code: public static OperationBuilder withOutputInterceptedBy(final ResponseContentInterceptor... buffers)
              throws IllegalStateException
     {
        return new Response() {
           @Override
           public void performHttp(HttpServletRewrite event, EvaluationContext context)
           {
              for (ResponseContentInterceptor buffer : buffers) {
                 RewriteWrappedResponse.getCurrentInstance(event.getRequest()).addContentInterceptor(buffer);
              }
           }
  
           @Override
           public String toString()
           {
              return "Response.withOutputInterceptedBy(" + Strings.join(Arrays.asList(buffers), ", ") + ")";
           }
        };
     }
docs: Create an {@link Operation} that adds the given {@link ResponseContentInterceptor} instances to the current
  {@link ServletResponse}. This will activate response buffering on the current {@link ServletRequest} - meaning
  that generated output will not be sent to the client until the entire request has completed and all registered
  {@link ResponseContentInterceptor} instances have been executed on the outbound response content.
  
  <p>
  <b>WARNING:</b> This will cause the <b>ENTIRE</b> response to be buffered in memory, which may cause performance
  issues on larger responses. Make sure you you really need to buffer the entire response! Favor using a
  {@link ResponseStreamWrapper} if desired behavior may be performed as a stream operation; this will result in far
  less memory overhead.
  
  @throws IllegalStateException When output has already been written to the client.