Spring classpath filtering via Gradle plugin

[sdeleuze]

We should be able to do that with something like:

compile("org.springframework:spring-web") {
		registerTransform {
			from.attribute(filtered, false).attribute(artifactType, "jar")
			to.attribute(filtered, true).attribute(artifactType, "jar")
			artifactTransform(FilterClasses::class.java)
		}
	}
}

// Same for spring-webflux, spring-context, spring-data-commons, etc.
class SpringFuWebFilter : ArtifactTransform() {
	
	private val classesToFilter = arrayOf(
			"org/springframework/remoting/**",
			"org/springframework/web/accept/**",
			"org/springframework/web/bind/**",
			"org/springframework/web/client/**",
			"org/springframework/web/context/**",
			"org/springframework/web/filter/**",
			"org/springframework/web/jsf/**",
			"org/springframework/web/method/**",
			"org/springframework/web/multipart/**",
		)
)

	override fun transform(input: File): List<File> {
		return if (...) listOf(input) else emptyList()
	}
}

See also https://github.com/gradle/gradle/blob/master/buildSrc/subprojects/packaging/src/main/kotlin/org/gradle/gradlebuild/packaging/MinifyPlugin.kt

[sdeleuze]

See also https://gist.github.com/bamboo/030ed98f1fb5c4853ac65455e67197dc.

[sdeleuze]

There is now a minimal sample with class filtering and some preliminary benchmarks.

[sdeleuze]

For the record, the former configuration I was using with ShadowJar:

tasks.withType<ShadowJar> {
	exclude("org/springframework/cglib/**",
			"org/springframework/beans/factory/groovy/**",
			"org/springframework/beans/factory/xml/**",
			"org/springframework/cache",
			"org/springframework/context/annotation",
			"org/springframework/context/support/*Xml*.class",
			"org/springframework/context/support/*Groovy*.class",
			"org/springframework/ejb/**",
			"org/springframework/instrument/classloading/**",
			"org/springframework/jmx/**",
			"org/springframework/jndi/**",
			"org/springframework/remoting/**",
			"org/springframework/scheduling/**",
			"org/springframework/scripting/**",
			"org/springframework/web/accept/**",
			"org/springframework/web/bind/**",
			"org/springframework/web/client/**",
			"org/springframework/web/context/**",
			"org/springframework/web/filter/**",
			"org/springframework/web/jsf/**",
			"org/springframework/web/method/**",
			"org/springframework/web/multipart/**",
			"org/springframework/util/xml/**")
}

[sdeleuze]

See https://github.com/gradle/gradle/tree/master/buildSrc/subprojects/packaging/src/main/kotlin/org/gradle/gradlebuild/packaging.

[sdeleuze]

This comment gives interesting insights about why it could be interesting to have a limited number of unused class when it comes to run application in the Cloud (here for Cloud Foundry but I think it could apply to other Cloud Java support).

[sdeleuze]

It seems Gradle 5.1 now provides a dedicated API: gradle/gradle@0514a4c !

[sdeleuze]

Initial plugin available in https://github.com/spring-projects/spring-fu/tree/gradle-plugin but I have not find yet why the artifact transformation is not invoked.

[sdeleuze]

Gradle 5.5 with official support and documentation for artifact transformation has been released.

[sdeleuze]

I think GraalVM native images or Jlink are better solution to this need.