实例解读Ajax与servlet交互的方法

本文以实例形式剖析了ajax与servlet的交互，并且代码中有较为详细的注释，以帮助大家阅读理解。具体的实现方法如下：

1.javascript部分

var req;
 /*通过异步传输xmlhttp发送参数到ajaxservlet，返回符合条件的xml文档*/
 var url;
 function getresult()
 { 
  var f=document.getelementbyid("form_pub");
  var key=f.s.options[f.s.selectedindex].text; //获取对select中文本的引用
 if (window.xmlhttprequest)
 {
  req = new xmlhttprequest();
  url = "ajaxservlet?action="+key+"&bm=utf-8";
 }else if (window.activexobject)
 {
 
  req = new activexobject("microsoft.xmlhttp");
  url = "ajaxservlet?action="+key+"&bm=gbk";
 }
 if(req)
 { 
  req.open("get",url, true); 
  req.setrequestheader("content-type", "text/html;charset=utf-8");
  //这里如果不设定头部则会导致 firfox 发送数据错误，servlet接受到的参数为乱码，在ie中正常
  req.onreadystatechange = complete; 
  req.send(null);
  //req.setrequestheader("content-type", "text/xml; charset=utf-8"); 
 }
 }
 /*分析返回的xml文档*/
 function complete(){
 if (req.readystate == 4)
 {
  if (req.status == 200)
  {
   var items=document.getelementbyid("belong");
  //以下为解析返回的xml文档  
   var xmldoc = req.responsexml;
   var node=xmldoc.getelementsbytagname("type_name");
   //var str=new array();
    var str=null;
    //清空工作
    items.innerhtml=""; //删除一个 select内的全部内容
 for(var i=0;i<node.length;i++)
    { 
     str=node[i];
     //alert(str.childnodes[0].nodevalue);
     var objectoption=document.createelement("option");
      items.options.add(objectoption);
     //firfox不支持innertext必须用textcontent代替
      if (window.activexobject)
      {objectoption.innertext=str.childnodes[0].nodevalue;}
      else
      {objectoption.textcontent=str.childnodes[0].nodevalue;}
    }
   }
  }
 }

2.servlet端：

package ajax;

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 data_getconn.getconn;//这个包是自己写的为获取对mysql的引用
import java.sql.*;//这个包必须有！！


public class ajaxservlet extends httpservlet{
 //private static final string content_type = "text/xml; charset=utf-8";//这里最好统一用utf-8进行编码
 public void init() throws servletexception{}
 public void doget(httpservletrequest request,httpservletresponse response) throws servletexception, ioexception
 {
 response.setcontenttype("text/xml; charset=utf-8");
 //以下两句为取消在本地的缓存
 response.setheader("cache-control", "no-cache");
  response.setheader("pragma", "no-cache");
 printwriter out = response.getwriter();
 string action = request.getparameter("action");
 string bm = request.getparameter("bm");
 
 if(("gbk").equals(bm))
 {
  action=new string(action.getbytes("iso-8859-1"),"gbk");//将获得的数据用gbk从新编码！（感谢董卫老师）
 }
 else
 {
   action=new string(action.getbytes("iso-8859-1"),"gbk");
 }
 try
  {
   getconn wq=new getconn();
   connection   con=wq.getcon();
   statement stmt=con.createstatement();
   resultset rs=stmt.executequery("select items from class where main='"+action+"'");
   stringbuffer sb = new stringbuffer();
    sb.append("<type>");
   while(rs.next())
   {
      
   sb.append("<type_name>"+rs.getstring(1)+"</type_name>");
     
   }
    //sb.append("<type_name>"+action+"</type_name>");
    sb.append("</type>"); 
    out.write(sb.tostring());//注意这里向jsp输出的流，在script中的截获方法
    out.close();
    stmt.close();
    con.close();
  }
  catch(exception ex)
  {
     
  }
 
 }
}