Allow users to opt out of including the layer tools in a layered jar

For Maven, the layer configuration is now an additional configuration
option instead of a layout type.

Closes gh-19866

spring-boot-project/spring-boot-docs/src/docs/asciidoc/spring-boot-features.adoc

@@ -7787,8 +7787,7 @@ This layering is designed to separate code based on how likely it is to change b
 Library code is less likely to change between builds, so it is placed in its own layers to allow tooling to re-use the layers from cache.
 Application code is more likely to change between builds so it is isolated in a separate layer.
 
-For Maven, layered jars can be created using a new `layout` type called `LAYERED_JAR`.
-See the {spring-boot-maven-plugin-docs}/#goals-build-image-parameters-details-layout[layout section] for more details.
+For Maven, refer to the {spring-boot-maven-plugin-docs}/#repackage-layered-jars[packaging layered jars section] for more details on creating a layered jar.
 For Gradle, refer to the {spring-boot-gradle-plugin-docs}/#packaging-layered-jars[packaging layered jars section] of the Gradle plugin documentation.
 
 ==== Writing the Dockerfile

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/asciidoc/packaging.adoc

@@ -287,3 +287,18 @@ The jar will then be split into layer folders which may include:
 * `snapshots-dependencies`
 * `dependencies`
 
+When you create a layered jar, the `spring-boot-layertools` jar will be added as a dependency to your jar.
+With this jar on the classpath, you can launch your application in a special mode which allows the bootstrap code to run something entirely different from your application, for example, something that extracts the layers.
+If you wish to exclude this dependency, you can do so in the following manner:
+
+[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
+.Groovy
+----
+include::../gradle/packaging/boot-jar-layered-exclude-tools.gradle[tags=layered]
+----
+
+[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
+.Kotlin
+----
+include::../gradle/packaging/boot-jar-layered-exclude-tools.gradle.kts[tags=layered]
+----
\ No newline at end of file

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/packaging/boot-jar-layered-exclude-tools.gradle

+plugins {
+	id 'java'
+	id 'org.springframework.boot' version '{version}'
+}
+
+bootJar {
+	mainClassName 'com.example.ExampleApplication'
+}
+
+// tag::layered[]
+bootJar {
+	layered {
+		includeLayerTools = false
+	}
+}
+// end::layered[]

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/packaging/boot-jar-layered-exclude-tools.gradle.kts

+import org.springframework.boot.gradle.tasks.bundling.BootJar
+
+plugins {
+	java
+	id("org.springframework.boot") version "{version}"
+}
+
+tasks.getByName<BootJar>("bootJar") {
+	mainClassName = "com.example.ExampleApplication"
+}
+
+// tag::layered[]
+tasks.getByName<BootJar>("bootJar") {
+	layered {
+		includeLayerTools = false
+	}
+}
+// end::layered[]

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/BootJar.java

@@ -40,6 +40,8 @@ import org.gradle.api.java.archives.Attributes;
 import org.gradle.api.specs.Spec;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.Internal;
+import org.gradle.api.tasks.Nested;
+import org.gradle.api.tasks.Optional;
 import org.gradle.api.tasks.bundling.Jar;
 
 import org.springframework.boot.loader.tools.Layer;
@@ -67,6 +69,8 @@ public class BootJar extends Jar implements BootArchive {
 
 	private Layers layers;
 
+	private LayerConfiguration layerConfiguration;
+
 	private static final String BOOT_INF_LAYERS = "BOOT-INF/layers";
 
 	private final List<String> dependencies = new ArrayList<>();
@@ -164,20 +168,33 @@ public class BootJar extends Jar implements BootArchive {
 		action.execute(enableLaunchScriptIfNecessary());
 	}
 
+	@Optional
+	@Nested
+	@Input
+	public LayerConfiguration getLayerConfiguration() {
+		return this.layerConfiguration;
+	}
+
 	/**
 	 * Configures the archive to have layers.
 	 */
 	public void layered() {
-		this.layers = Layers.IMPLICIT;
-		this.bootInf.into("lib", (spec) -> spec.from((Callable<File>) () -> {
-			String jarName = "spring-boot-jarmode-layertools.jar";
-			InputStream stream = getClass().getClassLoader().getResourceAsStream("META-INF/jarmode/" + jarName);
-			File taskTmp = new File(getProject().getBuildDir(), "tmp/" + getName());
-			taskTmp.mkdirs();
-			File layerToolsJar = new File(taskTmp, jarName);
-			FileCopyUtils.copy(stream, new FileOutputStream(layerToolsJar));
-			return layerToolsJar;
-		}));
+		enableLayers();
+		applyLayers();
+	}
+
+	private void applyLayers() {
+		if (this.layerConfiguration.isIncludeLayerTools()) {
+			this.bootInf.into("lib", (spec) -> spec.from((Callable<File>) () -> {
+				String jarName = "spring-boot-jarmode-layertools.jar";
+				InputStream stream = getClass().getClassLoader().getResourceAsStream("META-INF/jarmode/" + jarName);
+				File taskTmp = new File(getProject().getBuildDir(), "tmp/" + getName());
+				taskTmp.mkdirs();
+				File layerToolsJar = new File(taskTmp, jarName);
+				FileCopyUtils.copy(stream, new FileOutputStream(layerToolsJar));
+				return layerToolsJar;
+			}));
+		}
 		this.bootInf.eachFile((details) -> {
 			Layer layer = layerForFileDetails(details);
 			if (layer != null) {
@@ -188,6 +205,20 @@ public class BootJar extends Jar implements BootArchive {
 		this.bootInf.into("", (spec) -> spec.from(createLayersIndex()));
 	}
 
