Ajax的简单使用

爱被打了一巴掌 2022-04-23 10:16 213阅读 0赞

简介

GET和POST请求

ajax\_demo01.jsp

ajax\_demo01Servlet.java

ajax\_demo02servlet.java

结果

点击get请求的链接

点击post请求的链接

校验用户名是否存在

数据库

ajax\_demo02.jsp

UserDao.java

UserDaoImpl.java

CheckUsernameServlet.java

运行结果

--------------------

# 简介 #

AJAX = Asynchronous JavaScript and XML（异步的 JavaScript 和 XML）。

AJAX 不是新的编程语言，而是一种使用现有标准的新方法。

AJAX 是与服务器交换数据并更新部分网页的艺术，在不重新加载整个页面的情况下。

# GET和POST请求 #

## ajax\_demo01.jsp ##

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
    <!DOCTYPE html>
    
    <html>
    <head>
    <meta charset="UTF-8">
    <title>Insert title here</title>
    <script type="text/javascript">
    	//创建XMLHttpRequest对象
    	function ajaxFunction() {
    		var xmlHttp;
    		try { // Firefox, Opera 8.0+, Chrome, Safari, IE7+
    			xmlHttp = new XMLHttpRequest();
    		} catch (e) {
    			try {// Internet Explorer
    				xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
    			} catch (e) {
    				try {
    					xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    				} catch (e) {
    				}
    			}
    		}
    		return xmlHttp;
    	}
    
    	//执行get请求
    	function get() {
    		//1. 创建xmlhttprequest 对象
    		var request = ajaxFunction();
    
    		//2. 发送请求。
    		/*	
    			参数一： 请求类型  GET or  POST
    			参数二： 请求的路径
    			参数三： 是否异步， true  or false
    		 */
    		//request.open("GET", "ajax_demo01servlet", true);
    		request.open("GET", "ajax_demo01servlet?name=zhujunwei&age=18", true);
    		request.send();
    
    		//3.接收响应
    		request.onreadystatechange=function(){
    			if (request.readyState==4 && request.status==200){
    		    	alert(request.responseText);
    		    }
    		}
    	}
    	
    	//执行post请求
    	function post() {
    		//1. 创建xmlhttprequest 对象
    		var request = ajaxFunction();
    
    		//2. 发送请求。
    		request.open("POST", "ajax_demo02servlet", true);
    		
    		//提交表单数据
    		request.setRequestHeader("Content-type","application/x-www-form-urlencoded");
    		request.send("name=zhujunwei&age=18");
    
    		//3.接收响应
    		request.onreadystatechange=function(){
    			if (request.readyState==4 && request.status==200){
    		    	alert(request.responseText);
    		    }
    		}
    	}
    </script>
    </head>
    <body>
    	<h3><a href="#" onclick="get()">使用Ajax方式发送Get请求</a></h3><br>
    	<h3><a href="#" onclick="post()">使用Ajax方式发送Post请求</a></h3>
    </body>
    </html>

## ajax\_demo01Servlet.java ##

package com.zhujunwei.servlet;
    
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    @WebServlet("/ajax_demo01servlet")
    public class ajax_demo01servlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//接收参数
    		System.out.println("收到了一个GET请求。");
    		String name = request.getParameter("name");
    		String age = request.getParameter("age");
    		String get = "name="+name+"&age="+age ;
    		System.out.println(get);
    		//响应
    		response.setContentType("text/html;charset=utf-8");
    		response.getWriter().write("收到了请求："+get);
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

## ajax\_demo02servlet.java ##

package com.zhujunwei.servlet;
    
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    @WebServlet("/ajax_demo02servlet")
    public class ajax_demo02servlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//接收参数
    		System.out.println("收到了一个POST请求。");
    		String name = request.getParameter("name");
    		String age = request.getParameter("age");
    		String get = "name="+name+"&age="+age ;
    		System.out.println(get);
    		//响应
    		response.setContentType("text/html;charset=utf-8");
    		response.getWriter().write("收到了请求："+get);
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

