ajax经典应用案例 (jsp)

2022-07-15 80酷酷网 80kuku.com

　　ajax|js写index.jsp文件
<% page contentType="text/html;charset=gb2312"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>

<title>My JSP ’index.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="description" content="This is my page">
<link rel="stylesheet" type="text/css" href="styles.css">
</head>

<body>
<script type="text/javascript">
var req;

function validate() {
var idField = document.getElementById("userid");
var url = "servlet/ValidateServlet?id=" + escape(idField.value);
if (window.XMLHttpRequest) {
alert("0");
req = new XMLHttpRequest();
}else if (window.ActiveXObject) {
alert("1");
req = new ActiveXObject("Microsoft.XMLHTTP");
}
if(req){
req.open("GET", url, true);
req.onreadystatechange = callback;
req.send(null);
}
}
function callback() {
if (req.readyState == 4) {
if (req.status == 200) {
parseMessage();
// update the HTML DOM based on whether or not message is valid
}else{
alert ("Not able to retrieve description" + req.statusText);
}
}
}
function parseMessage() {
var message = req.responseXML.getElementsByTagName("message")[0];
var name = req.responseXML.getElementsByTagName("name")[0];
setMessage(message.firstChild.data,name.firstChild.data);
}
function setMessage(message,name) {
var userMessageElement = document.getElementById("userIdMessage");
userMessageElement.innerHTML = "<font color=\"red\">" + message + " you "+name+"</font>";
}
</script>
<div id="userIdMessage"></div>
<input type="text"
size="20"
id="userid"
name="id"
onkeyup="validate();">
</body>
</html>
[2] 写servlet/ValidateServlet.java类
/*
* 创建日期 2005-8-3
*
* TODO 要更改此生成的文件的模板，请转至
* 窗口－首选项－ Java －代码样式－代码模板
*/
package com;//com包需要自己创建.

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

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

/**
* author Administrator
*
* TODO 要更改此生成的类型注释的模板，请转至
* 窗口－首选项－ Java －代码样式－代码模板
*/
public class ValidateServlet extends HttpServlet {

/**
* Constructor of the object.
*/

private ServletContext context;
private HashMap users = new HashMap();

public ValidateServlet() {
super();
}

/**
* Destruction of the servlet.

*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}

/**
* The doGet method of the servlet.

*
* This method is called when a form has its tag value method equals to get.
*
* param request the request send by the client to the server
* param response the response send by the server to the client

* throws ServletException if an error occurred
* throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");

String targetId = request.getParameter("id");
System.out.println(targetId.trim());

if ((targetId != null) && users.containsKey(targetId.trim())) {

response.getWriter().write("<info><message>welcome</message><name>sdl</name></info>");
} else {

response.getWriter().write("<info><message>kill</message><name>bush</name></info>");
System.out.print("invalid");
}

}
/**
* Initialization of the servlet.

*
* throws ServletException if an error occure
*/
public void init(ServletConfig config) throws ServletException {
this.context = config.getServletContext();
users.put("greg","account data");
users.put("duke","account data");

}

}
[3]写web.xml文件<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>ValidateServlet</servlet-name>
<servlet-class>com.ValidateServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>ValidateServlet</servlet-name>
<url-pattern>/servlet/ValidateServlet</url-pattern>
</servlet-mapping>

</web-app>
[4]说明：
你可以在IE或FireFox里测试，在文本输入框里输入，当按键抬起，会在层中显示”kill you bush”。其中index.htm中的styles.css只是美化页面，没有列出来源代码。如果在servlet向客户端输出中文，需要编码转换。