+	public void layered(Action<LayerConfiguration> action) {
+		action.execute(enableLayers());
+		applyLayers();
+	}
+
+	private LayerConfiguration enableLayers() {
+		this.layers = Layers.IMPLICIT;
+		if (this.layerConfiguration == null) {
+			this.layerConfiguration = new LayerConfiguration();
+		}
+
+		return this.layerConfiguration;
+	}
+
 	private Layer layerForFileDetails(FileCopyDetails details) {
 		String path = details.getPath();
 		if (path.startsWith("BOOT-INF/lib/")) {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/LayerConfiguration.java

+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.gradle.tasks.bundling;
+
+import org.gradle.api.tasks.Input;
+
+/**
+ * Encapsulates the configuration for a layered jar.
+ *
+ * @author Madhura Bhave
+ * @since 2.3.0
+ */
+public class LayerConfiguration {
+
+	private boolean includeLayerTools = true;
+
+	/**
+	 * Whether to include the layer tools jar.
+	 * @return true if layer tools is included
+	 */
+	@Input
+	public boolean isIncludeLayerTools() {
+		return this.includeLayerTools;
+	}
+
+	public void setIncludeLayerTools(boolean includeLayerTools) {
+		this.includeLayerTools = includeLayerTools;
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/tasks/bundling/BootJarIntegrationTests.java

@@ -29,6 +29,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Integration tests for {@link BootJar}.
  *
  * @author Andy Wilkinson
+ * @author Madhura Bhave
  */
 class BootJarIntegrationTests extends AbstractBootArchiveIntegrationTests {
 
@@ -53,4 +54,13 @@ class BootJarIntegrationTests extends AbstractBootArchiveIntegrationTests {
 				.isEqualTo(TaskOutcome.SUCCESS);
 	}
 
+	@TestTemplate
+	void notUpToDateWhenBuiltWithLayersAndToolsAndThenWithLayersAndWithoutTools()
+			throws InvalidRunnerConfigurationException, UnexpectedBuildFailure, IOException {
+		assertThat(this.gradleBuild.build("-Playered=true", "bootJar").task(":bootJar").getOutcome())
+				.isEqualTo(TaskOutcome.SUCCESS);
+		assertThat(this.gradleBuild.build("-Playered=true", "-PexcludeTools=true", "bootJar").task(":bootJar")
+				.getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
+	}
+
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/tasks/bundling/BootJarTests.java

@@ -25,6 +25,7 @@ import java.util.jar.JarFile;
 import java.util.stream.Collectors;
 import java.util.zip.ZipEntry;
 
+import org.gradle.api.Action;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -129,6 +130,13 @@ class BootJarTests extends AbstractBootArchiveTests<BootJar> {
 		assertThat(entryNames).contains("BOOT-INF/layers/dependencies/lib/spring-boot-jarmode-layertools.jar");
 	}
 
+	@Test
+	void whenJarIsLayeredAndIncludeLayerToolsIsFalseThenLayerToolsAreNotAddedToTheJar() throws IOException {
+		List<String> entryNames = getEntryNames(
+				createLayeredJar((configuration) -> configuration.setIncludeLayerTools(false)));
+		assertThat(entryNames).doesNotContain("BOOT-INF/layers/dependencies/lib/spring-boot-jarmode-layertools.jar");
+	}
+
 	@Test
 	void classpathIndexPointsToBootInfLibs() throws IOException {
 		try (JarFile jarFile = new JarFile(createPopulatedJar())) {
@@ -145,13 +153,22 @@ class BootJarTests extends AbstractBootArchiveTests<BootJar> {
 		return getTask().getArchiveFile().get().getAsFile();
 	}
 
