Add Gradle Kotlin DSL support

This commit refactors the existing Groovy DSL writers in order to share code between the Groovy DSL and Kotlin DSL writers. See gh-851
2025-09-19 01:58:16 +08:00 · 2019-03-03 10:53:30 +01:00
parent 020d66be63
commit 239116b29a
51 changed files with 2262 additions and 239 deletions
--- a/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/Gradle3BuildWriter.java
+++ b/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/Gradle3BuildWriter.java
@@ -19,11 +19,11 @@ package io.spring.initializr.generator.buildsystem.gradle;
 import io.spring.initializr.generator.buildsystem.DependencyScope;

 /**
- * A {@link GradleBuildWriter} suitable for Gradle 3.
+ * A {@link GroovyDslGradleBuildWriter} suitable for Gradle 3.
 *
 * @author Stephane Nicoll
 */
-public class Gradle3BuildWriter extends GradleBuildWriter {
+public class Gradle3BuildWriter extends GroovyDslGradleBuildWriter {

 	protected String configurationForScope(DependencyScope type) {
 		switch (type) {
--- a/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleBuildWriter.java
+++ b/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleBuildWriter.java
@@ -43,23 +43,26 @@ import io.spring.initializr.generator.version.VersionProperty;
 import io.spring.initializr.generator.version.VersionReference;

 /**
- * A {@link GradleBuild} writer for {@code build.gradle}.
+ * A {@link GradleBuild} writer template for build.gradle and build.gradle.kts. A subclass
+ * of this class exists for the Groovy DSL and for the Kotlin DSL.
 *
 * @author Andy Wilkinson
 * @author Stephane Nicoll
 * @author Jean-Baptiste Nizet
 */
-public class GradleBuildWriter {
+public abstract class GradleBuildWriter {

-	public void writeTo(IndentingWriter writer, GradleBuild build) throws IOException {
+	public final void writeTo(IndentingWriter writer, GradleBuild build)
+			throws IOException {
 		writeImports(writer, build);
-		boolean buildScriptWritten = writeBuildscript(writer, build);
-		writePlugins(writer, build, buildScriptWritten);
+		writeBuildscript(writer, build);
+		writePlugins(writer, build);
 		writeProperty(writer, "group", build.getGroup());
 		writeProperty(writer, "version", build.getVersion());
-		writeProperty(writer, "sourceCompatibility", build.getSourceCompatibility());
+		writeJavaSourceCompatibility(writer, build);
+		writer.println();
 		writeConfigurations(writer, build);
-		writeRepositories(writer, build, writer::println);
+		writeRepositories(writer, build);
 		writeProperties(writer, build);
 		writeDependencies(writer, build);
 		writeBoms(writer, build);
@@ -75,61 +78,12 @@ public class GradleBuildWriter {
 		}
 	}

-	private boolean writeBuildscript(IndentingWriter writer, GradleBuild build) {
-		List<String> dependencies = build.getBuildscript().getDependencies();
-		Map<String, String> ext = build.getBuildscript().getExt();
-		if (dependencies.isEmpty() && ext.isEmpty()) {
-			return false;
-		}
-		writer.println("buildscript {");
-		writer.indented(() -> {
-			writeBuildscriptExt(writer, build);
-			writeBuildscriptRepositories(writer, build);
-			writeBuildscriptDependencies(writer, build);
-		});
-		writer.println("}");
-		return true;
-	}
+	protected abstract void writeBuildscript(IndentingWriter writer, GradleBuild build);

-	private void writeBuildscriptExt(IndentingWriter writer, GradleBuild build) {
-		writeNestedMap(writer, "ext", build.getBuildscript().getExt(),
-				(key, value) -> key + " = " + value);
-	}
+	protected abstract void writePlugins(IndentingWriter writer, GradleBuild build);

-	private void writeBuildscriptRepositories(IndentingWriter writer, GradleBuild build) {
-		writeRepositories(writer, build);
-	}
-
-	private void writeBuildscriptDependencies(IndentingWriter writer, GradleBuild build) {
-		writeNestedCollection(writer, "dependencies",
-				build.getBuildscript().getDependencies(),
-				(dependency) -> "classpath '" + dependency + "'");
-	}
-
-	private void writePlugins(IndentingWriter writer, GradleBuild build,
-			boolean buildScriptWritten) {
-		writeNestedCollection(writer, "plugins", build.getPlugins(), this::pluginAsString,
-				determineBeforeWriting(buildScriptWritten, writer));
-		writeCollection(writer, build.getAppliedPlugins(),
-				(plugin) -> "apply plugin: '" + plugin + "'", writer::println);
-		writer.println();
-	}
-
-	private Runnable determineBeforeWriting(boolean buildScriptWritten,
-			IndentingWriter writer) {
-		if (buildScriptWritten) {
-			return writer::println;
-		}
-		return null;
-	}
-
-	private String pluginAsString(GradlePlugin plugin) {
-		String string = "id '" + plugin.getId() + "'";
-		if (plugin.getVersion() != null) {
-			string += " version '" + plugin.getVersion() + "'";
-		}
-		return string;
-	}
+	protected abstract void writeJavaSourceCompatibility(IndentingWriter writer,
+			GradleBuild build);

 	private void writeConfigurations(IndentingWriter writer, GradleBuild build) {
 		Map<String, ConfigurationCustomization> configurationCustomizations = build
@@ -137,43 +91,24 @@ public class GradleBuildWriter {
 		if (configurationCustomizations.isEmpty()) {
 			return;
 		}
-		writer.println();
 		writer.println("configurations {");
 		writer.indented(() -> configurationCustomizations.forEach((name,
 				customization) -> writeConfiguration(writer, name, customization)));
 		writer.println("}");
+		writer.println("");
 	}

-	private void writeConfiguration(IndentingWriter writer, String configurationName,
-			ConfigurationCustomization configurationCustomization) {
-		if (configurationCustomization.getExtendsFrom().isEmpty()) {
-			writer.println(configurationName);
-		}
-		else {
-			writer.println(configurationName + " {");
-			writer.indented(() -> writer.println(String.format("extendsFrom %s",
-					String.join(", ", configurationCustomization.getExtendsFrom()))));
-			writer.println("}");
-		}
-	}
+	protected abstract void writeConfiguration(IndentingWriter writer,
+			String configurationName,
+			ConfigurationCustomization configurationCustomization);

