Spring cached 的 wrapper 类读取请求响应内容

0x01：wrapper 类说明

Servlet 的 request body 以及 response body 一旦流被读取了，就无法再次被读取了，因此这对于有些要做拦截业务请求来说，比较麻烦。那么如何处理这个业务场景呢？利用 filter，然后重写 HttpServletRequest 和 HttpServletResponse 包装一层，然后 proceed，最后 response 完之后在把cached 的 body 设置回原始响应。

Spring提供了 ContentCachingRequestWrapper 以及 ContentCachingResponseWrapper 两个类，来解决这类问题。

代码语言：javascript复制

ContentCachingRequestWrapper wrappedRequest = new ContentCachingRequestWrapper(request);
ContentCachingResponseWrapper wrappedResponse = new ContentCachingResponseWrapper(response);

读取完 Response body 之后

代码语言：javascript复制

wrappedResponse.copyBodyToResponse();

通过这个设置回去，就可以使得接口调用者可以正常接收响应了。

0x02：日志拦截实例

• 继承OncePerRequestFilter，顾名思义该filter能够确保在一次请求只通过一次该 filter
• 实现 Ordered，设置filter的执行顺序，一般设置最低级别执行

代码语言：javascript复制

package com.filter;

import java.io.IOException;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.core.Ordered;
import org.springframework.web.filter.OncePerRequestFilter;

public class LogFilter extends OncePerRequestFilter implements Ordered {

    @Override
    public int getOrder() {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {
        // TODO Auto-generated method stub

    }

}

完整代码大致如下

代码语言：javascript复制

package com.filter;

import java.io.IOException;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.Ordered;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;
import org.springframework.web.util.ContentCachingRequestWrapper;
import org.springframework.web.util.ContentCachingResponseWrapper;
import org.springframework.web.util.WebUtils;

@Component
public class LogFilter extends OncePerRequestFilter implements Ordered {

    @Value("${openLog}")
    private boolean openLog;
    @Override
    public int getOrder() {
        return Ordered.LOWEST_PRECEDENCE-8;
    }

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {
        ContentCachingRequestWrapper wrappedRequest = null;
        ContentCachingResponseWrapper wrappedResponse = null;
        try{
            if(openLog){
                printHender(request);
                printCookie(request);
                printParameter(request);
                wrappedRequest = new ContentCachingRequestWrapper(request);
                wrappedResponse = new ContentCachingResponseWrapper(response);
                printRequest(wrappedRequest);
                printResponse(wrappedResponse);
            }else{
                filterChain.doFilter(request, response);
            }
        }finally {
            if(wrappedResponse!=null){
                wrappedResponse.copyBodyToResponse();
            }
        }

    }

    /**
     * 打印返回体
     * 
     * @param wrappedRequest
     */
    private void printResponse(ContentCachingResponseWrapper wrappedResponse) {
        try{
            ContentCachingResponseWrapper resp =  WebUtils.getNativeResponse(wrappedResponse, ContentCachingResponseWrapper.class);
            byte[] responseBody = resp.getContentAsByteArray();
            String body = new String(responseBody, resp.getCharacterEncoding());
            //TODO 打印

        }catch (Exception e) {
            // TODO: handle exception
        }

    }

    /**
     * 打印请求体
     * 
     * @param wrappedRequest
     */
    private void printRequest(ContentCachingRequestWrapper wrappedRequest) {
        try{
            ContentCachingRequestWrapper req =  WebUtils.getNativeRequest(wrappedRequest, ContentCachingRequestWrapper.class);
            byte[] reqestBody = req.getContentAsByteArray();
            String body = new String(reqestBody, req.getCharacterEncoding());
            //TODO 打印

        }catch (Exception e) {
            // TODO: handle exception
        }
    }

    /**
     * 打印参数
     * 
     * @param request
     */
    private void printParameter(HttpServletRequest request) {
        // TODO Auto-generated method stub

    }

    /**
     * 打印cookie
     * 
     * @param request
     */
    private void printCookie(HttpServletRequest request) {
        // TODO Auto-generated method stub

    }

    /**
     * 打印请求头
     * 
     * @param request
     */
    private void printHender(HttpServletRequest request) {
        // TODO Auto-generated method stub
        
    }

}

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