How to Create Spring Boot Thin and Fat Jar in Same Spring Boot Maven Project - spring-boot

Question

I am having a need to build my spring boot project as both fat and thin jar,
Expected output: one fat jar and one thin jar
Actual output: both are fat jars. I extracted and checked, it contains BOOT-INF/lib having jars
Following is my build plugin configuration
spring boot version 2.4.3
spring boot thin version 1.0.25.RELEASE
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<id>create-fat-jar</id>
<goals>
<goal>repackage</goal>
<goal>build-info</goal>
</goals>
<configuration>
<mainClass>com.mycomp.ExampleApplication</mainClass>
<addResources>true</addResources>
<finalName>${project.artifactId}-fat-${project.version}</finalName>
</configuration>
</execution>
<execution>
<id>create-thin-jar</id>
<goals>
<goal>repackage</goal>
<goal>build-info</goal>
</goals>
<configuration>
<executable>false</executable>
<addResources>true</addResources>
<finalName>${project.artifactId}-thin-${project.version}</finalName>
<dependencies>
<dependency>
<groupId>org.springframework.boot.experimental</groupId>
<artifactId>spring-boot-thin-layout</artifactId>
<version>${springboot.thin.version}</version>
</dependency>
</dependencies>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
Please help me to resolve this issue.

Answer 1

There is an experimental thin layout project from Spring, try to use the below and it will help you.
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
<dependencies>
<dependency>
<groupId>org.springframework.boot.experimental</groupId>
<artifactId>spring-boot-thin-layout</artifactId>
<version>1.0.28.BUILD-SNAPSHOT</version>
</dependency>
</dependencies>
</plugin>
https://github.com/spring-projects-experimental/spring-boot-thin-launcher

Answer 2

I think creating a Fat jar in spring boot is very easy. The part of creating a Thin jar requires special changes in pom.xml file. Let me describe both scenarios here:
In both cases, the top part will be same:
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.2</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.package</groupId>
<artifactId>YourApplication</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>YourApplication</name>
<description>Your description</description>
<properties>
<java.version>1.8</java.version>
<mainClass>com.package.YourApplication.Main</mainClass>
</properties>
pom.xml for fat jar:
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
...
your other dependencies as well...
</dependencies>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>2.7.1</version>
<configuration>
<executable>true</executable>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
<plugin>
<artifactId>maven-jar-plugin</artifactId>
<version>3.0.2</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<mainClass>${mainClass}</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
<plugins>
The plugins are important. Because they provide specific build commands to maven.
Now, for thin jar creation:
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<!-- <scope>provided</scope>-->
</dependency>
...
your other dependencies as well...
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.19.1</version>
</plugin>
<plugin>
<artifactId>maven-dependency-plugin</artifactId>
<version>3.1.2</version>
<executions>
<execution>
<phase>install</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>${project.build.directory}/lib</outputDirectory>
<overWriteReleases>true</overWriteReleases>
<overWriteSnapshots>true</overWriteSnapshots>
<overWriteIfNewer>true</overWriteIfNewer>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<artifactId>maven-jar-plugin</artifactId>
<version>3.0.2</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
<mainClass>${mainClass}</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
</plugins>
<finalName>${project.artifactId}</finalName>
</build>
Here, you can see that in dependencies, tomcat provided scope is removed. Also, the plugins have changed. Executing mvn package then mvn install will generate the thin jar and copy all the dependencies outside the jar file in lib/ folder.
I hope this helps you. :)