请问jsp中如何实现在页面上对某个块的拖拽？

也可以用javascript。
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>无标题文档</title>
<script language="javascript">
var excursionX=0;
var excursionY=0;
function move(obj){
var td = window.event.srcElement;
if(event.y<=(obj.offsetTop+obj.offsetHeight)+10&&event.y>=(obj.offsetTop+obj.offsetHeight)-10){
obj.setCapture();
obj.onmousemove = resizeObj;
obj.onmouseup = dragend;
}else{
obj.style.cursor="move";
excursionX=event.x-obj.offsetLeft;
excursionY=event.y-obj.offsetTop;
obj.setCapture();
obj.onmousemove = dragstart;
obj.onmouseup = dragend;
}
}
function resizeObj(){
shadow.style.height = event.y;//-excursionX;
//shadow.style.top = event.y-excursionY;
}
function dragstart(){
if(event.x-excursionX>=0)
shadow.style.left = event.x-excursionX;
if(event.y-excursionY>=0)
shadow.style.top = event.y-excursionY;
}
function dragend(){
this.releaseCapture()
this.onmousemove = null;
}
</script>
</head>
<div class="title" id="shadow" style="width:200;position:absolute;border:5;" onMouseDown="move(this)">
<TABLE WIDTH=200 id=srcTd style="cursor:n-resize ">
  <TR>
<TD>11</TD>
<TD>12</TD>
</TR>
<TR>
<TD>21</TD>
<TD>22</TD>
</TR>
</TABLE>
</div><body>
</body>
</html>