一、入门log4j实例
    1.1 下载解压log4j.jar（地址：http://mirrors.hust.edu.cn/apache/logging/log4j/2.11.0/）
    log4j - 图1
    1.2 新建工程，导入jar包
    log4j - 图2

    1. package test6;
    3. import org.apache.log4j.Logger;
    4. /**
    5.  * @author mmb
    6.  * @function test log4j
    7.  * */
    8. public class Log4jTest {
    10.     private static Logger logger = Logger.getLogger(Log4jTest.class);  
    12.     public static void main(String [] args){
    14.         //BasicConfigurator.configure(); //自动快速地使用缺省Log4j环境。
    16.         logger.info("aaaa");
    18.         logger.debug("bbbb");
    20.         logger.error("cccc");
    22.     }
    23. }

    log4j.properties 文件

    1. ### log4j.properties 文件
    3. ### 设置###
    4. log4j.rootLogger = debug,stdout,D,E
    6. ### 输出信息到控制抬 ###
    7. log4j.appender.stdout = org.apache.log4j.ConsoleAppender
    8. log4j.appender.stdout.Target = System.out
    9. log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
    10. log4j.appender.stdout.layout.ConversionPattern = [%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS} method:%l%n%m%n
    12. ### 输出DEBUG 级别以上的日志到=E://logs/error.log ###
    13. log4j.appender.D = org.apache.log4j.DailyRollingFileAppender
    14. log4j.appender.D.File = E://logs/log.log
    15. log4j.appender.D.Append = true
    16. log4j.appender.D.Threshold = DEBUG 
    17. log4j.appender.D.layout = org.apache.log4j.PatternLayout
    18. log4j.appender.D.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss}  [ %t:%r ] - [ %p ]  %m%n
    20. ### 输出ERROR 级别以上的日志到=E://logs/error.log ###
    21. log4j.appender.E = org.apache.log4j.DailyRollingFileAppender
    22. log4j.appender.E.File =E://logs/error.log 
    23. log4j.appender.E.Append = true
    24. log4j.appender.E.Threshold = ERROR 
    25. log4j.appender.E.layout = org.apache.log4j.PatternLayout
    26. log4j.appender.E.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss}  [ %t:%r ] - [ %p ]  %m%n

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