Filter实现权限拦截

标签：resp req HttpServletResponse Filter import 拦截权限 servlet javax

此方法应用于登录注册时为了防止越级登陆后级目录页面实现主页等只能从登录成功后进入

Loginservlet

 1 import javax.servlet.ServletException;
 2 import javax.servlet.http.HttpServlet;
 3 import javax.servlet.http.HttpServletRequest;
 4 import javax.servlet.http.HttpServletResponse;
 5 import java.io.IOException;
 6 
 7 public class Loginservlet extends HttpServlet {
 8     @Override
 9     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
10         String username = req.getParameter("username");
11         if(username.equals("admin")){
12             req.getSession().setAttribute("USER_SESSION",req.getSession().getId());
13             resp.sendRedirect("/success.jsp");
14         }else{
15             resp.sendRedirect("/error.jsp");
16 
17         }
18     }
19 
20     @Override
21     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
22         doGet(req, resp);
23     }
24 }

此方法的方便之处在于在登录验证时将repuest得来得值转化为Session，这样值就储存在服务器中并赋予一个ID唯一确定方便后面调取，并可以在多个页面得取值

过滤器SysFilter

注意！：HttpServletReques继承ServletReques 没有getSession方法

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class SysFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain filterChain) throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        if (request.getSession().getAttribute("USER_SESSION")==null) {
            response.sendRedirect("/error.jsp");
        }
        filterChain.doFilter(req,resp);
    }

    @Override
    public void destroy() {
    }
}

XML配置

 1 <servlet>
 2             <servlet-name>Loginservlet</servlet-name>
 3             <servlet-class>com.zxy.servlet.Loginservlet</servlet-class>
 4         </servlet>
 5         <servlet-mapping>
 6             <servlet-name>Loginservlet</servlet-name>
 7             <url-pattern>/servlet/login</url-pattern>
 8         </servlet-mapping>
 9     
10         <servlet>
11             <servlet-name>Loginout</servlet-name>
12             <servlet-class>com.zxy.servlet.Loginout</servlet-class>
13         </servlet>
14         <servlet-mapping>
15             <servlet-name>Loginout</servlet-name>
16             <url-pattern>/servlet/out</url-pattern>
17         </servlet-mapping>
18 
19         <filter>
20             <filter-name>SysFilter</filter-name>
21             <filter-class>com.zxy.filter.SysFilter</filter-class>
22         </filter>
23         <filter-mapping>
24             <filter-name>SysFilter</filter-name>
25             <url-pattern>/success.jsp</url-pattern>
26         </filter-mapping>

注意！！！过滤器过滤路径一定要正确

loginout

 1 import javax.servlet.ServletException;
 2 import javax.servlet.http.HttpServlet;
 3 import javax.servlet.http.HttpServletRequest;
 4 import javax.servlet.http.HttpServletResponse;
 5 import java.io.IOException;
 6 
 7 public class Loginout extends HttpServlet {
 8     @Override
 9     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
10         Object user_session = req.getSession().getAttribute("USER_SESSION");
11         if(user_session!=null){
12             req.getSession().removeAttribute("USER_SESSION");
13             resp.sendRedirect("/login.jsp");
14         }else{
15             resp.sendRedirect("/login.jsp");
16         }
17     }
18 
19     @Override
20     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
21         doGet(req, resp);
22     }
23 }

只把Session建立的ID名的进行移除，避免了反复创建和关闭Session所带来的负担

Constant实体类

1 public class Constant {
2     public static String USER_SESSION="USER_SESSION";
3 }

login.jsp

 1 <html>
 2 <head>
 3     <title>Title</title>
 4 </head>
 5 <body>
 6 <h1>登录</h1>
 7     <form action="/servlet/login" method="post">
 8         <input type="text" name="username">
 9         <input type="submit">
10     </form>
11 </body>
12 </html>

success.jsp

 1 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 2 <html>
 3 <head>
 4     <title>Title</title>
 5 </head>
 6 <body>
 7 <%--不用过滤器在jsp页面实现，主页面只能从登录成功跳转过来--%>
 8 <%--<%--%>
 9 <%--    Object userSession = request.getSession().getAttribute("USER_SESSION");--%>
10 <%--    if(userSession==null){--%>
11 <%--        pageContext.forward("login.jsp");--%>
12 <%--    }--%>
13 <%--%>--%>
14 <h1>Success</h1>
15 <p><a href="/servlet/out">注销</a> </p>
16 </body>
17 </html>

error.jsp

 1 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 2 <html>
 3 <head>
 4     <title>Title</title>
 5 </head>
 6 <body>
 7 <h1>错误</h1>
 8 <p><a href="/login.jsp">返回登录</a> </p>
 9 </body>
10 </html>

标签：resp,req,HttpServletResponse,Filter,import,拦截,权限,servlet,javax
From： https://www.cnblogs.com/kidzxy/p/16794407.html

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