JSP+EXt2.0实现分页的方法

Ext.onReady(function(){
var sm = new Ext.grid.CheckboxSelectionModel();
var cm = new Ext.grid.ColumnModel([ 
  new Ext.grid.RowNumberer(), 
  sm, 
    {header:'编号',dataIndex:'id',sortable:true}, 
    {header:'名称',dataIndex:'name',sortable:true}, 
    {header:'性别',dataIndex:'sex',sortable:true,renderer:function(value){ 
    if(value=='male'){ 
     return " <span style='color:red;font-weight:bold;'>红男 </span> <img src='./img/125.gif'>"; 
    }else{ 
     return " <span style='color:green;font-weight:bold;'>绿女 </span> <img src='./img/123.gif'>"; 
    }
    }}, 
    {header:'描述',dataIndex:'descn',sortable:true} 
  ]); 
  cm.defaultSortable = true; 
  var ds = new Ext.data.Store({ 
    proxy: new Ext.data.HttpProxy({url:'page.jsp'}), 
    reader: new Ext.data.JsonReader({ 
        totalProperty: 'totalProperty', 
        root: 'root'
  }, 
  [ 
    {name: 'id',mapping:'id'}, 
    {name: 'name',mapping:'name'}, 
    {name:'sex',mapping:'sex'}, 
    {name: 'descn',mapping:'descn'} 
  ]), 
  remoteSort:true
  }); 
  var grid = new Ext.grid.GridPanel({ 
  el: 'grid', 
  title:'Ext Grid Test', 
  width:450, 
  height:410, 
  trackMouseOver:false, 
  loadMask: {msg:'正在加载数据，请稍侯……'}, 
  store:ds, 
  cm: cm, 
  sm:sm, 
  bbar: new Ext.PagingToolbar({ 
      pageSize: 5, 
      store: ds, 
      displayInfo: true, 
      displayMsg: '当前显示 {0} - {1}条记录 /共 {2}条记录', 
      emptyMsg: "No topics to display"
    }) 
  }); 
  grid.render(); 
  ds.load({params:{start:0, limit:5}}); 
});

<%@ page language="java" pageEncoding="UTF-8"%>
<% 
String start = request.getParameter("start"); 
String limit = request.getParameter("limit");
int index = Integer.parseInt(start); 
int pageSize = Integer.parseInt(limit); 
String json = "{totalProperty:100,root:["; 
String sex="";
for (int i = index; i < pageSize + index; i++) { 
if(i%2==0)
{
  sex="male";
}
else{
  sex="female";
}
  json += "{id:" + i + ",name:'" + i + "',sex:'"+sex+"',descn:'descn" + i 
  + "'}"; 
  if (i != pageSize + index - 1) { 
  json += ","; 
  } 
} 
json += "]}"; 
response.getWriter().write(json); 
System.out.print(json); 
%>