ASP.NET中ServerPush用法實(shí)例分析

/// summary>
/// ServerPush1 的摘要說(shuō)明
/// /summary>
public class ServerPush1 : IHttpHandler
{
  public void ProcessRequest(HttpContext context)
  {
   context.Response.ContentType = "application/json";
   string action = context.Request["action"];
   if (action == "send")//發(fā)送
   {
    string me = context.Request["me"];
    string toUserName = context.Request["toUserName"];
    string msg = context.Request["msg"];
    SQLHpler.ExecuteNonQuery("INSERT INTO T_Msgs(FromUserName,ToUserName,Msg) VALUES(@FromUserName,@ToUserName,@Msg)", new SqlParameter("@FromUserName", me),
     new SqlParameter("@ToUserName", toUserName),
     new SqlParameter("@Msg", msg));
    context.Response.Write(new JavaScriptSerializer().Serialize(new { Status = "ok" }));
   }
   else if (action == "receive")
   //登陸，并持續(xù)查詢、接收對(duì)方發(fā)過(guò)來(lái)的數(shù)據(jù)
   {
    //做一個(gè)簡(jiǎn)單的例子，以ServerPush1.ashx?me=sean
    //請(qǐng)把發(fā)給sean的消息發(fā)給我一條
    string me = context.Request["me"];
    while (true)
    {
     DataTable dt = SQLHpler.ExecuteQuery("SELECT TOP 1 * FROM T_Msgs WHERE ToUserName=@ToUserName",new SqlParameter("@ToUserName", me));
     if (dt.Rows.Count = 0)
     {
      Thread.Sleep(500);//沒找到，休息500ms再查詢，這樣避免對(duì)數(shù)據(jù)庫(kù)的查詢壓力，和占用WEB服務(wù)器CPU資源
      continue;//下一次while
     }
     else
     {
      DataRow row = dt.Rows[0];
      long id = (long)row["Id"];
      string fromUserName = (string)row["FromUserName"];
      string msg = (string)row["Msg"];
      //查詢完之后要?jiǎng)h除消息，否則會(huì)出現(xiàn)死循環(huán)，不停的給頁(yè)面輸出同一個(gè)消息
      SQLHpler.ExecuteNonQuery("DELETE FROM T_Msgs WHERE Id=@Id",new SqlParameter("@Id",id));
      //創(chuàng)建一個(gè)匿名對(duì)象，將查詢到的數(shù)據(jù)存到里面
      var data = new { FromUserName = fromUserName, Msg = msg, Id = id };
      string json = new JavaScriptSerializer().Serialize(data);//將匿名對(duì)象轉(zhuǎn)換為json
      context.Response.Write(json);//將請(qǐng)求結(jié)果以json格式返回
      break;
     }
    }
   }
   else
   {
    throw new Exception("action錯(cuò)誤");
   }
}

!DOCTYPE html>
html xmlns="http://www.w3.org/1999/xhtml">
head>
meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
title>/title>
script type="text/javascript" src="jquery-1.8.3.min.js">/script>
script type="text/javascript">
var rev = function () {
 var mine = $('#me').val();
 $.ajax({
  type: 'post', url: 'serverPush1.ashx',
  data: { action: 'receive', me: mine },//傳給serverPush.ashx根據(jù)me查找發(fā)給me的消息
  success: function (data) {
   $('#ulMsg').append($('li>' + data.FromUserName + '對(duì)我說(shuō)：' + data.Msg + '/li>'));
   rev();//收到消息后再向服務(wù)器請(qǐng)求數(shù)據(jù)，再給我一條消息
  },
  error: function () {
   rev();
   //哪怕網(wǎng)絡(luò)請(qǐng)求失?。ū热缬脩艟W(wǎng)絡(luò)故障），也再次發(fā)送請(qǐng)求
  }
 });
};
$(function () {
 //發(fā)送
 $('#btnSend').click(function () {
  var myName = $('#me').val();
  var toUserName = $('#toUserName').val();
  var msg = $('#msgContext').val();
  $.ajax({
   type: 'post', url: 'serverPush1.ashx',
   data: { action: 'send', me: myName, toUserName: toUserName, msg: msg },//根據(jù)用戶輸入的信息，傳到服務(wù)端ServerPush.ashx進(jìn)行插入操作
   success: function (data) {
    if (data.Status == 'ok') {//如果發(fā)送成功，
     $('#ulMsg').append($('li>我對(duì)' + toUserName + '說(shuō)：' + msg + '/li>'));
     $('#msgContext').val('');
    }
    else {
     alert('發(fā)送出錯(cuò)，返回報(bào)文無(wú)法識(shí)別');
    }
   },
   error: function () {
    alert('發(fā)送出錯(cuò)');
   }
  });
 });
 //登陸，接收數(shù)據(jù)
 $('#btnLogin').click(function () {
  rev();
  $(this).attr("disabled", "disabled");
 });
 /*
 $('#btnLogin').click(function () {//接收
  var mine = $('#me').val();
  $.ajax({
   type: 'post', url: 'serverPush1.ashx',
   data: { action: 'receive', me: mine },
   //傳給serverPush.ashx根據(jù)me查找發(fā)給me的消息
   success: function (data) {
    $('#ulMsg').append($('li>' + data.toUserName + '對(duì)我說(shuō)：' + data.msg + '/li>'));
   },
   error: function () {
    alert('接收失敗');
   }
  });
 });*/
});
/script>
/head>
body>
 發(fā)送人：input type="text" id="me" />input type="button" id="btnLogin" value="登陸" style=""/>br />
 接收人：input type="text" id="toUserName" />br />
 輸入消息：input type="text" id="msgContext" />input type="button" id="btnSend" value="發(fā)送" />br />
 聊天記錄：br />
 ul id="ulMsg">
 /ul>
/body>
/html>