Add support for source set and Spring profile specific application properties

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

@@ -189,6 +189,20 @@ 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 be used to contribute properties to
+the application configuration file of the generated project, that is
+`application.properties` or `application.yaml` depending on the requested
+`ConfigurationFileFormat`. Properties added directly to the `ApplicationProperties`
+argument are written to the configuration file of the main source set and the default
+profile. Properties for another source set or Spring profile can be added to the matching
+`section`, and a `src/{sourceSet}/resources/application[-{profile}]` file is generated
+for every section that contains properties, as shown in the following example:
+
+[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

@@ -16,12 +16,14 @@
 
 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;
 import io.spring.initializr.generator.condition.ConditionalOnPackaging;
 import io.spring.initializr.generator.packaging.war.WarPackaging;
 import io.spring.initializr.generator.spring.build.BuildCustomizer;
+import io.spring.initializr.generator.spring.properties.ApplicationPropertiesCustomizer;
 
 import org.springframework.context.annotation.Bean;
 
@@ -41,4 +43,18 @@ public BuildCustomizer<GradleBuild> warPluginContributor() {
 	}
 	// end::war-plugin-contributor[]
 
+	// tag::application-properties-customizer[]
+	@Bean
+	public ApplicationPropertiesCustomizer applicationPropertiesContributor() {
+		return (properties) -> {
+			// src/main/resources/application.properties (or .yaml)
+			properties.add("spring.application.name", "acme");
+			// src/test/resources/application.properties
+			properties.section(SourceSet.TEST).add("spring.datasource.url", "jdbc:h2:mem:acme");
+			// src/main/resources/application-dev.properties
+			properties.section(SourceSet.MAIN, "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 +1,90 @@
+/*
+ * 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.SourceSet;
+import io.spring.initializr.generator.project.contributor.ProjectContributor;
+import io.spring.initializr.generator.spring.properties.ApplicationProperties.SectionKey;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * Base {@link ProjectContributor} that contributes application configuration files to a
+ * project. A file is written per source set and Spring profile that has properties,
+ * following the {@code src/{sourceSet}/resources/application[-{profile}]} convention. The
+ * file for the main source set and the default profile is always written, even if it is
+ * empty.
+ *
+ * @author Denis A. Altoé Falqueto
+ * @see ApplicationProperties#section(SourceSet, String)
+ */
+public abstract class AbstractApplicationPropertiesContributor implements ProjectContributor {
+
+	private final ApplicationProperties properties;
+
+	private final String extension;
+
+	protected AbstractApplicationPropertiesContributor(ApplicationProperties properties, String extension) {
+		this.properties = properties;
+		this.extension = extension;
+	}
+
+	@Override
+	public void contribute(Path projectRoot) throws IOException {
+		writeSection(projectRoot, SourceSet.MAIN, null, this.properties);
+		for (Map.Entry<SectionKey, ApplicationProperties> entry : this.properties.getSections().entrySet()) {
+			ApplicationProperties section = entry.getValue();
+			if (!section.isEmpty()) {
+				writeSection(projectRoot, entry.getKey().sourceSet(), entry.getKey().profile(), section);
+			}
+		}
+	}
+
+	/**
+	 * Writes the given properties using the given writer.
+	 * @param properties the properties to write
+	 * @param writer the writer to use
+	 */
+	protected abstract void write(ApplicationProperties properties, PrintWriter writer);
+
+	private void writeSection(Path projectRoot, SourceSet sourceSet, @Nullable String profile,
+			ApplicationProperties properties) throws IOException {
+		Path output = projectRoot.resolve(resolveFileName(sourceSet, 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)) {
+			write(properties, writer);
+		}
+	}
+
+	private String resolveFileName(SourceSet sourceSet, @Nullable String profile) {
+		String profileSuffix = (profile != null) ? "-" + profile : "";
+		return "src/%s/resources/application%s.%s".formatted(sourceSet.getDirectoryName(), profileSuffix,
+				this.extension);
+	}
+
+}

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

@@ -18,16 +18,24 @@
 
 import java.io.PrintWriter;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.Map;
 
+import io.spring.initializr.generator.buildsystem.SourceSet;
 import org.jspecify.annotations.Nullable;
 
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
 /**
  * Application properties.
+ * <p>
+ * Properties added directly to this instance belong to the main source set and the
+ * default profile, and are written to {@code src/main/resources}. Properties for another
+ * source set or Spring profile can be added to the {@link #section(SourceSet, String)
+ * matching section}.
  *
  * @author Moritz Halbritter
  * @author Rodrigo Mibielli Peixoto
@@ -38,6 +46,57 @@ public class ApplicationProperties {
 
 	private final Map<String, Object> properties = new HashMap<>();
 
