Filter过滤器的写法

http://pengenjing.iteye.com/blog/1607248

这里写的过滤器用的是适配器模式，思路为：

先写一个类实现Filter，然后在让你写的过滤器来继承自这个类；

步骤：1.建一个AbstractFilter实现Filter;2.建一个类来继承AbstractFilter,还要在web.xml中配置；

web.xml中的配置:

<filter>
        <filter-name>validateFilter</filter-name>
        <filter-class>com.peng.ValidateFilter(这里写的是类的完全限定名)</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>validateFilter</filter-name>
        <url-pattern>/*(这里是让所有的通过)</url-pattern>
    </filter-mapping>

Abstractr.java

public abstract class AbstractFilter implements Filter{

    public void destroy() {}

    public abstract void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException ;

    public void init(FilterConfig filterConfig) throws ServletException {}

}

 下面是我自己写的过滤器:我给他取名为  ValidateFilter;

ValidateFilter.java

package com.kaishengit.web.filter;
import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.kaishengit.entity.User;
import com.kaishengit.util.Const;

public class ValidateFilter extends AbstractFilter{

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp,
            FilterChain chain) throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;

        //判断如果是index.jspx 放行
        String uri = request.getRequestURI();
        uri = uri.substring(uri.lastIndexOf("/")+1);
        //System.out.println("当前请求的路径: " + uri);



        if("".equals(uri) || "index.jsp".equals(uri) || "index.jspx".equals(uri) || "login.jspx".equals(uri) || uri.endsWith("png") || uri.endsWith("jpg")) {
            //所有人都能请求到的URI，放行
            chain.doFilter(request, response);
        } else {    //下面是判断是否有session，也就是用户是否已登录状态；
            HttpSession session = request.getSession();
            User user = (User) session.getAttribute(Const.USER_IN_SESSION);
            if(user == null) {
                System.out.println("URI:" + uri + ">>>>访问被拒绝！");
                response.sendRedirect("index.jspx?code=10002");
            } else {
                chain.doFilter(request, response);
            }
        }

    }

}