HttpServletRequest只能读取一次

第一种方案：继承HttpServletRequestWrapper

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 {
    /* 
     * 为了能多次读取，使用 apache.commons IOUtils 缓存inputstream
     */
    cachedBytes = new ByteArrayOutputStream();
    IOUtils.copy(super.getInputStream(), cachedBytes);
  }

 
  /*  input stream 可以读取缓存的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");
    }
  }
}

使用示例

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

    /* 把request封装进MultiReadHttpServletRequest */
    MultiReadHttpServletRequest multiReadRequest = new MultiReadHttpServletRequest((HttpServletRequest) request);

    /* 
     * 读取inputstream，执行自己的业务代码
     */
    doMyThing(multiReadRequest.getInputStream());
    //可以多次使用
    anotherUsage(multiReadRequest.getReader());
    chain.doFilter(multiReadRequest, response);
  }
}

第二种方案：使用ContentCachingRequestWrapper

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());
            // 使用了 requestBody后，必须执行这一行
            responseWrapper.copyBodyToResponse();

            // 使用了 requestBody执行自己的业务逻辑，例如：写日志

        }

    }

}