JSPDispatcher.java :  » REST » dyuproject » com » dyuproject » web » rest » Java Open Source

//========================================================================
//Copyright 2007-2008 David Yu dyuproject@gmail.com
//------------------------------------------------------------------------
//Licensed 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 com.dyuproject.web.rest;

import java.io.IOException;

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

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.dyuproject.util.Delim;


/**
 * Efficiently dispatches to the jsp servlet.
 * 
 * @author David Yu
 * @created May 16, 2008
 */

public final class JSPDispatcher extends AbstractLifeCycle implements ViewDispatcher
{    
     
    public static final String JSP = JSPDispatcher.class.getName();
    public static final String DEFAULT_BASE_DIR = "/WEB-INF/views/jsp/";
    public static final String DEFAULT_FILE_EXTENSION = "jsp";
    
    static final String[] NAMES = Delim.COMMA.split(System.getProperty("web.jsp_dispatcher_name", "jsp,_ah_jsp"));
    
    static final String INCLUDE_ATTR = "javax.servlet.include.servlet_path";
    
    private static final Logger log = LoggerFactory.getLogger(JSPDispatcher.class);
    
    private boolean _jetty;
    private String _baseDir, _fileExtension, _suffix;
    RequestDispatcher _jsp;
    
    public String getFileExtension()
    {
        return _fileExtension;
    }
    
    protected void init()
    {        
        if(_baseDir==null)
            _baseDir = DEFAULT_BASE_DIR;
        else if(_baseDir.charAt(_baseDir.length()-1)!='/')
            _baseDir += "/";
        
        if(_fileExtension==null)
        {
            String fileExtension = getWebContext().getProperty("jsp.file_extentsion");
            _fileExtension = fileExtension==null ? DEFAULT_FILE_EXTENSION : fileExtension;
        }
        else if(_fileExtension.charAt(0)=='.')
            _fileExtension = _fileExtension.substring(1);
        
        for(String s : NAMES)
        {
            if((_jsp=getWebContext().getServletContext().getNamedDispatcher(s))!=null)
            {
                log.info("dispatcher name: {}", s);
                break;
            }
        }
        
        if(_jsp==null)
            log.info("jsp named dispatcher not resolved, using request.getRequestDispatcher(uri) instead");
        else
            _jetty = _jsp.getClass().getName().startsWith("org.mortbay.jetty");
        
        log.info("baseDir: " + _baseDir);
        log.info("fileExtension: " + _fileExtension);    
        log.info("initialized.");
        
        _suffix = "." + _fileExtension;
    }
    
    public void dispatch(String uri, HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException
    {
        if(uri.charAt(0)!='/')
            uri = uri.endsWith(_suffix) ? _baseDir + uri : _baseDir + uri + _suffix;
        else if(!uri.endsWith(_suffix))
            uri += _suffix;
        
        request.setAttribute(WebContext.DISPATCH_ATTR, JSP);
        request.setAttribute(INCLUDE_ATTR, uri);
        // more efficient if in jetty
        if(_jetty)
        {               
            _jsp.include(request, response);
            return;
        }
        
        if(response.isCommitted())
            request.getRequestDispatcher(uri).include(request, response);
        else
            request.getRequestDispatcher(uri).forward(request, response);
    }
    
    public void setBaseDir(String baseDir)
    {
        if(isInitialized())
            throw new IllegalStateException("already initialized");
        
        _baseDir = baseDir;
    }

}