Added goal [fmc], support to find main class and set to specified property

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

@@ -44,7 +44,6 @@
 
 import org.springframework.boot.loader.tools.FileUtils;
 import org.springframework.boot.loader.tools.JavaExecutable;
-import org.springframework.boot.loader.tools.MainClassFinder;
 
 /**
  * Base class to run a spring application.
@@ -58,9 +57,7 @@
  * @see RunMojo
  * @see StartMojo
  */
-public abstract class AbstractRunMojo extends AbstractDependencyFilterMojo {
-
-	private static final String SPRING_BOOT_APPLICATION_CLASS_NAME = "org.springframework.boot.autoconfigure.SpringBootApplication";
+public abstract class AbstractRunMojo extends FindMainClassMojo {
 
 	/**
 	 * The Maven project.
@@ -167,14 +164,6 @@ public abstract class AbstractRunMojo extends AbstractDependencyFilterMojo {
 	@Parameter(property = "spring-boot.run.profiles")
 	private String[] profiles;
 
-	/**
-	 * The name of the main class. If not specified the first compiled class found that
-	 * contains a 'main' method will be used.
-	 * @since 1.0.0
-	 */
-	@Parameter(property = "spring-boot.run.main-class")
-	private String mainClass;
-
 	/**
 	 * Additional directories besides the classes directory that should be added to the
 	 * classpath.
@@ -420,23 +409,6 @@ private void addClasspath(List<String> args) throws MojoExecutionException {
 		}
 	}
 
-	private String getStartClass() throws MojoExecutionException {
-		String mainClass = this.mainClass;
-		if (mainClass == null) {
-			try {
-				mainClass = MainClassFinder.findSingleMainClass(this.classesDirectory,
-						SPRING_BOOT_APPLICATION_CLASS_NAME);
-			}
-			catch (IOException ex) {
-				throw new MojoExecutionException(ex.getMessage(), ex);
-			}
-		}
-		if (mainClass == null) {
-			throw new MojoExecutionException("Unable to find a suitable main class, please add a 'mainClass' property");
-		}
-		return mainClass;
-	}
-
 	protected URL[] getClassPathUrls() throws MojoExecutionException {
 		try {
 			List<URL> urls = new ArrayList<>();

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

@@ -0,0 +1,99 @@
+/*
+ * Copyright 2012-2021 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 org.apache.maven.plugin.MojoExecutionException;
+import org.apache.maven.plugin.MojoFailureException;
+import org.apache.maven.plugins.annotations.Execute;
+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.project.MavenProject;
+import org.springframework.boot.loader.tools.MainClassFinder;
+
+import java.io.File;
+import java.io.IOException;
+
+/**
+ * Help find main class and set it to the specified property.
+ *
+ * @author Phillip Webb
+ * @author Dave Syer
+ * @author Stephane Nicoll
+ * @author Björn Lindström
+ * @author Scott Frederick
+ * @author kerwin612
+ * @since 1.0.0
+ */
+@Mojo(name = "fmc", defaultPhase = LifecyclePhase.PREPARE_PACKAGE, requiresProject = true, threadSafe = true,
+		requiresDependencyResolution = ResolutionScope.RUNTIME)
+@Execute(phase = LifecyclePhase.PREPARE_PACKAGE)
+public class FindMainClassMojo extends AbstractDependencyFilterMojo {
+
+	private static final String SPRING_BOOT_APPLICATION_CLASS_NAME = "org.springframework.boot.autoconfigure.SpringBootApplication";
+
+	/**
+	 * The name of the main class. If not specified the first compiled class found that
+	 * contains a 'main' method will be used.
+	 * @since 1.0.0
+	 */
+	@Parameter(property = "spring-boot.run.main-class")
+	private String mainClass;
+
+	/**
+	 * Directory containing the classes and resource files that should be packaged into
+	 * the archive.
+	 * @since 1.0.0
+	 */
+	@Parameter(defaultValue = "${project.build.outputDirectory}", required = true)
+	private File classesDirectory;
+
+	@Parameter(defaultValue = "mainClass", required = true)
+	private String mainClassPropertyName;
+
+	@Parameter(defaultValue = "${project}", readonly = true, required = true)
+	private MavenProject project;
+
+	@Override
+	public void execute() throws MojoExecutionException, MojoFailureException {
+		String mainClass = getStartClass();
+		if (mainClass == null) {
+			throw new MojoExecutionException("Unable to find a suitable main class");
+		}
+		getLog().info("found main class: " + mainClass);
+		project.getProperties().put(mainClassPropertyName, mainClass);
+	}
+
+	protected String getStartClass() throws MojoExecutionException {
+		String mainClass = this.mainClass;
+		if (mainClass == null) {
+			try {
+				mainClass = MainClassFinder.findSingleMainClass(this.classesDirectory,
+						SPRING_BOOT_APPLICATION_CLASS_NAME);
+			}
+			catch (IOException ex) {
+				throw new MojoExecutionException(ex.getMessage(), ex);
+			}
+		}
+		if (mainClass == null) {
+			throw new MojoExecutionException("Unable to find a suitable main class, please add a 'mainClass' property");
+		}
+		return mainClass;
+	}
+
+}