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 ActionServlet extends HttpServlet { public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); //获取请求资源路径 String uri = request.getRequestURI(); String path = uri.substring( uri.lastIndexOf("https://www.jb51.net/"), uri.lastIndexOf(".")); if(path.equals("/get_text")){//get请求 out.println("来自星星的你"); } out.close(); } }
web.xml文件代码：
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee "> <display-name></display-name> <servlet> <servlet-name>ActionServlet</servlet-name> <servlet-class>web.ActionServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ActionServlet</servlet-name> <url-pattern>*.do</url-pattern> </servlet-mapping> </web-app>
3 使用Ajax对象发送POST请求
3.1 问题
使用Ajax对象发送POST类型的请求，并向服务器提交一小段文本，显示从服务器端返回的文本。
3.2 方案
遵循GET请求方式的4步基础上，多增加一个设定，设定请求头中的content-type属性的值为application/x-www-form-urlencoded
3.3 步骤
步骤一： 新建my.js文件
在WebRoot节点下，新增一个文件夹“js”。在该文件夹中新增一个文件，名为my.js。将获取XMLHttpRequest对象的方法拷贝到该文件中，便于更多页面重用该方法。
my.js 代码：
function getXhr() { var xhr = null; if (window.XMLHttpRequest) { xhr = new XMLHttpRequest(); } else { xhr = new ActiveXObject("Microsoft.XMLHttp"); } return xhr; }
步骤二： 新建ajax03.html页面
步骤三： 编写getText（）方法
<html> <head> <title>ajax03.html</title> <meta http-equiv="Content-Type" content="type=text/html;charset=UTF-8"> <script type="text/javascript" src="https://www.jb51.net/js/my.js"></script> <script type="text/javascript"> function getText(){ var xhr = getXhr(); xhr.onreadystatechange=function(){ if(xhr.readyState==4 && xhr.status==200){ alert(xhr.responseText); } }; xhr.open("post","post_text.do",true); xhr.setRequestHeader('content-type', 'application/x-www-form-urlencoded'); xhr.send("uname=daliu_it"); } </script> </head> <body> <!-- 使用Ajax对象发送POST类型请求，并获取文本 --> <input type="button" value="POST请求" /> </body> </html>
步骤四： 修改ActionServlet
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 ActionServlet extends HttpServlet { public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); request.setCharacterEncoding("UTF-8"); PrintWriter out = response.getWriter(); //获取请求资源路径 String uri = request.getRequestURI(); String path = uri.substring( uri.lastIndexOf("https://www.jb51.net/"), uri.lastIndexOf(".")); if(path.equals("/get_text")){//get请求 out.println("get请求-服务器返回的数据"); }else if(path.equals("/post_text")){//post请求 String name = request.getParameter("uname"); System.out.println(name); out.println("又来了一次的" + name); } out.close(); } }
步骤五： 运行，查看结果
3.4 完整代码
ajax03.html文件代码如下：