title: Request Response 重复读取
date: 2020-03-16 22:43:21
tags:

• http
  categories:
• 编程

背景

通常为了方便定位问题，我们需要记录接口的入参和出参。但由于 stream 不可重复读的特性，会导致无法预期的各种问题。

Wrapper

作为 request、response 的包装类，我们可以通过重写 getInputStream 和 getOutputStream 控制数据的流转，从而达到数据的可重复读取。

HttpServletRequestWrapper

package cn.caojiantao.spider;

import org.springframework.util.StreamUtils;

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.ByteArrayInputStream;
import java.io.IOException;

/**
 * @author caojiantao
 */
public class RequestWrapper extends HttpServletRequestWrapper {

    private byte[] data;

    public RequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        data = StreamUtils.copyToByteArray(request.getInputStream());
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(data);
        return new ServletInputStream() {
            @Override
            public boolean isFinished() {
                return false;
            }

            @Override
            public boolean isReady() {
                return false;
            }

            @Override
            public void setReadListener(ReadListener listener) {

            }

            @Override
            public int read() throws IOException {
                return byteArrayInputStream.read();
            }
        };
    }

    public byte[] toByteArray() throws IOException {
        return data;
    }
}

HttpServletResponseWrapper

package cn.caojiantao.spider;

import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

/**
 * @author caojiantao
 */
public class ResponseWrapper extends HttpServletResponseWrapper {

    private ByteArrayOutputStream byteArrayOutputStream;

    private ServletOutputStream servletOutputStream;

    public ResponseWrapper(HttpServletResponse response) {
        super(response);
        byteArrayOutputStream = new ByteArrayOutputStream();
        servletOutputStream = new ServletOutputStream() {
            @Override
            public boolean isReady() {
                return false;
            }

            @Override
            public void setWriteListener(WriteListener writeListener) {

            }

            @Override
            public void write(int b) throws IOException {
                response.getOutputStream().write(b);
                // 同时写入字节数组
                byteArrayOutputStream.write(b);
            }
        };
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        return servletOutputStream;
    }

    public byte[] toByteArray() {
        return byteArrayOutputStream.toByteArray();
    }
}

response.getOutputStream() 和 response.getWriter() 互斥，不能同时使用。

实例 - 日志过滤器

package cn.caojiantao.spider.configuration;

import cn.caojiantao.spider.RequestWrapper;
import cn.caojiantao.spider.ResponseWrapper;
import cn.caojiantao.spider.util.LogContext;
import cn.caojiantao.spider.util.NetUtils;
import lombok.extern.slf4j.Slf4j;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;

/**
 * @author caojiantao
 */
@Slf4j
@WebFilter(urlPatterns = {"/*"})
public class SpiderFilter implements Filter {

    private List<String> excludePathList = Arrays.asList("/", "/favicon.ico", "/index.html", "/css/*", "/js/*");

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        if (excludePathList.contains(request.getRequestURI())) {
            filterChain.doFilter(request, response);
            return;
        }

        // 追踪日志
        LogContext.setTraceId();
        // 包装流，可重复读取
        RequestWrapper requestWrapper = new RequestWrapper(request);
        ResponseWrapper responseWrapper = new ResponseWrapper(response);
        // 请求参数
        String traceId = LogContext.getTraceId();
        String method = request.getMethod();
        String uri = request.getRequestURI();
        String data = new String(requestWrapper.toByteArray());
        String query = request.getQueryString();
        String ip = NetUtils.getIpAddress(request);

        log.info("request traceId:{} method:{} uri:{} data:{} query:{} ip:{}", traceId, method, uri, data, query, ip);

        long t = System.currentTimeMillis();
        filterChain.doFilter(requestWrapper, responseWrapper);
        // 响应参数
        String resp = new String(responseWrapper.toByteArray());
        long cost = System.currentTimeMillis() - t;

        log.info("response traceId:{} method:{} uri:{} data:{} query:{} ip:{} response:{} cost:{}", traceId, method, uri, data, query, ip, resp, cost);

        LogContext.clear();
    }
}

这里 LogContext 为日志跟踪 traceId 管理，通过 ThreadLocal 来实现，方便问题定位。

package cn.caojiantao.spider.util;

import java.util.UUID;

/**
 * @author caojiantao
 */
public class LogContext {

    private static ThreadLocal<String> traceIdLocal = new ThreadLocal<>();

    public static void setTraceId() {
        String traceId = UUID.randomUUID().toString().replaceAll("-", "");
        setTraceId(traceId);
    }

    public static void setTraceId(String traceId) {
        traceIdLocal.set(traceId);
    }

    public static String getTraceId() {
        return traceIdLocal.get();
    }

    public static void clear() {
        traceIdLocal.remove();
    }
}