Ajax二级联动菜单实现原理及代码

index.jsp:

 
 
 
 
 


 
二级联动示例 
 


 
 
请选择 

 
北京 

 
天津 

 
山东 
 
请选择 

 


 
 



 
 
 

SelectServlet:

package com; 
import java.io.IOException; 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
/*** 
* 
* @author zdw 
* 
*/ 
public class SelectServlet extends HttpServlet 
{ 
private static final long serialVersionUID = 1L; 
public SelectServlet() 
{ 
super(); 
} 
public void destroy() 
{ 
super.destroy(); 
} 
public void doGet(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException 
{ 
// response.setCharacterEncoding("GBK"); 
response.setContentType("text/xml"); 
response.setHeader("Cache-Control", "no-cache"); 
request.setCharacterEncoding("GBK"); 
response.setCharacterEncoding("UTF-8"); 
String targetId = request.getParameter("id").toString(); 
System.out.println(targetId); 
// 获得请求中参数为id的值 
String xml_start = ""; 
String xml_end = ""; 
String xml = ""; 
if (targetId.equalsIgnoreCase("0")) 
{ 
xml = "0请选择"; 
} else if (targetId.equalsIgnoreCase("1")) 
{ 
xml = "1昌平"; 
xml  = "2丰台"; 
xml  = "3海淀"; 
xml  = "4朝阳"; 
} else if (targetId.equalsIgnoreCase("2")) 
{ 
xml = "1塘沽区"; 
xml  = "2汉沽区"; 
xml  = "3大港区"; 
xml  = "4东丽区"; 
} else 
{// 如果是3,则返回下面的字符 
xml = "1济南"; 
xml  = "2青岛"; 
xml  = "3淄博"; 
xml  = "4枣庄"; 
} 
String last_xml = xml_start   xml   xml_end; 
response.getWriter().write(last_xml); 
} 
public void doPost(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException 
{ 
doGet(request, response); 
} 
public void init() throws ServletException 
{ 
} 
}

web.xml:

SelectServletcom.SelectServletSelectServlet/selectindex.jsp