1.简介
LogBack是一个日志框架，它与Log4j可以说是同出一源，都出自Ceki Gülcü之手。（log4j的原型是早前由Ceki Gülcü贡献给Apache基金会的）
1.1 LogBack,Slf4j,Log4j之间的关系
Slf4j是The Simple Logging Facade for Java的简称，是一个简单日志门面抽象框架，它本身只提供了日志Facade API和一个简单的日志类实现，一般常配合Log4j，LogBack，java.util.logging使用。Slf4j作为应用层的Log接入时，程序可以根据实际应用场景动态调整底层的日志实现框架(Log4j/LogBack/JdkLog...)；
LogBack和Log4j都是开源日记工具库，LogBack是Log4j的改良版本，比Log4j拥有更多的特性，同时也带来很大性能提升。详细数据可参照下面地址：Reasons to prefer logback over log4j
LogBack官方建议配合Slf4j使用，这样可以灵活地替换底层日志框架。
(note: 为了优化log4j，以及更大性能的提升，Apache基金会已经着手开发了log4j 2.0, 其中也借鉴和吸收了logback的一些先进特性，目前log4j2还处于beta阶段)
1.2 LogBack的结构
LogBack被分为3个组件，logback-core, logback-classic 和 logback-access.
其中logback-core提供了LogBack的核心功能，是另外两个组件的基础。
logback-classic则实现了Slf4j的API，所以当想配合Slf4j使用时，需要将logback-classic加入classpath.
logback-access是为了集成Servlet环境而准备的，可提供HTTP-access的日志接口；
2. Slf4j+Logback的快速实践
2.1 资源准备
现在常用的是将slf4j+Logback进行配套使用，所以需要将slf4j-api.jar, logback-core.jar, log-classic.jar加入classpath.
之后编写logback.xml配置文件，同样该文件要加入classpath中，这样LogBack启动的时候会自动扫描到并加载。
(note: 若LogBack无法检索到相关的配置文件，则会启用默认配置，将日志按照默认格式输出于控制台)
2.2 logback.xml配置
LogBack的配置大概包括3部分，Appender,Logger,Root的配置。
下面通过一个配置文件的示例来快速了解logback的配置：
<?xml version="1.0" encoding="UTF-8"?>
<configuration debug="true" scan="true" scanPeriod="30 seconds">
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<!-- encoders are by default assigned the type
ch.qos.logback.classic.encoder.PatternLayoutEncoder -->
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%level] - %m%n</pattern>
<!-- 常用的Pattern变量,大家可打开该pattern进行输出观察 -->
<!--
<pattern>
%d{yyyy-MM-dd HH:mm:ss} [%level] - %msg%n
Logger: %logger
Class: %class
File: %file
Caller: %caller
Line: %line
Message: %m
Method: %M
Relative: %relative
Thread: %thread
Exception: %ex
xException: %xEx
nopException: %nopex
rException: %rEx
Marker: %marker
%n
</pattern>
-->
</encoder>
</appender>
<!-- 按日期区分的滚动日志 -->
<appender name="ERROR-OUT" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>logs/error.log</file>
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%class:%line] - %m%n</pattern>
</encoder>
<filter class="ch.qos.logback.classic.filter.LevelFilter">
<level>ERROR</level>
<onMatch>ACCEPT</onMatch>
<onMismatch>DENY</onMismatch>
</filter>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!-- daily rollover -->
<fileNamePattern>error.%d{yyyy-MM-dd}.log.zip</fileNamePattern>
<!-- keep 30 days' worth of history -->
<maxHistory>30</maxHistory>
</rollingPolicy>
</appender>
<!-- 按文件大小区分的滚动日志 -->
<appender name="INFO-OUT" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>logs/info.log</file>
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%class:%line] - %m%n</pattern>
</encoder>
<filter class="ch.qos.logback.classic.filter.LevelFilter">
<level>INFO</level>
<onMatch>ACCEPT</onMatch>
<onMismatch>DENY</onMismatch>
</filter>
<rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
<fileNamePattern>info.%i.log</fileNamePattern>
<minIndex>1</minIndex>
<maxIndex>3</maxIndex>
</rollingPolicy>
<triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
<maxFileSize>5MB</maxFileSize>
</triggeringPolicy>
</appender>
<!-- 按日期和大小区分的滚动日志 -->
<appender name="DEBUG-OUT" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>logs/debug.log</file>
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%class:%line] - %m%n</pattern>
</encoder>
<filter class="ch.qos.logback.classic.filter.LevelFilter">
<level>DEBUG</level>
<onMatch>ACCEPT</onMatch>
<onMismatch>DENY</onMismatch>
</filter>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!-- rollover daily -->
<fileNamePattern>debug-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
<timeBasedFileNamingAndTriggeringPolicy
class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
<!-- or whenever the file size reaches 100MB -->
<maxFileSize>100MB</maxFileSize>
</timeBasedFileNamingAndTriggeringPolicy>
</rollingPolicy>
</appender>
<!-- 级别阀值过滤 -->
<appender name="SUM-OUT" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>logs/sum.log</file>
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%class:%line] - %m%n</pattern>
</encoder>
<!-- deny all events with a level below INFO, that is TRACE and DEBUG -->
<filter class="ch.qos.logback.classic.filter.ThresholdFilter">
<level>INFO</level>
</filter>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!-- rollover daily -->
<fileNamePattern>debug-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
<timeBasedFileNamingAndTriggeringPolicy
