Add support for source set and Spring profile specific application properties

initializr-docs/src/main/asciidoc/configuration-guide.adoc

@@ -215,6 +215,20 @@ requires you to add a certain plugin to the build, you can provide a `BuildCusto
 that adds the plugin and the customizer will be called according to the order specified on
 it.
 
+Similarly, an `ApplicationPropertiesCustomizer` can contribute properties to the
+configuration files of the generated project, that is `application.properties` or
+`application.yaml` depending on the requested `ConfigurationFileFormat`. Properties added
+directly belong to the main source set and the default profile, `file` and `profile`
+address the other source sets and Spring profiles. Each combination is written to
++src/{sourceSet}/resources/application[-{profile}]+, with the extension of the requested
+format. Combinations without properties are skipped, except for the main source set and
+the default profile, which is always written:
+
+[source,java,indent=0]
+----
+include::{code-examples}/doc/generator/project/ProjectCustomizationExamples.java[tag=application-properties-customizer]
+----
+
 
 
 [[initializr-generator-spring-requirements]]

initializr-docs/src/main/java/io/spring/initializr/doc/generator/project/ProjectCustomizationExamples.java

@@ -16,6 +16,7 @@
 
 package io.spring.initializr.doc.generator.project;
 
+import io.spring.initializr.generator.buildsystem.SourceSet;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuildSystem;
 import io.spring.initializr.generator.condition.ConditionalOnBuildSystem;
@@ -25,13 +26,16 @@
 import io.spring.initializr.generator.project.ProjectDescriptionCustomizer;
 import io.spring.initializr.generator.project.ProjectDescriptionField;
 import io.spring.initializr.generator.spring.build.BuildCustomizer;
+import io.spring.initializr.generator.spring.properties.ApplicationPropertiesCustomizer;
 
 import org.springframework.context.annotation.Bean;
 
 /**
  * Examples of customizers.
  *
  * @author Stephane Nicoll
+ * @author Moritz Halbritter
+ * @author Denis A. Altoé Falqueto
  */
 public class ProjectCustomizationExamples {
 
@@ -69,4 +73,18 @@ private boolean isBelowJava17(String jvmVersion) {
 	}
 	// end::jvm-version-change-reason[]
 
+	// tag::application-properties-customizer[]
+	@Bean
+	public ApplicationPropertiesCustomizer applicationPropertiesCustomizer() {
+		return (properties) -> {
+			// src/main/resources/application.properties (or .yaml)
+			properties.add("spring.application.name", "acme");
+			// src/test/resources/application.properties (or .yaml)
+			properties.file(SourceSet.TEST).add("spring.datasource.url", "jdbc:h2:mem:acme");
+			// src/main/resources/application-dev.properties (or .yaml)
+			properties.profile("dev").add("logging.level.root", "DEBUG");
+		};
+	}
+	// end::application-properties-customizer[]
+
 }

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/properties/AbstractApplicationPropertiesContributor.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2012 - present 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
+ *
+ *      https://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.spring.properties;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import java.util.Map;
+
+import io.spring.initializr.generator.buildsystem.BuildSystem;
+import io.spring.initializr.generator.buildsystem.SourceSet;
+import io.spring.initializr.generator.configuration.format.ConfigurationFileFormat;
+import io.spring.initializr.generator.language.Language;
+import io.spring.initializr.generator.language.SourceStructure;
+import io.spring.initializr.generator.project.ProjectDescription;
+import io.spring.initializr.generator.project.contributor.ProjectContributor;
+
+import org.springframework.util.Assert;
+
+/**
+ * Base {@link ProjectContributor} that writes the application configuration files of a
+ * project, one per {@link ApplicationPropertiesFile} that has properties. The default
+ * file of the main source set is written even when empty.
+ *
+ * @author Denis A. Altoé Falqueto
+ * @author Moritz Halbritter
+ * @see ApplicationProperties
+ */
+abstract class AbstractApplicationPropertiesContributor implements ProjectContributor {
+
+	private final ApplicationProperties properties;
+
+	private final ProjectDescription description;
+
+	private final ConfigurationFileFormat format;
+
+	/**
+	 * Creates a new instance.
+	 * @param properties the application properties to contribute
+	 * @param description the description of the project, used to resolve the source
+	 * structures
+	 * @param format the format of the written files, defining their extension
+	 */
+	protected AbstractApplicationPropertiesContributor(ApplicationProperties properties, ProjectDescription description,
+			ConfigurationFileFormat format) {
+		this.properties = properties;
+		this.description = description;
+		this.format = format;
+	}
+
+	@Override
+	public void contribute(Path projectRoot) throws IOException {
+		BuildSystem buildSystem = this.description.getBuildSystem();
+		Assert.state(buildSystem != null, "'buildSystem' must not be null");
+		Language language = this.description.getLanguage();
+		Assert.state(language != null, "'language' must not be null");
+		for (SourceSet sourceSet : SourceSet.values()) {
+			contribute(buildSystem.getSource(projectRoot, language, sourceSet), sourceSet);
+		}
+	}
+
+	private void contribute(SourceStructure sourceStructure, SourceSet sourceSet) throws IOException {
+		for (Map.Entry<ProfileName, ApplicationPropertiesFile> entry : this.properties.files(sourceSet).entrySet()) {
+			ProfileName profile = entry.getKey();
+			ApplicationPropertiesFile file = entry.getValue();
+			// Generated projects always ship a main application file, even an empty one.
+			// Every other file is written only if it has properties.
+			boolean mainDefault = (sourceSet == SourceSet.MAIN) && ProfileName.DEFAULT.equals(profile);
+			if (file.isEmpty() && !mainDefault) {
+				continue;
+			}
+			writeFile(sourceStructure, profile, file);
+		}
+	}
+
+	private void writeFile(SourceStructure sourceStructure, ProfileName profile, ApplicationPropertiesFile file)
+			throws IOException {
+		Path output = resolveOutputFile(sourceStructure, profile);
+		if (!Files.exists(output)) {
+			Files.createDirectories(output.getParent());
+			Files.createFile(output);
+		}
+		try (PrintWriter writer = new PrintWriter(Files.newOutputStream(output, StandardOpenOption.APPEND), false,
+				StandardCharsets.UTF_8)) {
+			writeProperties(file.properties(), writer);
+		}
+	}
+
+	/**
+	 * Writes the given properties in the format of this contributor.
+	 * @param properties the properties to write, keyed by their dotted name
+	 * @param writer the writer to use
+	 */
+	protected abstract void writeProperties(Map<String, Object> properties, PrintWriter writer);
+
+	private Path resolveOutputFile(SourceStructure sourceStructure, ProfileName profile) {
+		String fileName = "application" + profile.fileSuffix() + this.format.fileExtension();
+		return sourceStructure.getResourcesDirectory().resolve(fileName);
+	}
+
+}