过滤器

2022-08-10 21:30:53 作者：互联网



/*
*作者：呆萌老师
*☑csdn认证讲师
*☑51cto高级讲师
*☑腾讯课堂认证讲师
*☑网易云课堂认证讲师
*☑华为开发者学堂认证讲师
*☑爱奇艺千人名师计划成员
*在这里给大家分享技术、知识和生活
*各种干货，记得关注哦！
*vx：it_daimeng
*/

过滤器是处于客户端与服务器资源文件之间的一道过滤网，在访问资源文件之前，通过一系列的过滤器对请求进行修改、判断等，把不符合规则的请求在中途拦截或修改。也可以对响应进行过滤，拦截或修改响应。

Filter也称之为过滤器，它是Servlet技术中最实用的技术，WEB开发人员通过Filter技术，对web服务器管理的所有web资源：例如Jsp, Servlet, 静态图片文件或静态 html 文件等进行拦截，从而实现一些特殊的功能。例如实现URL级别的权限访问控制、过滤敏感词汇、压缩响应信息等一些高级功能。

它主要用于对用户请求进行预处理，也可以对HttpServletResponse 进行后处理。使用Filter 的完整流程：Filter 对用户请求进行预处理，接着将请求交给Servlet 进行处理并生成响应，最后Filter 再对服务器响应进行后处理。

过滤器实现自动登录

package com.test.filter;

 

import java.io.IOException;

import java.net.URLDecoder;

import java.sql.SQLException;

 

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

 

import com.test.model.User;

 

public class AutoLoginFilter implements Filter{

 

         @Override

         public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

                           throws IOException, ServletException {

                 

                  HttpServletRequest req = (HttpServletRequest) request;

                  HttpServletResponse resp = (HttpServletResponse) response;

                  HttpSession session = req.getSession();

                 

                  //获得cookie中用户名和密码 进行登录的操作

                  //定义cookie_username

                  String cookie_username = null;

                  //定义cookie_password

                  String cookie_password = null;

                  //获得cookie

                  Cookie[] cookies = req.getCookies();

                  if(cookies!=null){

                           for(Cookie cookie : cookies){

                                    //获得名字是cookie_username和cookie_password

                                    if("username".equals(cookie.getName())){

                                             cookie_username = cookie.getValue();

                                             //恢复中文用户名

                                             cookie_username = URLDecoder.decode(cookie_username, "UTF-8");

                                   

                                              System.out.println("拿到用户名");

                                    }

                                    if("password".equals(cookie.getName())){

                                             cookie_password = cookie.getValue();

                                              System.out.println("拿到密码");

                                    }

                           }

                  }

                 

                  //判断username和password是否是null

                  if(cookie_username!=null&&cookie_password!=null){

                            System.out.println(cookie_username);

                            System.out.println(cookie_password);

                           //登录的代码

                           if(cookie_username.equals("zhangsan") && cookie_password.equals("123"))

                           {

                             //User user=new User(cookie_username,"127.0.0.1");

                             //将登录的用户的user对象存到session中

                             session.setAttribute("login_user", "zhangsan");

                            

                             System.out.println("放行");

                           }

                          

                  }

                  //放行

                  chain.doFilter(req, resp);

                 

         }

         @Override

         public void init(FilterConfig filterConfig) throws ServletException {

         }

         @Override

         public void destroy() {

                 

         }

}

 
package com.test.filter;

 

import java.io.IOException;

import java.net.URLDecoder;

import java.sql.SQLException;

 

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

 

import com.test.model.User;

 

public class AutoLoginFilter implements Filter{

 

         @Override

         public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

                           throws IOException, ServletException {

                 

                  HttpServletRequest req = (HttpServletRequest) request;

                  HttpServletResponse resp = (HttpServletResponse) response;

                  HttpSession session = req.getSession();

                 

                  //获得cookie中用户名和密码 进行登录的操作

                  //定义cookie_username

                  String cookie_username = null;

                  //定义cookie_password

                  String cookie_password = null;

                  //获得cookie

                  Cookie[] cookies = req.getCookies();

                  if(cookies!=null){

                           for(Cookie cookie : cookies){

                                    //获得名字是cookie_username和cookie_password

                                    if("username".equals(cookie.getName())){

                                             cookie_username = cookie.getValue();

                                             //恢复中文用户名

                                             cookie_username = URLDecoder.decode(cookie_username, "UTF-8");

                                   

                                              System.out.println("拿到用户名");

                                    }

                                    if("password".equals(cookie.getName())){

                                             cookie_password = cookie.getValue();

                                              System.out.println("拿到密码");

                                    }

                           }

                  }

                 

                  //判断username和password是否是null

                  if(cookie_username!=null&&cookie_password!=null){

                            System.out.println(cookie_username);

                            System.out.println(cookie_password);

                           //登录的代码

                           if(cookie_username.equals("zhangsan") && cookie_password.equals("123"))

                           {

                             //User user=new User(cookie_username,"127.0.0.1");

                             //将登录的用户的user对象存到session中

                             session.setAttribute("login_user", "zhangsan");

                            

                             System.out.println("放行");

                           }

                          

                  }

                  //放行

                  chain.doFilter(req, resp);

                 

         }

         @Override

         public void init(FilterConfig filterConfig) throws ServletException {

         }

         @Override

         public void destroy() {

                 

         }

}

 <filter>

  <filter-name>AutoLoginFilter</filter-name>  <filter-class>com.test.filter.AutoLoginFilter</filter-class>

  </filter>

  <filter-mapping>

  <filter-name>AutoLoginFilter</filter-name>

  <url-pattern>/*</url-pattern>

  </filter-mapping>

标签：username,cookie,过滤器,import,password,servlet,javax
来源： https://www.cnblogs.com/daimenglaoshi/p/16573962.html