globalserverpush.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.persistentcommunications;
import devspace.ajax.permutations.*;
import java.util.*;
import javax.servlet.http.*;
import devspace.testDrivenDevelopment.tracer.*;
import java.io.*;
import javax.servlet.*;

class UserState {
    private String _userIdentifier;
    private String _data;
    private VersionTracker _version;
    
    public UserState(String userIdentifier, String data, VersionTracker version) {
        _userIdentifier = userIdentifier;
        _data = _data;
        _version = version;
    }
    public String getUserIdentifier() {
        return _userIdentifier;
    }
    public String getData() {
        return _data;
    }
    public void setData( String value) {
        _data = value;
    }
    public VersionTracker getVersion() {
        return _version;
    }
}

public class GlobalServerPush extends RedirectionHttpHandlerBase {
    static String _buffer;
    static VersionTracker _version = new VersionTracker(10000);
    static Hashtable< String, UserState> _users = new Hashtable< String, UserState>();
    private final String constUseAction = "user-action";
    
    public GlobalServerPush() {
        assignUserResolver(new UserResolverImplementation());
    }
    
    protected String getBaseURL() {
        return "/persistentcommunications/globalserverpush";
    }
    protected String getURLEnding() {
        return _identifiedUser.getIdentifier();
    }
    boolean CanUserAccessResource(HttpServletRequest req) {
        String baseURL = getBaseURL();
        String requestURL = req.getRequestURI();
        GenerateOutput.Write( "GlobalServerPush.CanUserAccessResource", "RequestURI (" + requestURL + ") Base URI (" + baseURL + ")");
        String resource = requestURL.substring( baseURL.length() + 1);
        GenerateOutput.Write("GlobalServerPush.CanUserAccessResource",
                             "Testing if user (" + _identifiedUser.getIdentifier() + ") can access resource (" + resource + ")");
        
        return(resource.compareTo( _identifiedUser.getIdentifier()) == 0);
    }
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        if (CanUserAccessResource(req)) {
            /*String lastState = req.getHeader( constXStateHeader);
            if (lastState == null) {
                lastState = req.Params.Get(constXStateHeader);
            }
            GenerateOutput.Write("GlobalServerPush.DoGet", "lastState (" + lastState + ")");
            int lastCount = 0;
            if (lastState != null) {
                lastCount = int.Parse(lastState);
            }*/
            String resource = req.getRequestURI().substring( getBaseURL().length() + 1);
            UserState state = null;
            synchronized(_users) {
                if (_users.containsKey(resource)) {
                    state = (UserState)_users.get( resource);
                }
            }
            if (state == null) {
                resp.setStatus( 409, "User does not have a state");
                GenerateOutput.Write("GlobalServerPush.DoGet", "User does not have a state");
                return;
            }
            if (state.getVersion().getNew(req)) {
                synchronized(state) {
                    PrintWriter output = resp.getWriter();
                    output.write("Content (" + state.getData() + ") Version (" +
                                 state.getVersion().getVersionNumber() + ")");
                }
                state.getVersion().writeVersion( resp);
                GenerateOutput.Write("GlobalServerPush.DoGet", "Writing something changed");
            }
            else {
                resp.setStatus( 408, "No change");
                GenerateOutput.Write("GlobalServerPush.DoGet", "Writing nothing changed");
            }
        }
    }
    
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        if (CanUserAccessResource(req)) {
            GenerateOutput.Write("GlobalServerPush.DoPost", "Writing the resource state");
            ServletInputStream inpStream = req.getInputStream();
            byte[] toReadBuffer = new byte[req.getContentLength()];
            inpStream.read( toReadBuffer);
            String buffer = new String( toReadBuffer).toString();
            String resource = req.getRequestURI().substring(getBaseURL().length() + 1);
            UserState state = null;
            synchronized(_users) {
                if (_users.containsKey(resource)) {
                    state = _users.get( resource);
                }
                else {
                    state = new UserState(_identifiedUser.getIdentifier(), buffer, new VersionTracker(10000));
                    _users.put(resource, state);
                }
                state.setData( buffer);
            }
            state.getVersion().increment();
        }
    }
}