一. 為什么要用?

為啥用@Log ，簡(jiǎn)化代碼。是代碼更簡(jiǎn)潔。

二. 如何使用？

@CommonsLog
Creates private static final org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog(LogExample.class);
@Flogger
Creates private static final com.google.common.flogger.FluentLogger log = com.google.common.flogger.FluentLogger.forEnclosingClass();
@JBossLog
Creates private static final org.jboss.logging.Logger log = org.jboss.logging.Logger.getLogger(LogExample.class);
@Log
Creates private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(LogExample.class.getName());
@Log4j
Creates private static final org.apache.log4j.Logger log = org.apache.log4j.Logger.getLogger(LogExample.class);
@Log4j2
Creates private static final org.apache.logging.log4j.Logger log = org.apache.logging.log4j.LogManager.getLogger(LogExample.class);
@Slf4j
Creates private static final org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(LogExample.class);
@XSlf4j
Creates private static final org.slf4j.ext.XLogger log = org.slf4j.ext.XLoggerFactory.getXLogger(LogExample.class);
@CustomLog
Creates private static final com.foo.your.Logger log = com.foo.your.LoggerFactory.createYourLogger(LogExample.class);class Test {

import lombok.extern.java.Log;
import lombok.extern.slf4j.Slf4j;
@Log
public class LogExample {
    public static void main(String... args) {
        log.severe("Something's wrong here");
    }
}
@Slf4j
public class LogExampleOther {
    public static void main(String... args) {
        log.error("Something else is wrong here");
    }
}
@CommonsLog(topic="CounterLog")
public class LogExampleCategory {
    public static void main(String... args) {
        log.error("Calling the 'CounterLog' with a message");
    }
}

反編譯后的代碼如下： 發(fā)現(xiàn)了沒，和單例懶漢模型，雙檢查鎖機(jī)制是不是很像啊

public class LogExample {
  private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(LogExample.class.getName());
  public static void main(String... args) {
    log.severe("Something's wrong here");
  }
}

public class LogExampleOther {
  private static final org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(LogExampleOther.class);
  
  public static void main(String... args) {
    log.error("Something else is wrong here");
  }
}

public class LogExampleCategory {
  private static final org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog("CounterLog");

  public static void main(String... args) {
    log.error("Calling the 'CounterLog' with a message");
  }
}

三. 源碼

@Retention(RetentionPolicy.SOURCE)
@Target({ElementType.TYPE})
public @interface Log {
    String topic() default "";
}

四. 特別說明

本文已經(jīng)收錄在Lombok注解系列文章總覽中，并繼承上文中所提的特別說明