servlet后端过滤器的实现

清疚 2022-06-04 08:59 167阅读 0赞

javaEE过滤器的实现分为两步走

注意：这个类要继承Filter这个接口，

主要的代码是在dofilter这个方法中实现的，，大致思路是这样的，从session中取出用户的登录对象

然后进行判断如果这个对象不为空，就让他继续进行访问这个项目，如果为空就强制让他转到登录界面，提示他登录失效等等，

@Override
    public void init(FilterConfig filterConfig) throws ServletException {
    config=filterConfig;
    }
    
    
    @Override  
    public void doFilter(ServletRequest request, ServletResponse response,
                FilterChain chain) throws IOException, ServletException {
      // 获得在下面代码中要用的request,response,session对象
            HttpServletRequest servletRequest = (HttpServletRequest) request;
            HttpSession session = servletRequest.getSession();
            TbUser admin=(TbUser)session.getAttribute("admin");
            if(admin != null) {
                chain.doFilter(request, response);
            }else {
            // 当用户为登录或登录超时时提醒并跳转到登录界面
            String returnUrl = servletRequest.getContextPath() + "/login";
            response.getWriter().println("<script language=\"javascript\">" + "alert(\"登录失效！请重新登录\");"+ "if(window.opener==null){window.top.location.href=\"" + returnUrl
    + "\";}else{window.opener.top.location.href=\"" + returnUrl + "\";window.close();}</script>");
        return;
       }
    
    }
    
    @Override
    public void destroy() {
        this.config = null;
    }

**2.在你的web.xml中配置你的过滤路径，注意这时的过滤的就是你要访问的网址的路径，**

<filter>
            <filter-name>AdminFilter</filter-name>
            <filter-class>com.torrow.school.filter.AdminFilter</filter-class>
        </filter>
    
        <filter-mapping>
            <filter-name>AdminFilter</filter-name>
            <url-pattern>/link/*</url-pattern>
        </filter-mapping>
    
        <filter-mapping>
            <filter-name>AdminFilter</filter-name>
            <url-pattern>/category/*</url-pattern>
        </filter-mapping>
    
        <filter-mapping>
            <filter-name>AdminFilter</filter-name>
            <url-pattern>/general/*</url-pattern>
        </filter-mapping>
    
        <filter-mapping>
            <filter-name>AdminFilter</filter-name>
            <url-pattern>/message/*</url-pattern>
        </filter-mapping>
    
        <filter-mapping>
            <filter-name>AdminFilter</filter-name>
            <url-pattern>/others/*</url-pattern>
        </filter-mapping>
    
        <filter-mapping>
            <filter-name>AdminFilter</filter-name>
            <url-pattern>/news/*</url-pattern>
        </filter-mapping>
    
        <filter-mapping>
            <filter-name>AdminFilter</filter-name>
            <url-pattern>/user/*</url-pattern>
        </filter-mapping>