Commons-logging.jar:
One of the Apache Commons package contains log capabilities, and the JAR package that must be used. This package itself contains a Simple Logger, but the function is weak. When you run, it will look at the log4j in ClassPath. If there is, use log4j, if not, find java.util.logging with JDK1.4, if you can't find Simple Logger. Commons-logging.jar's appearance is a regret of a history. At the beginning, Apache strongly lobbyed SUN to join the log4j to JDK1.4, however JDK1.4 project team has been close to the time of the release JDK1.4 product, so rejection Apache Requirements, using their own java.util.logging, this package is far from log4j, and performance is also general. Later, Apache was developed comMMons-logging.jar used to compatible with two loggers. So use the log program written by Commons-Logging.jar, the bottom layer Logger can be switched, you can choose Log4j, java.util.logging, or the Simple Logger itself. However, I still recommend the use of log4j because log4j performance is high, and the log output time is almost equal to System.out, and a LOG is handled only 5us. You can find Hibernate's Log4j configured for you in Hibernate's SRC directory, you only need to go to the Apache website to download log4j. Commons-logging.jar is also a must-have JAR package.
