Logging HttpRequest parameters and request body

Question

I am trying to create a request log for my web app. I am using Spring 3. 0.

I implemented a class extending HandlerInterceptorAdapter and used the preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) to intercept the request.

In the method i want to be able to log the request body (my parameters are objects in XML that are written directly to the request body), and for that i use request.getReader();

The problem is - later on I will get an IllegalStateException when the spring controller tries to read the request.

Is there a way to do what I intend?

Answer 1

Simple implementation for small requests. Don't use it for multipart request.

package ru.rbs.logger.web;

import org.apache.commons.io.IOUtils;

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

class CachedRequestWrapper extends HttpServletRequestWrapper {
    private final byte[] cachedBody;

    CachedRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        IOUtils.copy(request.getInputStream(), bos);
        cachedBody = bos.toByteArray();
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        return new CachedServletInputStream();
    }

    byte[] toByteArray(){
        return cachedBody;
    }

    private class CachedServletInputStream extends ServletInputStream {
        private InputStream baseInputStream;

        CachedServletInputStream() throws IOException {
            baseInputStream = new ByteArrayInputStream(cachedBody);
        }

        @Override
        public boolean isFinished() {
            return false;
        }

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

        @Override
        public void setReadListener(ReadListener readListener) {

        }

        @Override
        public int read() throws IOException {
            return baseInputStream.read();
        }
    }
}

Answer 2

You can do this with a filter. The request parameters are easy to handle. However dealing with the request body will be much more difficult and will require wrapping the servlet request see: HttpServletRequest.

You will need to look how big the incoming request is and decide whether you want to store the request body as a tmp file or string.

You will need to override ServetRequest.getInputStream() with your file or saved string that used for logging.

If the request body is huge I recommend putting the input stream into a buffered input stream and then reading the start of the body.

public class LogRequest extends HttpServletRequestWrapper {

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

    @Override
    public ServletInputStream getInputStream() throws IOException {
        //read from tmp file or string.
    }

    @Override
    public BufferedReader getReader() throws IOException {
        //read from tmp file or string
    }

}