1､SLF4J引用

1) 手动引用

下载地址：https://github.com/qos-ch/slf4j/releases

2) 使用Maven配置依赖

Maven中pom.xml添加如下：

<dependency> 
  <groupId>org.slf4j</groupId>
  <artifactId>slf4j-jdk14</artifactId>
  <version>1.7.28</version>
</dependency>

2､使用示例代码

1) 简单记录代码

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class HelloWorld {
  public static void main(String[] args) {
    Logger logger = LoggerFactory.getLogger(HelloWorld.class);
    logger.info("Hello World");
  }
}

2) 典型用法代码

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class Wombat {
  final Logger logger = LoggerFactory.getLogger(Wombat.class);
  Integer t;
  Integer oldT;
  public void setTemperature(Integer temperature) {
    oldT = t;        
    t = temperature;
    logger.debug("Temperature set to {}. Old temperature was {}.", t, oldT);
    if(temperature.intValue() > 50) {
      logger.info("Temperature has risen above 50 degrees.");
    }
  }
} 

3) 简洁的API

logger.atInfo().log("Hello world");

等同于：

logger.info("Hello world.");

记录debug日志：

int newT = 15;
int oldT = 16;
// using traditional API
logger.debug("Temperature set to {}. Old temperature was {}.", newT, oldT);
// using fluent API, add arguments one by one and then log message
logger.atDebug().addArgument(newT).addArgument(oldT).log("Temperature set to {}. Old temperature was {}.");
// using fluent API, log message with arguments
logger.atDebug().log("Temperature set to {}. Old temperature was {}.", newT, oldT);
// using fluent API, add one argument and then log message providing one more argument
logger.atDebug().addArgument(newT).log("Temperature set to {}. Old temperature was {}.", oldT);
// using fluent API, add one argument with a Supplier and then log message with one more argument.
// Assume the method t16() returns 16.
logger.atDebug().addArgument(() -> t16()).log(msg, "Temperature set to {}. Old temperature was {}.", oldT);

等价于：

int newT = 15;
int oldT = 16;
// using classical API
logger.debug("oldT={} newT={} Temperature changed.", newT, oldT);
// using fluent API
logger.atDebug().addKeyValue("oldT", oldT).addKeyValue("newT", newT).log("Temperature changed.");   

相关文档：

http://www.slf4j.org/manual.html

https://github.com/qos-ch/slf4j