How to get SLF4J "Hello World" working with log4j?

Following is an example. You can see the details http://jkssweetlife.com/configure-slf4j-working-various-logging-frameworks/ and download the full codes here.

• Add following dependency to your pom if you are using maven, otherwise, just download the jar files and put on your classpath

  <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.7</version>
  </dependency>
  
  <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.7</version>
  </dependency>
  

• Configure log4j.properties

  log4j.rootLogger=TRACE, stdout
  log4j.appender.stdout=org.apache.log4j.ConsoleAppender
  log4j.appender.stdout.Target=System.out
  log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
  log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd'T'HH:mm:ss.SSS} %-5p [%c] - %m%n
  

• Java example

  public class Slf4jExample {
      public static void main(String[] args) {
  
          Logger logger = LoggerFactory.getLogger(Slf4jExample.class);
  
          final String message = "Hello logging!";
          logger.trace(message);
          logger.debug(message);
          logger.info(message);
          logger.warn(message);
          logger.error(message);
      }
  }
  

If you want to use slf4j simple, you need these jar files on your classpath:

• slf4j-api-1.6.1.jar
• slf4j-simple-1.6.1.jar

If you want to use slf4j and log4j, you need these jar files on your classpath:

• slf4j-api-1.6.1.jar
• slf4j-log4j12-1.6.1.jar
• log4j-1.2.16.jar

No more, no less. Using slf4j simple, you'll get basic logging to your console at INFO level or higher. Using log4j, you must configure it accordingly.