Short answer: You declare it in your jlink-call by adding logback to the module path and using the --bind-services option. In your module you only define an usage of SLF4j.
Long answer:
I made it work in a simple example with the following parts.
Starting from version 1.8.0 SLF4J is modularized and uses the ServiceLoader mechanism to find its logging backend.
Logback-classic:1.3.0-alpha4 is modularized, too, and declares a service both in META-INF/services/org.slf4j.spi.SLF4JServiceProvider and in its module descriptor:
provides org.slf4j.spi.SLF4JServiceProvider with ch.qos.logback.classic.spi.LogbackServiceProvider;
SLF4J declares in its module descriptor that it needs a SLF4JServiceProvider:
uses org.slf4j.spi.SLF4JServiceProvider
Therefore, in my POM (see below) I only declare a runtime dependency to Logback and my module descriptor only contains a "requires" clause to SLF4J.
My module "com.github.gv2011.j9mod.loguse" contains a main class that logs a statement to a SLF4J-Logger.
Further, it contains a logback.xml configuration file as resource. This file is accessible to Logback because it is a "miscellaneous resource", which is a resource not in a module package (see BuiltinClassLoader source).
Logback must be added explicitely to the runtime image via the jlink "--bind-services" option (because it is a service implementation).
Additionally, Logback and its dependencies must be available on the modulepath (jlink "--module-path" option).
Module descriptor:
module com.github.gv2011.j9mod.loguse {
requires org.slf4j;
}
pom.xml:
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.github.gv2011.j9mod</groupId>
<artifactId>j9mod-log-use</artifactId>
<version>0.0.1-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.8.0-beta4</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.3.0-alpha4</version>
<scope>runtime</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<release>11</release>
</configuration>
</plugin>
</plugins>
</build>
logback.xml:
<configuration>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<!-- "+++" just to make it obvious that this file is used: -->
<pattern>+++ %d{"yyyy-MM-dd'T'HH:mm:ss,SSSXXX", UTC} [%thread] %-5level %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<logger name="com.github.gv2011.j9mod.loguse.Main" level="INFO" />
<root level="WARN">
<appender-ref ref="STDOUT" />
</root>
</configuration>
Main-Class:
package com.github.gv2011.j9mod.loguse;
import static org.slf4j.LoggerFactory.getLogger;
import org.slf4j.Logger;
public class Main {
private static final Logger LOG = getLogger(Main.class);
public static void main(final String[] args) {
LOG.info("Tach.");
}
}
Output (Eclipse - Run As - Java Application):
+++ 2019-05-09T17:43:20,594Z [main] INFO com.github.gv2011.j9mod.loguse.Main - Tach.
jlink:
%JAVA_HOME%\bin\jlink.exe ^
--output target\image ^
--module-path ^
target\classes;^
%M2_REPO%\org\slf4j\slf4j-api\1.8.0-beta4\slf4j-api-1.8.0-beta4.jar;^
%M2_REPO%\ch\qos\logback\logback-classic\1.3.0-alpha4\logback-classic-1.3.0-alpha4.jar;^
%M2_REPO%\ch\qos\logback\logback-core\1.3.0-alpha4\logback-core-1.3.0-alpha4.jar ^
--bind-services ^
--launcher hello=com.github.gv2011.j9mod.loguse/com.github.gv2011.j9mod.loguse.Main ^
--add-modules com.github.gv2011.j9mod.loguse
Output (target/image/bin/hello):
+++ 2019-05-10T11:45:24,844Z [main] INFO com.github.gv2011.j9mod.loguse.Main - Tach.
Tested with openjdk-11.0.2_windows-x64, apache-maven-3.6.0 and eclipse-jee-2019-03-R-win32-x86_64 on Windows 10, 64 Bit.
