Use application plugin properties by convention when it is applied

bootRun's main and jvmArgs properties use mainClassName and
applicationDefaultJvmArgs respectively by convention.

bootJar and bootWar's mainClass property uses mainClassName by
convention.

spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/bundling/BundlingPluginFeatures.java

@@ -19,6 +19,7 @@ package org.springframework.boot.gradle.bundling;
 import java.util.Collections;
 import java.util.Set;
 import java.util.concurrent.Callable;
+import java.util.function.Supplier;
 
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
@@ -66,9 +67,8 @@ public class BundlingPluginFeatures implements PluginFeatures {
 		ArchivePublishArtifact artifact = new ArchivePublishArtifact(bootWar);
 		this.singlePublishedArtifact.addCandidate(artifact);
 		project.getComponents().add(new BootSoftwareComponent(artifact, "bootWeb"));
-		bootWar.conventionMapping("mainClass", () -> {
-			return new MainClassResolver(bootWar.getClasspath()).resolveMainClass();
-		});
+		bootWar.conventionMapping("mainClass",
+				mainClassConvention(project, bootWar::getClasspath));
 	}
 
 	private void configureBootJarTask(Project project) {
@@ -83,9 +83,18 @@ public class BundlingPluginFeatures implements PluginFeatures {
 		ArchivePublishArtifact artifact = new ArchivePublishArtifact(bootJar);
 		this.singlePublishedArtifact.addCandidate(artifact);
 		project.getComponents().add(new BootSoftwareComponent(artifact, "bootJava"));
-		bootJar.conventionMapping("mainClass", () -> {
-			return new MainClassResolver(bootJar.getClasspath()).resolveMainClass();
-		});
+		bootJar.conventionMapping("mainClass",
+				mainClassConvention(project, bootJar::getClasspath));
+	}
+
+	private Callable<Object> mainClassConvention(Project project,
+			Supplier<FileCollection> classpathSupplier) {
+		return () -> {
+			if (project.hasProperty("mainClassName")) {
+				return project.property("mainClassName");
+			}
+			return new MainClassResolver(classpathSupplier.get()).resolveMainClass();
+		};
 	}
 
 	private void configureBootArchivesUpload(Project project) {

spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/run/RunPluginFeatures.java

@@ -44,26 +44,25 @@ public class RunPluginFeatures implements PluginFeatures {
 		});
 	}
 
-	private void addBootRunTask(final Project project) {
-		final JavaPluginConvention javaConvention = project.getConvention()
+	private void addBootRunTask(Project project) {
+		JavaPluginConvention javaConvention = project.getConvention()
 				.getPlugin(JavaPluginConvention.class);
-
 		BootRun run = project.getTasks().create(RUN_APP_TASK_NAME, BootRun.class);
 		run.setDescription("Run the project with support for "
 				+ "auto-detecting main class and reloading static resources");
 		run.setGroup("application");
 		run.classpath(javaConvention.getSourceSets()
 				.findByName(SourceSet.MAIN_SOURCE_SET_NAME).getRuntimeClasspath());
-		run.getConventionMapping().map("jvmArgs", new Callable<Object>() {
-			@Override
-			public Object call() throws Exception {
+		run.getConventionMapping().map("jvmArgs", ((Callable<Object>) () -> {
 			if (project.hasProperty("applicationDefaultJvmArgs")) {
 				return project.property("applicationDefaultJvmArgs");
 			}
 			return Collections.emptyList();
-			}
-		});
+		}));
 		run.conventionMapping("main", () -> {
+			if (project.hasProperty("mainClassName")) {
+				return project.property("mainClassName");
+			}
 			return new MainClassResolver(run.getClasspath()).resolveMainClass();
 		});
 	}

spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/bundling/AbstractBootArchiveIntegrationTests.java

@@ -16,7 +16,9 @@
 
 package org.springframework.boot.gradle.bundling;
 
