Extract AotGenerateMojo to its own structure

This commit stops AotGenerateMojo from being an extension of the
regular run infrastructure and used the opportunity to extract a
number of utility classes to run a Java process.

As a result, not all features of running an application is supported
and exposed options now are targeted against AOT.

See gh-31682

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -16,6 +16,10 @@
 
 package org.springframework.boot.maven;
 
+import java.io.File;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.ArrayList;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
@@ -25,6 +29,8 @@ import org.apache.maven.artifact.Artifact;
 import org.apache.maven.plugin.AbstractMojo;
 import org.apache.maven.plugin.MojoExecutionException;
 import org.apache.maven.plugins.annotations.Parameter;
+import org.apache.maven.project.MavenProject;
+import org.apache.maven.shared.artifact.filter.collection.AbstractArtifactFeatureFilter;
 import org.apache.maven.shared.artifact.filter.collection.ArtifactFilterException;
 import org.apache.maven.shared.artifact.filter.collection.ArtifactsFilter;
 import org.apache.maven.shared.artifact.filter.collection.FilterArtifacts;
@@ -38,6 +44,13 @@ import org.apache.maven.shared.artifact.filter.collection.FilterArtifacts;
  */
 public abstract class AbstractDependencyFilterMojo extends AbstractMojo {
 
+	/**
+	 * The Maven project.
+	 * @since 3.0.0
+	 */
+	@Parameter(defaultValue = "${project}", readonly = true, required = true)
+	protected MavenProject project;
+
 	/**
 	 * Collection of artifact definitions to include. The {@link Include} element defines
 	 * mandatory {@code groupId} and {@code artifactId} properties and an optional
@@ -76,6 +89,26 @@ public abstract class AbstractDependencyFilterMojo extends AbstractMojo {
 		this.excludeGroupIds = excludeGroupIds;
 	}
 
+	protected List<URL> getDependencyURLs(ArtifactsFilter... additionalFilters) throws MojoExecutionException {
+		Set<Artifact> artifacts = filterDependencies(this.project.getArtifacts(), getFilters(additionalFilters));
+		List<URL> urls = new ArrayList<>();
+		for (Artifact artifact : artifacts) {
+			if (artifact.getFile() != null) {
+				urls.add(toURL(artifact.getFile()));
+			}
+		}
+		return urls;
+	}
+
+	protected URL toURL(File file) {
+		try {
+			return file.toURI().toURL();
+		}
+		catch (MalformedURLException ex) {
+			throw new IllegalStateException("Invalid URL for " + file, ex);
+		}
+	}
+
 	protected final Set<Artifact> filterDependencies(Set<Artifact> dependencies, FilterArtifacts filters)
 			throws MojoExecutionException {
 		try {
@@ -124,4 +157,17 @@ public abstract class AbstractDependencyFilterMojo extends AbstractMojo {
 		return cleaned.toString();
 	}
 
+	static class TestArtifactFilter extends AbstractArtifactFeatureFilter {
+
+		TestArtifactFilter() {
+			super("", Artifact.SCOPE_TEST);
+		}
+
+		@Override
+		protected String getArtifactFeature(Artifact artifact) {
+			return artifact.getScope();
+		}
+
+	}
+
 }

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

@@ -23,6 +23,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
@@ -36,14 +37,18 @@ import javax.tools.JavaFileObject;
 import javax.tools.StandardJavaFileManager;
 import javax.tools.ToolProvider;
 
+import org.apache.maven.execution.MavenSession;
 import org.apache.maven.plugin.MojoExecutionException;
 import org.apache.maven.plugin.MojoFailureException;
+import org.apache.maven.plugins.annotations.Component;
 import org.apache.maven.plugins.annotations.LifecyclePhase;
 import org.apache.maven.plugins.annotations.Mojo;
 import org.apache.maven.plugins.annotations.Parameter;
 import org.apache.maven.plugins.annotations.ResolutionScope;
+import org.apache.maven.toolchain.ToolchainManager;
 
