Log4j 1.x with maven: minimal howto

This post is a minimal howto for log4j version 1.

What a simple task ! but who never search a simple sample on the web send a little stone to me ;)

Feel free to copy paste anyway ;))

What are the dependencies

You will need to add log4j, slf4j and lombok (to use @Slf4j) :

 <properties>
  <!--General project configuration -->
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

  <lombok.version>1.16.6</lombok.version>
  <log4j.version>1.2.17</log4j.version>
  <slf4j.version>1.7.10</slf4j.version>
  <junit.version>4.12</junit.version>
 </properties>
 <dependencyManagement>
  <dependencies>
   <!-- @Slf4j annotation -->
   <dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>${lombok.version}</version>
    <scope>provided</scope>
   </dependency>
   <!-- ## LOGS ## -->
   <dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>${log4j.version}</version>
   </dependency>
   <dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-api</artifactId>
    <version>${slf4j.version}</version>
   </dependency>
   <dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>${slf4j.version}</version>
   </dependency>

How to use it

Simply add "@Slf4j" to your class, and then you could use "log" as logger.

import java.security.InvalidParameterException;

import lombok.extern.slf4j.Slf4j;

@Slf4j
public class MyClass {
    public MyClass() {
        log.debug("constructor YEP");
    }
    
    public void doIt(long value) {
        log.info("doIt {}", value);
        try {
            throw new InvalidParameterException("Zobby");
        } catch (Exception ee) {
            log.error("I'm so stupid: {} => {}", ee.getClass().getSimpleName(), ee.getMessage(), ee);
            log.warn("same without stack trace !: {} => {}", ee.getClass().getSimpleName(), ee.getMessage());
        }
    }
}

How to configure appenders

To configure log4j, add a log4j.properties file to your resources. Start by defining a console appender. This appender should appear in the rootLogger definition too. You could define the following content to start:

log4j.rootLogger=DEBUG, console

## Console appender 
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.threshold=DEBUG
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=%d %5p [%c{1}] %m%n

# package log levels
#
# Log4j bootstrap
#
log4j.logger.org.apache.http = INFO
log4j.logger.com.myapp = DEBUG
#

How to configure file appender

Update your rootLoger to refer to the logfile appender, and add a logfile appender definition:

log4j.rootLogger=DEBUG, console, logfile

## File appender
log4j.appender.logfile=org.apache.log4j.RollingFileAppender
log4j.appender.logfile.threshold=DEBUG
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d{ISO8601} - %-5.5p - %t - %c - %m%n
log4j.appender.logfile.file=MY_CUSTOMFILEHERE.log
log4j.appender.logfile.maxBackupIndex=5
log4j.appender.logfile.maxFileSize=2048KB
log4j.appender.logfile.append=true

How to configure graylog (splunk-like) appender

Update your rootLoger to refer to the graylog appender, and add a gelf appender definition:

### Graylog appender
log4j.appender.graylog2=org.graylog2.log.GelfAppender
log4j.appender.graylog2.graylogHost=tcp:mygraylogserver.net
log4j.appender.graylog2.graylogPort = 12201
#log4j.appender.graylog2.originHost=(default to the local hostname)
log4j.appender.graylog2.facility=gelf-java
log4j.appender.graylog2.layout=org.apache.log4j.PatternLayout
log4j.appender.graylog2.extractStacktrace=true
log4j.appender.graylog2.addExtendedInformation=true
log4j.appender.graylog2.additionalFields={'environment': '${projectEnvironment}', 'application': 'MyPoc','version': '${buildVersion}_${buildTimestamp}'}

How to configure NT event appender

Pre-requisites : add NTEventLogAppender.dll and NTEventLogAppender.amd64.dll to the current directory or to the java ld library path. You could append "-Djava.library.path=PATH" to your application if needed. Get this dll files from log4j zip distribution  ^{doc : https://wiki.apache.org/logging-log4j/NTEventLogAppender}

Update your rootLoger to refer to the ntappender appender, and add a new ntappender definition:

# NTEventLogAppender
log4j.appender.ntappender=org.apache.log4j.nt.NTEventLogAppender
log4j.appender.ntappender.Source=MyKillerApp
log4j.appender.ntappender.layout=org.apache.log4j.PatternLayout
log4j.appender.ntappender.layout.ConversionPattern=%d{ISO8601} - %-5.5p - %t - %c - %m%n

For this last usecase you will be able to see the app logs into Windows Event Log service :