The HttpClient introduced experimentally in Java 9 is now stable in Java 11, but not surprisingly, very few projects seem to actually use it. Documentation is almost non-existing.
One of the most commons asks while making a HTTP call is logging of request/response. How would you do that using the HttpClient, without of course, logging it manually in every single call? Is there an interceptor mechanism like that offered by all other HTTP clients?
If we look at jdk.internal.net.http.common.DebugLogger source code we can see a few loggers using System.Logger, which in turn will useSystem.LoggerFinder to select the logger framework. JUL is the default choice. The logger names are:
- jdk.internal.httpclient.debug
- jdk.internal.httpclient.websocket.debug
- jdk.internal.httpclient.hpack.debug
They can be enabled by setting them as a system property. For example running with -Djdk.internal.httpclient.debug=true will produce:
DEBUG: [main] [147ms] HttpClientImpl(1) proxySelector is sun.net.spi.DefaultProxySelector@6dde5c8c (user-supplied=false)
DEBUG: [main] [183ms] HttpClientImpl(1) ClientImpl (async) send https://http2.github.io/ GET
DEBUG: [main] [189ms] Exchange establishing exchange for https://http2.github.io/ GET,
proxy=null
DEBUG: [main] [227ms] PlainHttpConnection(?) Initial receive buffer size is: 43690
DEBUG: [main] [237ms] PlainHttpConnection(SocketTube(1)) registering connect event
DEBUG: [HttpClient-1-SelectorManager] [239ms] SelectorAttachment Registering jdk.internal.net.http.PlainHttpConnection$ConnectEvent@354bf356 for 8 (true)
...