006_Ajax发送POST请求
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006_Ajax发送POST请求
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1. 使用我们的Ajax动态WEB项目
2. 编写ajax_post.html
<!DOCTYPE html> <html><head><meta charset="utf-8" /><title>Ajax post请求获取字符串响应</title></head><body> <form action="" method="post">用户名: <input type="text" name="userName" autofocus="autofocus" onBlur="showHint(this.value)" /><span id="txtHint"></span><br />密码: <input type="password" name="password" /><br /><input type="submit" value="提交" /></form><script type="text/javascript">function showHint(userName){if(userName == undefined){document.getElementById("txtHint").innerHTML="请输入用户名";return;}// 创建XMLHttpRequest对象。XMLHttpRequest对象用于和服务器交换数据。var xmlHttp = new XMLHttpRequest();xmlHttp.onreadystatechange = function(){// 4请求完成, 200服务器返回状态OK。if(xmlHttp.readyState == 4 && xmlHttp.status == 200){// 获取字符串响应document.getElementById("txtHint").innerHTML=xmlHttp.responseText;}}// 使用XMLHttpRequest对象的open()和send()方法, 发送post请求到服务器。xmlHttp.open("post", "register.action", true);xmlHttp.setRequestHeader("Content-type","application/x-www-form-urlencoded; charset=UTF-8");xmlHttp.send("userName="+encodeURIComponent(userName));}</script></body> </html>3. 编写RegisterAction.java
package com.lywgames.ajax;import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;public class RegisterAction extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String userName = req.getParameter("userName");String result = "";if("zhangsan".equals(userName) || "lisi".equals(userName)) {result = "用户名已注册";}if(null == userName || userName.length() < 3) {result = "用户名不合法";}// 响应客户端的内容类型是text/html 编码是UTF-8(包含字符编码和网页编码)resp.setContentType("text/html;charset=UTF-8");resp.getWriter().write(result);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }4. 配置web.xml
5. 运行项目, 输入用户名lisi, 失去焦点
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