+	private final Map<SectionKey, ApplicationProperties> sections = new LinkedHashMap<>();
+
+	private final boolean root;
+
+	/**
+	 * Creates the application properties of the main source set and the default profile.
+	 */
+	public ApplicationProperties() {
+		this(true);
+	}
+
+	private ApplicationProperties(boolean root) {
+		this.root = root;
+	}
+
+	/**
+	 * Returns the application properties for the given source set and profile, creating
+	 * the section if necessary. Calling this method with {@link SourceSet#MAIN} and a
+	 * {@code null} profile returns this instance.
+	 * @param sourceSet the source set the properties belong to
+	 * @param profile the Spring profile the properties belong to, or {@code null} for the
+	 * default profile
+	 * @return the application properties for the given source set and profile
+	 * @throws IllegalStateException if called on a section rather than on the root
+	 * application properties
+	 */
+	public ApplicationProperties section(SourceSet sourceSet, @Nullable String profile) {
+		Assert.notNull(sourceSet, "'sourceSet' must not be null");
+		Assert.state(this.root, "Sections cannot be nested");
+		if (profile != null) {
+			Assert.hasText(profile, "'profile' must not be empty");
+		}
+		if (sourceSet == SourceSet.MAIN && profile == null) {
+			return this;
+		}
+		return this.sections.computeIfAbsent(new SectionKey(sourceSet, profile),
+				(key) -> new ApplicationProperties(false));
+	}
+
+	/**
+	 * Returns the application properties for the given source set and the default
+	 * profile, creating the section if necessary.
+	 * @param sourceSet the source set the properties belong to
+	 * @return the application properties for the given source set
+	 * @throws IllegalStateException if called on a section rather than on the root
+	 * application properties
+	 */
+	public ApplicationProperties section(SourceSet sourceSet) {
+		return section(sourceSet, null);
+	}
+
 	/**
 	 * Adds a new property.
 	 * @param key the key of the property
@@ -198,4 +257,22 @@ private void add(String key, Object value) {
 		this.properties.put(key, value);
 	}
 
+	boolean isEmpty() {
+		return this.properties.isEmpty();
+	}
+
+	Map<SectionKey, ApplicationProperties> getSections() {
+		return Collections.unmodifiableMap(this.sections);
+	}
+
+	/**
+	 * The source set and profile a section of application properties belongs to.
+	 *
+	 * @param sourceSet the source set the properties belong to
+	 * @param profile the Spring profile the properties belong to, or {@code null} for the
+	 * default profile
+	 */
+	record SectionKey(SourceSet sourceSet, @Nullable String profile) {
+	}
+
 }

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

@@ -16,43 +16,26 @@
 
 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 io.spring.initializr.generator.project.contributor.ProjectContributor;
 
 /**
- * A {@link ProjectContributor} that contributes a {@code application.properties} file to
- * a project.
+ * A {@link ProjectContributor} that contributes {@code application.properties} files to a
+ * project, one per source set and Spring profile that has properties.
  *
  * @author Stephane Nicoll
  * @author Moritz Halbritter
  */
-public class ApplicationPropertiesContributor implements ProjectContributor {
-
-	private static final String FILE = "src/main/resources/application.properties";
-
-	private final ApplicationProperties properties;
+public class ApplicationPropertiesContributor extends AbstractApplicationPropertiesContributor {
 
 	public ApplicationPropertiesContributor(ApplicationProperties properties) {
-		this.properties = properties;
+		super(properties, "properties");
 	}
 
 	@Override
-	public void contribute(Path projectRoot) throws IOException {
-		Path output = projectRoot.resolve(FILE);
-		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)) {
-			this.properties.writeProperties(writer);
-		}
+	protected void write(ApplicationProperties properties, PrintWriter writer) {
+		properties.writeProperties(writer);
 	}
 
 }

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

@@ -16,42 +16,25 @@
 
 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 io.spring.initializr.generator.project.contributor.ProjectContributor;
 
 /**
- * A {@link ProjectContributor} that contributes a {@code application.yaml} file to a
- * project.
+ * A {@link ProjectContributor} that contributes {@code application.yaml} files to a
+ * project, one per source set and Spring profile that has properties.
  *
  * @author Sijun Yang
  */
-public class ApplicationYamlPropertiesContributor implements ProjectContributor {
-
-	private static final String FILE = "src/main/resources/application.yaml";
-
-	private final ApplicationProperties properties;
+public class ApplicationYamlPropertiesContributor extends AbstractApplicationPropertiesContributor {
 
 	public ApplicationYamlPropertiesContributor(ApplicationProperties properties) {
-		this.properties = properties;
+		super(properties, "yaml");
 	}
 
 	@Override
-	public void contribute(Path projectRoot) throws IOException {
-		Path output = projectRoot.resolve(FILE);
-		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)) {
-			this.properties.writeYaml(writer);
-		}
+	protected void write(ApplicationProperties properties, PrintWriter writer) {
+		properties.writeYaml(writer);
 	}
 
 }