How to enable wire logging for a java HttpURLConnection traffic?

Question

I've used Jakarta commons HttpClient in another project and I would like the same wire logging output but using the "standard" HttpUrlConnection.

I've used Fiddler as a proxy but I would like to log the traffic directly from java.

Capturing what goes by the connection input and output streams is not enough because the HTTP headers are written and consumed by the HttpUrlConnection class, so I will not be able to log the headers.

Answer 1

According to Sun's HttpURLConnection source there is some logging support via JUL.

Setup (adjust path as required):

-Djava.util.logging.config.file=/full/path/to/logging.properties

logging.properties:

handlers= java.util.logging.ConsoleHandler
java.util.logging.ConsoleHandler.level = FINEST
sun.net.www.protocol.http.HttpURLConnection.level=ALL

This will log to the console, adjust as required to e.g. log to a file.

Example output:

2010-08-07 00:00:31 sun.net.www.protocol.http.HttpURLConnection writeRequests
FIN: sun.net.www.MessageHeader@16caf435 pairs: {GET /howto.html HTTP/1.1: null}{User-Agent: Java/1.6.0_20}{Host: www.rgagnon.com}{Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2}{Connection: keep-alive}
2010-08-07 00:00:31 sun.net.www.protocol.http.HttpURLConnection getInputStream
FIN: sun.net.www.MessageHeader@5ac0728 pairs: {null: HTTP/1.1 200 OK}{Date: Sat, 07 Aug 2010 04:00:33 GMT}{Server: Apache}{Accept-Ranges: bytes}{Content-Length: 17912}{Keep-Alive: timeout=5, max=64}{Connection: Keep-Alive}{Content-Type: text/html}

Note that this prints only headers without body.

See http://www.rgagnon.com/javadetails/java-debug-HttpURLConnection-problem.html for details.

There is also system property -Djavax.net.debug=all. But it's mainly useful for SSL debugging.