Ext2.2+json+jsp获取后台数据的问题 --Ajax

在学习Ext-2.2时，我们通常会先研究它自带的一些例子，今天发现一个关于paging的例子，它是运用php获取json格式数据的，
而我发现网上很多人都是通过java获取后台数据，所以我写了一个jsp获取json格式数据的例子，可供像我一样的初学者参考：
这里共涉及到几个关键的文件：paging.js 和paging.html（ext-2.2\examples\grid目录下） ,
paging.html 的代码不用变，只需要小改一下paging.js就可以了,
就是把 url: 'http://extjs.com/forum/topics-browse-remote.php' 这一行改成
url: 'paging_json.jsp' :

paging.js

/*
 * Ext JS Library 2.2.1
 * Copyright(c) 2006-2009, Ext JS, LLC.
 * [e-mail]
 *
 * http://extjs.com/license
 */

Ext.onReady(function(){

    // create the Data Store
    var store = new Ext.data.JsonStore({
        root: 'topics',
        totalProperty: 'totalCount',
        idProperty: 'threadid',
        remoteSort: true,

        fields: [
            'title', 'forumtitle', 'forumid', 'author',
            {name: 'replycount', type: 'int'},
            {name: 'lastpost', mapping: 'lastpost', type: 'date', dateFormat: 'timestamp'},
            'lastposter', 'excerpt'
        ],

        // load using script tags for cross domain, if the data in on the same domain as
        // this page, an HttpProxy would be better
        proxy: new Ext.data.ScriptTagProxy({
            //url: 'http://extjs.com/forum/topics-browse-remote.php'
            url: 'paging_json.jsp'
        })
    });
    store.setDefaultSort('lastpost', 'desc');


    // pluggable renders
    function renderTopic(value, p, record){
        return String.format(
                '<b><a href="http://extjs.com/forum/showthread.php?t={2}" target="_blank">{0}</a></b><a href="http://extjs.com/forum/forumdisplay.php?f={3}" target="_blank">{1} Forum</a>',
                value, record.data.forumtitle, record.id, record.data.forumid);
    }
    function renderLast(value, p, r){
        return String.format('{0}<br/>by {1}', value.dateFormat('M j, Y, g:i a'), r.data['lastposter']);
    }

    var pagingBar = new Ext.PagingToolbar({
        pageSize: 25,
        store: store,
        displayInfo: true,
        displayMsg: 'Displaying topics {0} - {1} of {2}',
        emptyMsg: "No topics to display",

        items:[
            '-', {
            pressed: true,
            enableToggle:true,
            text: 'Show Preview',
            cls: 'x-btn-text-icon details',
            toggleHandler: function(btn, pressed){
                var view = grid.getView();
                view.showPreview = pressed;
                view.refresh();
            }
        }]
    });

    var grid = new Ext.grid.GridPanel({
        el:'topic-grid',
        width:700,
        height:500,
        title:'ExtJS.com - Browse Forums',
        store: store,
        trackMouseOver:false,
        disableSelection:true,
        loadMask: true,

        // grid columns
        columns:[{
            id: 'topic', // id assigned so we can apply custom css (e.g. .x-grid-col-topic b { color:#333 })
            header: "Topic",
            dataIndex: 'title',
            width: 420,
            renderer: renderTopic,
            sortable: true
        },{
            header: "Author",
            dataIndex: 'author',
            width: 100,
            hidden: true,
            sortable: true
        },{
            header: "Replies",
            dataIndex: 'replycount',
            width: 70,
            align: 'right',
            sortable: true
        },{
            id: 'last',
            header: "Last Post",
            dataIndex: 'lastpost',
            width: 150,
            renderer: renderLast,
            sortable: true
        }],

        // customize view config
        viewConfig: {
            forceFit:true,
            enableRowBody:true,
            showPreview:true,
            getRowClass : function(record, rowIndex, p, store){
                if(this.showPreview){
                    p.body = '<p>'+record.data.excerpt+'</p>';
                    return 'x-grid3-row-expanded';
                }
                return 'x-grid3-row-collapsed';
            }
        },

        // paging bar on the bottom
        bbar: pagingBar
    });

    // render it
    grid.render();

    // trigger the data store load
    store.load({params:{start:0, limit:25}});
});



/**
 * @class Ext.ux.SliderTip
 * @extends Ext.Tip
 * Simple plugin for using an Ext.Tip with a slider to show the slider value
 */
Ext.ux.SliderTip = Ext.extend(Ext.Tip, {
    minWidth: 10,
    offsets : [0, -10],
    init : function(slider){
        slider.on('dragstart', this.onSlide, this);
        slider.on('drag', this.onSlide, this);
        slider.on('dragend', this.hide, this);
        slider.on('destroy', this.destroy, this);
    },

    onSlide : function(slider){
        this.show();
        this.body.update(this.getText(slider));
        this.doAutoWidth();
        this.el.alignTo(slider.thumb, 'b-t?', this.offsets);
    },

    getText : function(slider){
        return slider.getValue();
    }
});

