Java日志组件，Apache Log4j 2.0-beta3 发布

Apache Log4j 2 不兼容之前的版本。将你的项目更新至Log4j 2时需要注意地方：

• 需要Java 5
• 简化了XML配置，并且不兼容 Log4j 1.x
• 已经不支持通过property文件进行配置
• 现在可以通过JSON进行配置
• 尽管Log4j 2没有直接兼容 Log4j 1.x，但有提供一个桥接可以减少代码的变化。

The Apache Logging team is pleased to announce the Apache log4j 2.0-beta2 release!    Apache log4j is a well known framework for logging application behavior. Log4j 2 is an upgrade  to   Log4j that provides significant improvements over its predecessor, Log4j 1.x, and provides    many of the improvements available in Logback while fixing some inherent problems in Logback's    architecture.    This is the fourth release of Log4j 2 and is being made available to encourage use and feedback  from the community.    Bug fixes and enhancements    Changes in this version include:    New features:  o LOG4J2-35:  Add interval and modulate options to TimeBasedTriggeringPolicy to allow more  fine-grained control of          when file rolling should occur.   o LOG4J2-58:  Add support for filtering packages from stack traces.   o LOG4J2-84:  If system property "disableThreadContextStack" is set pushes to the ThreadContext  will be ignored. If          system property "disableThreadContext" is set both puts and pushes will be ignored.    o LOG4J2-83:  If system property "disableThreadContextMap" is set puts to the ThreadContext  will be ignored. If          system property "disableThreadContext" is set both puts and pushes will be ignored.    o Add support for ANSI colors by adding the highlight and style pattern converters. Fix pattern          parsing to allow nested patterns.   o Allow the status logging to be directed to stderr or to a file.   o Add getFormats to MultiformatMessage and allow StructuredDataMessage to format as XML.     Fixed Bugs:  o DefaultConfiguration was not starting the Console Appender.   o LOG4J2-92:  Converted DynamicThresholdFilter to use KeyValuePair. Fixed bugs in the Map-based  filters          to allow declaration of multiple values for a key to match the documentation.   o LOG4J2-88:  Many logging methods in AbstractLogger were set to an incorrect logging level.  catching was          using the THROWING marker and was set to debug instead of error.   o LOG4J2-91:  Log4j 1.2 adapter's Category class was missing 3 log methods.   o LOG4J2-84:  If the ThreadContext stack is empty the LogEvent will contain a null value to  reduce the overhead of          creating log events and in the size of the serialized object. Changed the ThreadContext  stack to use          a custom stack interface instead of java.util.Stack as that class is overly heavy.  This change will          cause an API incompatibility.   o LOG4J2-83:  If the ThreadContext map is empty the LogEvent will contain a null value to  reduce the overhead of creating          log events and in the size of the serialized object.   o LOG4J2-90:  Add documentation on client vs server mode to performance page.   o Move variable substitution from PatternLayout to appropriate converters to improve performance.      Changes:  o Made ParameterizedMessage, StringFormattedMessage and ThreadDumpMessage immutable. LocalizedMessage  is          immutable except that it will be updated with the logger name when it is added to  the LogEvent.     Apache Log4j 2.0-beta2 requires a minimum of Java 5 to build and run. Basic compatibility  with  Log4j 1.x is provided through the log4j12-api component, however it does not implement some  of the  very implementation specific classes and methods. The package names and Maven groupId have  been changed to  org.apache.logging.log4j to avoid any conflicts with log4j 1.x.    For complete information on Apache Log4j 2, including instructions on how to submit bug reports,  patches, or suggestions for improvement, see the Apache Apache Log4j 2 website:    http://logging.apache.org/log4j/2.x/