具备白名单、黑名单的Filter基类扩展

桃扇骨 2022-08-20 06:20 304阅读 0赞

**问题引入：**

比如定义了一个mapping,

<servlet-mapping> 
        <servlet-name>html_dispatcher</servlet-name> 
        <url-pattern>*.html</url-pattern> 
      </servlet-mapping>

就是说所有的.html请求都会由html\_dispatcher来处理，但现在的问题是：  
我希望某个文件夹下面的.html不用这个html\_dispatcher处理，而所有其它的.html请求不变。因为把所有其它的.html列出来实在太多了，多到我都不知道有多少。所以不能一一列出。

**很明显，可以使用在白名单里排除一部分黑名单来实现。**

大家在开发Java Web时，在使用过滤器时是比较挠头的，比如

<filter-mapping>
            <filter-name>TestFilter</filter-name>
            <url-pattern>/*</url-pattern>
        </filter-mapping>

url-pattern只能是如下三种：  
1、前缀匹配 /user/\*  
2、后缀匹配 \*.do  
3、绝对匹配 /myservlet

而且如果我想过滤多个url必须

<filter-mapping>
            <filter-name>TestFilter</filter-name>
            <url-pattern>/a</url-pattern>
        </filter-mapping>
        <filter-mapping>
            <filter-name>TestFilter</filter-name>
            <url-pattern>/b</url-pattern>
        </filter-mapping>

两个问题：  
1、有的朋友可能需要过滤\*.html 但要排除一部分（黑名单）；  
2、有的朋友可能需要过滤多个url，如/a /b，对于每一个url必须写一个filter-mapping比较繁琐；

因此我写了一个非常简单的具备白名单和黑名单功能的基类Filter，过滤url使用**Ant Path**：

package com.sishuok.web.filter;
    
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    
    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 org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.util.AntPathMatcher;
    import org.springframework.util.PathMatcher;
    /**
     *  
     *  配置方式
        <filter>
            <filter-name>TestFilter</filter-name>
            <filter-class>com.sishuok.web.filter.TestFilter</filter-class>
            
            <init-param>
                <param-name>blackListURL</param-name> 
                <param-value>
                    /aa
                    /bb/**
                    /cc/*
                </param-value>
            </init-param>
            <init-param>
                <param-name>whiteListURL</param-name> 
                <param-value>
                    /dd;/ee,/ff /list
                </param-value>
            </init-param>
        </filter>
        <filter-mapping>
        <filter-name>TestFilter</filter-name>
            <url-pattern>/*</url-pattern>
        </filter-mapping>
     * 
     * @author Zhang Kaitao
     *
     */
    public abstract class BaseFilter implements Filter {
        
    
        private FilterConfig config = null;
    
        private final String[] NULL_STRING_ARRAY = new String[0];
        private final String URL_SPLIT_PATTERN = "[, ;\r\n]";//逗号  空格 分号  换行
    
        private final PathMatcher pathMatcher = new AntPathMatcher();
    
        private final Logger logger = LoggerFactory.getLogger("url.filter");
    
        /**
         * 白名单
         */
        private String[] whiteListURLs = null;
    
        /**
         * 黑名单
         */
        private String[] blackListURLs = null;
    
        @Override
        public final void init(FilterConfig config) throws ServletException {
            this.config = config;
            this.initConfig();
            this.init();
        }
    
        /**
         * 子类覆盖
         * 
         * @throws ServletException
         */
        public void init() throws ServletException {
    
        }
    
        /**
         * 1、黑名单匹配 2、白名单匹配
         */
        @Override
        public final void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) 
            throws IOException, ServletException {
    
            HttpServletRequest httpRequest = (HttpServletRequest) request;
            HttpServletResponse httpResponse = (HttpServletResponse) response;
    
            String currentURL = httpRequest.getServletPath();
    
            logger.debug("url filter : current url : [{}]", currentURL);
    
            if (isBlackURL(currentURL)) {
                chain.doFilter(request, response);
                return;
            }
    
            if (isWhiteURL(currentURL)) {
                doFilter(httpRequest, httpResponse, chain);
                return;
            }
    
            logger.debug("url filter : no url list matches : [{}]  break", currentURL);
            chain.doFilter(request, response);
            return;
        }
    
        private boolean isWhiteURL(String currentURL) {
            for (String whiteURL : whiteListURLs) {
                if (pathMatcher.match(whiteURL, currentURL)) {
                    logger.debug("url filter : white url list matches : [{}] match [{}] continue", whiteURL, currentURL);
                    return true;
                }
                logger.debug("url filter : white url list not matches : [{}] match [{}]", whiteURL, currentURL);
            }
            return false;
        }
    
        private boolean isBlackURL(String currentURL) {
            for (String blackURL : blackListURLs) {
                if (pathMatcher.match(blackURL, currentURL)) {
                    logger.debug("url filter : black url list matches : [{}] match [{}] break", blackURL, currentURL);
                    return true;
                }
                logger.debug("url filter : black url list not matches : [{}] match [{}]", blackURL, currentURL);
            }
            return false;
        }
    
        /**
         * 子类覆盖
         * 
         * @param request
         * @param response
         * @param chain
         * @throws IOException
         * @throws ServletException
         */
        public void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
                throws IOException, ServletException {
            chain.doFilter(request, response);
        }
    
        /**
         * 子类覆盖
         */
        @Override
        public void destroy() {
    
        }
    
        private void initConfig() {
            String whiteListURLStr = this.config.getInitParameter("whiteListURL");
            whiteListURLs = strToArray(whiteListURLStr);
    
            String blackListURLStr = this.config.getInitParameter("blackListURL");
            blackListURLs = strToArray(blackListURLStr);
    
        }
    
        private String[] strToArray(String urlStr) {
            if (urlStr == null) {
                return NULL_STRING_ARRAY;
            }
            String[] urlArray = urlStr.split(URL_SPLIT_PATTERN);
    
            List<String> urlList = new ArrayList<String>();
    
            for (String url : urlArray) {
                url = url.trim();
                if (url.length() == 0) {
                    continue;
                }
    
                urlList.add(url);
            }
    
            return urlList.toArray(NULL_STRING_ARRAY);
        }
    
        public FilterConfig getConfig() {
            return config;
        }
    }

具体使用如下：

package com.sishuok.web.filter;
    
    import java.io.IOException;
    
    import javax.servlet.FilterChain;
    import javax.servlet.FilterConfig;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class TestFilter extends BaseFilter {
        
        @Override
        public void init() throws ServletException {
       //初始化
            FilterConfig config = getConfig();
        }
    
    
        @Override
        public void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
            throws IOException, ServletException {
    
            System.out.println("==============");
            chain.doFilter(request, response);
    
        }
    
        @Override
        public void destroy() {
       //销毁
        }
    
    }

xml配置如下：

<filter>
            <filter-name>TestFilter</filter-name>
            <filter-class>com.sishuok.web.filter.TestFilter</filter-class>
            
            <init-param>
                <param-name>blackListURL</param-name> 
                <param-value>
                    /aa
                    /bb/**
                    /cc/*
                </param-value>
            </init-param>
            <init-param>
                <param-name>whiteListURL</param-name> 
                <param-value>
                    /dd;/ee,/ff /list
                </param-value>
            </init-param>
        </filter>
        <filter-mapping>
            <filter-name>TestFilter</filter-name>
            <url-pattern>/*</url-pattern>
        </filter-mapping>