+import java.io.File;
 import java.io.IOException;
+import java.util.jar.JarFile;
 
 import org.gradle.testkit.runner.InvalidRunnerConfigurationException;
 import org.gradle.testkit.runner.TaskOutcome;
@@ -97,4 +99,17 @@ public abstract class AbstractBootArchiveIntegrationTests {
 				.getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
 	}
 
+	@Test
+	public void applicationPluginMainClassNameIsUsed() throws IOException {
+		assertThat(this.gradleBuild.build(this.taskName).task(":" + this.taskName)
+				.getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
+		try (JarFile jarFile = new JarFile(
+				new File(this.gradleBuild.getProjectDir(), "build/libs")
+						.listFiles()[0])) {
+			assertThat(jarFile.getManifest().getMainAttributes().getValue("Start-Class"))
+					.isEqualTo("com.example.CustomMain");
+		}
+
+	}
+
 }

spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/run/BootRunIntegrationTests.java

@@ -66,6 +66,24 @@ public class BootRunIntegrationTests {
 		assertThat(result.getOutput()).doesNotContain(urlOf("build/resources/main"));
 	}
 
+	@Test
+	public void applicationPluginMainClassNameIsUsed() throws IOException {
+		BuildResult result = this.gradleBuild.build("echoMainClassName");
+		assertThat(result.task(":echoMainClassName").getOutcome())
+				.isEqualTo(TaskOutcome.UP_TO_DATE);
+		assertThat(result.getOutput())
+				.contains("Main class name = com.example.CustomMainClass");
+	}
+
+	@Test
+	public void applicationPluginJvmArgumentsAreUsed() throws IOException {
+		BuildResult result = this.gradleBuild.build("echoJvmArguments");
+		assertThat(result.task(":echoJvmArguments").getOutcome())
+				.isEqualTo(TaskOutcome.UP_TO_DATE);
+		assertThat(result.getOutput())
+				.contains("JVM arguments = [-Dcom.foo=bar, -Dcom.bar=baz]");
+	}
+
 	private String urlOf(String path) throws IOException {
 		return new File(this.gradleBuild.getProjectDir().getCanonicalFile(), path).toURI()
 				.toURL().toString();

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

@@ -0,0 +1,11 @@
+buildscript {
+	dependencies {
+		classpath files(pluginClasspath.split(','))
+	}
+}
+
+apply plugin: 'java'
+apply plugin: 'org.springframework.boot'
+apply plugin: 'application'
+
+mainClassName = 'com.example.CustomMain'

spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/bundling/BootWarIntegrationTests-applicationPluginMainClassNameIsUsed.gradle

@@ -0,0 +1,11 @@
+buildscript {
+	dependencies {
+		classpath files(pluginClasspath.split(','))
+	}
+}
+
+apply plugin: 'war'
+apply plugin: 'org.springframework.boot'
+apply plugin: 'application'
+
+mainClassName = 'com.example.CustomMain'

spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/run/BootRunIntegrationTests-applicationPluginJvmArgumentsAreUsed.gradle

@@ -0,0 +1,14 @@
+buildscript {
+	dependencies {
+		classpath files(pluginClasspath.split(','))
+	}
+}
+
+apply plugin: 'application'
+apply plugin: 'org.springframework.boot'
+
+applicationDefaultJvmArgs = ['-Dcom.foo=bar', '-Dcom.bar=baz']
+
+task echoJvmArguments {
+	println 'JVM arguments = ' + bootRun.jvmArgs
+}

spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/run/BootRunIntegrationTests-applicationPluginMainClassNameIsUsed.gradle

@@ -0,0 +1,14 @@
+buildscript {
+	dependencies {
+		classpath files(pluginClasspath.split(','))
+	}
+}
+
+apply plugin: 'application'
+apply plugin: 'org.springframework.boot'
+
+mainClassName = 'com.example.CustomMainClass'
+
+task echoMainClassName {
+	println 'Main class name = ' + bootRun.main
+}