-	private void writeRepositories(IndentingWriter writer, GradleBuild build) {
-		writeRepositories(writer, build, null);
-	}
-
-	private void writeRepositories(IndentingWriter writer, GradleBuild build,
-			Runnable beforeWriting) {
+	protected final void writeRepositories(IndentingWriter writer, GradleBuild build) {
 		writeNestedCollection(writer, "repositories",
 				build.repositories().items().collect(Collectors.toList()),
-				this::repositoryAsString, beforeWriting);
+				this::repositoryAsString);
 	}

-	private String repositoryAsString(MavenRepository repository) {
-		if (MavenRepository.MAVEN_CENTRAL.equals(repository)) {
-			return "mavenCentral()";
-		}
-		return "maven { url '" + repository.getUrl() + "' }";
-	}
+	protected abstract String repositoryAsString(MavenRepository repository);

 	private void writeProperties(IndentingWriter writer, GradleBuild build) {
 		if (build.getExt().isEmpty() && build.getVersionProperties().isEmpty()) {
@@ -182,19 +117,17 @@ public class GradleBuildWriter {
 		Map<String, String> allProperties = new LinkedHashMap<>(build.getExt());
 		build.getVersionProperties().entrySet().forEach((entry) -> allProperties
 				.put(getVersionPropertyKey(entry), "'" + entry.getValue() + "'"));
-		writeNestedCollection(writer, "ext", allProperties.entrySet(),
-				(e) -> getFormattedProperty(e.getKey(), e.getValue()), writer::println);
+		writeExtraProperties(writer, allProperties);
 	}

+	protected abstract void writeExtraProperties(IndentingWriter writer,
+			Map<String, String> allProperties);
+
 	private String getVersionPropertyKey(Entry<VersionProperty, String> entry) {
 		return entry.getKey().isInternal() ? entry.getKey().toCamelCaseFormat()
 				: entry.getKey().toStandardFormat();
 	}

-	private String getFormattedProperty(String key, String value) {
-		return String.format("set('%s', %s)", key, value);
-	}
-
 	private void writeDependencies(IndentingWriter writer, GradleBuild build) {
 		Set<Dependency> sortedDependencies = new LinkedHashSet<>();
 		DependencyContainer dependencies = build.dependencies();
@@ -216,15 +149,7 @@ public class GradleBuildWriter {
 				this::dependencyAsString, writer::println);
 	}

-	private String dependencyAsString(Dependency dependency) {
-		String quoteStyle = determineQuoteStyle(dependency.getVersion());
-		String version = determineVersion(dependency.getVersion());
-		String type = dependency.getType();
-		return configurationForScope(dependency.getScope()) + " " + quoteStyle
-				+ dependency.getGroupId() + ":" + dependency.getArtifactId()
-				+ ((version != null) ? ":" + version : "")
-				+ ((type != null) ? "@" + type : "") + quoteStyle;
-	}
+	protected abstract String dependencyAsString(Dependency dependency);

 	protected String configurationForScope(DependencyScope type) {
 		switch (type) {
@@ -263,23 +188,18 @@ public class GradleBuildWriter {
 	}

 	private String bomAsString(BillOfMaterials bom) {
-		String quoteStyle = determineQuoteStyle(bom.getVersion());
 		String version = determineVersion(bom.getVersion());
-		return "mavenBom " + quoteStyle + bom.getGroupId() + ":" + bom.getArtifactId()
-				+ ":" + version + quoteStyle;
+		return bomAsString(bom, version);
 	}

-	private String determineQuoteStyle(VersionReference versionReference) {
-		return (versionReference != null && versionReference.isProperty()) ? "\"" : "'";
-	}
+	protected abstract String bomAsString(BillOfMaterials bom, String version);

-	private String determineVersion(VersionReference versionReference) {
+	protected final String determineVersion(VersionReference versionReference) {
 		if (versionReference != null) {
 			if (versionReference.isProperty()) {
 				VersionProperty property = versionReference.getProperty();
-				return "${"
-						+ (property.isInternal() ? property.toCamelCaseFormat()
-								: "property('" + property.toStandardFormat() + "')")
+				return "${" + (property.isInternal() ? property.toCamelCaseFormat()
+						: externalVersionPropertyAsString(property.toStandardFormat()))
 						+ "}";
 			}
 			return versionReference.getValue();
@@ -287,33 +207,17 @@ public class GradleBuildWriter {
 		return null;
 	}

-	private void writeTasksWithTypeCustomizations(IndentingWriter writer,
-			GradleBuild build) {
-		Map<String, GradleBuild.TaskCustomization> tasksWithTypeCustomizations = build
-				.getTasksWithTypeCustomizations();
-		tasksWithTypeCustomizations.forEach((typeName, customization) -> {
-			writer.println();
-			writer.println("tasks.withType(" + typeName + ") {");
-			writer.indented(() -> writeTaskCustomization(writer, customization));
-			writer.println("}");
-		});
-	}
+	protected abstract String externalVersionPropertyAsString(String standardFormat);

-	private void writeTaskCustomizations(IndentingWriter writer, GradleBuild build) {
-		Map<String, TaskCustomization> taskCustomizations = build.getTaskCustomizations();
-		taskCustomizations.forEach((name, customization) -> {
-			writer.println();
-			writer.println(name + " {");
-			writer.indented(() -> writeTaskCustomization(writer, customization));
-			writer.println("}");
-		});
-	}
+	protected abstract void writeTasksWithTypeCustomizations(IndentingWriter writer,
+			GradleBuild build);

-	private void writeTaskCustomization(IndentingWriter writer,
+	protected abstract void writeTaskCustomizations(IndentingWriter writer,
+			GradleBuild build);
+
+	protected final void writeTaskCustomization(IndentingWriter writer,
 			TaskCustomization customization) {
-		writeCollection(writer, customization.getInvocations(),
-				(invocation) -> invocation.getTarget() + " "
-						+ String.join(", ", invocation.getArguments()));
+		writeCollection(writer, customization.getInvocations(), this::invocationAsString);
 		writeMap(writer, customization.getAssignments(),
 				(key, value) -> key + " = " + value);
 		customization.getNested().forEach((property, nestedCustomization) -> {
@@ -323,12 +227,14 @@ public class GradleBuildWriter {
 		});
 	}

