1. 按日志级别区分文件输出

有些人习惯按日志信息级别输出到不同名称的文件中，如info.log，error.log，warn.log等，在log4j2中可通过配置Filters来实现。

假定需求是把INFO及以下级别的信息输出到info.log，WARN和ERROR级别的信息输出到error.log，FATAL级别输出到fatal.log，配置文件如下：

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1. <Configuration status="WARN" monitorInterval="300">  
2.     <properties>  
3.         <property name="LOG_HOME">D:/logs</property>  
4.     </properties>  
5.     <Appenders>  
6.         <Console name="Console" target="SYSTEM_OUT">  
7.             <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />  
8.         </Console>  
9.   
10.         <RollingRandomAccessFile name="InfoFile"  
11.             fileName="${LOG_HOME}/info.log"  
12.             filePattern="${LOG_HOME}/$${date:yyyy-MM}/info-%d{yyyy-MM-dd}-%i.log">  
13.             <Filters>  
14.                 <ThresholdFilter level="warn" onMatch="DENY" onMismatch="NEUTRAL" />  
15.                 <ThresholdFilter level="trace" onMatch="ACCEPT" onMismatch="DENY" />  
16.             </Filters>  
17.             <PatternLayout pattern="%date{yyyy-MM-dd HH:mm:ss.SSS} %level [%thread][%file:%line] - %msg%n" />  
18.             <Policies>  
19.                 <TimeBasedTriggeringPolicy />  
20.                 <SizeBasedTriggeringPolicy size="10 MB" />  
21.             </Policies>  
22.             <DefaultRolloverStrategy max="20" />  
23.         </RollingRandomAccessFile>  
24.           
25.         <RollingRandomAccessFile name="ErrorFile"  
26.             fileName="${LOG_HOME}/error.log"  
27.             filePattern="${LOG_HOME}/$${date:yyyy-MM}/error-%d{yyyy-MM-dd}-%i.log">  
28.             <Filters>  
29.                 <ThresholdFilter level="fatal" onMatch="DENY" onMismatch="NEUTRAL" />  
30.                 <ThresholdFilter level="warn" onMatch="ACCEPT" onMismatch="DENY" />  
31.             </Filters>  
32.             <PatternLayout pattern="%date{yyyy-MM-dd HH:mm:ss.SSS} %level [%thread][%file:%line] - %msg%n" />  
33.             <Policies>  
34.                 <TimeBasedTriggeringPolicy />  
35.                 <SizeBasedTriggeringPolicy size="10 MB" />  
36.             </Policies>  
37.             <DefaultRolloverStrategy max="20" />  
38.         </RollingRandomAccessFile>  
39.           
40.         <RollingRandomAccessFile name="FatalFile"  
41.             fileName="${LOG_HOME}/fatal.log"  
42.             filePattern="${LOG_HOME}/$${date:yyyy-MM}/fatal-%d{yyyy-MM-dd}-%i.log">  
43.             <Filters>  
44.                 <ThresholdFilter level="fatal" onMatch="ACCEPT" onMismatch="DENY" />  
45.             </Filters>  
46.             <PatternLayout pattern="%date{yyyy-MM-dd HH:mm:ss.SSS} %level [%thread][%file:%line] - %msg%n" />  
47.             <Policies>  
48.                 <TimeBasedTriggeringPolicy />  
49.                 <SizeBasedTriggeringPolicy size="10 MB" />  
50.             </Policies>  
51.             <DefaultRolloverStrategy max="20" />  
52.         </RollingRandomAccessFile>  
53.     </Appenders>  
54.   
55.     <Loggers>  
56.         <Root level="trace">  
57.             <AppenderRef ref="Console" />  
58.             <AppenderRef ref="InfoFile" />  
59.             <AppenderRef ref="ErrorFile" />  
60.             <AppenderRef ref="FatalFile" />  
61.         </Root>  
62.     </Loggers>  
63. </Configuration>  

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1. public static void main(String[] args) {  
2.     Logger logger = LogManager.getLogger(Client.class);  
3.     logger.trace("trace level");  
4.     logger.debug("debug level");  
5.     logger.info("info level");  
6.     logger.warn("warn level");  
7.     logger.error("error level");  
8.     logger.fatal("fatal level");  
9. }  

