SL4J及Logback

1.Commons Logging和log4j

前情提要:
Commons Logging和log4j好基友，一起走。Commons Logging负责充当日志API，log4j负责日志底层实现
搭配起来使用非常便于开发

2.SL4J和Logback

SL4J类似于commons logging，也是日志接口，而logback 类似于log4j，是一个日志的实现

3.为什么要用sl4j + logback的组合

有人对commons logging接口不满意，就高了sl4j
有人对log4j性能不满意，就搞了logback

4.commons Logging代码

int score = 99;
p.setScore(score);
log.info("Set score " + score + " for Person " + p.getName() + " ok.");

问题:拼接字符串是非常麻烦的事

5.sl4j接口写法

int score = 99;
p.setScore(score);
logger.info("Set score {} for Person {} ok.", score, p.getName());

sl4j的日志接口传入的是一个带占位符的字符串，后面变量自动替换占位符，使用非常自然

6.SL4J使用

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

class Main {
    final Logger logger = LoggerFactory.getLogger(getClass());
}

7.引包

slf4j-api-1.7.x.jar
logback-classic-1.2.x.jar
logback-core-1.2.x.jar

8.配置logback配置文件logback.xml放到classpath下

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

	<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
		<encoder>
			<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
		</encoder>
	</appender>

	<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
		<encoder>
			<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
			<charset>utf-8</charset>
		</encoder>
		<file>log/output.log</file>
		<rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
			<fileNamePattern>log/output.log.%i</fileNamePattern>
		</rollingPolicy>
		<triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
			<MaxFileSize>1MB</MaxFileSize>
		</triggeringPolicy>
	</appender>

	<root level="INFO">
		<appender-ref ref="CONSOLE" />
		<appender-ref ref="FILE" />
	</root>
</configuration>