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Ajax实现收藏论坛版块功能,并异步返回提示信息

2015-01-04 23:05 816 查看
一、描述

在论坛的版块页面上有一个收藏本版的超链接,点击该超链接即可收藏该版块,但是为了防止重复收藏,以及未登录就收藏的错误操作,我们采用Ajax异步返回收藏提示信息。

二、实现细节

1、在jsp页面中点击收藏超链接,执行其onclick事件中的方法,而不是跳转到某个新的页面。

2、在boardCollect.js文件中采用Ajax技术,执行后台的收藏版块的操作,并且异步写回提示信息。

3、根据返回的提示信息,显示页面中的相应提示信息控件。

三、源代码

1、boardCollect.js

// 创建请求
var http_request;
function createXMLHttpRequest(){
http_request=false;
if(window.XMLHttpRequest){
http_request=new XMLHttpRequest(); //初始化http_request
if(http_request.overrideMimeType){
http_request.overrideMimeType("text/html");
}
}else if(window.ActiveXObject){
try{
http_request=new ActiveXObject("Msxml2.XMLHTTP"); //在IE中创建XMLHttpRequest对象,新版IE
}catch(e){
try{
http_request=new ActiveXObject("Microsoft.XMLHTTP"); //在IE中创建XMLHttpRequest对象旧版IE
}catch(e){}
}
}

if(!http_request){
window.alert("不能创建XMLHttpRequest对象实例");
return false;
}
}

function boardCollect(id){
showCollects("boardCollect.action?boardId="+id);
}

function showCollects(url){
//调用createXMLHttpRequest创建http_request
createXMLHttpRequest();
//onreadystatechange状态发生变化,返回processRequest方法进行处理
http_request.onreadystatechange=processRequest;
http_request.open("GET",url,true);
http_request.send(null);
}

// 处理返回信息的函数
function processRequest(){
if(http_request.readyState==4){
if(http_request.status==200){
//正常返回,获取返回的responseText数据
var com = eval('('+http_request.responseText+')');
var feedback = com.feedback;
if(feedback=="true"){
//收藏成功
document.getElementById("ntcwin").style.display="block";
function remove(){
document.getElementById("ntcwin").style.display="none";
}
//显示1.5秒后消失
setInterval(remove,1500);

}else if(feedback=="already collect"){
//已经收藏,不能重复收藏,将页面上提示重复收藏的div显示出来
document.getElementById("fwin_a_favorite").style.display="block";
}else{
//未登录就收藏,修改页面上errorInfo显示的提示的错误信息
document.getElementById("errorInfo").innerHTML="抱歉,您还未登录没有此权限,请登录后重试";
document.getElementById("fwin_a_favorite").style.display="block";
}

}
}
}
//隐藏tcl对应的div
function hideWindow(tcl){
document.getElementById(tcl).style.display="none";
}
2、board.jsp(有些css代码没有上传,也许会出现显示格式问题)

<%@ page language="java" pageEncoding="UTF-8"%>
<%@ taglib uri="/struts-tags" prefix="s"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%>

<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" " http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml">

<head >
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>版块收藏</title>

<style type="text/css">
.pbt {
margin-bottom: 10px;
}
.ie6 .pbt .ftid a, .ie7 .pbt .ftid a {
margin-top: 1px;
}
.cl:after {
clear: both;
content: ".";
display: block;
height: 0;
visibility: hidden;
}
</style>
<script type="text/javascript" src="boardCollect.js"></script>
</head>
<body>

