Http Servlet 请求在读取一次后从 POST 正文中丢失参数

顺便说一句，解决此问题的另一种方法是不使用筛选器链，而是构建自己的拦截器组件，也许使用可以对解析的请求正文进行操作的方面。它也可能更有效，因为您只需将请求转换为您自己的模型对象一次。InputStream

但是，我仍然认为希望多次读取请求正文是合理的，尤其是在请求在筛选器链中移动时。我通常会将筛选器链用于某些操作，这些操作希望保留在 HTTP 层，与服务组件分离。

正如Will Hartung所建议的，我通过扩展，消耗请求和基本上缓存字节来实现这一点。HttpServletRequestWrapperInputStream

public class MultiReadHttpServletRequest extends HttpServletRequestWrapper {
  private ByteArrayOutputStream cachedBytes;

  public MultiReadHttpServletRequest(HttpServletRequest request) {
    super(request);
  }

  @Override
  public ServletInputStream getInputStream() throws IOException {
    if (cachedBytes == null)
      cacheInputStream();

      return new CachedServletInputStream();
  }
    
  @Override
  public BufferedReader getReader() throws IOException{
    return new BufferedReader(new InputStreamReader(getInputStream()));
  }

  private void cacheInputStream() throws IOException {
    /* Cache the inputstream in order to read it multiple times. For
     * convenience, I use apache.commons IOUtils
     */
    cachedBytes = new ByteArrayOutputStream();
    IOUtils.copy(super.getInputStream(), cachedBytes);
  }

 
  /* An input stream which reads the cached request body */
  private static class CachedServletInputStream extends     ServletInputStream {

    private final ByteArrayInputStream buffer;

    public CachedServletInputStream(byte[] contents) {
      this.buffer = new ByteArrayInputStream(contents);
    }

    @Override
    public int read() {
      return buffer.read();
    }

    @Override
    public boolean isFinished() {
      return buffer.available() == 0;
    }

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

    @Override
    public void setReadListener(ReadListener listener) {
  throw new RuntimeException("Not implemented");
    }
  }
}

现在，通过在通过筛选器链传递原始请求之前包装原始请求，可以多次读取请求正文：

public class MyFilter implements Filter {
  @Override
  public void doFilter(ServletRequest request, ServletResponse response,
        FilterChain chain) throws IOException, ServletException {

    /* wrap the request in order to read the inputstream multiple times */
    MultiReadHttpServletRequest multiReadRequest = new MultiReadHttpServletRequest((HttpServletRequest) request);

    /* here I read the inputstream and do my thing with it; when I pass the
     * wrapped request through the filter chain, the rest of the filters, and
     * request handlers may read the cached inputstream
     */
    doMyThing(multiReadRequest.getInputStream());
    //OR
    anotherUsage(multiReadRequest.getReader());
    chain.doFilter(multiReadRequest, response);
  }
}

此解决方案还允许您通过这些方法多次读取请求正文，因为底层调用是 ，这当然会读取缓存的请求 。getParameterXXXgetInputStream()InputStream

编辑

对于较新版本的界面。您需要提供更多方法的实现，例如 等。请按照下面评论中提供的内容来参考此问题。ServletInputStreamisReadysetReadListener

我知道我迟到了，但这个问题仍然与我有关，这篇SO帖子是Google中最受欢迎的文章之一。我将继续发布我的解决方案，希望其他人可以节省几个小时。

在我的情况下，我需要用他们的身体记录所有请求和响应。使用Spring Framework，答案实际上非常简单，只需使用ContentCachingRequestWrapper和ContentCachingResponseWrapper。

import org.springframework.web.util.ContentCachingRequestWrapper;
import org.springframework.web.util.ContentCachingResponseWrapper;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class LoggingFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void destroy() {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {

        ContentCachingRequestWrapper requestWrapper = new ContentCachingRequestWrapper((HttpServletRequest) request);
        ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper((HttpServletResponse) response);

        try {
            chain.doFilter(requestWrapper, responseWrapper);
        } finally {

            String requestBody = new String(requestWrapper.getContentAsByteArray());
            String responseBody = new String(responseWrapper.getContentAsByteArray());
            // Do not forget this line after reading response content or actual response will be empty!
            responseWrapper.copyBodyToResponse();

            // Write request and response body, headers, timestamps etc. to log files

        }

    }

}