Support config yaml files embedded in env vars via spring.config.import

Author: chicobento

spring-boot-project/spring-boot/build.gradle

@@ -107,6 +107,8 @@ dependencies {
 	testImplementation("com.microsoft.sqlserver:mssql-jdbc")
 	testImplementation("com.mysql:mysql-connector-j")
 	testImplementation("com.sun.xml.messaging.saaj:saaj-impl")
+	// TODO: Define strategy for mocking env vars and if/which 3pp to use
+	testImplementation("uk.org.webcompere:system-stubs-core:2.1.7")
 	testImplementation("io.projectreactor:reactor-test")
 	testImplementation("io.r2dbc:r2dbc-h2")
 	testImplementation("jakarta.inject:jakarta.inject-api")

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessor.java

@@ -32,7 +32,9 @@
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
 import org.springframework.core.io.DefaultResourceLoader;
+import org.springframework.core.io.ProtocolResolver;
 import org.springframework.core.io.ResourceLoader;
+import org.springframework.core.io.support.SpringFactoriesLoader;
 
 /**
  * {@link EnvironmentPostProcessor} that loads and applies {@link ConfigData} to Spring's
@@ -92,7 +94,13 @@ public void postProcessEnvironment(ConfigurableEnvironment environment, SpringAp
 	void postProcessEnvironment(ConfigurableEnvironment environment, ResourceLoader resourceLoader,
 			Collection<String> additionalProfiles) {
 		this.logger.trace("Post-processing environment to add config data");
-		resourceLoader = (resourceLoader != null) ? resourceLoader : new DefaultResourceLoader();
+		if (resourceLoader == null) {
+			DefaultResourceLoader defaultResourceLoader = new DefaultResourceLoader();
+			SpringFactoriesLoader.forDefaultResourceLocation(defaultResourceLoader.getClassLoader())
+				.load(ProtocolResolver.class)
+				.forEach(defaultResourceLoader::addProtocolResolver);
+			resourceLoader = defaultResourceLoader;
+		}
 		getConfigDataEnvironment(environment, resourceLoader, additionalProfiles).processAndApply();
 	}
 

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/LocationResourceLoader.java

@@ -74,7 +74,7 @@ boolean isPattern(String location) {
 	Resource getResource(String location) {
 		validateNonPattern(location);
 		location = StringUtils.cleanPath(location);
-		if (!ResourceUtils.isUrl(location)) {
+		if (!ResourceUtils.isUrl(location) && !location.contains(":")) {
 			location = ResourceUtils.FILE_URL_PREFIX + location;
 		}
 		return this.resourceLoader.getResource(location);

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/StandardConfigDataReference.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.context.config;
 
+import java.util.Locale;
+
 import org.springframework.boot.env.PropertySourceLoader;
 import org.springframework.util.StringUtils;
 
@@ -51,7 +53,8 @@ class StandardConfigDataReference {
 	StandardConfigDataReference(ConfigDataLocation configDataLocation, String directory, String root, String profile,
 			String extension, PropertySourceLoader propertySourceLoader) {
 		this.configDataLocation = configDataLocation;
-		String profileSuffix = (StringUtils.hasText(profile)) ? "-" + profile : "";
+		String profileSuffix = (StringUtils.hasText(profile))
+				? root.startsWith("env:") ? "_" + profile.toUpperCase(Locale.ROOT) : "-" + profile : "";
 		this.resourceLocation = root + profileSuffix + ((extension != null) ? "." + extension : "");
 		this.directory = directory;
 		this.profile = profile;

