Raise the minimum version of Gradle to 4.0

Closes gh-9516

spring-boot-docs/src/main/asciidoc/build-tool-plugins.adoc

@@ -166,7 +166,7 @@ Advanced configuration options and examples are available in the
 == Spring Boot Gradle plugin
 The Spring Boot Gradle Plugin provides Spring Boot support in Gradle, allowing you to
 package executable jar or war archives, run Spring Boot applications and use the
-dependency management provided by `spring-boot-dependencies`. It requires Gradle 3.4 or
+dependency management provided by `spring-boot-dependencies`. It requires Gradle 4.0 or
 later. Please refer to the plugin's documentation to learn more:
 
 * Reference ({spring-boot-gradle-plugin}/reference/html[HTML] and

spring-boot-docs/src/main/asciidoc/getting-started.adoc

@@ -38,7 +38,7 @@ diverge from the defaults.
 == System Requirements
 Spring Boot {spring-boot-version} requires http://www.java.com[Java 8] and Spring
 Framework {spring-version} or above. Explicit build support is provided for Maven
-(3.2+), and Gradle 3 (3.4 or later).
+(3.2+), and Gradle 4.
 
 
 [[getting-started-system-requirements-servlet-containers]]
@@ -185,8 +185,8 @@ scope.
 
 [[getting-started-gradle-installation]]
 ==== Gradle installation
-Spring Boot is compatible with Gradle 3 (3.4 or later). If you don't already have Gradle
-installed you can follow the instructions at http://www.gradle.org/.
+Spring Boot is compatible with Gradle 4. If you don't already have Gradle installed you
+can follow the instructions at http://www.gradle.org/.
 
 Spring Boot dependencies can be declared using the `org.springframework.boot` `group`.
 Typically your project will declare dependencies to one or more

spring-boot-docs/src/main/asciidoc/index.adoc

@@ -51,7 +51,7 @@ Phillip Webb; Dave Syer; Josh Long; Stéphane Nicoll; Rob Winch; Andy Wilkinson;
 :propdeps-plugin: https://github.com/spring-projects/gradle-plugins/tree/master/propdeps-plugin
 :ant-manual: http://ant.apache.org/manual
 :code-examples: ../java/org/springframework/boot
-:gradle-user-guide: https://docs.gradle.org/3.4.1/userguide
+:gradle-user-guide: https://docs.gradle.org/4.0.2/userguide
 :hibernate-documentation: http://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html
 :jetty-documentation: https://www.eclipse.org/jetty/documentation/9.4.x
 :tomcat-documentation: https://tomcat.apache.org/tomcat-8.5-doc

spring-boot-tools/spring-boot-gradle-plugin/build.gradle

 plugins {
 	id 'java'
 	id 'eclipse'
-	id 'org.sonarqube' version '2.2.1'
 }
 
 repositories {

spring-boot-tools/spring-boot-gradle-plugin/gradle/wrapper/gradle-wrapper.properties

-#Thu Mar 16 20:08:41 GMT 2017
+#Thu Jul 27 14:32:22 BST 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-3.4-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.0.2-bin.zip

spring-boot-tools/spring-boot-gradle-plugin/src/main/asciidoc/index.adoc

@@ -36,7 +36,7 @@ Andy Wilkinson
 The Spring Boot Gradle Plugin provides Spring Boot support in https://gradle.org[Gradle],
 allowing you to package executable jar or war archives, run Spring Boot applications, and
 use the dependency management provided by `spring-boot-dependencies`. Spring Boot's
-Gradle plugin requires Gradle 3.4 or later.
+Gradle plugin requires Gradle 4.0 or later.
 
 In addition to this user guide, {api-documentation}[API documentation] is also available.
 

