Use ObjectFactory rather than Usages to create Usage on Gradle 4.0

Usages has been removed in Gradle 4.0 and replaced with the use of
a new ObjectFactory API that can be used to create a Usage. This
commit uses reflection to access the ObjectFactory from the Project
and use it to create a Usage when an attempt to use Usages fails.

Closes gh-9364

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

@@ -92,7 +92,7 @@ final class JavaPluginAction implements PluginApplicationAction {
 	private void configureArtifactPublication(Project project, BootJar bootJar) {
 		ArchivePublishArtifact artifact = new ArchivePublishArtifact(bootJar);
 		this.singlePublishedArtifact.addCandidate(artifact);
-		project.getComponents().add(new SpringBootSoftwareComponent(artifact,
+		project.getComponents().add(new SpringBootSoftwareComponent(project, artifact,
 				SpringBootPlugin.BOOT_JAVA_SOFTWARE_COMPONENT_NAME));
 	}
 

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

@@ -19,6 +19,7 @@ package org.springframework.boot.gradle.plugin;
 import java.util.Collections;
 import java.util.Set;
 
+import org.gradle.api.Project;
 import org.gradle.api.artifacts.ModuleDependency;
 import org.gradle.api.artifacts.PublishArtifact;
 import org.gradle.api.attributes.Usage;
@@ -37,9 +38,33 @@ final class SpringBootSoftwareComponent implements SoftwareComponentInternal {
 
 	private final String name;
 
-	SpringBootSoftwareComponent(PublishArtifact artifact, String name) {
+	private final Usage usage;
+
+	SpringBootSoftwareComponent(Project project, PublishArtifact artifact, String name) {
 		this.artifact = artifact;
 		this.name = name;
+		this.usage = createUsage(project);
+	}
+
+	private static Usage createUsage(Project project) {
+		try {
+			return Usages.usage("master");
+		}
+		catch (Throwable ex) {
+			return createUsageUsingObjectFactory(project);
+		}
+	}
+
+	private static Usage createUsageUsingObjectFactory(Project project) {
+		try {
+			Object objects = project.getClass().getMethod("getObjects").invoke(project);
+			return (Usage) objects.getClass()
+					.getMethod("named", Class.class, String.class)
+					.invoke(objects, Usage.class, "master");
+		}
+		catch (Throwable ex) {
+			throw new RuntimeException(ex);
+		}
 	}
 
 	@Override
@@ -49,22 +74,23 @@ final class SpringBootSoftwareComponent implements SoftwareComponentInternal {
 
 	@Override
 	public Set<UsageContext> getUsages() {
-		return Collections.singleton(new BootUsageContext(this.artifact));
+		return Collections.singleton(new BootUsageContext(this.usage, this.artifact));
 	}
 
 	private static final class BootUsageContext implements UsageContext {
 
-		private static final Usage USAGE = Usages.usage("master");
+		private final Usage usage;
 
 		private final PublishArtifact artifact;
 
-		private BootUsageContext(PublishArtifact artifact) {
+		private BootUsageContext(Usage usage, PublishArtifact artifact) {
+			this.usage = usage;
 			this.artifact = artifact;
 		}
 
 		@Override
 		public Usage getUsage() {
-			return USAGE;
+			return this.usage;
 		}
 
 		@Override

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

@@ -55,7 +55,7 @@ class WarPluginAction implements PluginApplicationAction {
 		bootWar.providedClasspath(providedRuntimeConfiguration(project));
 		ArchivePublishArtifact artifact = new ArchivePublishArtifact(bootWar);
 		this.singlePublishedArtifact.addCandidate(artifact);
-		project.getComponents().add(new SpringBootSoftwareComponent(artifact,
+		project.getComponents().add(new SpringBootSoftwareComponent(project, artifact,
 				SpringBootPlugin.BOOT_WEB_SOFTWARE_COMPONENT_NAME));
 		bootWar.conventionMapping("mainClass",
 				new MainClassConvention(project, bootWar::getClasspath));