Logback Set log file name programmatically
By：Roy.LiuLast updated：2019-08-17
In Logback, it is easy to set a log file name programmatically :
- In logback.xml, declares a variable like ${log.name}
- In Java, set the variable via System.setProperty("log.name", "abc")
1. Full example
1.1 A logback file, we will set the ${log.name} variable later.
src/main/resources/logback.xml
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<property name="PRO_HOME" value="/home/mkyong/ant/logs" />
<property name="USER_HOME" value="${PRO_HOME}" />
<timestamp key="bySecond" datePattern="yyyyMMdd.HHmmss" />
<appender name="FILE-ENGINE-ERROR" class="ch.qos.logback.core.FileAppender">
<file>${USER_HOME}/${log.name}.error</file>
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<appender name="FILE-ENGINE" class="ch.qos.logback.core.FileAppender">
<file>${USER_HOME}/${log.name}-${bySecond}.log</file>
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{35} - %msg%n</pattern>
</encoder>
</appender>
<logger name="com.mkyong.core" level="debug" additivity="false">
<appender-ref ref="FILE-ENGINE" />
</logger>
<logger name="org.springframework" level="error" additivity="false">
<appender-ref ref="FILE-ENGINE-ERROR" />
</logger>
<root level="error">
<appender-ref ref="FILE-ENGINE-ERROR" />
</root>
</configuration>
1.2 In Java, just set the file name via System.setProperty
AntRunApp.java
package com.mkyong.core;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class AntRunApp {
private final Logger logger = LoggerFactory.getLogger(AntRunApp.class);
public static void main(String[] args) {
//Set this before the logger start.
System.setProperty("log.name", "mkyong");
AntRunApp obj = new AntRunApp();
obj.start();
private void start() {
logger.debug("------ Starting Ant------");
//...
Output
Debug log file path /home/mkyong/ant/logs/mkyong-20150323.221959.log Error log file path /home/mkyong/ant/logs/mkyong.error
2. log.name.rir_IS_UNDEFINED.log
2.1 A common error, normally it is caused by the static logger. For example.
AntRunApp.java
package com.mkyong.core;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class AntRunApp {
// static, this logger will be initialized before the program is run.
// All logs will be redirected to log.name.rir_IS_UNDEFINED.log
private static final Logger logger = LoggerFactory.getLogger(AntRunApp.class);
private void start() {
System.setProperty("log.name", "mkyong");
logger.debug("------ Starting Ant------");
//...
To fix it, just delete the static type.
2.2 If you logs before the System.setProperty, this will also cause the common Logback variable UNDEFINED error.
AntRunApp.java
package com.mkyong.core;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class AntRunApp {
private final Logger logger = LoggerFactory.getLogger(AntRunApp.class);
private void start() {
//Please set the log name first!
logger.debug("------ Starting Ant------");
System.setProperty("log.name", "mkyong");
References
From：一号门
Previous:Gradle and JUnit example
COMMENTS