package com.test.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
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;

public class LoginFilter implements Filter{

	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
			FilterChain filterChain) throws IOException, ServletException {
		// 判斷是否是http請求  
        if (!(servletRequest instanceof HttpServletRequest)  
                || !(servletResponse instanceof HttpServletResponse)) {  
            throw new ServletException(  
                    "OncePerRequestFilter just supports HTTP requests");  
        }  
        // 獲得在下面程式碼中要用的request,response,session物件  
        HttpServletRequest httpRequest = (HttpServletRequest) servletRequest;  
        HttpServletResponse httpResponse = (HttpServletResponse) servletResponse;  
        HttpSession session = httpRequest.getSession(true);  
  
        String[] strs = { "loginpage", "login", "logout", "static" }; // 路徑中包含這些字串的,可以不用登入直接訪問  
        StringBuffer url = httpRequest.getRequestURL();  
          
        /** 
         * 過濾掉根目錄 
         */  
        String path = httpRequest.getContextPath();  
        String protAndPath = httpRequest.getServerPort() == 80 ? "" : ":"  
                + httpRequest.getServerPort();  
        String basePath = httpRequest.getScheme() + "://"  
                + httpRequest.getServerName() + protAndPath + path + "/";  
        if (basePath.equalsIgnoreCase(url.toString())) {  
            filterChain.doFilter(servletRequest, servletResponse);  
            return;  
        }  
        // 特殊用途的路徑可以直接訪問  
        if (strs != null && strs.length > 0) {  
            for (String str : strs) {  
                if (url.indexOf(str) >= 0) {  
                    filterChain.doFilter(servletRequest, servletResponse);  
                    return;  
                }  
            }  
        }  
        // 從session中獲取使用者資訊  
        String loginInfo = (String) session.getAttribute("username");  
        if (null != loginInfo && !"".equals(loginInfo)) {  
            // 使用者存在繼續訪問此  
            filterChain.doFilter(servletRequest, servletResponse);  
        } else {  
            // 使用者不存在返回登入
            String returnUrl = httpRequest.getContextPath();  
            httpRequest.setCharacterEncoding("UTF-8");  
            httpResponse.setContentType("text/html; charset=UTF-8"); // 轉碼  
            httpResponse  
                    .getWriter()  
                    .println(  
                            "<script language=\"javascript\">alert(\"您還沒有登入，請先登入!\");if(window.opener==null){window.top.location.href=\""  
                                    + returnUrl  
                                    + "\";}else{window.opener.top.location.href=\""  
                                    + returnUrl  
                                    + "\";window.close();}</script>");  
            return;  
        } 
		
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		// TODO Auto-generated method stub
		
	}

}
 

四、最後驗證攔截器設定,直接用我們之前寫的user業務請求來訪問:http://localhost:9690/test/index.do

攔截成功！