-import org.springframework.boot.loader.tools.RunProcess;
+import org.springframework.boot.maven.CommandLineBuilder.ClasspathBuilder;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Invoke the AOT engine on the application.
@@ -55,10 +60,35 @@ import org.springframework.boot.loader.tools.RunProcess;
 @Mojo(name = "aot-generate", defaultPhase = LifecyclePhase.PREPARE_PACKAGE, threadSafe = true,
 		requiresDependencyResolution = ResolutionScope.COMPILE_PLUS_RUNTIME,
 		requiresDependencyCollection = ResolutionScope.COMPILE_PLUS_RUNTIME)
-public class AotGenerateMojo extends AbstractRunMojo {
+public class AotGenerateMojo extends AbstractDependencyFilterMojo {
 
 	private static final String AOT_PROCESSOR_CLASS_NAME = "org.springframework.boot.AotProcessor";
 
+	/**
+	 * The current Maven session. This is used for toolchain manager API calls.
+	 */
+	@Parameter(defaultValue = "${session}", readonly = true)
+	private MavenSession session;
+
+	/**
+	 * The toolchain manager to use to locate a custom JDK.
+	 */
+	@Component
+	private ToolchainManager toolchainManager;
+
+	/**
+	 * Directory containing the classes and resource files that should be packaged into
+	 * the archive.
+	 */
+	@Parameter(defaultValue = "${project.build.outputDirectory}", required = true)
+	private File classesDirectory;
+
+	/**
+	 * Skip the execution.
+	 */
+	@Parameter(property = "spring-boot.aot.skip", defaultValue = "false")
+	private boolean skip;
+
 	/**
 	 * Directory containing the generated sources.
 	 */
@@ -77,11 +107,40 @@ public class AotGenerateMojo extends AbstractRunMojo {
 	@Parameter(defaultValue = "${project.build.directory}/spring-aot/main/classes", required = true)
 	private File generatedClasses;
 
+	/**
+	 * List of JVM system properties to pass to the AOT process.
+	 */
+	@Parameter
+	private Map<String, String> systemPropertyVariables;
+
+	/**
+	 * JVM arguments that should be associated with the AOT process. On command line, make
+	 * sure to wrap multiple values between quotes.
+	 */
+	@Parameter(property = "spring-boot.aot.jvmArguments")
+	private String jvmArguments;
+
+	/**
+	 * Name of the main class to use as the source for the AOT process. If not specified
+	 * the first compiled class found that contains a 'main' method will be used.
+	 */
+	@Parameter(property = "spring-boot.aot.main-class")
+	private String mainClass;
+
+	/**
+	 * Spring profiles to take into account for AOT processing.
+	 */
+	@Parameter
+	private String[] profiles;
+
 	@Override
-	protected void run(File workingDirectory, String startClassName, Map<String, String> environmentVariables)
-			throws MojoExecutionException, MojoFailureException {
+	public void execute() throws MojoExecutionException, MojoFailureException {
+		if (this.skip) {
+			getLog().debug("skipping execution as per configuration.");
+			return;
+		}
 		try {
-			generateAotAssets(workingDirectory, startClassName, environmentVariables);
+			generateAotAssets();
 			compileSourceFiles();
 			copyAll(this.generatedResources.toPath().resolve("META-INF/native-image"),
 					this.classesDirectory.toPath().resolve("META-INF/native-image"));
@@ -92,52 +151,39 @@ public class AotGenerateMojo extends AbstractRunMojo {
 		}
 	}
 