-	private <T> void writeNestedCollection(IndentingWriter writer, String name,
+	protected abstract String invocationAsString(TaskCustomization.Invocation invocation);
+
+	protected final <T> void writeNestedCollection(IndentingWriter writer, String name,
 			Collection<T> collection, Function<T, String> itemToStringConverter) {
 		this.writeNestedCollection(writer, name, collection, itemToStringConverter, null);
 	}

-	private <T> void writeNestedCollection(IndentingWriter writer, String name,
+	protected final <T> void writeNestedCollection(IndentingWriter writer, String name,
 			Collection<T> collection, Function<T, String> converter,
 			Runnable beforeWriting) {
 		if (!collection.isEmpty()) {
@@ -347,8 +253,9 @@ public class GradleBuildWriter {
 		writeCollection(writer, collection, converter, null);
 	}

-	private <T> void writeCollection(IndentingWriter writer, Collection<T> collection,
-			Function<T, String> itemToStringConverter, Runnable beforeWriting) {
+	protected final <T> void writeCollection(IndentingWriter writer,
+			Collection<T> collection, Function<T, String> itemToStringConverter,
+			Runnable beforeWriting) {
 		if (!collection.isEmpty()) {
 			if (beforeWriting != null) {
 				beforeWriting.run();
@@ -357,25 +264,13 @@ public class GradleBuildWriter {
 		}
 	}

-	private <T, U> void writeNestedMap(IndentingWriter writer, String name, Map<T, U> map,
-			BiFunction<T, U, String> converter) {
-		if (!map.isEmpty()) {
-			writer.println(name + " {");
-			writer.indented(() -> writeMap(writer, map, converter));
-			writer.println("}");
-		}
-	}
-
-	private <T, U> void writeMap(IndentingWriter writer, Map<T, U> map,
+	protected final <T, U> void writeMap(IndentingWriter writer, Map<T, U> map,
 			BiFunction<T, U, String> converter) {
 		map.forEach((key, value) -> writer.println(converter.apply(key, value)));
 	}

-	private void writeProperty(IndentingWriter writer, String name, String value) {
-		if (value != null) {
-			writer.println(String.format("%s = '%s'", name, value));
-		}
-	}
+	protected abstract void writeProperty(IndentingWriter writer, String name,
+			String value);

 	private static Collection<Dependency> filterDependencies(
 			DependencyContainer dependencies, DependencyScope... types) {
--- a/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleSettingsWriter.java
+++ b/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleSettingsWriter.java
@@ -22,15 +22,19 @@ import io.spring.initializr.generator.buildsystem.MavenRepository;
 import io.spring.initializr.generator.io.IndentingWriter;

 /**
- * A {@link GradleBuild} writer for {@code settings.gradle}.
+ * A {@link GradleBuild} writer template for {@code settings.gradle} and
+ * {@code settings.gradle.kts}. A subclass of this class exists for the Groovy DSL and for
+ * the Kotlin DSL.
 *
 * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
 */
-public class GradleSettingsWriter {
+public abstract class GradleSettingsWriter {

-	public void writeTo(IndentingWriter writer, GradleBuild build) throws IOException {
+	public final void writeTo(IndentingWriter writer, GradleBuild build)
+			throws IOException {
 		writePluginManagement(writer, build);
-		writer.println("rootProject.name = '" + build.getArtifact() + "'");
+		writer.println("rootProject.name = " + wrapWithQuotes(build.getArtifact()));
 	}

 	private void writePluginManagement(IndentingWriter writer, GradleBuild build) {
@@ -62,7 +66,8 @@ public class GradleSettingsWriter {
 		writer.indented(() -> {
 			writer.println("eachPlugin {");
 			writer.indented(() -> {
-				writer.println("if (requested.id.id == 'org.springframework.boot') {");
+				writer.println("if (requested.id.id == "
+						+ wrapWithQuotes("org.springframework.boot") + ") {");
 				writer.indented(() -> writer.println(
 						"useModule(\"org.springframework.boot:spring-boot-gradle-plugin:${requested.version}\")"));
 				writer.println("}");
@@ -76,7 +81,11 @@ public class GradleSettingsWriter {
 		if (MavenRepository.MAVEN_CENTRAL.equals(repository)) {
 			return "mavenCentral()";
 		}
-		return "maven { url '" + repository.getUrl() + "' }";
+		return "maven { " + urlAssignment(repository.getUrl()) + " }";
 	}

