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package org.eclipse.jetty.server.handler;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jetty.server.Request;


/* ------------------------------------------------------------ */
/** ScopedHandler.
 * 
 * A ScopedHandler is a HandlerWrapper where the wrapped handlers
 * each define a scope.   When {@link #handle(String, Request, HttpServletRequest, HttpServletResponse)}
 * is called on the first ScopedHandler in a chain of HandlerWrappers,
 * the {@link #doScope(String, Request, HttpServletRequest, HttpServletResponse)} method is 
 * called on all contained ScopedHandlers, before the 
 * {@link #doHandle(String, Request, HttpServletRequest, HttpServletResponse)} method 
 * is called on all contained handlers.
 * 
 * 

For example if Scoped handlers A, B & C were chained together, then * the calling order would be:

 * A.handle(...)
 *   A.doScope(...)
 *     B.doScope(...)
 *       C.doScope(...)
 *         A.doHandle(...)
 *           B.doHandle(...)
 *              C.doHandle(...)   
 * 
 * 
 * 

If non scoped handler X was in the chained A, B, X & C, then * the calling order would be:

 * A.handle(...)
 *   A.doScope(...)
 *     B.doScope(...)
 *       C.doScope(...)
 *         A.doHandle(...)
 *           B.doHandle(...)
 *             X.handle(...)
 *               C.handle(...)
 *                 C.doHandle(...)   
 * 
 * 
 * 

A typical usage pattern is:

 *     private static class MyHandler extends ScopedHandler
 *     {
 *         public void doScope(String target, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
 *         {
 *             try
 *             {
 *                 setUpMyScope();
 *                 super.doScope(target,request,response);
 *             }
 *             finally
 *             {
 *                 tearDownMyScope();
 *             }
 *         }
 *         
 *         public void doHandle(String target, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
 *         {
 *             try
 *             {
 *                 doMyHandling();
 *                 super.doHandle(target,request,response);
 *             }
 *             finally
 *             {
 *                 cleanupMyHandling();
 *             }
 *         }
 *     }
 * 
*/ public abstract class ScopedHandler extends HandlerWrapper { private static final ThreadLocal __outerScope= new ThreadLocal(); protected ScopedHandler _outerScope; protected ScopedHandler _nextScope; /* ------------------------------------------------------------ */ /** * @see org.eclipse.jetty.server.handler.HandlerWrapper#doStart() */ @Override protected void doStart() throws Exception { try { _outerScope=__outerScope.get(); if (_outerScope==null) __outerScope.set(this); super.doStart(); _nextScope= (ScopedHandler)getChildHandlerByClass(ScopedHandler.class); } finally { if (_outerScope==null) __outerScope.set(null); } } /* ------------------------------------------------------------ */ /* */ @Override public final void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { if (_outerScope==null) doScope(target,baseRequest,request, response); else doHandle(target,baseRequest,request, response); } /* ------------------------------------------------------------ */ /* * Scope the handler */ public abstract void doScope(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException; /* ------------------------------------------------------------ */ /* * Scope the handler */ public final void nextScope(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { // this method has been manually inlined in several locations, but // is called protected by an if(never()), so your IDE can find those // locations if this code is changed. if (_nextScope!=null) _nextScope.doScope(target,baseRequest,request, response); else if (_outerScope!=null) _outerScope.doHandle(target,baseRequest,request, response); else doHandle(target,baseRequest,request, response); } /* ------------------------------------------------------------ */ /* * Do the handler work within the scope. */ public abstract void doHandle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException; /* ------------------------------------------------------------ */ /* * Do the handler work within the scope. */ public final void nextHandle(String target, final Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { // this method has been manually inlined in several locations, but // is called protected by an if(never()), so your IDE can find those // locations if this code is changed. if (_nextScope!=null && _nextScope==_handler) _nextScope.doHandle(target,baseRequest,request, response); else if (_handler!=null) _handler.handle(target,baseRequest, request, response); } /* ------------------------------------------------------------ */ protected boolean never() { return false; } }




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