-	private void generateAotAssets(File workingDirectory, String startClassName,
-			Map<String, String> environmentVariables) throws MojoExecutionException {
-		List<String> args = new ArrayList<>();
-		addJvmArgs(args);
-		addClasspath(args);
-		args.add(AOT_PROCESSOR_CLASS_NAME);
-		// Adding arguments that are necessary for generation
-		args.add(startClassName);
-		args.add(this.generatedSources.toString());
-		args.add(this.generatedResources.toString());
-		args.add(this.generatedClasses.toString());
-		args.add(this.project.getGroupId());
-		args.add(this.project.getArtifactId());
-		addArgs(args);
+	private void generateAotAssets() throws MojoExecutionException {
+		String applicationClass = (this.mainClass != null) ? this.mainClass
+				: SpringBootApplicationClassFinder.findSingleClass(this.classesDirectory);
+		List<String> aotArguments = new ArrayList<>();
+		aotArguments.add(applicationClass);
+		aotArguments.add(this.generatedSources.toString());
+		aotArguments.add(this.generatedResources.toString());
+		aotArguments.add(this.generatedClasses.toString());
+		aotArguments.add(this.project.getGroupId());
+		aotArguments.add(this.project.getArtifactId());
+		if (!ObjectUtils.isEmpty(this.profiles)) {
+			aotArguments.add("--spring.profiles.active=" + String.join(",", this.profiles));
+		}
+		// @formatter:off
+		List<String> args = CommandLineBuilder.forMainClass(AOT_PROCESSOR_CLASS_NAME)
+				.withSystemProperties(this.systemPropertyVariables)
+				.withJvmArguments(new RunArguments(this.jvmArguments).asArray())
+				.withClasspath(getClassPathUrls())
+				.withArguments(aotArguments.toArray(String[]::new))
+				.build();
+		// @formatter:on
 		if (getLog().isDebugEnabled()) {
 			getLog().debug("Generating AOT assets using command: " + args);
 		}
-		int exitCode = forkJvm(workingDirectory, args, environmentVariables);
-		if (!hasTerminatedSuccessfully(exitCode)) {
-			throw new MojoExecutionException("AOT generation process finished with exit code: " + exitCode);
-		}
+		JavaProcessExecutor processExecutor = new JavaProcessExecutor(this.session, this.toolchainManager);
+		processExecutor.run(this.project.getBasedir(), args, Collections.emptyMap());
 	}
 
-	private int forkJvm(File workingDirectory, List<String> args, Map<String, String> environmentVariables)
-			throws MojoExecutionException {
-		try {
-			RunProcess runProcess = new RunProcess(workingDirectory, getJavaExecutable());
-			return runProcess.run(true, args, environmentVariables);
-		}
-		catch (Exception ex) {
-			throw new MojoExecutionException("Could not exec java", ex);
-		}
-	}
-
-	@Override
-	protected URL[] getClassPathUrls() throws MojoExecutionException {
-		try {
-			List<URL> urls = new ArrayList<>();
-			addUserDefinedDirectories(urls);
-			addProjectClasses(urls);
-			addDependencies(urls, getFilters(new TestArtifactFilter()));
-			return urls.toArray(new URL[0]);
-		}
-		catch (IOException ex) {
-			throw new MojoExecutionException("Unable to build classpath", ex);
-		}
+	private URL[] getClassPathUrls() throws MojoExecutionException {
+		List<URL> urls = new ArrayList<>();
+		urls.add(toURL(this.classesDirectory));
+		urls.addAll(getDependencyURLs(new TestArtifactFilter()));
+		return urls.toArray(URL[]::new);
 	}
 
 	private void compileSourceFiles() throws IOException, MojoExecutionException {
@@ -148,7 +194,8 @@ public class AotGenerateMojo extends AbstractRunMojo {
 		JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 		try (StandardJavaFileManager fm = compiler.getStandardFileManager(null, null, null)) {
 			List<String> options = new ArrayList<>();
-			addClasspath(options);
+			options.add("-cp");
+			options.add(ClasspathBuilder.build(Arrays.asList(getClassPathUrls())));
 			options.add("-d");
 			options.add(this.classesDirectory.toPath().toAbsolutePath().toString());
 			Iterable<? extends JavaFileObject> compilationUnits = fm.getJavaFileObjectsFromPaths(sourceFiles);