+	protected abstract String wrapWithQuotes(String value);
+
+	protected abstract String urlAssignment(String url);
+
 }
--- a/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleBuildWriter.java
+++ b/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleBuildWriter.java
@@ -0,0 +1,202 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+import java.util.List;
+import java.util.Map;
+import java.util.function.BiFunction;
+
+import io.spring.initializr.generator.buildsystem.BillOfMaterials;
+import io.spring.initializr.generator.buildsystem.Dependency;
+import io.spring.initializr.generator.buildsystem.MavenRepository;
+import io.spring.initializr.generator.io.IndentingWriter;
+import io.spring.initializr.generator.version.VersionReference;
+
+/**
+ * A {@link GradleBuild} writer for {@code build.gradle}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class GroovyDslGradleBuildWriter extends GradleBuildWriter {
+
+	@Override
+	protected void writeBuildscript(IndentingWriter writer, GradleBuild build) {
+		List<String> dependencies = build.getBuildscript().getDependencies();
+		Map<String, String> ext = build.getBuildscript().getExt();
+		if (dependencies.isEmpty() && ext.isEmpty()) {
+			return;
+		}
+		writer.println("buildscript {");
+		writer.indented(() -> {
+			writeBuildscriptExt(writer, build);
+			writeBuildscriptRepositories(writer, build);
+			writeBuildscriptDependencies(writer, build);
+		});
+		writer.println("}");
+		writer.println();
+	}
+
+	private void writeBuildscriptExt(IndentingWriter writer, GradleBuild build) {
+		writeNestedMap(writer, "ext", build.getBuildscript().getExt(),
+				(key, value) -> key + " = " + value);
+	}
+
+	private void writeBuildscriptRepositories(IndentingWriter writer, GradleBuild build) {
+		writeRepositories(writer, build);
+	}
+
+	private void writeBuildscriptDependencies(IndentingWriter writer, GradleBuild build) {
+		writeNestedCollection(writer, "dependencies",
+				build.getBuildscript().getDependencies(),
+				(dependency) -> "classpath '" + dependency + "'");
+	}
+
+	@Override
+	protected void writePlugins(IndentingWriter writer, GradleBuild build) {
+		writeNestedCollection(writer, "plugins", build.getPlugins(),
+				this::pluginAsString);
+		writeCollection(writer, build.getAppliedPlugins(),
+				(plugin) -> "apply plugin: '" + plugin + "'", writer::println);
+		writer.println();
+	}
+
+	private String pluginAsString(GradlePlugin plugin) {
+		String string = "id '" + plugin.getId() + "'";
+		if (plugin.getVersion() != null) {
+			string += " version '" + plugin.getVersion() + "'";
+		}
+		return string;
+	}
+
+	@Override
+	protected void writeJavaSourceCompatibility(IndentingWriter writer,
+			GradleBuild build) {
+		writeProperty(writer, "sourceCompatibility", build.getSourceCompatibility());
+	}
+
+	@Override
+	protected void writeConfiguration(IndentingWriter writer, String configurationName,
+			GradleBuild.ConfigurationCustomization configurationCustomization) {
+		if (configurationCustomization.getExtendsFrom().isEmpty()) {
+			writer.println(configurationName);
+		}
+		else {
+			writer.println(configurationName + " {");
+			writer.indented(() -> writer.println(String.format("extendsFrom %s",
+					String.join(", ", configurationCustomization.getExtendsFrom()))));
+			writer.println("}");
+		}
+	}
+
+	@Override
+	protected String repositoryAsString(MavenRepository repository) {
+		if (MavenRepository.MAVEN_CENTRAL.equals(repository)) {
+			return "mavenCentral()";
+		}
+		return "maven { url '" + repository.getUrl() + "' }";
+	}
+
+	@Override
+	protected void writeExtraProperties(IndentingWriter writer,
+			Map<String, String> allProperties) {
+		writeNestedCollection(writer, "ext", allProperties.entrySet(),
+				(e) -> getFormattedExtraProperty(e.getKey(), e.getValue()),
+				writer::println);
+	}
+
+	private String getFormattedExtraProperty(String key, String value) {
+		return String.format("set('%s', '%s')", key, value);
+	}
+
+	@Override
+	protected String dependencyAsString(Dependency dependency) {
+		String quoteStyle = determineQuoteStyle(dependency.getVersion());
+		String version = determineVersion(dependency.getVersion());
+		String type = dependency.getType();
+		return configurationForScope(dependency.getScope()) + " " + quoteStyle
+				+ dependency.getGroupId() + ":" + dependency.getArtifactId()
+				+ ((version != null) ? ":" + version : "")
+				+ ((type != null) ? "@" + type : "") + quoteStyle;
+	}
+
+	private String determineQuoteStyle(VersionReference versionReference) {
+		return (versionReference != null && versionReference.isProperty()) ? "\"" : "'";
+	}
+
+	@Override
+	protected String bomAsString(BillOfMaterials bom, String version) {
+		String quoteStyle = determineQuoteStyle(bom.getVersion());
+		return "mavenBom " + quoteStyle + bom.getGroupId() + ":" + bom.getArtifactId()
+				+ ":" + version + quoteStyle;
+	}
+
+	@Override
+	protected String externalVersionPropertyAsString(String standardFormat) {
+		return "property('" + standardFormat + "')";
+	}
+
+	@Override
+	protected void writeTasksWithTypeCustomizations(IndentingWriter writer,
+			GradleBuild build) {
+		Map<String, GradleBuild.TaskCustomization> tasksWithTypeCustomizations = build
+				.getTasksWithTypeCustomizations();
+
+		tasksWithTypeCustomizations.forEach((typeName, customization) -> {
+			writer.println();
+			writer.println("tasks.withType(" + typeName + ") {");
+			writer.indented(() -> writeTaskCustomization(writer, customization));
+			writer.println("}");
+		});
+	}
+
+	@Override
+	protected void writeTaskCustomizations(IndentingWriter writer, GradleBuild build) {
+		Map<String, GradleBuild.TaskCustomization> taskCustomizations = build
+				.getTaskCustomizations();
+
+		taskCustomizations.forEach((name, customization) -> {
+			writer.println();
+			writer.println(name + " {");
+			writer.indented(() -> writeTaskCustomization(writer, customization));
+			writer.println("}");
+		});
+	}
+
+	@Override
+	protected String invocationAsString(
+			GradleBuild.TaskCustomization.Invocation invocation) {
+		return invocation.getTarget() + " "
+				+ String.join(", ", invocation.getArguments());
+	}
+
+	@Override
+	protected void writeProperty(IndentingWriter writer, String name, String value) {
+		if (value != null) {
+			writer.println(String.format("%s = '%s'", name, value));
+		}
+	}
+
+	private <T, U> void writeNestedMap(IndentingWriter writer, String name, Map<T, U> map,
+			BiFunction<T, U, String> converter) {
+		if (!map.isEmpty()) {
+			writer.println(name + " {");
+			writer.indented(() -> writeMap(writer, map, converter));
+			writer.println("}");
+		}
+	}
+
+}
--- a/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleSettingsWriter.java
+++ b/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleSettingsWriter.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+/**
+ * A {@link GradleBuild} writer for {@code settings.gradle}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class GroovyDslGradleSettingsWriter extends GradleSettingsWriter {
+
+	@Override
+	protected String wrapWithQuotes(String value) {
+		return "'" + value + "'";
+	}
+
+	@Override
+	protected String urlAssignment(String url) {
+		return "url " + wrapWithQuotes(url);
+	}
+
+}
--- a/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleBuildWriter.java
