javaweb利用filter拦截未授权请求

项目上有个小需求，要限制访问者的IP，屏蔽未授权的请求。该场景使用过滤器来做再合适不过了。

SecurityFilter.java：

public class SecurityFilter implements Filter {

    private Log log = LogFactory.getLog(SecurityFilter.class);

    private List<String> whitelist = new ArrayList<String>();

    private List<String> regexlist = new ArrayList<String>();

    private static final String _JSON_CONTENT = "application/json; charset=UTF-8";

    private static final String _HTML_CONTENT = "text/html; charset=UTF-8";

    private static final String _403_JSON = "{'code': '403', 'msg': '访问被拒绝，客户端未授权！'}";

    private static final String _403_HTML = "<html><body><div style='text-align:center'><h1 style='margin-top: 10px;'>403 Forbidden!</h1><hr><span>@lichmama</span></div></body></html>";

    @Override

    public void destroy() {

    }

    @Override

    public void doFilter(ServletRequest servletrequest, ServletResponse servletresponse, FilterChain filterchain)

            throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) servletrequest;

        HttpServletResponse response = (HttpServletResponse) servletresponse;

        if (isSecurityRequest(request)) {

            filterchain.doFilter(request, response);

        } else {

            log.info("拒绝来自[" + request.getRemoteAddr() + "]的访问请求：" + request.getRequestURI());

            response.setStatus(403);

            if (isAjaxRequest(request)) {

                response.setContentType(_JSON_CONTENT);

                response.getWriter().print(_403_JSON);

            } else {

                response.setContentType(_HTML_CONTENT);

                response.getWriter().print(_403_HTML);

            }

        }

    }

    @Override

    public void init(FilterConfig filterconfig) throws ServletException {

        String allowedIP = filterconfig.getInitParameter("allowedIP");

        if (allowedIP != null && allowedIP.length() > 0) {

            for (String item : allowedIP.split(",\\s*")) {

                // 支持通配符*

                if (item.contains("*")) {

                    String regex = item.replace(".", "\\.").replace("*", "\\d{1,3}");

                    regexlist.add(regex);

                } else {

                    whitelist.add(item);

                }

            }

        }

    }

    /**

     * 判断当前请求是否来自可信任的地址

     *

     * @param request

     * @return

     */

    private boolean isSecurityRequest(HttpServletRequest request) {

        String ip = request.getRemoteAddr();

        for (String item : whitelist) {

            if (ip.equals(item))

                return true;

        }

        for (String item : regexlist) {

            if (ip.matches(item))

                return true;

        }

        return false;

    }

    /**

     * 判断请求是否是AJAX请求

     * @param request

     * @return

     */

    private boolean isAjaxRequest(HttpServletRequest request) {

        String header = request.getHeader("X-Requested-With");

        if (header != null && header.length() > 0) {

            if ("XMLHttpRequest".equalsIgnoreCase(header))

                return true;

        }

        return false;

    }

}

web.xml增加配置：

    <filter>

        <filter-name>securityFilter</filter-name>

        <filter-class>com.lichmama.webdemo.filter.SecurityFilter</filter-class>

        <init-param>

            <param-name>allowedIP</param-name>

            <param-value>192.168.5.*</param-value>

        </init-param>

    </filter>  

    <filter-mapping>

        <filter-name>securityFilter</filter-name>

        <url-pattern>/*</url-pattern>

    </filter-mapping>

尝试访问，结果如下：

*如何在Filter中获取Response的内容？这个问题之前还真没思考过，搜索了下得知如下方法可行：

1.实现一个PrintWriterWrapper，用于替换ServletResponse中的Writer

package com.lichmama.webdemo;

import java.io.PrintWriter;

import java.io.Writer;

public class PrintWriterWrapper extends PrintWriter {

    private StringBuilder buff;

    public PrintWriterWrapper(Writer writer) {

        super(writer);

        buff = new StringBuilder();

    }

    @Override

    public void write(int i) {

        super.write(i);

        buff.append(i);

    }

    @Override

    public void write(char[] ac, int i, int j) {

        super.write(ac, i, j);

        buff.append(ac, i, j);

    }

    @Override

    public void write(char[] ac) {

        super.write(ac);

        buff.append(ac);

    }

    @Override

    public void write(String s, int i, int j) {

        super.write(s, i, j);

        buff.append(s, i, j);

    }

    @Override

    public void write(String s) {

        super.write(s);

        buff.append(s);

    }

    @Override

    public void flush() {

        super.flush();

        buff.delete(0, buff.length());

    }

    public String getContent() {

        return buff.toString();

    }

}

2.实现一个ResponseWrapper，用于替换过滤链（FilterChain）中的ServletResponse：

package com.lichmama.webdemo;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpServletResponseWrapper;

public class ResponseWrapper extends HttpServletResponseWrapper {

    private PrintWriterWrapper writer;

    public ResponseWrapper(HttpServletResponse response) {

        super(response);

    }

    @Override

    public PrintWriter getWriter() throws IOException {

        if (writer == null)

            writer = new PrintWriterWrapper(super.getWriter());

        return writer;

    }

}

3.编写Filter实现获取Response的内容捕获：

package com.lichmama.webdemo.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.HttpServletResponse;

import com.lichmama.webdemo.PrintWriterWrapper;

import com.lichmama.webdemo.ResponseWrapper;

public class TestFilter implements Filter {

    @Override

    public void init(FilterConfig filterconfig) throws ServletException {

    }

    @Override

    public void doFilter(ServletRequest servletrequest, ServletResponse servletresponse, FilterChain filterchain)

            throws IOException, ServletException {

        ResponseWrapper responsewrapper = new ResponseWrapper((HttpServletResponse) servletresponse);

        filterchain.doFilter(servletrequest, responsewrapper);

        PrintWriterWrapper writerWrapper = (PrintWriterWrapper) responsewrapper.getWriter();

        // TODO retrieve content from PrintWriterWrapper

        String content = writerWrapper.getContent();

    }

    @Override

    public void destroy() {

    }

}

that's it~

巴特西

javaweb利用filter拦截未授权请求

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