<div id="append_parent">
<!--fwin_a_favorite为信息已经收藏的提示信息,当该用户已经收藏了这个版块则提示 -->
<div id="fwin_a_favorite" class="fwinmask" style="position: fixed; z-index: 201; left: 438.5px; top: 72.5px;display:none;" initialized="true">
<table class="fwin" cellspacing="0" cellpadding="0">
<tbody>
<tr>
<td class="m_l" )"="" ondblclick="hideWindow('fwin_a_favorite')" style="cursor:move"> </td>
<td id="fwin_content_a_favorite" class="m_c" style="" fwin="a_favorite">
<h3 id="fctrl_a_favorite" class="flb" style="cursor: move;">
<em>提示信息</em>
<span>
<a class="flbc" title="关闭" onclick="hideWindow('fwin_a_favorite');" href="javascript:;">关闭</a>
</span>
</h3>
<div class="c altw">
<div id="errorInfo" class="alert_error">
抱歉,您已收藏,请勿重复收藏
</div>
</div>
<p class="o pns">
<button id="closebtn" class="pn pnc" onclick="hideWindow('fwin_a_favorite');" type="button" fwin="a_favorite">
<strong>确定</strong>
</button>
</p>
</td>
<td class="m_r" "="" ondblclick="hideWindow('a_favorite')" onmousedown="dragMenu($('fwin_a_favorite'), event, 1)" style="cursor:move"></td>
</tr>
</tbody>
</table>
</div>

<!--"ntcwin"为第一次收藏该版块的提示 -->
<div id="ntcwin" class="popuptext" style="position: fixed;left: 502.5px; top: 191px; display:none; " initialized="true">
<table class="popupcredit" cellspacing="0" cellpadding="0">
<tbody>
<tr>
<td class="pc_l"> </td>
<td class="pc_c">
<div class="pc_inner">
<i>信息收藏成功 </i>
</div>
</td>
<td class="pc_r"> </td>
</tr>
</tbody>
</table>
</div>
</div>

<!--"a_favorite"超链接提供用户收藏版块的功能,点击该链接就可以调用Ajax异步收藏版块并返回提示信息 -->
<div class="pbt cl">
<a id="a_favorite" class="fa_fav" onclick="boardCollect(${rd.boardName.board_id});" href="javascript:void(0);">
收藏本版
<strong id="number_favorite" class="xi1">
<c:if test="${rd.boardName.board_collectNum > 0}">
<span id="number_favorite_num">(${rd.boardName.board_collectNum})</span>
</c:if>
</strong>
</a>
</div>
</body>
</html>

3、后台处理收藏版块的java源代码

/**
*收藏版块
*/

public String boardCollect(){
System.out.println("enter boardCollect try boardId="+boardId);

try {

HttpServletResponse response;
response=ServletActionContext.getResponse();
response.setContentType( "text/json;charset=utf-8");
response.setHeader( "Cache-Control", "no-cache");
response.setHeader( "Pargma", "no-cache");
PrintWriter out;
out = response.getWriter();
//mcpForumPost = mcpForumPostDAO.findById(postId);
JSONObject js = new JSONObject();
ScpnUser u=(ScpnUser)this.getSession().get("user");

if(u!=null){

//判断该用户是否已经收藏该版块
String exitBoardCollect = "SELECT COUNT(*) FROM mcp_forum_board_collect where user_id= "+u.getUserId()+" and board_id="+boardId;

System.out.println("exitBoardCollect:"+exitBoardCollect);
Integer count=jdbcTemplate.queryForInt(exitBoardCollect);
if(count>0){
js.put("feedback", "already collect");
}else{

Timestamp currentTime = new Timestamp(System.currentTimeMillis());
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String time = sdf.format(currentTime);

//将收藏记录插入版块收藏表
String insertBoardCollect = "INSERT INTO mcp_forum_board_collect(board_id,user_id,board_collect_time) VALUES ("+boardId+","+u.getUserId()+",'"+time+"')";
System.out.println("insertPostCollect:"+insertBoardCollect);

jdbcTemplate.update(insertBoardCollect);

//更新版块收藏数量
String updateColNum = "UPDATE mcp_forum_board SET board_collectNum=1 where board_id="+boardId;
System.out.println("updateColNum:"+updateColNum);

jdbcTemplate.update(updateColNum);
userLogger.insert(UserLogger.UPDATE, u.getAccount()+"收藏版块");
js.put("feedback", "true");
}

}else {
js.put("feedback", "not login");
}

out.write(js.toString());
out.close();

} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}

return null;
}
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