+++ b/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleBuildWriter.java
@@ -0,0 +1,203 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import io.spring.initializr.generator.buildsystem.BillOfMaterials;
+import io.spring.initializr.generator.buildsystem.Dependency;
+import io.spring.initializr.generator.buildsystem.MavenRepository;
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild.ConfigurationCustomization;
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild.TaskCustomization;
+import io.spring.initializr.generator.io.IndentingWriter;
+
+/**
+ * A {@link GradleBuild} writer for {@code build.gradle.kts}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class KotlinDslGradleBuildWriter extends GradleBuildWriter {
+
+	private static final Map<String, String> sourceCompatibilitiesToJavaVersion = createSourceCompatibilitiesToJavaVersion();
+
+	private static Map<String, String> createSourceCompatibilitiesToJavaVersion() {
+		Map<String, String> result = new HashMap<>();
+		for (int version = 6; version <= 10; version++) {
+			result.put(Integer.toString(version), "VERSION_1_" + version);
+			result.put("1." + version, "VERSION_1_" + version);
+		}
+		for (int version = 11; version <= 12; version++) {
+			result.put(Integer.toString(version), "VERSION_" + version);
+			result.put("1." + version, "VERSION_" + version);
+		}
+
+		return Collections.unmodifiableMap(result);
+	}
+
+	@Override
+	protected void writeBuildscript(IndentingWriter writer, GradleBuild build) {
+		if (!(build.getBuildscript().getDependencies().isEmpty()
+				&& build.getBuildscript().getExt().isEmpty())) {
+			throw new IllegalStateException(
+					"build.gradle.kts scripts shouldn't need a buildscript");
+		}
+	}
+
+	@Override
+	protected void writePlugins(IndentingWriter writer, GradleBuild build) {
+		writeNestedCollection(writer, "plugins", build.getPlugins(), this::pluginAsString,
+				null);
+		writer.println();
+
+		if (!build.getAppliedPlugins().isEmpty()) {
+			throw new IllegalStateException(
+					"build.gradle.kts scripts shouldn't apply plugins. They should use the plugins block instead.");
+		}
+	}
+
+	private String pluginAsString(GradlePlugin plugin) {
+		String result = shortPluginNotation(plugin.getId());
+		if (result == null) {
+			result = "id(\"" + plugin.getId() + "\")";
+		}
+		if (plugin.getVersion() != null) {
+			result += " version \"" + plugin.getVersion() + "\"";
+		}
+		return result;
+	}
+
+	private String shortPluginNotation(String pluginId) {
+		if (pluginId.equals("java") || pluginId.equals("war")
+				|| pluginId.equals("groovy")) {
+			return pluginId;
+		}
+
+		String kotlinPluginPrefix = "org.jetbrains.kotlin.";
+		if (pluginId.startsWith(kotlinPluginPrefix)) {
+			return "kotlin(\"" + pluginId.substring(kotlinPluginPrefix.length()) + "\")";
+		}
+
+		return null;
+	}
+
+	@Override
+	protected void writeJavaSourceCompatibility(IndentingWriter writer,
+			GradleBuild build) {
+		writer.println("java.sourceCompatibility = JavaVersion."
+				+ sourceCompatibilitiesToJavaVersion.get(build.getSourceCompatibility()));
+	}
+
+	@Override
+	protected void writeConfiguration(IndentingWriter writer, String configurationName,
+			ConfigurationCustomization configurationCustomization) {
+		if (configurationCustomization.getExtendsFrom().isEmpty()) {
+			writer.println(configurationName);
+		}
+		else {
+			writer.println(configurationName + " {");
+			writer.indented(() -> writer.println(String.format("extendsFrom(%s)",
+					configurationCustomization.getExtendsFrom().stream()
+							.map((c) -> "configurations." + c + ".get()")
+							.collect(Collectors.joining(", ")))));
+			writer.println("}");
+		}
+	}
+
+	@Override
+	protected String repositoryAsString(MavenRepository repository) {
+		if (MavenRepository.MAVEN_CENTRAL.equals(repository)) {
+			return "mavenCentral()";
+		}
+		return "maven { url = uri(\"" + repository.getUrl() + "\") }";
+	}
+
+	@Override
+	protected String dependencyAsString(Dependency dependency) {
+		String version = determineVersion(dependency.getVersion());
+		String type = dependency.getType();
+		return configurationForScope(dependency.getScope()) + "(\""
+				+ dependency.getGroupId() + ":" + dependency.getArtifactId()
+				+ ((version != null) ? ":" + version : "")
+				+ ((type != null) ? "@" + type : "") + "\")";
+	}
+
+	@Override
+	protected void writeExtraProperties(IndentingWriter writer,
+			Map<String, String> allProperties) {
+		writeCollection(writer, allProperties.entrySet(),
+				(e) -> getFormattedExtraProperty(e.getKey(), e.getValue()),
+				writer::println);
+	}
+
+	private String getFormattedExtraProperty(String key, String value) {
+		return String.format("extra[\"%s\"] = \"%s\"", key, value);
+	}
+
+	@Override
+	protected String bomAsString(BillOfMaterials bom, String version) {
+		return "mavenBom(\"" + bom.getGroupId() + ":" + bom.getArtifactId() + ":"
+				+ version + "\")";
+	}
+
+	@Override
+	protected String externalVersionPropertyAsString(String standardFormat) {
+		return "property(\"" + standardFormat + "\")";
+	}
+
+	@Override
+	protected void writeTasksWithTypeCustomizations(IndentingWriter writer,
+			GradleBuild build) {
+		Map<String, TaskCustomization> tasksWithTypeCustomizations = build
+				.getTasksWithTypeCustomizations();
+
+		tasksWithTypeCustomizations.forEach((typeName, customization) -> {
+			writer.println();
+			writer.println("tasks.withType<" + typeName + "> {");
+			writer.indented(() -> writeTaskCustomization(writer, customization));
+			writer.println("}");
+		});
+	}
+
+	@Override
+	protected void writeTaskCustomizations(IndentingWriter writer, GradleBuild build) {
+		Map<String, TaskCustomization> taskCustomizations = build.getTaskCustomizations();
+
+		taskCustomizations.forEach((name, customization) -> {
+			writer.println();
+			writer.println("tasks." + name + " {");
+			writer.indented(() -> writeTaskCustomization(writer, customization));
+			writer.println("}");
+		});
+	}
+
+	@Override
+	protected String invocationAsString(TaskCustomization.Invocation invocation) {
+		return invocation.getTarget() + "(" + String.join(", ", invocation.getArguments())
+				+ ")";
+	}
+
+	@Override
+	protected void writeProperty(IndentingWriter writer, String name, String value) {
+		if (value != null) {
+			writer.println(String.format("%s = \"%s\"", name, value));
+		}
+	}
+
+}
--- a/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleSettingsWriter.java
+++ b/initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleSettingsWriter.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+/**
+ * A {@link GradleBuild} writer for {@code settings.gradle.kts}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class KotlinDslGradleSettingsWriter extends GradleSettingsWriter {
+
+	@Override
+	protected String wrapWithQuotes(String value) {
+		return "\"" + value + "\"";
+	}
+
+	@Override
+	protected String urlAssignment(String url) {
+		return "url = uri(\"" + url + "\")";
+	}
+
+}
--- a/initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleBuildWriterTests.java
+++ b/initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleBuildWriterTests.java
@@ -30,13 +30,13 @@ import org.junit.jupiter.api.Test;
 import static org.assertj.core.api.Assertions.assertThat;

