JCL learning

The full name is Jakarta Commons Logging, which is a general log API provided by Apache.

It provides a unified interface for "all Java log implementations", and it also provides a log implementation, but the function is very weak (SimpleLog).So it is generally not used alone.He allows developers to use different specific log implementation tools: Log4j, Jdk's own log (JUL)

JCL has two basic abstract classes: Log (the base logger) and LogFactory (responsible for creating Log instances).

1. Getting started with JCL

• Build maven project
• Add dependency

  commons-loggingcommons-logging1.2

• Introduction code

  public class JCLTest {@Testpublic void testQuick() throws Exception {// Get the log logger objectLog log = LogFactory.getLog(JCLTest.class);// output of logginglog.info("hello info");}}

Why do we use the log facade:

1. Interface-oriented development, no longer depends on specific implementation classes.Reduce code coupling
2. The project can flexibly switch the log framework by importing different log implementation classes
3. Unified API, easy for developers to learn and use
4. Unified configuration is convenient for project log management

2, JCL principle

1. Dynamically load the Log implementation class through LogFactory

2. An array of log implementations supported by the log facade

private static final String[] classesToDiscover =new String[]{"org.apache.commons.logging.impl.Log4JLogger","org.apache.commons.logging.impl.Jdk14Logger","org.apache.commons.logging.impl.Jdk13LumberjackLogger","org.apache.commons.logging.impl.SimpleLog"};

3. Get the specific log implementation

for(int i = 0; i < classesToDiscover.length && result == null; ++i) {result = this.createLogFromClass(classesToDiscover[i], logCategory,true);}