Raise the minimum supported version of Gradle to 4.4

Closes gh-14418

Author: wilkinsona

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

@@ -168,7 +168,7 @@ Advanced configuration options and examples are available in the
 == Spring Boot Gradle Plugin
 The Spring Boot Gradle Plugin provides Spring Boot support in Gradle, letting you package
 executable jar or war archives, run Spring Boot applications, and use the dependency
-management provided by `spring-boot-dependencies`. It requires Gradle 4.0 or later. Please
+management provided by `spring-boot-dependencies`. It requires Gradle 4.4 or later. Please
 refer to the plugin's documentation to learn more:
 
 * Reference ({spring-boot-gradle-plugin}/reference/html[HTML] and

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

@@ -50,7 +50,7 @@ Explicit build support is provided for the following build tools:
 |3.2+
 
 |Gradle
-|4.x
+|4.4+
 |===
 
 
@@ -199,8 +199,8 @@ scope.
 
 [[getting-started-gradle-installation]]
 ==== Gradle Installation
-Spring Boot is compatible with Gradle 4. If you do not already have Gradle installed, you
-can follow the instructions at https://gradle.org.
+Spring Boot is compatible with Gradle 4.4 and later. If you do not already have Gradle
+installed, you can follow the instructions at https://gradle.org.
 
 Spring Boot dependencies can be declared by using the `org.springframework.boot` `group`.
 Typically, your project declares dependencies to one or more

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/gradle/wrapper/gradle-wrapper.jar

@@ -1,6 +1,5 @@
-#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-4.0.2-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.4.1-bin.zip

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

@@ -33,11 +33,11 @@ DEFAULT_JVM_OPTS=""
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD="maximum"
 
-warn ( ) {
+warn () {
     echo "$*"
 }
 
-die ( ) {
+die () {
     echo
     echo "$*"
     echo
@@ -155,7 +155,7 @@ if $cygwin ; then
 fi
 
 # Escape application args
-save ( ) {
+save () {
     for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
     echo " "
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/gradlew

@@ -37,7 +37,7 @@ 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 4.0 or later.
+Gradle plugin requires Gradle 4.4 or later.
 
 In addition to this user guide, {api-documentation}[API documentation] is also available.
 

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

@@ -84,8 +84,8 @@ public void apply(Project project) {
 	}
 
 	private void verifyGradleVersion() {
-		if (GradleVersion.current().compareTo(GradleVersion.version("4.0")) < 0) {
-			throw new GradleException("Spring Boot plugin requires Gradle 4.0 or later."
+		if (GradleVersion.current().compareTo(GradleVersion.version("4.4")) < 0) {
+			throw new GradleException("Spring Boot plugin requires Gradle 4.4 or later."
 					+ " The current version is " + GradleVersion.current());
 		}
 	}

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

@@ -53,7 +53,7 @@
  */
 class BootZipCopyAction implements CopyAction {
 
-	private static final long CONSTANT_TIME_FOR_ZIP_ENTRIES = new GregorianCalendar(1980,
+	static final long CONSTANT_TIME_FOR_ZIP_ENTRIES = new GregorianCalendar(1980,
 			Calendar.FEBRUARY, 1, 0, 0, 0).getTimeInMillis();
 
 	private final File output;

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/BootZipCopyAction.java

@@ -38,8 +38,8 @@
  */
 public final class GradleCompatibilitySuite extends Suite {
 
-	private static final List<String> GRADLE_VERSIONS = Arrays.asList("default", "4.1",
-			"4.2", "4.3", "4.4.1", "4.5.1", "4.6", "4.7", "4.8.1", "4.9", "4.10");
+	private static final List<String> GRADLE_VERSIONS = Arrays.asList("default", "4.5.1",
+			"4.6", "4.7", "4.8.1", "4.9", "4.10");
 
 	public GradleCompatibilitySuite(Class<?> clazz) throws InitializationError {
 		super(clazz, createRunners(clazz));

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

@@ -39,19 +39,19 @@ public class SpringBootPluginIntegrationTests {
 
 	@Test
 	public void failFastWithVersionOfGradleLowerThanRequired() {
-		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");
+		BuildResult result = this.gradleBuild.gradleVersion("4.3").buildAndFail();
+		assertThat(result.getOutput()).contains("Spring Boot plugin requires Gradle 4.4"
+				+ " or later. The current version is Gradle 4.3");
 	}
 
 	@Test
 	public void succeedWithVersionOfGradleHigherThanRequired() {
-		this.gradleBuild.gradleVersion("4.0.1").build();
+		this.gradleBuild.gradleVersion("4.4.1").build();
 	}
 
 	@Test
 	public void succeedWithVersionOfGradleMatchingWhatIsRequired() {
-		this.gradleBuild.gradleVersion("4.0").build();
+		this.gradleBuild.gradleVersion("4.4").build();
 	}
 
 	@Test