java开发过程当中为了找问题方便或是统计信息方便,总免不了要打各类日志。以前的各个项目都是配置好的,maven配置的时候,会看到各类类型的Log包:slf4j、log4j、commons-log、logback等等,看着就烦,今天仔细了解了一下,有点收获,记录一下html
原由java
使用JAVA的kafka api写main方法进行开发测试,发现总报错apache
1api 2app 3maven |
log4j:WARN No appenders could be found for logger (kafka.utils.VerifiableProperties).性能 log4j:WARN Please initialize the log4j system properly.测试 log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.spa |
解决过程scala
第一直觉是缺乏log4j的配置。好办,classpath下加入log4j.properties(log4j默认应该是直接找classpath下的这个文件,固然,能够直接指定加载哪一个文件),OK,不报错了
恰好最近的一个项目使用的是logback,并且网上也查了,logback性能要优于log4j(没有作过测试,先盲目从众吧),就想直接引入logback。
POM中加入logback的依赖
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<dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-core</artifactId> <version>1.1.2</version> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-access</artifactId> <version>1.1.2</version> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> <version>1.1.2</version> </dependency> |
启动,报错
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log4j:WARN No appenders could be found for logger (kafka.utils.VerifiableProperties). log4j:WARN Please initialize the log4j system properly. log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info. SLF4J: Class path contains multiple SLF4J bindings. SLF4J: Found binding in [jar:file:/C:/Users/zhaohuayu/.m2/repository/org/slf4j/slf4j-log4j12/1.6.1/slf4j-log4j12-1.6.1.jar!/org/slf4j/impl/StaticLoggerBinder.class] SLF4J: Found binding in [jar:file:/C:/Users/zhaohuayu/.m2/repository/ch/qos/logback/logback-classic/1.1.2/logback-classic-1.1.2.jar!/org/slf4j/impl/StaticLoggerBinder.class] SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation. SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory] |
哦,Class path contains multiple SLF4J bindings。
原来slf4j提供的是一个抽象的接口,实现能够是log4j、logback等,可是,运行时候只能有一个接口实现类。以前引入的kafka包,已经包含了对log4j的依赖,我又引入logback的包,冲突了
好办,去掉对Log4j的依赖
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<dependency> <groupId>org.apache.kafka</groupId> <artifactId>kafka_2.10</artifactId> <version>0.8.2.0</version> <exclusions> <exclusion> <groupId>log4j</groupId> <artifactId>log4j</artifactId> </exclusion> <exclusion> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-core</artifactId> <version>1.1.2</version> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-access</artifactId> <version>1.1.2</version> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> <version>1.1.2</version> </dependency> |
这下总OK了吧,运行:
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Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/log4j/Logger at kafka.utils.Logging$class.logger(Logging.scala:24) at kafka.utils.VerifiableProperties.logger$lzycompute(VerifiableProperties.scala:26) at kafka.utils.VerifiableProperties.logger(VerifiableProperties.scala:26) at kafka.utils.Logging$class.info(Logging.scala:67) at kafka.utils.VerifiableProperties.info(VerifiableProperties.scala:26) at kafka.utils.VerifiableProperties.verify(VerifiableProperties.scala:217) at kafka.producer.ProducerConfig.<init>(ProducerConfig.scala:57) at KafkaProducer.getClient(KafkaProducer.java:26) at KafkaProducer.sendMsg(KafkaProducer.java:35) at KafkaProducer.main(KafkaProducer.java:41) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140) |
what?
kafka.utils.Logging里包含了对log4j类的引用……
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package kafka.utils;
import kafka.utils.Log4jController.; import org.apache.log4j.Logger; |
怎么办?难道使用kafka的项目必须使用log4j?
总有解决方案,
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<dependency> <groupId>org.slf4j</groupId> <artifactId>log4j-over-slf4j</artifactId> <version>1.7.7</version> </dependency> |
再次运行,OK,日志正常打印了
总结
1、slf4j提供各类抽象接口,日志应该基于slf4j的API进行日志打印,这样不管迁移到那个项目,只须要配一个实现类log4j or logback,都能正常打印日志
2、slf4j的实现类不能有多个,否则冲突
3、若是项目中有直接引用log4j的,能够加入log4j-over-slf4j,把旧的日志log4j适配到slf4j,这时候,再使用logback就能够了。
分享一个博客中解决各个项目模块中,各类日志杂乱的方案
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<dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>${org.slf4j-version}</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>jcl-over-slf4j</artifactId> <version>${org.slf4j-version}</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>log4j-over-slf4j</artifactId> <version>${org.slf4j-version}</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>jul-to-slf4j</artifactId> <version>${org.slf4j-version}</version> </dependency> <dependency> <groupId>org.jboss.logging</groupId> <artifactId>jboss-logging</artifactId> <version>3.1.4.GA</version> </dependency> |
固然,前提是须要把各个项目中依赖的log实现exclusion掉