statefilter.java

ajax patterns 这是关于ajax设计模式方面的原代码

/*
    Copyright 2006 Christian Gross http://www.devspace.com
    From the book Ajax Patterns and Best Practices

   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 devspace.ajax.statenavigation;
import javax.servlet.http.*;
import javax.servlet.*;
import java.io.*;

public class StateFilter extends TriggerFilter {
    private FilterConfig _filterConfig;
    private StateManager _stateManager;
    private String _resourceStateContentType;
    private String _XPageState;
    private String _XPageWindowName;
    private String _URLStateIdentifier;
    private int _URLStateIdentifierLength;
    private String _XPageOriginalURL;
    
    
    public void init(FilterConfig filterConfig) throws ServletException {
        _filterConfig = filterConfig;
        _resourceStateContentType = filterConfig.getInitParameter( "resource-state-content-type");
        _XPageState = filterConfig.getInitParameter( "page-state-header");
        _XPageWindowName = filterConfig.getInitParameter( "page-window-name");
        _URLStateIdentifier = filterConfig.getInitParameter( "url-state-identifier");
        _URLStateIdentifierLength = _URLStateIdentifier.length();
        _XPageOriginalURL = filterConfig.getInitParameter( "page-original-url");
        try {
            //String strClass = filterConfig.getInitParameter("state-manager");
            //_stateManager = (StateManager)StateFilter.class.getClassLoader().loadClass(
            //    filterConfig.getInitParameter("state-manager")).newInstance();
            _stateManager = new StateManagerImpl();
        }
        catch (Exception e) {
            throw new ServletException( "Could not instantiate _stateManager", e);
        }
        
    }
    private class Data {
        public String _method;
        public String _stateHeader;
        public String _windowName;
        public int _operation;
        public String _path;
        public void reset() {
            _method = null;
            _stateHeader = null;
            _operation = OP_NONE;
            _path = null;
            _windowName = null;
        }
    }
    private static final int OP_NONE = 0;
    private static final int OP_RETRIEVE = 1;
    private static final int OP_POST = 2;
    
    public Object initializeRequest() {
        return new Data();
    }
    public void destroyRequest( Object objData) {
        
    }
    
    public boolean isTrigger( Object inpdata, HttpServletRequest httprequest, HttpServletResponse httpresponse) {
        String tail = httprequest.getRequestURI().substring(
            httprequest.getRequestURI().length() - _URLStateIdentifierLength);
        String stateHeader = httprequest.getHeader( _XPageState);
        Data data = (Data)inpdata;

        if( tail.compareTo( _URLStateIdentifier) == 0) {
            data._path = httprequest.getRequestURI().substring( 0,
                httprequest.getRequestURI().length() - _URLStateIdentifierLength);
        }
        else {
            if( stateHeader == null) {
                return false;
            }
            data._path = httprequest.getRequestURI();
        }
        
        data._method = httprequest.getMethod();
        data._stateHeader = stateHeader;
        data._operation = OP_NONE;
        data._windowName = httprequest.getHeader( _XPageWindowName);
        if( data._method.compareTo( "GET") == 0) {
            data._operation = OP_RETRIEVE;
            return true;
        }
        else if( data._method.compareTo( "PUT") == 0 || data._method.compareTo( "POST") == 0) {
            if( _resourceStateContentType.compareTo( httprequest.getContentType()) == 0) {
                data._path = httprequest.getHeader( _XPageOriginalURL);
                data._operation = OP_POST;
                return true;
            }
        }
        data.reset();
        return false;
    }
    public void runFilter(Object inpdata, HttpServletRequest httprequest, HttpServletResponse httpresponse, FilterChain chain) throws IOException, ServletException {
        Data data = (Data)inpdata;
        if( data._operation == OP_RETRIEVE) {
            State state;
            if( data._stateHeader.compareTo( "none") == 0) {
                state = _stateManager.getEmptyState( data._path, data._windowName);
            }
            else {
                state = _stateManager.copyState( data._stateHeader, data._path, data._windowName);
            }
            httpresponse.setContentType( _resourceStateContentType);
            httpresponse.setHeader( _XPageState, state.getStateIdentifier());
            httpresponse.setStatus( 200, "success");
            PrintWriter out = httpresponse.getWriter();
            out.print( state.getBuffer());
            return;
        }
        else if( data._operation == OP_POST) {
            ServletInputStream input = httprequest.getInputStream();
            byte[] bytearray = new byte[ httprequest.getContentLength()];
            input.read( bytearray);
            State state = _stateManager.copyState( data._stateHeader, data._path, data._windowName);
            state.setBuffer( new String( bytearray).toString());
            httpresponse.addHeader( _XPageState, state.getStateIdentifier());
            chain.doFilter( httprequest, httpresponse);
            return;
        }
    }
    
    public void destroy() {
    }
}