Servlet输入流输出流只能消费一次的问题

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servlet的requestbody以及response的body一旦流被读取了，就无法再次消费了，因此这对于有要拦截请求，记录相关信息的时候，带来一个潜在的坑。那么如何处理这个呢，利用filter，wrapper一层，然后proceed，最后response完之后在把cached的body设置回原始响应。如果你的项目应用到了Spring，那么Spring已帮你实现了此类需求。直接上代码(基于Spring BOOT)

1、拦截器

/**
 * Filter配置
 *
 * @author lengyu
 * @date 2017-04-21 21:56
 */
@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean streamFilterRegistration() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setDispatcherTypes(DispatcherType.REQUEST);
        registration.setFilter(new StreamFilter());
        registration.addUrlPatterns("/*");
        registration.setName("streamFilter");
        registration.setOrder(3);
        return registration;
    }
}

2、拦截器实现类

/**
 * 使用ContentCachingRequestWrapper来包装HttpServletRequest，
 * 使用ContentCachingResponseWrapper来包装HttpServletResponse，
 *
 * @author lengyu
 * @date
 */
public class StreamFilter implements Filter {
    private static final Logger log = LoggerFactory.getLogger(StreamFilter.class);

    @Override
    public void init(FilterConfig config) throws ServletException {
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        String contentType = request.getContentType();
        HttpServletResponse resp = (HttpServletResponse) response;
        String method = req.getMethod();

        boolean hasApiUri = req.getRequestURI().startsWith("/api/");
        boolean auth = StringUtils.isBlank(HttpContextUtils.getRequestToken(req, Const.AUTHORIZATION_KEY));
        if ((!(request instanceof HttpServletRequest) || auth) && !hasApiUri) {
            chain.doFilter(request, response);
            return;
        }

        if ((contentType != null) && (contentType.startsWith("multipart/form-data")) && ("POST".equalsIgnoreCase(method))) {
            log.info("==> 当前请求为文件上传，不作请求日志收集");
        } else {
            Date startTime = new Date();
            ContentCachingRequestWrapper requestWrapper = new ContentCachingRequestWrapper(req);
            ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper(resp);
            try {
                chain.doFilter(requestWrapper, responseWrapper);
            } finally {
                String requestBody = req.getQueryString();
                if (StringUtils.isEmpty(requestBody)) {
                    requestBody = new String(requestWrapper.getContentAsByteArray());
                }
                String responseBody = new String(responseWrapper.getContentAsByteArray());
                LogInfo logInfo = LogInfo.build(req, startTime, requestBody, responseBody);
                String json = logInfo.toJson();

                VhscProperties vhscProperties = (VhscProperties) SpringHelper.getBean("vhscProperties");
                boolean isNotice = logInfo.getWasteTime() > vhscProperties.getRespNoticeTime();
                log.info("[日志归档] - {}", json);
                if (isNotice) {
                    log.warn("[性能告警] - {}", json);
                }
                responseWrapper.copyBodyToResponse();
            }
        }
    }
    @Override
    public void destroy() {
    }
}

3、日志BEAN

/**
 * 请求日志信息收集
 *
 * @author lengyu
 * @version 2.0
 * @date 2017/9/2 22:45
 */
public class LogInfo implements Serializable {
    private String threadToken;//请求线程ID
    private String scheme;//协议
    private String host;//主机
    private int port;//端口
    private String method;//请求方法
    private String path;//请求路径
    private Object params;//请求参数
    private Object result;//返回值
    private String clientIp;//客户端IP
    private String serverIp;//当前服务节点IP
    private Map headers;//请求头
    private String remoteUser;//当前登陆人

    @JSONField(format = "yyyy-MM-dd HH:mm:ss.SSS")
    private Date startTime = new Date();//请求开始时间
    @JSONField(format = "yyyy-MM-dd HH:mm:ss.SSS")
    private Date endTime;//请求结束时间

    public String toJson() {
        return JSONObject.toJSONString(this);
    }


    /**
     * 消耗时长=请求开始时间-请求结束时间
     *
     * @return
     */
    public Long getWasteTime() {
        return this.endTime.getTime() - this.startTime.getTime();
    }

    /**
     * 生成日志对象
     *
     * @param req
     */
    public static LogInfo build(HttpServletRequest req, Date startTime, String requestBody, String responseBody) {
        LogInfo info = new LogInfo();
        info.threadToken = LogThreadTokenConvert.getThreadToken();
        info.scheme = req.getScheme();
        info.host = req.getServerName();
        info.port = req.getServerPort();
        info.path = req.getRequestURI();
        info.method = req.getMethod();
        info.clientIp = IPUtils.getIpAddr(req);
        info.serverIp = req.getLocalAddr();
        info.startTime = startTime;
        info.endTime = new Date();

        try {
            SysUserEntity sysUserEntity = ShiroUtils.getUserEntity();
            if (sysUserEntity != null) {
                info.remoteUser = sysUserEntity.getUserId() + ":" + sysUserEntity.getUsername();
            }
        } catch (Exception e) {
            info.remoteUser = req.getRemoteUser();
            e.printStackTrace();
        }

        VhscProperties vp = (VhscProperties) SpringHelper.getBean("vhscProperties");
        if (vp.getHasHeaders()) {
            info.headers = getHeaderMap(req);
        }
        if (vp.getHasParams()) {
            try {
                info.params = JSONObject.parseObject(requestBody);
            } catch (JSONException e) {
                info.params = requestBody;
            }
        }
        if (vp.getHasResult()) {
            try {
                info.result = JSONObject.parseObject(responseBody);
            } catch (JSONException e) {
                info.result = responseBody;
            }
        }
        return info;
    }

    public static Map getHeaderMap(HttpServletRequest req) {
        Map map = new HashMap<>();
        Enumeration enu = req.getHeaderNames();//取得全部头信息
        while (enu.hasMoreElements()) {//以此取出头Name
            String headerName = (String) enu.nextElement();
            String headerValue = req.getHeader(headerName);//取出头信息Value
            map.put(headerName, headerValue);
        }
        return map;
    }
/***省略GET/SET***/
}