class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
<!-- or whenever the file size reaches 100MB -->
<maxFileSize>100MB</maxFileSize>
</timeBasedFileNamingAndTriggeringPolicy>
</rollingPolicy>
</appender>
<root level="debug">
<appender-ref ref="STDOUT" />
<appender-ref ref="ERROR-OUT" />
<appender-ref ref="INFO-OUT" />
<appender-ref ref="DEBUG-OUT" />
<appender-ref ref="SUM-OUT" />
</root>
</configuration>
另一个更简单的：
<?xml version="1.0" encoding="UTF-8"?>
<configuration debug="true" scan="false" scanPeriod="30 seconds">
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<!-- encoders are by default assigned the type
ch.qos.logback.classic.encoder.PatternLayoutEncoder -->
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%level] - %m%n</pattern>
</encoder>
</appender>
<!-- 按日期区分的滚动日志 -->
<appender name="APP" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>logs/app.log</file>
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%class:%line] - %m%n</pattern>
</encoder>
<filter class="ch.qos.logback.classic.filter.ThresholdFilter">
<level>INFO</level>
</filter>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!-- daily rollover -->
<fileNamePattern>app.%d{yyyy-MM-dd}.log</fileNamePattern>
<!-- keep 30 days' worth of history -->
<maxHistory>30</maxHistory>
</rollingPolicy>
</appender>
<!-- 按日期和大小区分的滚动日志 -->
<appender name="DEBUG-OUT" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>logs/debug.log</file>
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%class:%line] - %m%n</pattern>
</encoder>
<filter class="ch.qos.logback.classic.filter.LevelFilter">
<level>DEBUG</level>
<onMatch>ACCEPT</onMatch>
<onMismatch>DENY</onMismatch>
</filter>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!-- rollover daily -->
<fileNamePattern>debug-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
<timeBasedFileNamingAndTriggeringPolicy
class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
<!-- or whenever the file size reaches 100MB -->
<maxFileSize>30MB</maxFileSize>
</timeBasedFileNamingAndTriggeringPolicy>
</rollingPolicy>
</appender>
<root level="debug">
<appender-ref ref="STDOUT" />
<appender-ref ref="APP" />
<appender-ref ref="DEBUG-OUT" />
</root>
</configuration>
2.3 示例
public class Slf4jTest {
private static Logger Log = LoggerFactory.getLogger(Slf4jTest.class);
@Test
public void testLogBack(){
Log.debug("Test the MessageFormat for {} to {} endTo {}", 1,2,3);
Log.info("Test the MessageFormat for {} to {} endTo {}", 1,2,3);
Log.error("Test the MessageFormat for {} to {} endTo {}", 1,2,3);
try{
throw new IllegalStateException("try to throw an Exception");
}catch(Exception e){
Log.error(e.getMessage(),e);
}
}
}
输出：
2013-12-30 21:37:18 [DEBUG] - Test the MessageFormat for 1 to 2 endTo 3
2013-12-30 21:37:18 [INFO] - Test the MessageFormat for 1 to 2 endTo 3
2013-12-30 21:37:18 [ERROR] - Test the MessageFormat for 1 to 2 endTo 3
2013-12-30 21:37:18 [ERROR] - try to throw an Exception
java.lang.IllegalStateException: try to throw an Exception
at logs.Slf4jTest.testLogBack(Slf4jTest.java:19) ~[bin/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.6.0_18]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) ~[na:1.6.0_18]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) ~[na:1.6.0_18]
at java.lang.reflect.Method.invoke(Method.java:597) ~[na:1.6.0_18]
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47) [junit.jar:na]
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) [junit.jar:na]
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44) [junit.jar:na]
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) [junit.jar:na]
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271) [junit.jar:na]
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70) [junit.jar:na]
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) [junit.jar:na]
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238) [junit.jar:na]
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63) [junit.jar:na]
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236) [junit.jar:na]
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53) [junit.jar:na]
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229) [junit.jar:na]
at org.junit.runners.ParentRunner.run(ParentRunner.java:309) [junit.jar:na]
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197) [.cp/:na]
简易教程基本到这里就差不多了，希望大家都能很快上手。
附带上示例中所用到的类库：slf4j+logback运行类库下载
想了解更多的信息，可访问下面地址：