 /**
- * Tests for {@link GradleBuildWriter}
+ * Tests for {@link GroovyDslGradleBuildWriter}
 *
 * @author Andy Wilkinson
 * @author Jean-Baptiste Nizet
 * @author Stephane Nicoll
 */
-class GradleBuildWriterTests {
+class GroovyDslGradleBuildWriterTests {

 	@Test
 	void gradleBuildWithCoordinates() throws IOException {
@@ -426,7 +426,7 @@ class GradleBuildWriterTests {
 	}

 	private List<String> generateBuild(GradleBuild build) throws IOException {
-		GradleBuildWriter writer = new GradleBuildWriter();
+		GradleBuildWriter writer = new GroovyDslGradleBuildWriter();
 		StringWriter out = new StringWriter();
 		writer.writeTo(new IndentingWriter(out), build);
 		return TextTestUtils.readAllLines(out.toString());
--- a/initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleSettingsWriterTests.java
+++ b/initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleSettingsWriterTests.java
@@ -27,11 +27,12 @@ import org.junit.jupiter.api.Test;
 import static org.assertj.core.api.Assertions.assertThat;

 /**
- * Tests for {@link GradleSettingsWriter}.
+ * Tests for {@link GroovyDslGradleSettingsWriter}.
 *
 * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
 */
-class GradleSettingsWriterTests {
+class GroovyDslGradleSettingsWriterTests {

 	@Test
 	void gradleBuildWithMavenCentralPluginRepository() throws IOException {
@@ -81,7 +82,7 @@ class GradleSettingsWriterTests {
 	}