/*
 * Ext JS Library 2.2.1
 * Copyright(c) 2006-2009, Ext JS, LLC.
 * [e-mail]
 * 
 * http://extjs.com/license
 */

Ext.onReady(function(){

    // create the Data Store
    var store = new Ext.data.JsonStore({
        root: 'topics',
        totalProperty: 'totalCount',
        idProperty: 'threadid',
        remoteSort: true,

        fields: [
            'title', 'forumtitle', 'forumid', 'author',
            {name: 'replycount', type: 'int'},
            {name: 'lastpost', mapping: 'lastpost', type: 'date', dateFormat: 'timestamp'},
            'lastposter', 'excerpt'
        ],

        // load using script tags for cross domain, if the data in on the same domain as
        // this page, an HttpProxy would be better
        proxy: new Ext.data.ScriptTagProxy({
            //url: 'http://extjs.com/forum/topics-browse-remote.php'
            url: 'paging_json.jsp'
        })
    });
    store.setDefaultSort('lastpost', 'desc');


    // pluggable renders
    function renderTopic(value, p, record){
        return String.format(
                '<b><a href="http://extjs.com/forum/showthread.php?t={2}" target="_blank">{0}</a></b><a href="http://extjs.com/forum/forumdisplay.php?f={3}" target="_blank">{1} Forum</a>',
                value, record.data.forumtitle, record.id, record.data.forumid);
    }
    function renderLast(value, p, r){
        return String.format('{0}<br/>by {1}', value.dateFormat('M j, Y, g:i a'), r.data['lastposter']);
    }

    var pagingBar = new Ext.PagingToolbar({
        pageSize: 25,
        store: store,
        displayInfo: true,
        displayMsg: 'Displaying topics {0} - {1} of {2}',
        emptyMsg: "No topics to display",
        
        items:[
            '-', {
            pressed: true,
            enableToggle:true,
            text: 'Show Preview',
            cls: 'x-btn-text-icon details',
            toggleHandler: function(btn, pressed){
                var view = grid.getView();
                view.showPreview = pressed;
                view.refresh();
            }
        }]
    });

    var grid = new Ext.grid.GridPanel({
        el:'topic-grid',
        width:700,
        height:500,
        title:'ExtJS.com - Browse Forums',
        store: store,
        trackMouseOver:false,
        disableSelection:true,
        loadMask: true,

        // grid columns
        columns:[{
            id: 'topic', // id assigned so we can apply custom css (e.g. .x-grid-col-topic b { color:#333 })
            header: "Topic",
            dataIndex: 'title',
            width: 420,
            renderer: renderTopic,
            sortable: true
        },{
            header: "Author",
            dataIndex: 'author',
            width: 100,
            hidden: true,
            sortable: true
        },{
            header: "Replies",
            dataIndex: 'replycount',
            width: 70,
            align: 'right',
            sortable: true
        },{
            id: 'last',
            header: "Last Post",
            dataIndex: 'lastpost',
            width: 150,
            renderer: renderLast,
            sortable: true
        }],

        // customize view config
        viewConfig: {
            forceFit:true,
            enableRowBody:true,
            showPreview:true,
            getRowClass : function(record, rowIndex, p, store){
                if(this.showPreview){
                    p.body = '<p>'+record.data.excerpt+'</p>';
                    return 'x-grid3-row-expanded';
                }
                return 'x-grid3-row-collapsed';
            }
        },

        // paging bar on the bottom
        bbar: pagingBar
    });

    // render it
    grid.render();

    // trigger the data store load
    store.load({params:{start:0, limit:25}});
});



/**
 * @class Ext.ux.SliderTip
 * @extends Ext.Tip
 * Simple plugin for using an Ext.Tip with a slider to show the slider value
 */
Ext.ux.SliderTip = Ext.extend(Ext.Tip, {
    minWidth: 10,
    offsets : [0, -10],
    init : function(slider){
        slider.on('dragstart', this.onSlide, this);
        slider.on('drag', this.onSlide, this);
        slider.on('dragend', this.hide, this);
        slider.on('destroy', this.destroy, this);
    },

    onSlide : function(slider){
        this.show();
        this.body.update(this.getText(slider));
        this.doAutoWidth();
        this.el.alignTo(slider.thumb, 'b-t?', this.offsets);
    },

    getText : function(slider){
        return slider.getValue();
    }
});

paging_json.jsp

<%@ page language="java" pageEncoding="UTF-8"%>
<%
String json = "{totalCount:2,topics:[{threadid:1,forumid:1,forumtitle:'Ext;Help',title:'How to add hrefs dynamically into accordion panel',author:'venu',lastposter:'venu',lastpost:1235010582,excerpt:'ccccccccccccccccccccc',replycount:3},{threadid:2,forumid:2,forumtitle:'Ext;Help',title:'How to add hrefs dynamically into accordion panel',author:'venu',lastposter:'venu',lastpost:1235010592,excerpt:'dddddddddddddddd.',replycount:3}]}";
response.getWriter().write(json);
System.out.print(json);
%>