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

@@ -0,0 +1,135 @@
+/*
+ * Copyright 2012-2022 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;
+
+import java.io.File;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * Helper class to build the command-line arguments of a java process.
+ *
+ * @author Stephane Nicoll
+ */
+final class CommandLineBuilder {
+
+	private final List<String> options = new ArrayList<>();
+
+	private final List<URL> classpathElements = new ArrayList<>();
+
+	private final String mainClass;
+
+	private final List<String> arguments = new ArrayList<>();
+
+	private CommandLineBuilder(String mainClass) {
+		this.mainClass = mainClass;
+	}
+
+	static CommandLineBuilder forMainClass(String mainClass) {
+		return new CommandLineBuilder(mainClass);
+	}
+
+	CommandLineBuilder withJvmArguments(String... jvmArguments) {
+		if (jvmArguments != null) {
+			this.options.addAll(Arrays.stream(jvmArguments).filter(Objects::nonNull).toList());
+		}
+		return this;
+	}
+
+	CommandLineBuilder withSystemProperties(Map<String, String> systemProperties) {
+		if (systemProperties != null) {
+			systemProperties.entrySet().stream().map((e) -> SystemPropertyFormatter.format(e.getKey(), e.getValue()))
+					.forEach(this.options::add);
+		}
+		return this;
+	}
+
+	CommandLineBuilder withClasspath(URL... elements) {
+		this.classpathElements.addAll(Arrays.asList(elements));
+		return this;
+	}
+
+	CommandLineBuilder withArguments(String... arguments) {
+		if (arguments != null) {
+			this.arguments.addAll(Arrays.stream(arguments).filter(Objects::nonNull).toList());
+		}
+		return this;
+	}
+
+	List<String> build() {
+		List<String> commandLine = new ArrayList<>();
+		if (!this.options.isEmpty()) {
+			commandLine.addAll(this.options);
+		}
+		if (!this.classpathElements.isEmpty()) {
+			commandLine.add("-cp");
+			commandLine.add(ClasspathBuilder.build(this.classpathElements));
+		}
+		commandLine.add(this.mainClass);
+		if (!this.arguments.isEmpty()) {
+			commandLine.addAll(this.arguments);
+		}
+		return commandLine;
+	}
+
+	static class ClasspathBuilder {
+
+		static String build(List<URL> classpathElements) {
+			StringBuilder classpath = new StringBuilder();
+			for (URL element : classpathElements) {
+				if (classpath.length() > 0) {
+					classpath.append(File.pathSeparator);
+				}
+				classpath.append(toFile(element));
+			}
+			return classpath.toString();
+		}
+
+		private static File toFile(URL element) {
+			try {
+				return new File(element.toURI());
+			}
+			catch (URISyntaxException ex) {
+				throw new IllegalArgumentException(ex);
+			}
+		}
+
+	}
+
+	/**
+	 * Format System properties.
+	 */
+	private static class SystemPropertyFormatter {
+
+		static String format(String key, String value) {
+			if (key == null) {
+				return "";
+			}
+			if (value == null || value.isEmpty()) {
+				return String.format("-D%s", key);
+			}
+			return String.format("-D%s=\"%s\"", key, value);
+		}
+
+	}
+
+}

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

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2012-2022 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;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.maven.execution.MavenSession;
+import org.apache.maven.plugin.MojoExecutionException;
+import org.apache.maven.toolchain.Toolchain;
+import org.apache.maven.toolchain.ToolchainManager;
+
+import org.springframework.boot.loader.tools.JavaExecutable;
+import org.springframework.boot.loader.tools.RunProcess;
+
+/**
+ * Ease the execution of a Java process using Maven's toolchain support.
+ *
+ * @author Stephane Nicoll
+ */
+class JavaProcessExecutor {
+
+	private static final int EXIT_CODE_SIGINT = 130;
+
+	private final MavenSession mavenSession;
+
+	private final ToolchainManager toolchainManager;
+
+	JavaProcessExecutor(MavenSession mavenSession, ToolchainManager toolchainManager) {
+		this.mavenSession = mavenSession;
+		this.toolchainManager = toolchainManager;
+	}
+
+	int run(File workingDirectory, List<String> args, Map<String, String> environmentVariables)
+			throws MojoExecutionException {
+		RunProcess runProcess = new RunProcess(workingDirectory, getJavaExecutable());
+		try {
+			int exitCode = runProcess.run(true, args, environmentVariables);
+			if (!hasTerminatedSuccessfully(exitCode)) {
+				throw new MojoExecutionException("Process terminated with exit code: " + exitCode);
+			}
+			return exitCode;
+		}
+		catch (IOException ex) {
+			throw new MojoExecutionException("Process execution failed", ex);
+		}
+	}
+
+	private boolean hasTerminatedSuccessfully(int exitCode) {
+		return (exitCode == 0 || exitCode == EXIT_CODE_SIGINT);
+	}
+
+	private String getJavaExecutable() {
+		Toolchain toolchain = this.toolchainManager.getToolchainFromBuildContext("jdk", this.mavenSession);
+		String javaExecutable = (toolchain != null) ? toolchain.findTool("java") : null;
+		return (javaExecutable != null) ? javaExecutable : new JavaExecutable().toString();
+	}
+
+}

