Log4j info和error输出到不同文件

傷城~ 2021-06-24 14:37 519阅读 0赞

### Threshold ###

log4j提供了Appender的Threshold属性，可以设置该appender输出什么级别的日志。看一个例子：

log4j.rootLogger=info,stdout,infolog,warnlog,errorlog
    
    log4j.appender.stdout=org.apache.log4j.ConsoleAppender
    log4j.appender.stdout.Target=System.out
    log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
    log4j.appender.stdout.layout.ConversionPattern=[%d{MM-dd HH:mm:ss}] [%p] [%c:%L] %m%n
    
    log4j.appender.infolog = org.apache.log4j.DailyRollingFileAppender
    log4j.appender.infolog.Threshold = INFO
    log4j.appender.infolog.File = /data/logs/logtest/test.log
    log4j.appender.infolog.layout = org.apache.log4j.PatternLayout
    log4j.appender.infolog.layout.ConversionPattern = [%d{MM-dd HH:mm:ss}] [%p] [%c:%L] %m%n
    
    log4j.appender.warnlog = org.apache.log4j.DailyRollingFileAppender
    log4j.appender.warnlog.Threshold = WARN
    log4j.appender.warnlog.File = /data/logs/logtest/test_warn.log
    log4j.appender.warnlog.layout = org.apache.log4j.PatternLayout
    log4j.appender.warnlog.layout.ConversionPattern = [%d{MM-dd HH:mm:ss}] [%p] [%c:%L] %m%n
    
    log4j.appender.errorlog = org.apache.log4j.DailyRollingFileAppender
    log4j.appender.errorlog.Threshold = ERROR
    log4j.appender.errorlog.File = /data/logs/logtest/test_error.log
    log4j.appender.errorlog.layout = org.apache.log4j.PatternLayout
    log4j.appender.errorlog.layout.ConversionPattern = [%d{MM-dd HH:mm:ss}] [%p] [%c:%L] %m%n

经过测试发现，在test.log文件中同时输出了info、warn和error级别的日志，test\_warn.log中也同时输出了warn、error级别的日志。原因是因为：log4j.appender.D.Threshold 表示打印大于、等于该级别的日志，由于ALL < DEBUG < INFO < WARN < ERROR < FATAL < OFF，所以warn、error级别日志在info中也打印了出来。

上面的结果显然不是我们想要的，因为这样的话相当于info日志中含有所有的日志信息，不但造成冗余，而且也会让warn日志跟error日志显得没有存在的必要。更多的情况下我们希望info日志中只有INFO级别的日志，warn日志中只有WARN级别的日志，同样error日志中也只有ERROR级别的日志。

### 解决方案 ###

**1、log4j的filter：**

log4j.rootLogger=info,stdout,infolog,warnlog,errorlog
    
    log4j.appender.stdout=org.apache.log4j.ConsoleAppender
    log4j.appender.stdout.Target=System.out
    log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
    log4j.appender.stdout.layout.ConversionPattern=[%d{MM-dd HH:mm:ss}] [%p] [%c:%L] %m%n
    
    log4j.appender.infolog = org.apache.log4j.DailyRollingFileAppender
    log4j.appender.infolog.Threshold = INFO
    log4j.appender.infolog.File = /data/logs/logtest/test.log
    log4j.appender.infolog.layout = org.apache.log4j.PatternLayout
    log4j.appender.infolog.layout.ConversionPattern = [%d{MM-dd HH:mm:ss}] [%p] [%c:%L] %m%n
    log4j.appender.infolog.filter.infoFilter = org.apache.log4j.varia.LevelRangeFilter
    log4j.appender.infolog.filter.infoFilter.LevelMin = INFO
    log4j.appender.infolog.filter.infoFilter.LevelMax = INFO
    
    log4j.appender.warnlog = org.apache.log4j.DailyRollingFileAppender
    log4j.appender.warnlog.Threshold = WARN
    log4j.appender.warnlog.File = /data/logs/logtest/test_warn.log
    log4j.appender.warnlog.layout = org.apache.log4j.PatternLayout
    log4j.appender.warnlog.layout.ConversionPattern = [%d{MM-dd HH:mm:ss}] [%p] [%c:%L] %m%n
    log4j.appender.warnlog.filter.warnFilter = org.apache.log4j.varia.LevelRangeFilter
    log4j.appender.warnlog.filter.warnFilter.LevelMin = WARN
    log4j.appender.warnlog.filter.warnFilter.LevelMax=WARN
    
    log4j.appender.errorlog = org.apache.log4j.DailyRollingFileAppender
    log4j.appender.errorlog.Threshold = ERROR
    log4j.appender.errorlog.File = /data/logs/logtest/test_error.log
    log4j.appender.errorlog.layout = org.apache.log4j.PatternLayout
    log4j.appender.errorlog.layout.ConversionPattern = [%d{MM-dd HH:mm:ss}] [%p] [%c:%L] %m%n

经测试，上面的配置可以实现：info级别的日志只在test.log中打印；error级别的只打印在test\_error.log中，warn级别的打印在test\_warn.log中。

**2、重写RollingFileAppender类中的isAsSevereAsThreshold方法：**

这种方式在网上看到的，这里记录下。默认的isAsSevereAsThreshold方法的实现为：

public  boolean isAsSevereAsThreshold(Priority priority) {
        return this.threshold == null  || priority.isGreaterOrEqual(this.threshold);
    }

如果没有设置threshold属性则全部打印，否则打印大于等于threshold属性的日志。我们继承该类并重写此方法，如下：

public class MyLog4jAppender extends RollingFileAppender {
        @Override
        public  boolean isAsSevereAsThreshold(Priority priority) {
            return  priority != null && this.threshold == null  && priority.isGreaterOrEqual(this.threshold) && this.getThreshold().isGreaterOrEqual(priority);
        }
    }

接下来在log4j.properties文件中修改log4j.appender.info=com.xxx.MyLog4jAppender即可。

参考：[https://segmentfault.com/a/1190000011702524][https_segmentfault.com_a_1190000011702524]

[https_segmentfault.com_a_1190000011702524]: https://segmentfault.com/a/1190000011702524