1.新建module,slf4j-demo
2.pom.xml添加依赖
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>log-study</artifactId>
<groupId>com.lxcourse</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>sfl4j-demo</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.28</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.28</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
3.编写测试类Slf4jDemo.java
package com.lxcourse.slf4j;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* @author doubledumbao
* Slf4j快速入门
*/
public class Slf4jDemo {
public static final Logger LOGGER = LoggerFactory.getLogger(Slf4jDemo.class);
@Test
public void testQuick(){
LOGGER.error("error");
LOGGER.warn("warn");
LOGGER.info("info");
LOGGER.debug("debug");
LOGGER.trace("trace");
String name = "lxcourse";
String url = "https://www.lxcourse.cn";
LOGGER.info("网站:{},网址:{}",name,url);
try {
int a = 10/0;
} catch (Exception e) {
LOGGER.error("发生异常{}","hello",e);
}
}
}
4.slf4j绑定logback
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>log-study</artifactId>
<groupId>com.lxcourse</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>sfl4j-demo</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.28</version>
</dependency>
<!--
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.28</version>
</dependency>
-->
<!-- logback日志 -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
5.slf4j绑定slf4j-nop
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>log-study</artifactId>
<groupId>com.lxcourse</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>sfl4j-demo</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.28</version>
</dependency>
<!-- slf4j 内置简单日志
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.27</version>
</dependency>
-->
<!-- logback日志
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
-->
<!-- 绑定为NOP,静默丢弃所有日志记录。 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-nop</artifactId>
<version>1.7.28</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
6.slf4j绑定log4j
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>log-study</artifactId>
<groupId>com.lxcourse</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>sfl4j-demo</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.28</version>
</dependency>
<!-- slf4j 内置简单日志
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.27</version>
</dependency>
-->
<!-- logback日志
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
-->
<!-- 绑定为NOP,静默丢弃所有日志记录。
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-nop</artifactId>
<version>1.7.28</version>
</dependency>
-->
<!-- 绑定log4j 1.2版(一种广泛使用的日志记录框架)。您还需要将log4j.jar放在类路径上。 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.28</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
添加log4j.properties
log4j.rootLogger=trace,console
# 指定控制台日志输出的appender
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.conversionPattern = [%-5p] %r %C %M %d{yyyy-MM-dd HH:mm:ss} %m%n
7.slf4j绑定jdk14
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>log-study</artifactId>
<groupId>com.lxcourse</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>sfl4j-demo</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.28</version>
</dependency>
<!-- slf4j 内置简单日志
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.27</version>
</dependency>
-->
<!-- logback日志
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
-->
<!-- 绑定为NOP,静默丢弃所有日志记录。
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-nop</artifactId>
<version>1.7.28</version>
</dependency>
-->
<!-- 绑定log4j 1.2版(一种广泛使用的日志记录框架)。您还需要将log4j.jar放在类路径上。
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.28</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
-->
<!-- 绑定JUL日志 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-jdk14</artifactId>
<version>1.7.28</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
8.使用slf4j的日志绑定流程:
-
添加slf4j-api的依赖
-
使用slf4j的API在项目中进行统一的日志记录
-
绑定具体的日志实现框架
3.1 绑定已经实现了slf4j的日志框架,直接添加对应依赖
3.2 绑定没有实现slf4j的日志框架,先添加日志的适配器,再添加实现类的依赖
-
slf4j有且仅有一个日志实现框架的绑定(如果出现多个默认使用第一个依赖日志实现)
9.slf4j桥接器
比如原来项目中使用的log4j,依赖如下:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>log-study</artifactId>
<groupId>com.lxcourse</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>slf4j-bridge-demo</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
log4j.properties
log4j.rootLogger=trace,console
# 指定控制台日志输出的appender
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.conversionPattern = [%-5p] %r %C %M %d{yyyy-MM-dd HH:mm:ss} %m%n
测试代码:
package com.lxcourse.log4j;
import org.apache.log4j.Logger;
import org.junit.Test;
/**
* @author doubledumbao
*/
public class Log4jDemo {
public static Logger LOGGER = Logger.getLogger(Log4jDemo.class);
@Test
public void testQuick(){
LOGGER.error("error");
LOGGER.warn("warn");
LOGGER.info("info");
LOGGER.debug("debug");
LOGGER.trace("trace");
}
}
现在将日志框架替换为slf4j+logback
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>log-study</artifactId>
<groupId>com.lxcourse</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>slf4j-bridge-demo</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<!-- 注释掉log4j的依赖
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
-->
<!-- slf4j的依赖 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.28</version>
</dependency>
<!-- logback的依赖 -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
<!-- log4j桥接器 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>log4j-over-slf4j</artifactId>
<version>1.7.28</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
注意问题:
-
jcl-over-slf4j.jar和 slf4j-jcl.jar不能同时部署。前一个jar文件将导致JCL将日志系统的选择委托给 SLF4J,后一个jar文件将导致SLF4J将日志系统的选择委托给JCL,从而导致无限循环。
-
log4j-over-slf4j.jar和slf4j-log4j12.jar不能同时出现
-
jul-to-slf4j.jar和slf4j-jdk14.jar不能同时出现
-
所有的桥接都只对Logger日志记录器对象有效,如果程序中调用了内部的配置类或者是Appender,Filter等对象,将无法产生效果。
10.SLF4J原理解析
- SLF4J通过LoggerFactory加载日志具体的实现对象。
- LoggerFactory在初始化的过程中,会通过performInitialization()方法绑定具体的日志实现。
- 在绑定具体实现的时候,通过类加载器,加载org/slf4j/impl/StaticLoggerBinder.class
- 所以,只要是一个日志实现框架,在org.slf4j.impl包中提供一个自己的StaticLoggerBinder类,在其中提供具体日志实现的LoggerFactory就可以被SLF4J所加载