创建Login.jsp、success.jsp、error.jsp：
login.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<form action="/servlet/login" method="post">
<input type="text" name="username">
<input type="submit">
</form>
</body>
</html>
success.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1>主页</h1>
<p><a href="/servlet/logout">注销</a> </p>
</body>
</html>
error.jsp
error.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1>wrong</h1>
<a href="/Login.jsp">返回登陆页面</a>
</body>
</html>
创建SysFilter、LoginOut、LoginServlet
package www.test.listener;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class SysFilter<req> implements Filter {
public void init(FilterConfig filterConfig) throws ServletException {
}
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
HttpServletRequest request=(HttpServletRequest)req;
HttpServletResponse response=(HttpServletResponse)resp;
if(request.getSession().getAttribute("USER_SESSION")==null){
response.sendRedirect("/error.jsp");
}
chain.doFilter(request,response);
}
public void destroy() {
}
}
package www.test.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoginOut extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Object user_session = req.getSession().getAttribute("USER_SESSION");
if (user_session!=null){
req.getSession().removeAttribute("USER_SESSION");
resp.sendRedirect("/Login.jsp");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
package www.test.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取前端请求的参数
String username=req.getParameter("username");
if (username.equals("admin")){
req.getSession().setAttribute("USER_SESSION",req.getSession().getId());
resp.sendRedirect("/Sys/success.jsp");
}else {
System.out.println("fail");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
配置web.xml
<servlet>
<servlet-name>Loginin</servlet-name>
<servlet-class>www.test.servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Loginin</servlet-name>
<url-pattern>/servlet/login</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>Loginout</servlet-name>
<servlet-class>www.test.servlet.LoginOut</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Loginout</servlet-name>
<url-pattern>/servlet/logout</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>SysFilter</servlet-name>
<servlet-class>www.test.listener.SysFilter</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>SysFilter</servlet-name>
<url-pattern>/sys/*</url-pattern>
</servlet-mapping>
