Add Maven and Gradle option for the loader implementation to use

Add properties to the Maven and Gradle plugins so that users can
switch between the two loader modules.

See gh-37669

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

@@ -75,6 +75,26 @@ class JarIntegrationTests extends AbstractArchiveIntegrationTests {
 		});
 	}
 
+	@TestTemplate
+	void whenJarWithClassicLoaderIsRepackagedInPlaceOnlyRepackagedJarIsInstalled(MavenBuild mavenBuild) {
+		mavenBuild.project("jar-with-classic-loader").goals("install").execute((project) -> {
+			File original = new File(project, "target/jar-with-classic-loader-0.0.1.BUILD-SNAPSHOT.jar.original");
+			assertThat(original).isFile();
+			File repackaged = new File(project, "target/jar-with-classic-loader-0.0.1.BUILD-SNAPSHOT.jar");
+			assertThat(launchScript(repackaged)).isEmpty();
+			assertThat(jar(repackaged)).manifest((manifest) -> {
+				manifest.hasMainClass("org.springframework.boot.loader.launch.JarLauncher");
+				manifest.hasStartClass("some.random.Main");
+				manifest.hasAttribute("Not-Used", "Foo");
+			}).hasEntryWithName("org/springframework/boot/loader/launch/JarLauncher.class");
+			assertThat(buildLog(project))
+				.contains("Replacing main artifact " + repackaged + " with repackaged archive,")
+				.contains("The original artifact has been renamed to " + original)
+				.contains("Installing " + repackaged + " to")
+				.doesNotContain("Installing " + original + " to");
+		});
+	}
+
 	@TestTemplate
 	void whenAttachIsDisabledOnlyTheOriginalJarIsInstalled(MavenBuild mavenBuild) {
 		mavenBuild.project("jar-attach-disabled").goals("install").execute((project) -> {

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-with-classic-loader/pom.xml

@@ -0,0 +1,58 @@
+<?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-with-classic-loader</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>
+					</execution>
+				</executions>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-jar-plugin</artifactId>
+				<version>@maven-jar-plugin.version@</version>
+				<configuration>
+					<archive>
+						<manifest>
+							<mainClass>some.random.Main</mainClass>
+						</manifest>
+						<manifestEntries>
+							<Not-Used>Foo</Not-Used>
+						</manifestEntries>
+					</archive>
+					<loaderImplementation>CLASSIC</loaderImplementation>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-context</artifactId>
+			<version>@spring-framework.version@</version>
+		</dependency>
+		<dependency>
+			<groupId>jakarta.servlet</groupId>
+			<artifactId>jakarta.servlet-api</artifactId>
+			<version>@jakarta-servlet.version@</version>
+			<scope>provided</scope>
+		</dependency>
+	</dependencies>
+</project>

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/projects/jar-with-classic-loader/src/main/java/org/test/SampleApplication.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2012-2023 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/main/java/org/springframework/boot/maven/AbstractPackagerMojo.java

@@ -47,6 +47,7 @@ import org.springframework.boot.loader.tools.Layouts.Jar;
 import org.springframework.boot.loader.tools.Layouts.None;
 import org.springframework.boot.loader.tools.Layouts.War;
 import org.springframework.boot.loader.tools.Libraries;
+import org.springframework.boot.loader.tools.LoaderImplementation;
 import org.springframework.boot.loader.tools.Packager;
 import org.springframework.boot.loader.tools.layer.CustomLayers;
 
@@ -128,6 +129,15 @@ public abstract class AbstractPackagerMojo extends AbstractDependencyFilterMojo
 		return null;
 	}
 
+	/**
+	 * Return the loader implementation that should be used.
+	 * @return the loader implementation or {@code null}
+	 * @since 3.2.0
+	 */
+	protected LoaderImplementation getLoaderImplementation() {
+		return null;
+	}
+
 	/**
 	 * Return the layout factory that will be used to determine the {@link LayoutType} if
 	 * no explicit layout is set.
@@ -145,6 +155,7 @@ public abstract class AbstractPackagerMojo extends AbstractDependencyFilterMojo
 	 */
 	protected <P extends Packager> P getConfiguredPackager(Supplier<P> supplier) {
 		P packager = supplier.get();
+		packager.setLoaderImplementation(getLoaderImplementation());
 		packager.setLayoutFactory(getLayoutFactory());
 		packager.addMainClassTimeoutWarningListener(new LoggingMainClassTimeoutWarningListener(this::getLog));
 		packager.setMainClass(this.mainClass);

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

@@ -48,6 +48,7 @@ import org.springframework.boot.loader.tools.EntryWriter;
 import org.springframework.boot.loader.tools.ImagePackager;
 import org.springframework.boot.loader.tools.LayoutFactory;
 import org.springframework.boot.loader.tools.Libraries;
+import org.springframework.boot.loader.tools.LoaderImplementation;
 import org.springframework.util.StringUtils;
 
 /**
@@ -187,6 +188,13 @@ public abstract class BuildImageMojo extends AbstractPackagerMojo {
 	@Parameter
 	private LayoutType layout;
 
+	/**
+	 * The loader implementation that should be used.
+	 * @since 3.2.0
+	 */
+	@Parameter
+	private LoaderImplementation loaderImplementation;
+
 	/**
 	 * The layout factory that will be used to create the executable archive if no
 	 * explicit layout is set. Alternative layouts implementations can be provided by 3rd
@@ -206,6 +214,11 @@ public abstract class BuildImageMojo extends AbstractPackagerMojo {
 		return this.layout;
 	}
 
+	@Override
+	protected LoaderImplementation getLoaderImplementation() {
+		return this.loaderImplementation;
+	}
+
 	/**
 	 * Return the layout factory that will be used to determine the
 	 * {@link AbstractPackagerMojo.LayoutType} if no explicit layout is set.

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

@@ -36,6 +36,7 @@ import org.springframework.boot.loader.tools.DefaultLaunchScript;
 import org.springframework.boot.loader.tools.LaunchScript;
 import org.springframework.boot.loader.tools.LayoutFactory;
 import org.springframework.boot.loader.tools.Libraries;
+import org.springframework.boot.loader.tools.LoaderImplementation;
 import org.springframework.boot.loader.tools.Repackager;
 
 /**
@@ -161,6 +162,13 @@ public class RepackageMojo extends AbstractPackagerMojo {
 	@Parameter(property = "spring-boot.repackage.layout")
 	private LayoutType layout;
 
+	/**
+	 * The loader implementation that should be used.
+	 * @since 3.2.0
+	 */
+	@Parameter
+	private LoaderImplementation loaderImplementation;
+
 	/**
 	 * The layout factory that will be used to create the executable archive if no
 	 * explicit layout is set. Alternative layouts implementations can be provided by 3rd
@@ -180,6 +188,11 @@ public class RepackageMojo extends AbstractPackagerMojo {
 		return this.layout;
 	}
 
+	@Override
+	protected LoaderImplementation getLoaderImplementation() {
+		return this.loaderImplementation;
+	}
+
 	/**
 	 * Return the layout factory that will be used to determine the
 	 * {@link AbstractPackagerMojo.LayoutType} if no explicit layout is set.