在一个jsp页面实现二级下拉框联动，实时读取数据库数据，这个方法非常使用，只需要修改很小的地方就可以使用。设计的文件，serch.jsp，main.js，bytetostr.js，
先讲一下main.js，这是javascript，其中注重修改jsp页面名称。
function findObject(fName,initValue)...{
var xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
xmlhttp.open("POST","searchmx.jsp?findObject="+fName+"%26amp;initValue="+initValue,false);//注重修改jsp页面
xmlhttp.send();
document.getElementById(fName).innerHTML=bytes2BSTR(xmlhttp.responsebody); //bytes2BSTR函数在bytetostr.js中
}
其次为bytetostr.js，这是vbscript，这个不需要修改任何内容，他的主要功能就是读取数据转换字符串用的。
Function bytes2BSTR(vIn)
dim i
strReturn = ""
For i = 1 To LenB(vIn)
ThisCharCode = AscB(MidB(vIn,i,1))
If ThisCharCode %26lt; %26amp;H80 Then
strReturn = strReturn %26amp; Chr(ThisCharCode)
Else
NextCharCode = AscB(MidB(vIn,i+1,1))
strReturn = strReturn %26amp; Chr(CLng(ThisCharCode) * %26amp;H100 + CInt(NextCharCode))
i = i + 1
End If
Next
bytes2BSTR = strReturn
End Function
接下来就是serch.jsp页面，只需要修改div中的id为你想要的名字，再将一开始的包更换一下，已经sql语句改下就可以了，有不明白的可以参与讨论
%26lt;%@ page contentType="text/html; charset=gb2312" language="java" import="com.sjth.zdsygl.vo.*,com.sjth.zdsygl.biz.*,java.util.*,com.sjth.zdsygl.jdbc.*,java.sql.ResultSet"%%26gt;//导入相应的包
%26lt;%
//这部分代码用于执行查询数据库，返回字符串
if (request.getParameter("findObject")!=null)...{
if (request.getParameter("findObject").equals("hy_dm"))...{
DBConnect conn = null;
ResultSet rs = null;
try...{
out.print("%26lt;select name='hy_dm' onchange="javascript:findObject('hymx_dm',this.value)"%26gt;");
String sql = "select * from dm_hy group by left(hy_dm,7)";
conn = new DBConnect();
conn.setPstmt(sql);
rs = conn.executeQuery(sql);
while(rs.next())...{
out.print("%26lt;option value='"+rs.getString("hy_dm")+"'%26gt;"+rs.getString("hy_mc")+"%26lt;/option%26gt;");
}
out.print("%26lt;/select%26gt;");
}
catch (Exception e)...{
}
finally...{
try...{
if (rs != null)
rs.close();
if (conn != null)
conn.close();
}
catch (Exception e)...{
e.printStackTrace();
}
}
}
if (request.getParameter("findObject").equals("hymx_dm"))...{
DBConnect conn = null;
ResultSet rs = null;
try...{
out.print("%26lt;select name='hymx_dm' %26gt;");
String sql = null;
if (request.getParameter("initValue").equals(""))...{
sql = "select * from dm_hy";
}
else...{
sql = "select * from dm_hy where hy_dm like '"+request.getParameter("initValue")+"%'";
}
conn = new DBConnect();
conn.setPstmt(sql);
rs = conn.executeQuery(sql);
while(rs.next())...{
out.print("%26lt;option value='"+rs.getString("hy_dm")+"'%26gt;"+rs.getString("hy_mc")+"%26lt;/option%26gt;");
}
out.print("%26lt;/select%26gt;");
}
catch (Exception e)...{
}
finally...{
try...{
if (rs != null)
rs.close();
if (conn != null)
conn.close();
}
catch (Exception e)...{
e.printStackTrace();
}
}
}
return;
}
%%26gt;
%26lt;html%26gt;
%26lt;head%26gt;
%26lt;link href="css/table.css" type="text/css" rel="stylesheet"%26gt;
%26lt;script language=vbscript src="css/bytetostr.js"%26gt;%26lt;/script%26gt;
%26lt;script language=javascript src="css/main.js"%26gt;%26lt;/script%26gt;//导入两个js文件
%26lt;/head%26gt;
%26lt;body%26gt;
%26lt;div%26gt;所属行业%26lt;/div%26gt;
%26lt;div id="hy_dm"%26gt;%26lt;/div%26gt; //用来显示返回的字符串
%26lt;div %26gt;所属明细行业%26lt;/div%26gt;
%26lt;div id="hymx_dm"%26gt;%26lt;/div%26gt;//用来显示返回的字符串
%26lt;/body%26gt;
%26lt;/html%26gt;
%26lt;script language="javascript"%26gt;
findObject("hy_dm","");
findObject("hymx_dm","");//这两条是页面执行是调用
%26lt;/script%26gt;
欢迎大家讨论