java网络编程－Ajax+servlet实例

    Ajax异步请求,servlet产生随机数据,Html页面无刷新显示。
运行环境：jdk1.5+tomcat 5.5

一、ajaxServlet.java

package com;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Random;
public class ajaxServlet extends HttpServlet{

private static final String CONTENT_TYPE="text/xml; charset=gb2312";
public void init() throws ServletException{}
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException{
 response.setContentType(CONTENT_TYPE);
 response.setHeader("Cache-Control","no-cache");
 response.setHeader("Pragma","no-cache");
 response.setDateHeader("Expires",0); 
 PrintWriter out=response.getWriter();
 String action=request.getParameter("action");
if(("send").equals(action)){  
  Random random = new Random();
  String AA=Integer.toString(Math.abs(random.nextInt()));
  String BB=Integer.toString(Math.abs(random.nextInt()));
  String CC=Integer.toString(Math.abs(random.nextInt()));
  String DD=Integer.toString(Math.abs(random.nextInt()));
  StringBuffer sb=new StringBuffer();
  sb.append(AA);  sb.append("@@@");
  sb.append(BB);  sb.append("@@@");
  sb.append(CC);  sb.append("@@@");
  sb.append(DD);
  out.write(sb.toString());
  out.close();
  } }}
      

二、testajax.html

function getResult(){
  var url = "/Tajax/AajaxServlet?action=send";
  if (window.XMLHttpRequest) { 
    req = new XMLHttpRequest(); 
  }else if (window.ActiveXObject){ 
    req = new ActiveXObject("Microsoft.XMLHTTP"); 
  } 
  if(req){ 
     req.open("GET",url, true); 
     req.onreadystatechange = complete; 
     req.send(null); 
  } 
} 
/*分析返回的文本文档*/
function complete(){
  if (req.readyState == 4) { 
    if (req.status == 200) { 
      // alert(req.responseText); 
      var strResult = unescape(req.responseText);
      var arrResult = strResult.split("@@@");
      RemoveRow();  //删除以前的数据.
      num1 = arrResult; //字段num1的值
      num2 = arrResult; //字段num2的值
      num3 = arrResult;
      num4 = arrResult;
      row1= tb.insertRow();
      cell1 = row1.insertCell();
      cell1.innerText = num1;
      cell2 = row1.insertCell();
      cell2.innerText = num2;
      row2= tb.insertRow();
      cell3 = row2.insertCell();
      cell3.innerText = num3;
      cell4 = row2.insertCell();
      cell4.innerText = num4;
    } else { 
      alert('There was a problem with the request.'); 
    } 
  } 
} 
 function RemoveRow(){//保留第一行表头,其余数据均删除.
    var iRows = tb.rows.length;
    for(var i=0;i<font size="3">&lt;</font> iRows-1;i++){
       tb.deleteRow(1);
    }
 }
 function MyShow(){//2秒自动刷新一次,2秒取得一次数据.

  }

　 三、web.xml

运行图：