Calculate amount of input and output traffic

Question

Can someone help with ideas how I can calculate amount of traffic(in/out).

I have app that gets API requests, each request stored in DB for statistic. I need store traffic size for each request and response.

From HttpServletRequest I can get size of request easily but how I can ger response size?

Also ProceedingJoinPoint used.

Answer 1

You can count the bytes written by wrapping the OutputStream used in HttpServletResponse (by wrapping the response as well)

public class CountingFilter implements Filter {

   public void doFilter(...) {
       chain.doFilter(request, new SizeCountingHttpServletResponse(response));
   }

   public static class SizeCountingHttpServletResponse extends HttpServletResponseWrapper {

      ....
      @Override
      public OutputStream getOutputStream() {
          return new CountingOutputStream(super.getOutputStream());
      }
      // same with getWriter()..
   }

   public static class CountingOuputStream extends OutputStream {
       private int size;
       // delegate all methods to the original OutputStream
       // count the number of byte written and store in the 'size' field.
   }

}