1，创建封装用户信息类，新建一个名为User的类
public class User {
private String username;
private String password;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
2，创建servlet名为IndexServlet的类，用于显示网页的首页
```java
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 javax.servlet.http.HttpSession;
import java.io.IOException;
@WebServlet("/IndexServlet")
public class IndexServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
HttpSession session=request.getSession();
User user=(User)session.getAttribute("user");
if (user==null){
response.getWriter().print("您还没有登录，请<a href='login.html'>登录</a>");
}
else {
response.getWriter().print("您已登录，欢迎你，"+user.getUsername()+"!");
response.getWriter().print("<a href='LogoutServlet'>退出</a>");
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
3，编写LoginServlet，该servlet用于显示用户登录成功后的界面
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 java.io.IOException;
import java.io.PrintWriter;
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
String username=request.getParameter("username");
String password=request.getParameter("password");
PrintWriter out=response.getWriter();
if ("gxs".equals(username)&&("123".equals(password))){
User user=new User();
user.setUsername(username);
user.setPassword(password);
request.getSession().setAttribute("user",user);
response.sendRedirect("IndexServlet");
}
else {
out.write("用户名或密码错误，登录失败");
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
4，编写LogoutServlet，该servlet用于显示用户注销功能
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 java.io.IOException;
@WebServlet("/LogoutServlet")
public class LogoutServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.getSession().removeAttribute("user");
response.sendRedirect("IndexServlet");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
5，在web目录下创建一个名为login的HTML文件，该文件包含用户登录表单信息
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<form action="LoginServlet" method="post">
用户名:<input name="username" type="text"/><br/>
密码:<input name="password" type="text"/><br/>
<input type="submit" value="提交"id="bt">
</form>
</body>
</html>