2 异步写日志

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1. <Configuration status="WARN" monitorInterval="300">  
2.     <properties>  
3.         <property name="LOG_HOME">D:/logs</property>  
4.         <property name="FILE_NAME">mylog</property>  
5.     </properties>  
6.   
7.     <Appenders>  
8.         <Console name="Console" target="SYSTEM_OUT">  
9.             <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />  
10.         </Console>  
11.         <RollingRandomAccessFile name="MyFile"  
12.             fileName="${LOG_HOME}/${FILE_NAME}.log"  
13.             filePattern="${LOG_HOME}/$${date:yyyy-MM}/${FILE_NAME}-%d{yyyy-MM-dd HH-mm}-%i.log">  
14.             <PatternLayout  
15.                 pattern="%date{yyyy-MM-dd HH:mm:ss.SSS} %level [%thread][%file:%line] - %msg%n" />  
16.             <Policies>  
17.                 <TimeBasedTriggeringPolicy interval="1" />  
18.                 <SizeBasedTriggeringPolicy size="10 MB" />  
19.             </Policies>  
20.             <DefaultRolloverStrategy max="20" />  
21.         </RollingRandomAccessFile>  
22.         <Async name="Async">  
23.             <AppenderRef ref="MyFile" />  
24.         </Async>  
25.     </Appenders>  
26.   
27.     <Loggers>  
28.         <Logger name="asynclog" level="trace" additivity="false" >  
29.             <AppenderRef ref="Async" />  
30.         </Logger>  
31.         <Root level="error">  
32.             <AppenderRef ref="Console" />  
33.         </Root>  
34.     </Loggers>  
35. </Configuration>  

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1. public static void main(String[] args) {  
2.     Logger logger = LogManager.getLogger("asynclog");  
3.     logger.trace("trace level");  
4.     logger.debug("debug level");  
5.     logger.info("info level");  
6.     logger.warn("warn level");  
7.     logger.error("error level");  
8.     logger.fatal("fatal level");  
9. }  

3 输出到MongoDB

添加依赖：

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1. <dependency>  
2.     <groupId>org.apache.logging.log4j</groupId>  
3.     <artifactId>log4j-nosql</artifactId>  
4.     <version>2.5</version>  
5. </dependency>  
6. <dependency>  
7.     <groupId>org.mongodb</groupId>  
8.     <artifactId>mongo-java-driver</artifactId>  
9.     <version>3.2.2</version>  
10. </dependency>  

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1. <Configuration status="WARN" monitorInterval="300">  
2.     <Appenders>  
3.         <Console name="Console" target="SYSTEM_OUT">  
4.             <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />  
5.         </Console>  
6.   
7.         <NoSql name="databaseAppender">  
8.             <MongoDb databaseName="test" collectionName="errorlog"  
9.                 server="localhost" port="27017" />  
10.         </NoSql>  
11.     </Appenders>  
12.   
13.     <Loggers>  
14.         <Logger name="mongolog" level="trace" additivity="false">  
15.             <AppenderRef ref="databaseAppender" />  
16.         </Logger>  
17.         <Root level="error">  
18.             <AppenderRef ref="Console" />  
19.         </Root>  
20.     </Loggers>  
21. </Configuration>  

4 输出到Flume

Flume配置(flume-conf.properties)

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1. agent1.sources=source1   
2. agent1.sinks=sink1   
3. agent1.channels=channel1   
4.   
5. agent1.sources.source1.type=avro  
6. agent1.sources.source1.channels=channel1  
7. agent1.sources.source1.bind=0.0.0.0  
8. agent1.sources.source1.port=41414  
9.   
10. agent1.sinks.sink1.type=file_roll   
11. agent1.sinks.sink1.sink.directory=D:/log  
12. agent1.sinks.sink1.channel=channel1  
13. agent1.sinks.sink1.sink.rollInterval=86400  
14. agent1.sinks.sink1.sink.batchSize=100  
15. agent1.sinks.sink1.sink.serializer=text  
16. agent1.sinks.sink1.sink.serializer.appendNewline = false  
17.   
18. agent1.channels.channel1.type=file   
19. agent1.channels.channel1.checkpointDir=D:/log/checkpoint   
20. agent1.channels.channel1.dataDirs=D:/log/data  

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1. flume-ng.cmd agent --conf ../conf/ --conf-file ../conf/flume-conf.properties -name agent1  

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1. <dependency>  
2.     <groupId>org.apache.logging.log4j</groupId>  
3.     <artifactId>log4j-flume-ng</artifactId>  
4.     <version>2.5</version>  
5. </dependency>  

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1. <Configuration status="WARN" monitorInterval="300">  
2.     <Appenders>  
3.         <Flume name="eventLogger" compress="false">  
4.             <Agent host="127.0.0.1" port="41414" />  
5.             <RFC5424Layout enterpriseNumber="18060" includeMDC="true" appName="MyApp" />  
6.         </Flume>  
7.     </Appenders>  
8.     <Loggers>  
9.         <Root level="trace">  
10.             <AppenderRef ref="eventLogger" />  
11.         </Root>  
12.     </Loggers>  
13. </Configuration>