Filter&&Listener

比眉伴天荒 2024-03-27 12:40 77阅读 0赞

**目录**

一、Filter快速入门

二、Filter的执行流程

三、Filter使用细节

3.1 Filter拦截路径配置

3.2 过滤器链

四、案例——登录验证

五、Listener（监听器）

--------------------

![a25f1734e84849a2921bf5cb0224bbd8.png][]

## 一、Filter快速入门 ##

## ![1007b8469c104c179ac2d372fc64f11e.png][] ##

## 二、Filter的执行流程 ##

![6925af864f8c451da703d55d55e82ffc.png][]

## 三、Filter使用细节 ##

### 3.1 Filter拦截路径配置 ###

![e80c3cf5942640c3803484be61090d7e.png][]

### 3.2 过滤器链 ###

### ![f777cf237aea4d6a8637ceb9075c4248.png][] ###

## ![eb10dee8a88540959525e8b075a6ee0f.png][] 四、案例——登录验证 ##

![52dc5fa85e394724b6f68d72c75cc41b.png][]

package com.itheima.web.fiter;
    
    import javax.servlet.*;
    import javax.servlet.annotation.*;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    
    /**
     * 登录验证的过滤器
     */
    @WebFilter( "/*")
    public class LoginFilter implements Filter {
    
        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
    
            //判断访问资源路径是否和登录注册相关
            String[] urls = {"/login.jsp","/imgs/","/css/","/loginServlet","/register.jsp","/register","/checkCodeServlet"};
    
            HttpServletRequest req = (HttpServletRequest) request;
    
            //获取当前访问的资源路径
            String url = req.getRequestURL().toString();
    
            //循环判断iter
            for (String u : urls) {
                if (url.contains(u)){
                    //找到了
                    //放行
                    chain.doFilter(request, response);
                    return;
                }
            }
    
    
            //1.判断session中是否有user对象
            HttpSession session = req.getSession();
            Object user = session.getAttribute("user");
    
            //2.判断user是否为Null
            if (user != null){
                //登陆过
                //放行
                chain.doFilter(request, response);
            }else{
                //没有登录，存储提示信息，拦截，并跳转到登陆界面
                req.setAttribute("login_msg", "您尚未登录！");
                req.getRequestDispatcher("/login.jsp").forward(request, response);
    
            }
    
    
        }
    
        public void init(FilterConfig config) throws ServletException {
        }
    
        public void destroy() {
        }
    
    
    }

## 五、Listener（监听器） ##

![569fddfb84584df69446610c568bec35.png][]

![c6d491ebc0024cbc848a1a5d5c469474.png][]

[a25f1734e84849a2921bf5cb0224bbd8.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/fc273d78e8024b1fa6c7ef89c6d2af96.png
[1007b8469c104c179ac2d372fc64f11e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/1436069201664c408029c343c8deb500.png
[6925af864f8c451da703d55d55e82ffc.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/9ef98ffd81ea4cc9a7341b8af0f84996.png
[e80c3cf5942640c3803484be61090d7e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/653d75b9c8844a6288721d6d85a9feb2.png
[f777cf237aea4d6a8637ceb9075c4248.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/0101d291880345cd942cb547079a161c.png
[eb10dee8a88540959525e8b075a6ee0f.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/5babc0afb3e74a738483b0f15ba28e4b.png
[52dc5fa85e394724b6f68d72c75cc41b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/8b035bc999c94d51ab5d945e1647771f.png
[569fddfb84584df69446610c568bec35.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/fb7a1cf17e284d5d9bb31b59470b5346.png
[c6d491ebc0024cbc848a1a5d5c469474.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/f394b25464e84d1b89792ce6eb9db646.png

Filter&&Listener

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