Switch logger backend to Log4j 2

Nuxeo now uses Log4j 2 as its logging backend instead of Log4j. Two logging APIs are generally available in Nuxeo: Commons Logging Log4j 2 API SLF4J is still available, but Log4j 2 API are preferred by reason of its lambda support. Breaking change Log4jHelper.setQuiet and Log4jHelper.setDebug was removed due to its usage of Log4j API which are now impossible with Log4j 2. These APIs were replaced by Log4jHelper.setLevel . Compared to previous implementation, setLevel API doesn't change appender's threshold, it just acts on logger's levels. LogCaptureFeature.Filter has also changed without backward compatibility because it exposed a Log4j internal class. This has been replaced by corresponding Log4j 2 internal class. File rollover has changed. Files are now compressed using gzip and pattern has been generalised to NAME-YYYY-MM-dd.log.gz . For instance: server.log.2018-01-01 becomes server-2018-01-01.log.gz Watch log4j file for reload has been removed in favor of built-in logic in Log4j2. These properties are no longer read: org.nuxeo.runtime.log4jwatch.disabled org.nuxeo.runtime.log4jwatch.delay See Automatic Reconfiguration in Log4j 2 documentation to have watch file behavior. Code behavior change LogCaptureFeature behavior has changed. Now log Result is cleaned between each tests. You'll have an isolated result to assert for @Before / @After /test methods. You may need to add the slf4j dependency if you were using it in your source code: <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> </dependency> New LogCaptureFeature.FilterOn now accepts a logger class instead of a logger name You can now use Log4j 2 API in your code