image.png

JCL入门

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<dependency>
	<groupId>commons-logging</groupId>
	<artifactId>commons-logging</artifactId>
	<version>1.2</version>
</dependency>

默认使用JUL作为日志底层实现，当导入log4j的包的时候自动进行转换。

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@Test
public void testQuick(){
	Log log = LogFactory.getLog(JCLTest.class);
	BasicConfigurator.configure();
	log.fatal("s");
	log.error("error");
	log.warn("warning");
	log.info("info");
	log.debug("debug");
	log.trace("trace");
}

JCL原理

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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"
};

流程如下：
org.apache.commons.logging.LogFactory#getLog(java.lang.Class)
org.apache.commons.logging.impl.LogFactoryImpl#getInstance(java.lang.String)
org.apache.commons.logging.impl.LogFactoryImpl#newInstance
org.apache.commons.logging.impl.LogFactoryImpl#discoverLogImplementation

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