if( tpClassName != null ) {
try {
Class c=Class.forName( tpClassName );
result=(TagHandlerPool)c.newInstance();
} catch (Exception e) {
e.printStackTrace();
result=null;
}
}
if( result==null ) result=new TagHandlerPool();
result.init(config);
return result;
}
protected void init( ServletConfig config ) {
int maxSize=-1;
String maxSizeS=getOption(config, OPTION_MAXSIZE, null);
if( maxSizeS != null ) {
try {
maxSize=Integer.parseInt(maxSizeS);
} catch( Exception ex) {
maxSize=-1;
}
}
if( maxSize <0 ) {
maxSize=Constants.MAX_POOL_SIZE;
}
this.handlers = new Tag[maxSize];
this.current = -1;
this.resourceInjector = (ResourceInjector)
config.getServletContext().getAttribute(
Constants.JSP_RESOURCE_INJECTOR_CONTEXT_ATTRIBUTE);
}
/**
* Constructs a tag handler pool with the default capacity.
*/
public TagHandlerPool() {
// Nothing - jasper generated servlets call the other constructor,
// this should be used in future + init .
}
/**
* Constructs a tag handler pool with the given capacity.
*
* @param capacity Tag handler pool capacity
* @deprecated Use static getTagHandlerPool
*/
public TagHandlerPool(int capacity) {
this.handlers = new Tag[capacity];
this.current = -1;
}
/**
* 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 {
Tag handler = null;
synchronized( this ) {
if (current >= 0) {
handler = handlers[current--];
return handler;
}
}
// Out of sync block - there is no need for other threads to
// wait for us to construct a tag for this thread.
Tag tagHandler = null;
try {
tagHandler = (Tag) handlerClass.newInstance();
if (resourceInjector != null) {
resourceInjector.inject(tagHandler);
}
} catch (Exception e) {
throw new JspException(e.getMessage(), e);
}
return tagHandler;
}
/**
* 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) {
synchronized( this ) {
if (current < (handlers.length - 1)) {
handlers[++current] = handler;
return;
}
}
// There is no need for other threads to wait for us to release
handler.release();
}
/**
* Calls the release() method of all available tag handlers in this tag
* handler pool.
*/
public synchronized void release() {
for (int i=current; i>=0; i--) {
handlers[i].release();
}
}
protected static String getOption( ServletConfig config, String name, String defaultV) {
if( config == null ) return defaultV;
String value=config.getInitParameter(name);
if( value != null ) return value;
if( config.getServletContext() ==null )
return defaultV;
value=config.getServletContext().getInitParameter(name);
if( value!=null ) return value;
return defaultV;
}
}
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