请选择            江苏            安徽                  

package web;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;public class ActionServlet extends HttpServlet {    public void service(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        request.setCharacterEncoding("utf-8");        //获取请求资源路径        String uri=request.getRequestURI();        //截取  /list        String action=uri.substring(uri.lastIndexOf("/"),uri.lastIndexOf("."));        //设置返回的类型        response.setContentType("text/html;charset=utf-8");        //获取输出流        PrintWriter out=response.getWriter();        if("/checkUname".equals(action)){        /*    //模拟服务器正在处理中。。。            try {                Thread.sleep(3000);            } catch (InterruptedException e) {                e.printStackTrace();            }*/            /*模拟服务器异常             * if(true){                throw new ServletException("有错啦---");            }*/            //接受用户传入的用户名，判断用户名是否一致            String name=request.getParameter("uname");            System.out.println(name);            //假设zs已经被占用            if("zs".equals(name)){                out.print("用户名被占用");            }else{                out.print("用户名可以用");            }        }else if("/city".equals(action)){            //获取页面传过来的省份            String proV=request.getParameter("proV");            if("1".equals(proV)){                out.print("-1,请选择省份");            }else if("js".equals(proV)){                //返回江苏的城市                out.print("nj:南京;yz:扬州");            }else if("ah".equals(proV)){                //返回安徽对应的城市                out.print("hf:合肥;wh:芜湖");            }        }        out.close();    }}

         
     
              用户名：
                      
      
      
        密码：
                    
      
      
      
        
                      
     

function getXhr(){        var xhr=null;        if(window.XMLHttpRequest){
   //浏览器是否有ajax对象            xhr=new XMLHttpRequest();        }else{
   //低版本ie            xhr=new ActiveXObject("Microsoft.XMLHttp");        }        return xhr;    }

         获取ajax对象

     
       
          
       
        ActionServlet
           
       
        web.ActionServlet
         
        
          
       
        ActionServlet
           
       
        *.do
         
        
          
       
        index.jsp