 	private List<String> generateSettings(GradleBuild build) throws IOException {
-		GradleSettingsWriter writer = new GradleSettingsWriter();
+		GradleSettingsWriter writer = new GroovyDslGradleSettingsWriter();
 		StringWriter out = new StringWriter();
 		writer.writeTo(new IndentingWriter(out), build);
 		return TextTestUtils.readAllLines(out.toString());
--- a/initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleBuildWriterTests.java
+++ b/initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleBuildWriterTests.java
@@ -0,0 +1,457 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Arrays;
+import java.util.List;
+
+import io.spring.initializr.generator.buildsystem.DependencyScope;
+import io.spring.initializr.generator.io.IndentingWriter;
+import io.spring.initializr.generator.version.VersionProperty;
+import io.spring.initializr.generator.version.VersionReference;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+
+/**
+ * Tests for {@link KotlinDslGradleBuildWriter}
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class KotlinDslGradleBuildWriterTests {
+
+	@Test
+	void gradleBuildWithImports() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addImportedType(
+				"org.springframework.boot.gradle.tasks.buildinfo.BuildInfo");
+		build.addImportedType("org.jetbrains.kotlin.gradle.tasks.KotlinCompile");
+		build.addImportedType("org.jetbrains.kotlin.gradle.tasks.KotlinCompile"); // same
+																					// import
+																					// added
+																					// twice
+
+		List<String> lines = generateBuild(build);
+		assertThat(lines.subList(0, 3)).containsExactly(
+				"import org.jetbrains.kotlin.gradle.tasks.KotlinCompile",
+				"import org.springframework.boot.gradle.tasks.buildinfo.BuildInfo", "");
+	}
+
+	@Test
+	void gradleBuildWithCoordinates() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.setGroup("com.example");
+		build.setVersion("1.0.1-SNAPSHOT");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).contains("group = \"com.example\"",
+				"version = \"1.0.1-SNAPSHOT\"");
+	}
+
+	@Test
+	void gradleBuildWithSourceCompatibility11() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.setSourceCompatibility("11");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).contains("java.sourceCompatibility = JavaVersion.VERSION_11");
+	}
+
+	@Test
+	void gradleBuildWithSourceCompatibility1Dot8() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.setSourceCompatibility("1.8");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).contains("java.sourceCompatibility = JavaVersion.VERSION_1_8");
+	}
+
+	@Test
+	void gradleBuildWithBuildscriptDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.buildscript((buildscript) -> buildscript.dependency(
+				"org.springframework.boot:spring-boot-gradle-plugin:2.1.0.RELEASE"));
+
+		assertThatIllegalStateException().isThrownBy(() -> {
+			generateBuild(build);
+		});
+	}
+
+	@Test
+	void gradleBuildWithBuildscriptExtProperty() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.buildscript((buildscript) -> buildscript.ext("kotlinVersion", "\1.2.51\""));
+		assertThatIllegalStateException().isThrownBy(() -> {
+			generateBuild(build);
+		});
+	}
+
+	@Test
+	void gradleBuildWithBuiltinPlugin() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addPlugin("java");
+		build.addPlugin("war");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("plugins {", "    java", "    war", "}");
+	}
+
+	@Test
+	void gradleBuildWithKotlinPluginAndVersion() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addPlugin("org.jetbrains.kotlin.jvm", "1.3.21");
+		build.addPlugin("org.jetbrains.kotlin.plugin.spring", "1.3.21");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("plugins {",
+				"    kotlin(\"jvm\") version \"1.3.21\"",
+				"    kotlin(\"plugin.spring\") version \"1.3.21\"", "}");
+	}
+
+	@Test
+	void gradleBuildWithPluginAndVersion() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addPlugin("org.springframework.boot", "2.1.0.RELEASE");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("plugins {",
+				"    id(\"org.springframework.boot\") version \"2.1.0.RELEASE\"", "}");
+	}
+
+	@Test
+	void gradleBuildWithApplyPlugin() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.applyPlugin("io.spring.dependency-management");
+
+		assertThatIllegalStateException().isThrownBy(() -> generateBuild(build));
+	}
+
+	@Test
+	void gradleBuildWithMavenCentralRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.repositories().add("maven-central");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("repositories {", "    mavenCentral()", "}");
+	}
+
+	@Test
+	void gradleBuildWithRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.repositories().add("spring-milestones", "Spring Milestones",
+				"https://repo.spring.io/milestone");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("repositories {",
+				"    maven { url = uri(\"https://repo.spring.io/milestone\") }", "}");
+	}
+
+	@Test
+	void gradleBuildWithSnapshotRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.repositories().add("spring-snapshots", "Spring Snapshots",
+				"https://repo.spring.io/snapshot", true);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("repositories {",
+				"    maven { url = uri(\"https://repo.spring.io/snapshot\") }", "}");
+	}
+
+	@Test
+	void gradleBuildWithPluginRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("spring-milestones", "Spring Milestones",
+				"https://repo.spring.io/milestone");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).doesNotContain("repositories {");
+	}
+
+	@Test
+	void gradleBuildWithTaskWithTypesCustomizedWithNestedAssignments()
+			throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.customizeTasksWithType("KotlinCompile", (task) -> {
+			task.nested("kotlinOptions", (kotlinOptions) -> {
+				kotlinOptions.set("freeCompilerArgs", "listOf(\"-Xjsr305=strict\")");
+				kotlinOptions.set("jvmTarget", "\"1.8\"");
+			});
+		});
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("tasks.withType<KotlinCompile> {",
+				"    kotlinOptions {",
+				"        freeCompilerArgs = listOf(\"-Xjsr305=strict\")",
+				"        jvmTarget = \"1.8\"", "    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithTaskCustomizedWithInvocations() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.customizeTask("asciidoctor", (task) -> {
+			task.invoke("inputs.dir", "snippetsDir");
+			task.invoke("dependsOn", "test");
+		});
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("tasks.asciidoctor {",
+				"    inputs.dir(snippetsDir)", "    dependsOn(test)", "}");
+	}
+
+	@Test
+	void gradleBuildWithTaskCustomizedWithAssignments() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.customizeTask("compileKotlin", (task) -> {
+			task.set("kotlinOptions.freeCompilerArgs", "listOf(\"-Xjsr305=strict\")");
+			task.set("kotlinOptions.jvmTarget", "\"1.8\"");
+		});
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("tasks.compileKotlin {",
+				"    kotlinOptions.freeCompilerArgs = listOf(\"-Xjsr305=strict\")",
+				"    kotlinOptions.jvmTarget = \"1.8\"", "}");
+	}
+
+	@Test
+	void gradleBuildWithTaskCustomizedWithNestedCustomization() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.customizeTask("compileKotlin", (compileKotlin) -> compileKotlin
+				.nested("kotlinOptions", (kotlinOptions) -> {
+					kotlinOptions.set("freeCompilerArgs", "listOf(\"-Xjsr305=strict\")");
+					kotlinOptions.set("jvmTarget", "\"1.8\"");
+				}));
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("tasks.compileKotlin {", "    kotlinOptions {",
+				"        freeCompilerArgs = listOf(\"-Xjsr305=strict\")",
+				"        jvmTarget = \"1.8\"", "    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithExt() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.setGroup("com.example.demo");
+		build.setArtifact("demo");
+		build.ext("java.version", "1.8").ext("alpha", "a");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("extra[\"alpha\"] = \"a\"",
+				"extra[\"java.version\"] = \"1.8\"");
+	}
+
+	@Test
+	void gradleBuildWithVersionProperties() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addVersionProperty(VersionProperty.of("version.property"), "1.2.3");
+		build.addInternalVersionProperty("internal.property", "4.5.6");
+		build.addExternalVersionProperty("external.property", "7.8.9");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("extra[\"external.property\"] = \"7.8.9\"",
+				"extra[\"internalProperty\"] = \"4.5.6\"",
+				"extra[\"versionProperty\"] = \"1.2.3\"");
+	}
+
+	@Test
+	void gradleBuildWithVersionedDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("kotlin-stdlib", "org.jetbrains.kotlin",
+				"kotlin-stdlib-jdk8", VersionReference.ofProperty("kotlin.version"),
+				DependencyScope.COMPILE);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    implementation(\"org.jetbrains.kotlin:kotlin-stdlib-jdk8:${kotlinVersion}\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithExternalVersionedDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("acme", "com.example", "acme",
+				VersionReference.ofProperty(VersionProperty.of("acme.version", false)),