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

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2012-2022 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;
+
+import java.io.File;
+import java.io.IOException;
+
+import org.apache.maven.plugin.MojoExecutionException;
+
+import org.springframework.boot.loader.tools.MainClassFinder;
+
+/**
+ * Find a single Spring Boot Application class match based on directory.
+ *
+ * @author Stephane Nicoll
+ * @see MainClassFinder
+ */
+abstract class SpringBootApplicationClassFinder {
+
+	private static final String SPRING_BOOT_APPLICATION_CLASS_NAME = "org.springframework.boot.autoconfigure.SpringBootApplication";
+
+	static String findSingleClass(File classesDirectory) throws MojoExecutionException {
+		try {
+			String mainClass = MainClassFinder.findSingleMainClass(classesDirectory,
+					SPRING_BOOT_APPLICATION_CLASS_NAME);
+			if (mainClass != null) {
+				return mainClass;
+			}
+			throw new MojoExecutionException("Unable to find a suitable main class, please add a 'mainClass' property");
+		}
+		catch (IOException ex) {
+			throw new MojoExecutionException(ex.getMessage(), ex);
+		}
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/java/org/springframework/boot/maven/CommandLineBuilderTests.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2012-2022 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;
+
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.maven.sample.ClassWithMainMethod;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link CommandLineBuilder}.
+ *
+ * @author Stephane Nicoll
+ */
+class CommandLineBuilderTests {
+
+	public static final String CLASS_NAME = ClassWithMainMethod.class.getName();
+
+	@Test
+	void buildWithNullJvmArgumentsIsIgnored() {
+		assertThat(CommandLineBuilder.forMainClass(CLASS_NAME).withJvmArguments((String[]) null).build())
+				.containsExactly(CLASS_NAME);
+	}
+
+	@Test
+	void buildWithNullIntermediateJvmArgumentIsIgnored() {
+		assertThat(CommandLineBuilder.forMainClass(CLASS_NAME).withJvmArguments("-verbose:class", null, "-verbose:gc")
+				.build()).containsExactly("-verbose:class", "-verbose:gc", CLASS_NAME);
+	}
+
+	@Test
+	void buildWithJvmArgument() {
+		assertThat(CommandLineBuilder.forMainClass(CLASS_NAME).withJvmArguments("-verbose:class").build())
+				.containsExactly("-verbose:class", CLASS_NAME);
+	}
+
+	@Test
+	void buildWithNullSystemPropertyIsIgnored() {
+		assertThat(CommandLineBuilder.forMainClass(CLASS_NAME).withSystemProperties(null).build())
+				.containsExactly(CLASS_NAME);
+	}
+
+	@Test
+	void buildWithSystemProperty() {
+		assertThat(CommandLineBuilder.forMainClass(CLASS_NAME).withSystemProperties(Map.of("flag", "enabled")).build())
+				.containsExactly("-Dflag=\"enabled\"", CLASS_NAME);
+	}
+
+	@Test
+	void buildWithNullArgumentsIsIgnored() {
+		assertThat(CommandLineBuilder.forMainClass(CLASS_NAME).withArguments((String[]) null).build())
+				.containsExactly(CLASS_NAME);
+	}
+
+	@Test
+	void buildWithNullIntermediateArgumentIsIgnored() {
+		assertThat(CommandLineBuilder.forMainClass(CLASS_NAME).withArguments("--test", null, "--another").build())
+				.containsExactly(CLASS_NAME, "--test", "--another");
+	}
+
+}