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

@@ -68,8 +68,8 @@ public class SpringBootPlugin implements Plugin<Project> {
 	}
 
 	private void verifyGradleVersion() {
-		if (GradleVersion.current().compareTo(GradleVersion.version("3.4")) < 0) {
-			throw new GradleException("Spring Boot plugin requires Gradle 3.4 or later."
+		if (GradleVersion.current().compareTo(GradleVersion.version("4.0")) < 0) {
+			throw new GradleException("Spring Boot plugin requires Gradle 4.0 or later."
 					+ " The current version is " + GradleVersion.current());
 		}
 	}

spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/junit/GradleCompatibilitySuite.java

@@ -38,8 +38,8 @@ import org.springframework.boot.gradle.testkit.GradleBuild;
  */
 public final class GradleCompatibilitySuite extends Suite {
 
-	private static final List<String> GRADLE_VERSIONS = Arrays.asList("default", "3.4.1",
-			"3.5", "3.5.1", "4.0", "4.0.1", "4.1-rc-1");
+	private static final List<String> GRADLE_VERSIONS = Arrays.asList("default",
+			"4.1-rc-1");
 
 	public GradleCompatibilitySuite(Class<?> clazz) throws InitializationError {
 		super(clazz, createRunners(clazz));

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

@@ -36,19 +36,19 @@ public class SpringBootPluginIntegrationTests {
 
 	@Test
 	public void failFastWithVersionOfGradleLowerThanRequired() {
-		BuildResult result = this.gradleBuild.gradleVersion("3.3").buildAndFail();
-		assertThat(result.getOutput()).contains("Spring Boot plugin requires Gradle 3.4"
-				+ " or later. The current version is Gradle 3.3");
+		BuildResult result = this.gradleBuild.gradleVersion("3.5.1").buildAndFail();
+		assertThat(result.getOutput()).contains("Spring Boot plugin requires Gradle 4.0"
+				+ " or later. The current version is Gradle 3.5.1");
 	}
 
 	@Test
 	public void succeedWithVersionOfGradleHigherThanRequired() {
-		this.gradleBuild.gradleVersion("3.5").build();
+		this.gradleBuild.gradleVersion("4.0.1").build();
 	}
 
 	@Test
 	public void succeedWithVersionOfGradleMatchingWhatIsRequired() {
-		this.gradleBuild.gradleVersion("3.4").build();
+		this.gradleBuild.gradleVersion("4.0").build();
 	}
 
 }

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

@@ -51,7 +51,7 @@ public class BootRunIntegrationTests {
 		new File(this.gradleBuild.getProjectDir(), "src/main/resources").mkdirs();
 		BuildResult result = this.gradleBuild.build("bootRun");
 		assertThat(result.task(":bootRun").getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
-		assertThat(result.getOutput()).contains("1. " + urlOf(mainJavaOutput()));
+		assertThat(result.getOutput()).contains("1. " + urlOf("build/classes/java/main"));
 		assertThat(result.getOutput()).contains("2. " + urlOf("build/resources/main"));
 		assertThat(result.getOutput()).doesNotContain(urlOf("src/main/resources"));
 	}
@@ -65,7 +65,7 @@ public class BootRunIntegrationTests {
 		BuildResult result = this.gradleBuild.build("bootRun");
 		assertThat(result.task(":bootRun").getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
 		assertThat(result.getOutput()).contains("1. " + urlOf("src/main/resources"));
-		assertThat(result.getOutput()).contains("2. " + urlOf(mainJavaOutput()));
+		assertThat(result.getOutput()).contains("2. " + urlOf("build/classes/java/main"));
 		assertThat(result.getOutput()).doesNotContain(urlOf("build/resources/main"));
 	}
 
@@ -87,13 +87,6 @@ public class BootRunIntegrationTests {
 				.contains("JVM arguments = [-Dcom.foo=bar, -Dcom.bar=baz]");
 	}
 
-	private String mainJavaOutput() {
-		String gradleVersion = this.gradleBuild.getGradleVersion();
-		return "build/classes/"
-				+ (gradleVersion != null && gradleVersion.startsWith("4.") ? "java/" : "")
-				+ "main";
-	}
-
 	private String urlOf(String path) throws IOException {
 		return new File(this.gradleBuild.getProjectDir().getCanonicalFile(), path).toURI()
 				.toURL().toString();