Add buildpack option for image building

[scottfrederick]

The pack CLI build command supports a buildpack option that allows the user to customize the list of buildpacks used to build the image. Buildpack references are supported in the form of <buildpack>@<version>, path to a buildpack directory, path/URL to a buildpack .tar or .tgz file, or the name of a buildpack image packaged in the builder.

This option could be useful to users of the Spring Boot Maven plugin spring-boot:build-image goal and Gradle plugin bootBuildImage task.

[dogilvie]

We would like to use this feature to be able to select the JVM chosen. Currently the built image selects Bellsoft Liberica and this cannot be modified.

[eddumelendez]

@dogilvie the workaround for 2.3 can be pack build hello-pedestal \ --builder "gcr.io/paketo-buildpacks/builder:base" \ --buildpack gcr.io/paketo-buildpacks/amazon-corretto or any other jdk available

[dogilvie]

@dogilvie the workaround for 2.3 can be pack build hello-pedestal \ --builder "gcr.io/paketo-buildpacks/builder:base" \ --buildpack gcr.io/paketo-buildpacks/amazon-corretto or any other jdk available

How do I utilize this in the context of spring boot? Our image is built using the spring-boot-maven-plugin

<plugin>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-maven-plugin</artifactId>
	<configuration>
		<layers>
			<enabled>true</enabled>
		</layers>
	</configuration>
</plugin>

[snicoll]

@dogilvie this feature is not implemented yet so you'll have to create your own builder in the meantime (as @eddumelendez mentioned) and use your custom builder rather than the default. Doing so is explained in the documentation (for instance here for Maven). If you have more questions, please follow-up on StackOverflow.

[scottfrederick]

The pack CLI supports several options for referencing the source of a buildpack. Of these options, the following will be supported by the Boot plugins in the initial feature implementation:

• CNB builder resource - [urn:cnb:builder:]<id>[@<version>]
• File system directory - [file://]<path>
• File system gzipped tar file - [file://]<path>/<file name>
• OCI image - [docker://]<image name>[:<tag>|@<digest>]

The remaining options can be implemented as demand dictates:

• Downloaded gzipped tar file - http[s]://<host>/<path>
• CNB registry resource - urn:cnb:registry:<id>[@<version>]