+				DependencyScope.COMPILE);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    implementation(\"com.example:acme:${property(\"acme.version\")}\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithExtAndVersionProperties() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.setGroup("com.example.demo");
+		build.setArtifact("demo");
+		build.addInternalVersionProperty("test-version", "1.0");
+		build.addExternalVersionProperty("alpha-version", "0.1");
+		build.ext("myProperty", "42");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("extra[\"myProperty\"] = \"42\"",
+				"extra[\"alpha-version\"] = \"0.1\"", "extra[\"testVersion\"] = \"1.0\"");
+	}
+
+	@Test
+	void gradleBuildWithConfiguration() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.addConfiguration("developmentOnly");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("configurations {", "    developmentOnly",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithConfigurationCustomization() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.customizeConfiguration("developmentOnly",
+				(configuration) -> configuration.extendsFrom("compile"));
+		build.customizeConfiguration("developmentOnly",
+				(configuration) -> configuration.extendsFrom("testCompile"));
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("configurations {", "    developmentOnly {",
+				"        extendsFrom(configurations.compile.get(), configurations.testCompile.get())",
+				"    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithConfigurationCustomizations() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.customizeConfiguration("developmentOnly",
+				(configuration) -> configuration.extendsFrom("compile"));
+		build.customizeConfiguration("testOnly",
+				(configuration) -> configuration.extendsFrom("testCompile"));
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("configurations {", "    developmentOnly {",
+				"        extendsFrom(configurations.compile.get())", "    }",
+				"    testOnly {", "        extendsFrom(configurations.testCompile.get())",
+				"    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithAnnotationProcessorDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("annotation-processor", "org.springframework.boot",
+				"spring-boot-configuration-processor",
+				DependencyScope.ANNOTATION_PROCESSOR);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    annotationProcessor(\"org.springframework.boot:spring-boot-configuration-processor\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithCompileDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("root", "org.springframework.boot",
+				"spring-boot-starter", DependencyScope.COMPILE);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    implementation(\"org.springframework.boot:spring-boot-starter\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithRuntimeDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("driver", "com.example", "jdbc-driver",
+				VersionReference.ofValue("1.0.0"), DependencyScope.RUNTIME);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    runtimeOnly(\"com.example:jdbc-driver:1.0.0\")", "}");
+	}
+
+	@Test
+	void gradleBuildWithProvidedRuntimeDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("tomcat", "org.springframework.boot",
+				"spring-boot-starter-tomcat", DependencyScope.PROVIDED_RUNTIME);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    providedRuntime(\"org.springframework.boot:spring-boot-starter-tomcat\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithTestCompileDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("test", "org.springframework.boot",
+				"spring-boot-starter-test", DependencyScope.TEST_COMPILE);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    testImplementation(\"org.springframework.boot:spring-boot-starter-test\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithCompileOnlyDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("test", "org.springframework.boot",
+				"spring-boot-starter-foobar", DependencyScope.COMPILE_ONLY);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    compileOnly(\"org.springframework.boot:spring-boot-starter-foobar\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithTestRuntimeDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("embed-mongo", "de.flapdoodle.embed",
+				"de.flapdoodle.embed.mongo", DependencyScope.TEST_RUNTIME);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    testRuntimeOnly(\"de.flapdoodle.embed:de.flapdoodle.embed.mongo\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithNonNullArtifactTypeDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("root", "org.springframework.boot",
+				"spring-boot-starter", null, DependencyScope.COMPILE, "tar.gz");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    implementation(\"org.springframework.boot:spring-boot-starter@tar.gz\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithBom() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.boms().add("test", "com.example", "my-project-dependencies",
+				VersionReference.ofValue("1.0.0.RELEASE"));
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencyManagement {", "    imports {",
+				"        mavenBom(\"com.example:my-project-dependencies:1.0.0.RELEASE\")",
+				"    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithOrderedBoms() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.boms().add("bom1", "com.example", "my-project-dependencies",
+				VersionReference.ofValue("1.0.0.RELEASE"), 5);
+		build.boms().add("bom2", "com.example", "root-dependencies",
+				VersionReference.ofProperty("root.version"), 2);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencyManagement {", "    imports {",
+				"        mavenBom(\"com.example:my-project-dependencies:1.0.0.RELEASE\")",
+				"        mavenBom(\"com.example:root-dependencies:${rootVersion}\")",
+				"    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithCustomVersion() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.setVersion("1.2.4.RELEASE");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).contains("version = \"1.2.4.RELEASE\"");
+	}
+
+	private List<String> generateBuild(GradleBuild build) throws IOException {
+		GradleBuildWriter writer = new KotlinDslGradleBuildWriter();
+		StringWriter out = new StringWriter();
+		writer.writeTo(new IndentingWriter(out), build);
+		return Arrays.asList(out.toString().split("\\r?\\n"));
+	}
+
+}
--- a/initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleSettingsWriterTests.java
+++ b/initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleSettingsWriterTests.java
@@ -0,0 +1,90 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Arrays;
+import java.util.List;
+
+import io.spring.initializr.generator.io.IndentingWriter;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link KotlinDslGradleSettingsWriter}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class KotlinDslGradleSettingsWriterTests {
+
+	@Test
+	void gradleBuildWithMavenCentralPluginRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("maven-central");
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("pluginManagement {", "    repositories {",
+				"        mavenCentral()", "        gradlePluginPortal()", "    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithPluginRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("spring-milestones", "Spring Milestones",
+				"https://repo.spring.io/milestone");
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("pluginManagement {", "    repositories {",
+				"        maven { url = uri(\"https://repo.spring.io/milestone\") }",
+				"        gradlePluginPortal()", "    }", "    resolutionStrategy {",
+				"        eachPlugin {",
+				"            if (requested.id.id == \"org.springframework.boot\") {",
+				"                useModule(\"org.springframework.boot:spring-boot-gradle-plugin:${requested.version}\")",
+				"            }", "        }", "    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithSnapshotPluginRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("spring-snapshots", "Spring Snapshots",
+				"https://repo.spring.io/snapshot", true);
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("pluginManagement {", "    repositories {",
+				"        maven { url = uri(\"https://repo.spring.io/snapshot\") }",
+				"        gradlePluginPortal()", "    }", "    resolutionStrategy {",
+				"        eachPlugin {",
+				"            if (requested.id.id == \"org.springframework.boot\") {",
+				"                useModule(\"org.springframework.boot:spring-boot-gradle-plugin:${requested.version}\")",
+				"            }", "        }", "    }", "}");
+	}
+
+	@Test
+	void artifactIdShouldBeUsedAsTheRootProjectName() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.setArtifact("my-application");
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("rootProject.name = \"my-application\"");
+	}
+
+	private List<String> generateSettings(GradleBuild build) throws IOException {
+		GradleSettingsWriter writer = new KotlinDslGradleSettingsWriter();
+		StringWriter out = new StringWriter();
+		writer.writeTo(new IndentingWriter(out), build);
+		return Arrays.asList(out.toString().split("\\r?\\n"));
+	}
+
+}