accp8.0转换教材第10章Ajax和jQuery理解与练习

C/S （Client/Server）结构，即大家熟知的客户机和服务器结构。

B/S（Browser/Server）结构即浏览器和服务器结构。

认识ajax 、XMLHttpRequest、使用jquery实现ajax、处理json格式的响应数据、使用原生态JavaScript实现ajax

一.杂记

1.传统web技术和ajax的请求方式不同 ajax是只获得需要的元素传统刷新全部

2.ajax的全称是“Asynchronous Javascript And XML”（异步JavaScript和XML）

3.ajax的工作流程用户界面通过JavaScript到ajax发送http请求---服务器（处理请求）

再返回xml/json/html数据到ajax引擎再由dom+css返回到用户界面

4.XMLHttpRequest提供异步发送请求能力

常用方法

open(String method,String url,boolean async)创建一个新的HTTP请求、

send(String data) 发送请求到服务器端、

setRequestHeader(String header,String value)设置请求的某个HTTP头信息、

5.老版本的IE浏览器和新版的即大部分浏览器的创建XMLHttpRequest不一样

6.事件onreadystatechange：回调函数

二.上机部分

1.实现检查注册用户的邮箱是否存在（使用原生态JavaScript实现ajax）

</form>
<script type="text/javascript" language="JavaScript">
function checkemail() {
//alert("hnjkl");
//创建XMLHttpRequest对象
if(window.XMLHttpRequest){//返回true时说明是新版本IE浏览器或其他浏览器
xmlHttpRequest=new XMLHttpRequest();
}else{//返回false时说明是老版本IE浏览器
xmlHttpRequest=new XMLHttpRequest("Microsoft.XMLHTTP");
}
//设置回调函数
xmlHttpRequest.onreadystatechange=callBack;
//获取用户名文本框的值
var email=$("#email").val();
//初始化XMLHttpRequest组件
var url="userServlet?email="+email;//服务器端URL地址，name为用户名文本框的值
xmlHttpRequest.open("GET",url,true);
//发送请求
xmlHttpRequest.send(null);
//回调函数callBack（）中处理服务器响应的关键代码
function callBack(){
if(xmlHttpRequest.readyState==4&&xmlHttpRequest.status==200){
var date=xmlHttpRequest.responseText;
if(date=="true"){
$("#samp").html("邮箱已被占用");//samp为显示消息的samp的id
}else{
$("#samp").html("邮箱可注册");
}
}
}
}

</script>
</div>

在servlet中代码如下

package web;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class userServlet extends HttpServlet{

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub

request.setCharacterEncoding("UTF-8");
boolean emailCheck=false;
String email=request.getParameter("email");
if("22@qq.com".equals(email)){
emailCheck=true;

}
else {
emailCheck=false;
}
response.setContentType("text/html;charset=UTF-8");
PrintWriter out=response.getWriter();
out.print(emailCheck);
out.flush();
out.close();

}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding("UTF-8");
this.doGet(request, response);
}
}

2.使用$.ajax()方法实现异步检查注册邮箱是否已存在

</form>
<script type="text/javascript" language="JavaScript">
function checkemail(){
var email=$("#email").val();
$.ajax({
"url" :"userServlet",
"type" :"get",
"data" :"email="+email,
"dataType" :"text",
"success" :callBack,
"error" :function () {
alert("出现错误");
}
});
function callBack(data) {
if(data=="true"){
$("#samp").html("邮箱已被占用");//samp为显示消息的samp的id
}else{
$("#samp").html("邮箱可注册");
}
}

}
</script>
</div>

3.以常见页面元素展示JSON数据

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'workthree.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

<script type="text/javascript" src="js/jquery-1.8.3.js"></script>
<script type="text/javascript">
$(document).ready(function(){
var personary=["大东-河南省周口13838381438市-","小顺-广东省xx市"];
var person=[{"id":"1001","name":"大东","address":"河南省周口市","phone":"13838381438"},
{"id":"1002","name":"小圳","address":"湖南省xx市","phone":"13838381438"},
{"id":"1003","name":"小顺","address":"广东省xx市","phone":"13838381438"},
{"id":"1004","name":"小莫","address":"河北省xx市","phone":"13838381438"}];
var $divv=$("#con");
var $table=$(" <table border='1' ></table>").append("<tr><td>ID</td><td>姓名</td><td>住址</td><td>手机</td></tr>");
$divv.append($table);
$(person).each(function(){
$table.append("<tr><td>"+this.id+"</td><td>"
+this.name+"</td><td>"
+this.address+"</td><td>"
+this.phone+"</td></tr>");
});

//2.下拉框
var $ary=$(personary);
//var $ul=$("#arul");
var $sel=$("#arse");
$ary.each(function(i) {
$sel.append("<option value='"+(i+1)+"'>"+this+"</option>");
});
});
</script>

</head>

<body>

</div>
<div id="conn">
<select id="arse"></select>
</div>
</body>
</html>

4.在ajax中使用JSON生成管理员新闻管理页面

//在这里页面就不上传了如有需要完整项目代码在csdn能找到搜狗搜索（accp8.0转换教材第X章）就能下载

//最主要的是js

/**
* Created by Administrator on 2017/7/4.
*/
$(function(){
$.ajax({
"url":"userServlet2",
"type":"POST",
"data":"por=user",
"dataType":"json",
"success":callBack
});
$("#news").click(function(){
initnews();
});
$("#topics").click(function(){
inittopics();
});
});

//servlet代码

package web;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import dao.newlist;
import dao.topdao;
import daoImpl.newlistimpl;
import daoImpl.topimpl;
import entity.news;
import entity.top;

public class userServlet2 extends HttpServlet{

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub

//doPost(request, response);

}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub

request.setCharacterEncoding("UTF-8");
String por=request.getParameter("por");
if(por.equals("news")){
newlist nd=new newlistimpl();
List<news> listnews=nd.allnewslist();
StringBuffer newssub=new StringBuffer("[");
for(int i=0;;){
news n=listnews.get(i);
newssub.append("{"title":""+n.getNtitle()+"","author":""+n.getAuthour()+""}");
i++;
if(i==listnews.size()){
break;
}else{
newssub.append(",");
}
}
newssub.append("]");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out=response.getWriter();
out.print(newssub);
out.flush();
out.close();

}
else if(por.equals("top")){
topdao nd=new topimpl();
List<top> listtop=nd.alltop();
StringBuffer topsub=new StringBuffer("[");
for(int i=0;;){
top top=listtop.get(i);
topsub.append("{"topics":""+top.getTcontent()+""}");
i++;
if(i==listtop.size()){
break;
}else{
topsub.append(",");
}
}
topsub.append("]");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out=response.getWriter();
out.print(topsub);
out.flush();
out.close();
}
}
}

5.在ajax中使用JSON生成主题管理页面

//在上机四中

五.总结部分

1.传统的web开发技术通过浏览器发送请求而ajax通过JavaScript的xmlhttprequest对象发送

传统的响应的是一个完整页面而JavaScript返回需要的数据

2.Ajax 的关键元素

→JavaScript语言：Ajax技术的主要开发语言

→XML/JSON/HTML:用来封装数据

→DOM（文档对象模型）：修改页面元素

→CSS：改变样式

→Ajax引擎：即XMLHttpRequest对象

3.创建XMLHttpRequest对象的方式（两种新的和旧的）

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原文在博客园http://www.cnblogs.com/a782126844/有需要可以联系扣扣：2265682997