servlet简单应用

在web.xml文件中设置两个web应用的初始化参数，username，password

定义一个loginServlet.html，里边定义两个请求字段：username，password、发送请求到loginServet

在创建一个LoginServlet,在其中获取请求的username和password。比对其和web.xml文件中定义的请求参数是否一致

若一致，响应Hello：xxx ，否则响应Sorry:xxx xxx为username

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>ServletPractice</display-name>
    <!-- LoginServlet -->
  <servlet>
   <servlet-name>LoginServlet</servlet-name>
   <servlet-class>com.alin.LoginServlet</servlet-class>
   <init-param>
       <param-name>username</param-name>
       <param-value>bluehonour</param-value>
   </init-param>
   <init-param>
       <param-name>password</param-name>
       <param-value>123456</param-value>
   </init-param>
  </servlet>
  <servlet-mapping>
      <servlet-name>LoginServlet</servlet-name>
      <url-pattern>/loginServlet</url-pattern>
  </servlet-mapping>
</web-app>

loginServlet.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <form action="loginServlet" method="post">
        username:<input type="text" name="username"/>
        password:<input type="text" name="password"/>
        <br>
        <input type="submit" value="Submit"/>
    </form>
</body>
</html>

LoginServlet.java

package com.alin;

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

import javax.servlet.ServletConfig;
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("/LoginServlet")
public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletConfig config = this.getServletConfig();
        String username1 = config.getInitParameter("username");
        String password1 = config.getInitParameter("password");

        String username = request.getParameter("username");
        String password = request.getParameter("password");

        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");
        PrintWriter out = response.getWriter();
        if(username.equals(username1) && password.equals(password1)) {
            out.println("<html><head><title>响应界面</title></head><body>");
            out.println("<div style=\"color:red\">");
            out.println("Hello "+username+"</div>");
            out.println("</body></html>");
        } else {
            out.println("Sorry "+username);
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

结果如下
参考xml

<param-name>username</param-name>
<param-value>bluehonour</param-value>
<param-name>password</param-name>
<param-value>123456</param-value>