ajax+jsp异步无刷新从DB取数据

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ajax+jsp异步无刷新从DB取数据

ajax应用的基本流程

1、从web表单中获取需要的数据

2 、建立到服务器的url

3 、打开到服务器的连接

4、设置服务器在完成后要运行的函数

5 、发送请求

ajax.html

<html>
<head>
<script src="selectcustomer.js"></script>
</head>
<form name="form">
    select a customer
<select name="customers" onchange="showCustomer(document.form.customers.options[document.form.customers.selectedIndex].text)">
    <option value="1">000100</option>
    <option value="2">000101</option>
    <option value="3">000102</option>
</select>
</form>
<p>
<div id="txtHint"><b>Customer info will be listed here.</b></div>
</p>
</html>

selectcustomer.js

var xmlHttp;
function showCustomer(str)
{
xmlHttp=GetXmlHttpObject();
if(xmlHttp==null)
{
alert("Browser does not support HTTP Request");
return ;
}
var url="ajax.jsp";
url=url+"?q="+str;
url=url+"&sid="+Math.random();
xmlHttp.onreadystatechange=stateChanged;
xmlHttp.open("GET",url,true);
xmlHttp.send(null);

}

function stateChanged()
{
if(xmlHttp.readyState==4||xmlHttp.readyState=="complete")
{
document.getElementById("txtHint").innerHTML=xmlHttp.responseText;
}
}

function GetXmlHttpObject()
{
var objXMLHttp=null;
if(window.XMLHttpRequest)
{
objXMLHttp=new XMLHttpRequest();

}
else if(window.ActiveXObject)
{
objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
return objXMLHttp;
}

ajax.jsp

<%@page contentType="text/html; charset=gb2312" import="java.sql.*"%>
<html>
<body>
<%
   String sql=(String)request.getParameter("q");
    //out.println(q);
   String str="select * from customers where customerid='"+sql+"'";
   //String str1="select * from customers";
   Class.forName("org.gjt.mm.mysql.Driver").newInstance();
   Connection con=java.sql.DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","");
   Statement stmt=con.createStatement();
    ResultSet rst=stmt.executeQuery(str);
%>
<table>
<%
    while(rst.next())
    {
%>
   <tr>
     <td><%=rst.getString("customerid")%></td>
     <td><%=rst.getString("customername")%></td>
     <td><%=rst.getString("companyname")%></td>
     <td><%=rst.getString("contactname")%></td>
     <td><%=rst.getString("address")%></td>
     <td><%=rst.getString("postalcode")%></td>
   </tr>
<%   }
    //关闭连接、释放资源
    rst.close();
    stmt.close();
    con.close();
%>
   </table>
</body>
</html>