JarCastingThin Jar Launcher
Maven Plugin
The Maven plugin aims to provide a lightweight solution, to build thin jars, which get its dependencies at launch time via a proper locally installed Maven distribution.
The Central Repository integration is in process.
Thin Jar Goal
To build a thin jar, based on the original jar artifact, simply add the following plugin to your distributable jar artifact...
<plugin>
<groupId>org.develrulez.thinjar</groupId>
<artifactId>thin-jar-maven-plugin</artifactId>
<version>a.b.c</version>
<executions>
<execution>
<goals>
<goal>thin-jar</goal>
</goals>
<configuration>
<mainClass>${add_your_main_class_here}</mainClass>
</configuration>
</execution>
</executions>
</plugin>
... and you'll get an additional artifact to your default jar with the suffix -thin.jar.
This thin jar artifact can basically be executed the traditional way:
java -jar *-thin.jar
Before the actual main class is executed, the launcher sets up a lib directory in the jars base directory, where the required application runtime dependencies are getting stored.
Thin Linux Executable Goal
Based on the Coderwall article 'How to make a JAR file Linux executable', this goal uses the ability to append a generic binary payload to a Linux shell script.
<!-- Ommited plugin configuration and mandatory previous thin jar goal execution -->
<execution>
<id>thin-linux-executable</id>
<goals>
<goal>thin-linux-executable</goal>
</goals>
<configuration>
<!--
Optional: Maven artifact, which contains the launch script to use.
A string of the form groupId:artifactId:version[:packaging[:classifier]]
-->
<artifact>org.springframework.boot:spring-boot-loader-tools:${spring-boot.version}</artifact>
<!--
Optional: Relative or absolute launch script path.
-->
<script>org/springframework/boot/loader/tools/launch.script</script>
</configuration>
</execution>
- Resulting artifact: target/*-thin.run
- Configuration management: See documentation
The above execution configuration example demonstrates the usage of a launch script which is used by the spring-boot-maven-plugin, to produce executable jars.
Thin Windows Executable Goal
... via launch4j.
<!-- Ommited plugin configuration and mandatory previous thin jar goal execution -->
<execution>
<id>thin-windows-executable</id>
<goals>
<goal>thin-windows-executable</goal>
</goals>
</execution>
- Resulting artifact: target/*-thin.exe
- Configuration management: See documentation
Known 'inconsistencies'
Spring Boot Developer Tools
When the artifact spring-boot-devtools is a part of your project dependencies without any further configuration, following error may occur after launching the thin jar:
2017-10-20 18:35:09.438 INFO 4088 --- [ restartedMain] com.example.ExampleApplication : Started ExampleApplication in 1.931 seconds (JVM running for 8.351)
Exception in thread "main" java.lang.IllegalStateException: Unable to execute starter class 'com.example.ExampleApplication'.
at org.develrulez.thinjar.Launcher.launch(Launcher.java:41)
at org.develrulez.thinjar.Launcher.main(Launcher.java:25)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.develrulez.thinjar.Launcher.launch(Launcher.java:39)
... 1 more
Caused by: org.springframework.boot.devtools.restart.SilentExitExceptionHandler$SilentExitException
at org.springframework.boot.devtools.restart.SilentExitExceptionHandler.exitCurrentThread(SilentExitExceptionHandler.java:90)
at org.springframework.boot.devtools.restart.Restarter.immediateRestart(Restarter.java:184)
at org.springframework.boot.devtools.restart.Restarter.initialize(Restarter.java:163)
at org.springframework.boot.devtools.restart.Restarter.initialize(Restarter.java:552)
at org.springframework.boot.devtools.restart.RestartApplicationListener.onApplicationStartingEvent(RestartApplicationListener.java:67)
at org.springframework.boot.devtools.restart.RestartApplicationListener.onApplicationEvent(RestartApplicationListener.java:45)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:167)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:122)
at org.springframework.boot.context.event.EventPublishingRunListener.starting(EventPublishingRunListener.java:69)
at org.springframework.boot.SpringApplicationRunListeners.starting(SpringApplicationRunListeners.java:48)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:292)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107)
at com.example.ExampleApplication.main(ExampleApplication.java:10)
... 6 more
In this case you can disable the restart feature of Spring Boot's developer tools by combining it with a specialized property check:
package com.example;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class ExampleApplication {
public static void main(String[] args) {
// Don't fear a NullPointerException, because this check is null-resistent.
if(Boolean.valueOf(System.getProperty("thinjar.launcher.active"))){
System.setProperty("spring.devtools.restart.enabled", "false");
}
SpringApplication.run(ExampleApplication.class, args);
}
}
... or you have to look out for another solution. Suggestions will be accepted with a special thanks