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

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.

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);
    }
}

you need to add 3 dependency ( API+ API implementation + log4j dependency) 
Add also this 
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.5</version>
</dependency>

# And to see log in command line , set log4j.properties 

# Root logger option
log4j.rootLogger=INFO, file, 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 HH:mm:ss} %-5p %c{1}:%L - %m%n

#And to see log in file  , set log4j.properties 
# Direct log messages to a log file
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=./logs/logging.log
log4j.appender.file.MaxFileSize=10MB
log4j.appender.file.MaxBackupIndex=10
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

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

Related

Recent Posts