presence.cs

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.
*/
using System;
using System.Web;
using Devspace.Commons.Tracer;
using System.IO;
using System.Collections.Generic;
using System.Collections;

namespace Devspace.Ajax.PersistentCommunications {
    
    public class GlobalPresence : AuthenticatedHttpHandlerBase  {
        protected internal string constUserIdentifier = "user-identifier";
        static VersionTracker _version = new VersionTracker( 10000);
        static List<string> _users = new List<string>();
        private const string constXStateHeader = "X-Last-State";
        private const string constUseAction = "user-action";
        
        public GlobalPresence() {
            AssignUserResolver( new UserResolverImplementation());
        }
        protected internal override void DoGet(HttpRequest req, HttpResponse resp) {
            string lastState = req.Headers.Get(constXStateHeader);
            if (lastState == null) {
                lastState = req.Params.Get(constXStateHeader);
            }
            GenerateOutput.Write("GlobalPresence.DoGet", "lastState (" + lastState + ")");
            int lastCount = 0;
            if (lastState != null) {
                lastCount = int.Parse(lastState);
            }
            if (_version.GetNew(lastCount)) {
                lock (_version) {
                    TextWriter output = resp.Output;
                    GenerateOutput.Write("GlobalPresence.DoGet", "Before writing users");
                    foreach( string user in _users) {
                        output.WriteLine( "<b>" + user + "</b><br />");
                        GenerateOutput.Write("GlobalPresence.DoGet", "Writing user (" + user + ")");
                    }
                    GenerateOutput.Write("GlobalPresence.DoGet", "After writing users");
                }
                resp.AddHeader(constXStateHeader, _version.VersionNumber.ToString());
                GenerateOutput.Write("GlobalPresence.DoGet", "Writing something changed");
            }
            else {
                resp.StatusDescription = "No change";
                resp.StatusCode = 408;
                GenerateOutput.Write("GlobalPresence.DoGet", "Writing nothing changed");
            }
        }
        protected internal override void DoPost(HttpRequest req, HttpResponse resp) {
            lock( _version) {
                string action = GetVariable( req, constUseAction);
                if( action == "add") {
                    GenerateOutput.Write("GlobalPresence.DoPost", "Added a user (" + GetVariable( req, constUserIdentifier) + ")");
                    _users.Add( GetVariable( req, constUserIdentifier));
                }
                else if( action == "remove") {
                    GenerateOutput.Write("GlobalPresence.DoPost", "Removed a user (" + GetVariable( req, constUserIdentifier) + ")");
                    _users.Remove( GetVariable( req, constUserIdentifier));
                }
                else {
                    GenerateOutput.Write("GlobalPresence.DoPost", "Did nothing, not right!");
                }
            }
            _version.Increment();
        }
    }
}