jsp里用Ajax做的select的两级级联，带数据库。

jsp里用Ajax做的select的两级级联，带数据库。

jsp里的两个select：

< select name = " lei "  onchange = " callServer(this.options[this.selectedIndex].text) " >
<%
rs = stmt.executeQuery( " select dfl from dhyfl " );
while (rs.next()){
%>
< option ><%= rs.getString( " dfl " )  %></ option >
<%
}
%>
</ select >< select name = " smallLei " ></ select >

jsp底部的Ajax：

< script language = " javascript " >
var xmlHttp = false ;
try  {
   xmlHttp  =   new  XMLHttpRequest();
}  catch  (trymicrosoft) {
      try  {
       xmlHttp  =   new  ActiveXObject( " Msxml2.XMLHTTP " );
     }  catch  (othermicrosoft) {
        try  {
         xmlHttp  =   new  ActiveXObject( " Microsoft.XMLHTTP " );
       }  catch  (failed) {
          
       }  
     }
   }
function callServer(smallLei){
    var url = " <%=request.getContextPath()%>/smallLei?lei= "   +  smallLei;
    xmlHttp.open( " get " ,url, " true " );
    xmlHttp.onreadystatechange  = upsmlei;
    xmlHttp.send( null );
}
function upsmlei(){
     if (xmlHttp.readyState  ==   4 ){
         if (xmlHttp.status == 200 ){
            var smlei  =  document.all.smallLei;
            smlei.options.length = 0 ;
            var arr = xmlHttp.responseText.split( " | " );
             for (var i = 0 ;i < arr.length - 1 ;i ++ ){
                smlei.add( new  Option(arr[i],arr[i]));
            }
        }
    }
}
</ script >

Ajax的servlet：

package  cqrx.ajax;

import  java.io.IOException;
import  java.io.PrintWriter;
import  java.sql.ResultSet;
import  java.sql.Statement;

import  javax.servlet.ServletException;
import  javax.servlet.http.HttpServlet;
import  javax.servlet.http.HttpServletRequest;
import  javax.servlet.http.HttpServletResponse;

import  cqrx.zgdsc.Conn;

public   class  SmallLei  extends  HttpServlet {

     public  SmallLei() {
         super ();
    }

     public   void  destroy() {
         super .destroy();
    }

     public   void  doGet(HttpServletRequest request, HttpServletResponse response)
             throws  ServletException, IOException {

                response.setContentType( " text/html;charset=gb2312 " );
        PrintWriter out  =  response.getWriter();
             String lei  =  request.getParameter( " lei " );
             lei  =   new  String(lei.getBytes( " ISO8859-1 " ),  " GB2312 " );
             out.print(lei);
             Conn c  =   new  Conn();
             Statement stmt  =   null ;
             ResultSet rs  =   null ;
              try  {
             stmt  =  c.getConn().createStatement();
             String sql  =   " select sfl from shyfl where dfl =' "   +  lei  +   " ' " ;
             rs  =  stmt.executeQuery(sql);
             String str  =   "" ;
              while  (rs.next()) {
             str  =  str  +  rs.getString( 1 )  +   " | " ;
             }
             out.print(str);
            
             }  catch  (Exception e) {
             System.out.print(e.getMessage());
        }  finally  {
            out.flush();
            out.close();
        }
    }

     public   void  doPost(HttpServletRequest request, HttpServletResponse response)
             throws  ServletException, IOException {
        doGet(request, response);
    }

     public   void  init()  throws  ServletException {
    }

}