javaspring-bootbuildpack

Add additional Java libraries to the spring boot container

Since some libraries contain licenses that do not allow distribution, customers who want to run our software must get the libraries by themselves and add these to the spring boot application.

Previously, we added the spring boot uber jar to a container and used the PropertiesLauncher and the LOADER_PATH so that the customer can mount the library in the container and adapt the classpath.

Now that we want to switch for the image generation to buildpack, just like mvn spring-boot:build-image would do. As the application is unpacked in the image, it seems to me that the PropertiesLauncher and LOADER_PATH would no longer work.

What is the recommended way to add third party Java libraries to a buildback-built spring boot container?

Solution

  • Turns out the configuration of the spring-boot-maven-plugin was wrong. The configuration <layout>ZIP<layout> was only active for the repackage goal, but not for the build-image goal.

    After correctly configuring <layout>ZIP<layout> for the build-image goal, the generated buildpack-image uses the org.springframework.boot.loader.launch.PropertiesLauncher which allows again the use of the LOADER_PATH.

    To clarify, this was my wrong configuration:

    <plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <version>${version.spring-boot}</version>
    <executions>
        <execution>
            <goals>
                <goal>build-info</goal>
                <goal>repackage</goal>
            </goals>
            <configuration>
                <layout>ZIP</layout>
                <classifier>app</classifier>
            </configuration>
        </execution>
    </executions>
</plugin>

    The fixed configuration, where the layout (and also the classifier) is always present regardless of the actual spring-boot-maven-plugin goal:

    <plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <version>${version.spring-boot}</version>
    <configuration>
        <layout>ZIP</layout>
        <classifier>app</classifier>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>build-info</goal>
                <goal>repackage</goal>
            </goals>
        </execution>
    </executions>
</plugin>