-	private File createLayeredJar() throws IOException {
+	private File createLayeredJar(Action<LayerConfiguration> action) throws IOException {
 		addContent();
-		getTask().layered();
+		if (action != null) {
+			getTask().layered(action);
+		}
+		else {
+			getTask().layered();
+		}
 		executeTask();
 		return getTask().getArchiveFile().get().getAsFile();
 	}
 
+	private File createLayeredJar() throws IOException {
+		return createLayeredJar(null);
+	}
+
 	private void addContent() throws IOException {
 		BootJar bootJar = getTask();
 		bootJar.setMainClassName("com.example.Main");

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/bundling/BootJarIntegrationTests.gradle

@@ -11,6 +11,8 @@ bootJar {
 		}
 	}
 	if (project.hasProperty('layered') && project.getProperty('layered')) {
-		layered()
+		layered {
+			includeLayerTools = project.hasProperty('excludeTools') && project.getProperty('excludeTools') ? false : true
+		}
 	}
 }

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/docs/asciidoc/packaging.adoc

@@ -397,3 +397,56 @@ This example excludes any artifact belonging to the `com.foo` group:
 		</build>
 	</project>
 ----
+
+
+
+[[repackage-layered-jars]]
+==== Packaging layered jars
+By default, the repackaged jar contains the application's classes and dependencies in `BOOT-INF/classes` and `BOOT-INF/lib` respectively.
+For cases where a docker image needs to be built from the contents of the jar, the jar format can be enhanced to support layer folders.
+To use this feature, the layering feature must be enabled:
+
+[source,xml,indent=0,subs="verbatim,attributes"]
+----
+	<project>
+		<build>
+			<plugins>
+				<plugin>
+					<groupId>org.springframework.boot</groupId>
+					<artifactId>spring-boot-maven-plugin</artifactId>
+					<version>{gradle-project-version}</version>
+					<configuration>
+						<layered>
+							<enabled>true</enabled>
+						</layered>
+					</configuration>
+				</plugin>
+			</plugins>
+		</build>
+	</project>
+----
+
+When you create a layered jar, the `spring-boot-layertools` jar will be added as a dependency to your jar.
+With this jar on the classpath, you can launch your application in a special mode which allows the bootstrap code to run something entirely different from your application, for example, something that extracts the layers.
+If you wish to exclude this dependency, you can do so in the following manner:
+
+[source,xml,indent=0,subs="verbatim,attributes"]
+----
+	<project>
+		<build>
+			<plugins>
+				<plugin>
+					<groupId>org.springframework.boot</groupId>
+					<artifactId>spring-boot-maven-plugin</artifactId>
+					<version>{gradle-project-version}</version>
+					<configuration>
+						<layered>
+							<enabled>true</enabled>
+							<includeLayerTools>false</enabled>
+						</layered>
+					</configuration>
+				</plugin>
+			</plugins>
+		</build>
+	</project>
+----
\ No newline at end of file

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/java/org/springframework/boot/maven/JarIntegrationTests.java

@@ -287,7 +287,21 @@ class JarIntegrationTests extends AbstractArchiveIntegrationTests {
 			File repackaged = new File(project, "jar/target/jar-layered-0.0.1.BUILD-SNAPSHOT.jar");
 			assertThat(jar(repackaged)).hasEntryWithNameStartingWith("BOOT-INF/layers/application/classes/")
 					.hasEntryWithNameStartingWith("BOOT-INF/layers/dependencies/lib/jar-release")
-					.hasEntryWithNameStartingWith("BOOT-INF/layers/snapshot-dependencies/lib/jar-snapshot");
+					.hasEntryWithNameStartingWith("BOOT-INF/layers/snapshot-dependencies/lib/jar-snapshot")
+					.hasEntryWithNameStartingWith(
+							"BOOT-INF/layers/dependencies/lib/spring-boot-jarmode-layertools.jar");
+		});
+	}
+
+	@TestTemplate
+	void whenJarIsRepackagedWithTheLayeredLayoutAndLayerToolsExcluded(MavenBuild mavenBuild) {
+		mavenBuild.project("jar-layered-no-layer-tools").execute((project) -> {
+			File repackaged = new File(project, "jar/target/jar-layered-0.0.1.BUILD-SNAPSHOT.jar");
+			assertThat(jar(repackaged)).hasEntryWithNameStartingWith("BOOT-INF/layers/application/classes/")
+					.hasEntryWithNameStartingWith("BOOT-INF/layers/dependencies/lib/jar-release")
+					.hasEntryWithNameStartingWith("BOOT-INF/layers/snapshot-dependencies/lib/jar-snapshot")
+					.doesNotHaveEntryWithNameStartingWith(
+							"BOOT-INF/layers/dependencies/lib/spring-boot-jarmode-layertools.jar");
 		});
 	}
 

