【学习笔记】Filter过滤器实现登录验证
用户登录了才能访问某个页面，不登录无法访问该页面
package servlet;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import util.Constant;
import java.io.IOException;
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String username = req.getParameter("username");
if (username.equals("admin")){
req.getSession().setAttribute(Constant.USER_SESSION,"admin");
resp.sendRedirect("/sys/success.jsp");
}else {
resp.sendRedirect("/error/error.jsp");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
注销Servlet：
package servlet;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import util.Constant;
import java.io.IOException;
public class Logout extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
if (req.getSession().getAttribute(Constant.USER_SESSION) != null){
req.getSession().removeAttribute(Constant.USER_SESSION);
resp.sendRedirect("/login.jsp");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}登录页：
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录</title>
</head>
<body>
<form action="/servlet/login" method="post">
<input type="text" name="username">
<input type="submit" value="登录">
</form>
</body>
</html>错误页面：
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录失败</title>
</head>
<body>
<h1>登录失败</h1>
<h2>没有权限，或用户名错误</h2>
<a href="/login.jsp">回到登录页</a>
</body>
</html>登录成功页：
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>首页</title>
</head>
<body>
<h1>登录成功</h1>
<a href="/servlet/logout">注销</a>
</body>
</html>
过滤器Filter：
package Filter;
import jakarta.servlet.*;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import util.Constant;
import java.io.IOException;
public class LoginFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
Filter.super.init(filterConfig);
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) servletRequest;
HttpServletResponse response = (HttpServletResponse) servletResponse;
if (request.getSession().getAttribute(Constant.USER_SESSION) == null){
response.sendRedirect("/error/error.jsp");
}
filterChain.doFilter(servletRequest,servletResponse);
}
@Override
public void destroy() {
Filter.super.destroy();
}
}