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)
- {
- }
- }
- }