Use Java configuration for Gradle build

See gh-1427

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/gradle/GradleKtsProjectGenerationConfigurationTests.java

@@ -120,7 +120,10 @@ class GradleKtsProjectGenerationConfigurationTests {
 				"",
 				"group = \"com.example\"",
 				"version = \"0.0.1-SNAPSHOT\"",
-				"java.sourceCompatibility = JavaVersion.VERSION_11",
+				"",
+				"java {",
+				"    sourceCompatibility = JavaVersion.VERSION_11",
+				"}",
 				"",
 				"repositories {",
 				"    mavenCentral()",

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/gradle/GradleProjectGenerationConfigurationTests.java

@@ -118,7 +118,10 @@ class GradleProjectGenerationConfigurationTests {
 				"",
 				"group = 'com.example'",
 				"version = '0.0.1-SNAPSHOT'",
-				"sourceCompatibility = '11'",
+				"",
+				"java {",
+				"    sourceCompatibility = '11'",
+				"}",
 				"",
 				"repositories {",
 				"    mavenCentral()",

initializr-generator-spring/src/test/resources/project/gradle/annotation-processor-dependency-build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 configurations {
 	compileOnly {

initializr-generator-spring/src/test/resources/project/gradle/annotation-processor-dependency-build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 configurations {
 	compileOnly {

initializr-generator-spring/src/test/resources/project/gradle/bom-ordering-build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/bom-ordering-build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/bom-property-build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/bom-property-build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/compile-only-dependency-build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/compile-only-dependency-build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/kotlin-java11-build.gradle.gen

@@ -9,7 +9,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '11'
+
+java {
+	sourceCompatibility = '11'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/kotlin-java11-build.gradle.kts.gen

@@ -9,7 +9,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_11
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_11
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/repositories-build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/repositories-build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/repositories-milestone-build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/repositories-milestone-build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/version-override-build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/gradle/version-override-build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/groovy/next/build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '17'
+
+java {
+	sourceCompatibility = '17'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/groovy/next/build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_17
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_17
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/groovy/standard/build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/groovy/standard/build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/groovy/standard/war-build.gradle.gen

@@ -7,7 +7,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/groovy/standard/war-build.gradle.kts.gen

@@ -7,7 +7,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/java/standard/build.gradle.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/java/standard/build.gradle.kts.gen

@@ -6,7 +6,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/java/standard/war-build.gradle.gen

@@ -7,7 +7,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/java/standard/war-build.gradle.kts.gen

@@ -7,7 +7,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/kotlin/standard/build.gradle.gen

@@ -9,7 +9,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/kotlin/standard/build.gradle.kts.gen

@@ -9,7 +9,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/kotlin/standard/war-build.gradle.gen

@@ -10,7 +10,10 @@ plugins {
 
 group = 'com.example'
 version = '0.0.1-SNAPSHOT'
-sourceCompatibility = '1.8'
+
+java {
+	sourceCompatibility = '1.8'
+}
 
 repositories {
 	mavenCentral()

initializr-generator-spring/src/test/resources/project/kotlin/standard/war-build.gradle.kts.gen

@@ -10,7 +10,10 @@ plugins {
 
 group = "com.example"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 repositories {
 	mavenCentral()

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleBuildWriter.java

@@ -65,6 +65,7 @@ public abstract class GradleBuildWriter {
 		writePlugins(writer, build);
 		writeProperty(writer, "group", settings.getGroup());
 		writeProperty(writer, "version", settings.getVersion());
+		writer.println();
 		writeJavaSourceCompatibility(writer, settings);
 		writer.println();
 		writeConfigurations(writer, build.configurations());

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleBuildWriter.java

@@ -88,7 +88,10 @@ public class GroovyDslGradleBuildWriter extends GradleBuildWriter {
 
 	@Override
 	protected void writeJavaSourceCompatibility(IndentingWriter writer, GradleBuildSettings settings) {
-		writeProperty(writer, "sourceCompatibility", settings.getSourceCompatibility());
+		writer.println("java {");
+		writer.indented(
+				() -> writer.println(String.format("sourceCompatibility = '%s'", settings.getSourceCompatibility())));
+		writer.println("}");
 	}
 
 	@Override

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleBuildWriter.java

@@ -82,7 +82,10 @@ public class KotlinDslGradleBuildWriter extends GradleBuildWriter {
 
 	@Override
 	protected void writeJavaSourceCompatibility(IndentingWriter writer, GradleBuildSettings settings) {
-		writer.println("java.sourceCompatibility = " + getJavaVersionConstant(settings.getSourceCompatibility()));
+		writer.println("java {");
+		writer.indented(() -> writer.println(
+				String.format("sourceCompatibility = %s", getJavaVersionConstant(settings.getSourceCompatibility()))));
+		writer.println("}");
 	}
 
 	private String getJavaVersionConstant(String jvmVersion) {

initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GradleBuildWriterTests.java

@@ -16,8 +16,11 @@
 
 package io.spring.initializr.generator.buildsystem.gradle;
 
+import java.io.StringWriter;
 import java.util.Set;
 
+import io.spring.initializr.generator.io.IndentingWriter;
+import io.spring.initializr.generator.io.SimpleIndentStrategy;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -90,4 +93,19 @@ public abstract class GradleBuildWriterTests {
 
 	protected abstract String write(GradleBuild build);
 
+	/**
+	 * A helper method that tests if java configuration is written properly
+	 * @param format in which source compatibility must be written
+	 * @param jvmVersion for the java
+	 * @return the string representation for java configuration
+	 */
+	protected String javaConfigurationWriter(String format, String jvmVersion) {
+		StringWriter stringWriter = new StringWriter();
+		IndentingWriter writer = new IndentingWriter(stringWriter, new SimpleIndentStrategy("\t"));
+		writer.println("java {");
+		writer.indented(() -> writer.println(String.format(format, jvmVersion)));
+		writer.println("}");
+		return stringWriter.toString().replace("\r\n", "\n");
+	}
+
 }

initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleBuildWriterTests.java

@@ -52,7 +52,8 @@ class GroovyDslGradleBuildWriterTests extends GradleBuildWriterTests {
 	void gradleBuildWithSourceCompatibility() {
 		GradleBuild build = new GradleBuild();
 		build.settings().sourceCompatibility("11");
-		assertThat(write(build).lines()).contains("sourceCompatibility = '11'");
+		String javaConfiguration = javaConfigurationWriter("sourceCompatibility = '%s'", "11");
+		assertThat(write(build)).contains(javaConfiguration);
 	}
 
 	@Test

initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleBuildWriterTests.java

@@ -60,7 +60,8 @@ class KotlinDslGradleBuildWriterTests extends GradleBuildWriterTests {
 	void gradleBuildWithSourceCompatibility15(String sourceCompatibility, String javaVersionConstant) {
 		GradleBuild build = new GradleBuild();
 		build.settings().sourceCompatibility(sourceCompatibility);
-		assertThat(write(build)).contains("java.sourceCompatibility = " + javaVersionConstant);
+		String javaConfiguration = javaConfigurationWriter("sourceCompatibility = %s", javaVersionConstant);
+		assertThat(write(build)).contains(javaConfiguration);
 	}
 
 	static Stream<Arguments> sourceCompatibilityParameters() {