spring boot bootBuildImage applying war on tomcat image

Question

With spring boot and task bootBuildImage(gradle), is it possible build an image based on say a tomcat image, and copy the war file into relevant webapp directory, as opposed to running an application fatjar?

I know this is possible with jib.

Thanks

Answer 1

This is possible when using the Paketo buildpacks (the default with Spring Boot's bootBuildImage Gradle task), because Paketo includes a Tomcat buildpack .

It does require some configuration of the Spring Boot Gradle plugin to get a non-executable war file so that the Paketo Tomcat buildpack will detect the correct application type and configure Tomcat with the war file.

Add the following configuration to the build.gradle file to instruct Spring Boot to create a non-executable war file as shown in the Spring Boot documentation :

war {
    enabled = true
}

bootWar {
    classifier = 'boot'
}

Also add the following configuration so the bootBuildImage task will use the non-executable war file:

bootBuildImage {
    jar = war.archiveFile
}

After these changes, running bootBuildImage should show that the apache-tomcat buildpack is participating in the image generation:

 > Running creator
[creator]     ===> DETECTING
[creator]     5 of 18 buildpacks participating
[creator]     paketo-buildpacks/ca-certificates   1.0.1
[creator]     paketo-buildpacks/bellsoft-liberica 5.2.1
[creator]     paketo-buildpacks/apache-tomcat     3.1.0
[creator]     paketo-buildpacks/dist-zip          2.2.2
[creator]     paketo-buildpacks/spring-boot       3.5.0

Without the additional configuration you would see the paketo-buildpacks/executable-jar buildpack instead of paketo-buildpacks/apache-tomcat , indicating that the fat executable jar was used to launch the application instead of a war deployed to Tomcat.