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered-no-layer-tools/jar-release/pom.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>org.springframework.boot.maven.it</groupId>
+	<artifactId>jar-release</artifactId>
+	<version>0.0.1.RELEASE</version>
+	<packaging>jar</packaging>
+	<name>jar</name>
+	<description>Release Jar dependency</description>
+</project>

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered-no-layer-tools/jar-snapshot/pom.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>org.springframework.boot.maven.it</groupId>
+	<artifactId>jar-snapshot</artifactId>
+	<version>0.0.1.BUILD-SNAPSHOT</version>
+	<packaging>jar</packaging>
+	<name>jar</name>
+	<description>Snapshot Jar dependency</description>
+</project>

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered-no-layer-tools/jar/pom.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>org.springframework.boot.maven.it</groupId>
+	<artifactId>jar-layered</artifactId>
+	<version>0.0.1.BUILD-SNAPSHOT</version>
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+		<maven.compiler.source>@java.version@</maven.compiler.source>
+		<maven.compiler.target>@java.version@</maven.compiler.target>
+	</properties>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>@project.groupId@</groupId>
+				<artifactId>@project.artifactId@</artifactId>
+				<version>@project.version@</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>repackage</goal>
+						</goals>
+						<configuration>
+							<layered>
+								<enabled>true</enabled>
+								<includeLayerTools>false</includeLayerTools>
+							</layered>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot.maven.it</groupId>
+			<artifactId>jar-snapshot</artifactId>
+			<version>0.0.1.BUILD-SNAPSHOT</version>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot.maven.it</groupId>
+			<artifactId>jar-release</artifactId>
+			<version>0.0.1.RELEASE</version>
+		</dependency>
+	</dependencies>
+</project>

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered-no-layer-tools/jar/src/main/java/org/test/SampleApplication.java

+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.test;
+
+public class SampleApplication {
+
+	public static void main(String[] args) {
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered-no-layer-tools/pom.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>org.springframework.boot.maven.it</groupId>
+	<artifactId>aggregator</artifactId>
+	<version>0.0.1.BUILD-SNAPSHOT</version>
+	<packaging>pom</packaging>
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+		<maven.compiler.source>@java.version@</maven.compiler.source>
+		<maven.compiler.target>@java.version@</maven.compiler.target>
+	</properties>
+	<modules>
+		<module>jar-snapshot</module>
+		<module>jar-release</module>
+		<module>jar</module>
+	</modules>
+</project>

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-layered/jar/pom.xml

@@ -22,7 +22,9 @@
 							<goal>repackage</goal>
 						</goals>
 						<configuration>
-							<layout>LAYERED_JAR</layout>
+							<layered>
+								<enabled>true</enabled>
+							</layered>
 						</configuration>
 					</execution>
 				</executions>

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/AbstractPackagerMojo.java

@@ -104,6 +104,13 @@ public abstract class AbstractPackagerMojo extends AbstractDependencyFilterMojo
 	@Parameter(defaultValue = "false")
 	public boolean includeSystemScope;
 
+	/**
+	 * Layer configuration with the option to exclude layer tools jar.
+	 * @since 2.3.0
+	 */
+	@Parameter
+	private Layered layered;
+
 	/**
 	 * Return a {@link Packager} configured for this MOJO.
 	 * @param <P> the packager type
@@ -119,6 +126,10 @@ public abstract class AbstractPackagerMojo extends AbstractDependencyFilterMojo
 			getLog().info("Layout: " + this.layout);
 			packager.setLayout(this.layout.layout());
 		}
+		if (this.layered != null && this.layered.isEnabled()) {
+			packager.setLayout(new LayeredJar());
+			packager.setIncludeRelevantJarModeJars(this.layered.isIncludeLayerTools());
+		}
 		return packager;
 	}
 
@@ -158,11 +169,6 @@ public abstract class AbstractPackagerMojo extends AbstractDependencyFilterMojo
 		 */
 		JAR(new Jar()),
 
-		/**
-		 * Layered Jar Layout.
-		 */
-		LAYERED_JAR(new LayeredJar()),
-
 		/**
 		 * War Layout.
 		 */

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/Layered.java

+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.maven;
+
+/**
+ * Layer configuration options.
+ *
+ * @author Madhura Bhave
+ * @since 2.3.0
+ */
+public class Layered {
+
+	private boolean enabled;
+
+	private boolean includeLayerTools = true;
+
+	/**
+	 * Whether layered jar layout is enabled.
+	 * @return true if the layered layout is enabled.
+	 */
+	public boolean isEnabled() {
+		return this.enabled;
+	}
+
+	/**
+	 * Whether to include the layer tools jar.
+	 * @return true if layer tools should be included
+	 */
+	public boolean isIncludeLayerTools() {
+		return this.includeLayerTools;
+	}
+
+}