java 过滤器filter使用案例

主要需要 过滤器类  和配置文件

1.过滤器类 SessionFilter

package com.service;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

public class SessionFilter implements javax.servlet.Filter {
    public void destroy() {
        System.out.println("----Filter销毁----");
    }

    public void doFilter(ServletRequest arg0, ServletResponse arg1,
                         FilterChain arg2) throws IOException, ServletException {

        HttpServletRequest request=(HttpServletRequest) arg0;
        HttpServletResponse response=(HttpServletResponse) arg1;
        HttpSession session=request.getSession();
        String path=request.getRequestURI();
        Integer uid=(Integer)session.getAttribute("userid");
        if(path.indexOf("/login.jsp")>-1){//登录页面不过滤
            arg2.doFilter(arg0, arg1);//递交给下一个过滤器
            return;
        }
        if(path.indexOf("/register.jsp")>-1){//注册页面不过滤
            arg2.doFilter(request, response);
            return;
        }

        if(uid!=null){//已经登录
            arg2.doFilter(request, response);//放行，递交给下一个过滤器

        }else{
            response.sendRedirect("/user/login");
        }
    }
    public void init(FilterConfig arg0) throws ServletException {
        System.out.println("----Filter初始化----");
    }
}

2.配置web.xml

  <filter>
    <filter-name>SessionFilter</filter-name>
    <!--过滤器-->
    <filter-class>com.service.SessionFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>SessionFilter</filter-name>
    <!--需要过滤的路径-->
    <url-pattern>/home/*</url-pattern>
    <!--<url-pattern>/user/*</url-pattern>-->
  </filter-mapping>