## 结果 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70][]

### 点击get请求的链接 ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70 1][]

### 点击post请求的链接 ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70 2][]

# 校验用户名是否存在 #

## 数据库 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70 3][]

## ajax\_demo02.jsp ##

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
    <!DOCTYPE html>
    
    <html>
    <head>
    <meta charset="UTF-8">
    <title>Insert title here</title>
    <script type="text/javascript">
    	//创建XMLHttpRequest对象
    	function ajaxFunction() {
    		var xmlHttp;
    		try { // Firefox, Opera 8.0+, Chrome, Safari, IE7+
    			xmlHttp = new XMLHttpRequest();
    		} catch (e) {
    			try {// Internet Explorer
    				xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
    			} catch (e) {
    				try {
    					xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    				} catch (e) {
    				}
    			}
    		}
    		return xmlHttp;
    	}
    
    	//检查用户名是否存在
    	function checkUserName() {
    		//取得用户名
    		var username = document.getElementById("username").value;
    		//1. 创建xmlhttprequest 对象
    		var request = ajaxFunction();
    
    		//2. 发送请求。
    		request.open("POST", "CheckUsernameServlet", true);
    		
    		//提交表单数据
    		request.setRequestHeader("Content-type","application/x-www-form-urlencoded");
    		request.send("username="+username);
    
    		//3.接收响应
    		request.onreadystatechange=function(){
    			if (request.readyState==4 && request.status==200){
    				var data = request.responseText;
    				if(data == 1){
    					document.getElementById("span01").innerHTML = "<font color='red'>用户名存在!</font>";
    				}else{
    					document.getElementById("span01").innerHTML = "<font color='green'>用户名不存在!</font>";
    		   		}
    			}
    		}
    	}
    </script>
    </head>
    <body>
    	<table border="1" width="500">
    		<tr>
    			<td>用户名：</td>
    			<td><input type="text" name="username" id="username" onblur="checkUserName()"/><span id="span01"></span></td>
    		</tr>
    		<tr>
    			<td>密码：</td>
    			<td><input type="password" name="password"/></td>
    		</tr>
    	</table>
    </body>
    </html>

## UserDao.java ##

package com.zhujunwei.dao;
    
    public interface UserDao {
    	public boolean checkUserName(String username);
    }

## UserDaoImpl.java ##

package com.zhujunwei.daoImpl;
    
    import org.apache.commons.dbutils.handlers.ScalarHandler;
    
    import com.zhujunwei.dao.UserDao;
    import com.zhujunwei.util.CommonCRUDUtil;
    
    public class UserDaoImpl implements UserDao	{
    
    	@Override
    	public boolean checkUserName(String username) {
    		String sql = "select count(*) from user where username =?";
    		Long result = (Long) CommonCRUDUtil.query(sql, new ScalarHandler<Object>(), username);
    		return result>0;
    	}
    
    }

## CheckUsernameServlet.java ##

package com.zhujunwei.servlet;
    
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.zhujunwei.dao.UserDao;
    import com.zhujunwei.daoImpl.UserDaoImpl;
    
    /**
     * 检查用户名是否存在的servlet
     * @author zhujunwei
     * 2019年2月7日 上午11:23:30
     */
    @WebServlet("/CheckUsernameServlet")
    public class CheckUsernameServlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    	
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//1. 检测是否存在
    		String username = request.getParameter("username");
    //		System.out.println("username="+username);
    		
    		UserDao dao = new UserDaoImpl();
    		boolean isExist = dao.checkUserName(username);
    		//2.  通知页面，到底有还是没有。
    		if(isExist){
    			response.getWriter().println(1);  //存在用户名
    		}else{
    			response.getWriter().println(2); //不存在该用户名
    		}
    	}	
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

## 运行结果 ##

![20190207195916159.gif][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70]: /images/20220321/e1f36d91ff194a99991898811d4d4222.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70 1]: /images/20220321/705581b8ff7341c1b1a98da3fee398d0.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70 2]: /images/20220321/c9fc3c5b273c4f5994578c83024d428e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMyOTY1MTg3_size_16_color_FFFFFF_t_70 3]: /images/20220321/1351c232188b4a6791740b0ac9d557d1.png
[20190207195916159.gif]: /images/20220321/ccd8f88528ec4953857230eda87a80a3.png