Support building an image when using war packaging with Maven

[ondrejlerch]

I am trying to create OCI image via:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <version>2.3.4.RELEASE</version>
    <executions>
        <execution>
            <goals>
                <goal>build-image</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <layout>WAR</layout>
    </configuration>
</plugin>

where my packaging is war:

<packaging>war</packaging>

But I am getting exception:

java.lang.IllegalArgumentException: Source must refer to an existing file, got ...jar
    at org.springframework.util.Assert.isTrue (Assert.java:121)
    at org.springframework.boot.loader.tools.Packager.<init> (Packager.java:96)
    at org.springframework.boot.loader.tools.ImagePackager.<init> (ImagePackager.java:40)
    at org.springframework.boot.maven.BuildImageMojo.lambda$getApplicationContent$1 (BuildImageMojo.java:171)
    at org.springframework.boot.maven.AbstractPackagerMojo.getConfiguredPackager (AbstractPackagerMojo.java:130)
    at org.springframework.boot.maven.BuildImageMojo.getApplicationContent (BuildImageMojo.java:171)
    at org.springframework.boot.maven.BuildImageMojo.lambda$getBuildRequest$0 (BuildImageMojo.java:156)
    at org.springframework.boot.buildpack.platform.build.BuildRequest.getApplicationContent (BuildRequest.java:181)
    at org.springframework.boot.buildpack.platform.build.Lifecycle.createContainer (Lifecycle.java:165)
    at org.springframework.boot.buildpack.platform.build.Lifecycle.run (Lifecycle.java:146)
    at org.springframework.boot.buildpack.platform.build.Lifecycle.execute (Lifecycle.java:113)
    at org.springframework.boot.buildpack.platform.build.Builder.executeLifecycle (Builder.java:122)
    at org.springframework.boot.buildpack.platform.build.Builder.build (Builder.java:71)
    at org.springframework.boot.maven.BuildImageMojo.buildImage (BuildImageMojo.java:148)
    at org.springframework.boot.maven.BuildImageMojo.execute (BuildImageMojo.java:140)

Looking at org.springframework.boot.maven.BuildImageMojo:182:

private File getJarFile() {
    // We can use 'project.getArtifact().getFile()' because that was done in a
    // forked lifecycle and is now null
    StringBuilder name = new StringBuilder(this.finalName);
    if (StringUtils.hasText(this.classifier)) {
        name.append("-").append(this.classifier);
    }
    name.append(".jar");
    return new File(this.sourceDirectory, name.toString());
}

it seems to me that just jar packaging is supported.

Shouldn't be war (and other) packaging be supported as well?

Or is there some configuration option that I missed out?

Thanks for your feedback and great work on Spring ecosystem!

[wilkinsona]

Image building is only supported with jar packaging at the moment. Unless you are using JSPs, there's no need to use war packaging and jar packaging is strongly recommended.

#22821 also relates to this. It is tracking support for building layered wars with Maven.

[wilkinsona]

This is already possible with Gradle, although it requires a little bit of manual configuration to make bootBuildImage use the output of bootWar rather than bootJar. I've opened #23825 to track improving that.

[ondrejlerch]

In my scenario jar packaging is totally fine so I will switch to that from war as you suggested.

However, I suggest to mention jar limitation in maven plugin documentation:
https://docs.spring.io/spring-boot/docs/current/maven-plugin/reference/html/#build-image
Layout parameter documentation confused me:
https://docs.spring.io/spring-boot/docs/current/maven-plugin/reference/html/#goals-build-image-parameters-details-layout
"Possible values are JAR, WAR, ZIP, DIR, NONE."

If JSPs require WAR packaging then I still suggest to add WAR packaging support for mvn spring-boot:build-image.

[wilkinsona]

Thanks, @ondrejlerch. You make a good point about the documentation. I've opened #24105 to straighten that out.

[wilkinsona]

We need some feedback from @nebhale (see #23825 for details) to progress this one.

[spring-projects-issues]

If you would like us to look at this issue, please provide the requested information. If the information is not provided within the next 7 days this issue will be closed.

[wilkinsona]

We've had that feedback now and the default builder now behaves differently depending on whether the war artifact has a Main-Class manifest attribute. When present, the war is launched using the embedded container. We absent, the war is deployed to Tomcat.

[scottfrederick]

A separate issue #24522 has been created to improve the current error message.