Filter過濾器的寫法

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

這里寫的過濾器用的是適配器模式，思路為：

先寫一個類實現Filter，然后在讓你寫的過濾器來繼承自這個類；

 

步驟：1.建一個AbstractFilter實現Filter;2.建一個類來繼承AbstractFilter,還要在web.xml中配置；

 

web.xml中的配置:

 

<filter>
        <filter-name>validateFilter</filter-name>
        <filter-class>com.peng.ValidateFilter(這里寫的是類的完全限定名)</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>validateFilter</filter-name>
        <url-pattern>/*(這里是讓所有的通過)</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 {}

}

 

 下面是我自己寫的過濾器:我給他取名為  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;

        //判斷如果是index.jspx 放行
        String uri = request.getRequestURI();
        uri = uri.substring(uri.lastIndexOf("/")+1);
        //System.out.println("當前請求的路徑: " + uri);



        if("".equals(uri) || "index.jsp".equals(uri) || "index.jspx".equals(uri) || "login.jspx".equals(uri) || uri.endsWith("png") || uri.endsWith("jpg")) {
            //所有人都能請求到的URI，放行
            chain.doFilter(request, response);
        } else {    //下面是判斷是否有session，也就是用戶是否已登錄狀態；
            HttpSession session = request.getSession();
            User user = (User) session.getAttribute(Const.USER_IN_SESSION);
            if(user == null) {
                System.out.println("URI:" + uri + ">>>>訪問被拒絕！");
                response.sendRedirect("index.jspx?code=10002");
            } else {
                chain.doFilter(request, response);
            }
        }

    }

}