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/io/EnvironmentVariableProtocolResolver.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2012-2025 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 org.springframework.boot.io;
+
+import org.springframework.core.io.ProtocolResolver;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
+
+/**
+ * {@link ProtocolResolver} for resources contained in environment variables.
+ *
+ * @author Francisco Bento
+ */
+class EnvironmentVariableProtocolResolver implements ProtocolResolver {
+
+	@Override
+	public Resource resolve(String location, ResourceLoader resourceLoader) {
+		return EnvironmentVariableResource.fromUri(location);
+	}
+
+}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/io/EnvironmentVariableResource.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2012-2025 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 org.springframework.boot.io;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+
+import org.springframework.core.io.AbstractResource;
+import org.springframework.core.io.Resource;
+
+/**
+ * {@link Resource} implementation for system environment variables.
+ *
+ * @author Francisco Bento
+ * @since 3.5.0
+ */
+public class EnvironmentVariableResource extends AbstractResource {
+
+	/** Pseudo URL prefix for loading from an environment variable: "env:". */
+	public static final String PSEUDO_URL_PREFIX = "env:";
+
+	/** Pseudo URL prefix indicating that the environment variable is base64-encoded. */
+	public static final String BASE64_ENCODED_PREFIX = "base64:";
+
+	private final String envVar;
+
+	private final boolean isBase64;
+
+	public EnvironmentVariableResource(final String envVar, final boolean isBase64) {
+		this.envVar = envVar;
+		this.isBase64 = isBase64;
+	}
+
+	public static EnvironmentVariableResource fromUri(String url) {
+		if (url.startsWith(PSEUDO_URL_PREFIX)) {
+			String envVar = url.substring(PSEUDO_URL_PREFIX.length());
+			boolean isBase64 = false;
+			if (envVar.startsWith(BASE64_ENCODED_PREFIX)) {
+				envVar = envVar.substring(BASE64_ENCODED_PREFIX.length());
+				isBase64 = true;
+			}
+			return new EnvironmentVariableResource(envVar, isBase64);
+		}
+		return null;
+	}
+
+	@Override
+	public boolean exists() {
+		return System.getenv(this.envVar) != null;
+	}
+
+	@Override
+	public String getDescription() {
+		return "Environment variable '" + this.envVar + "'";
+	}
+
+	@Override
+	public InputStream getInputStream() throws IOException {
+		return new ByteArrayInputStream(getContents());
+	}
+
+	protected byte[] getContents() {
+		String value = System.getenv(this.envVar);
+		if (this.isBase64) {
+			return Base64.getDecoder().decode(value);
+		}
+		return value.getBytes(StandardCharsets.UTF_8);
+	}
+
+}

spring-boot-project/spring-boot/src/main/resources/META-INF/spring.factories

@@ -104,4 +104,5 @@ org.springframework.boot.orm.jpa.JpaDependsOnDatabaseInitializationDetector
 
 # Resource Locator Protocol Resolvers
 org.springframework.core.io.ProtocolResolver=\
-org.springframework.boot.io.Base64ProtocolResolver
+org.springframework.boot.io.Base64ProtocolResolver,\
+org.springframework.boot.io.EnvironmentVariableProtocolResolver

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessorIntegrationTests.java

@@ -20,8 +20,10 @@
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Base64;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
@@ -621,6 +623,62 @@ void runWhenImportWithProfileVariantOrdersPropertySourcesCorrectly() {
 			.isEqualTo("application-import-with-profile-variant-imported-dev");
 	}
 
+	@Test
+	void runWhenImportYamlFromEnvironmentVariable() throws Exception {
+		ConfigurableApplicationContext context = uk.org.webcompere.systemstubs.SystemStubs
+			.withEnvironmentVariable("MY_CONFIG_YAML", """
+					my:
+					  value: from-env-first-doc
+					---
+					my:
+					  value: from-env-second-doc
+					""")
+			.execute(() -> this.application
+				.run("--spring.config.location=classpath:application-import-yaml-from-environment.properties"));
+		assertThat(context.getEnvironment().getProperty("my.value")).isEqualTo("from-env-second-doc");
+	}
+
+	@Test
+	void runWhenImportYamlFromEnvironmentVariableWithProfileVariant() throws Exception {
+		this.application.setAdditionalProfiles("dev");
+		ConfigurableApplicationContext context = uk.org.webcompere.systemstubs.SystemStubs
+			.withEnvironmentVariables("MY_CONFIG_YAML", """
+					my:
+					  value: my_config_yaml
+					""", "MY_CONFIG_YAML_DEV", """
+					my:
+					  value: my_config_yaml_dev
+					""")
+			.execute(() -> this.application.run(
+					"--spring.config.location=classpath:application-import-yaml-from-environment-with-profile-variant.properties"));
+		assertThat(context.getEnvironment().getProperty("my.value")).isEqualTo("my_config_yaml_dev");
+	}
+
+	@Test
+	void runWhenImportBase64YamlFromEnvironmentVariable() throws Exception {
+		ConfigurableApplicationContext context = uk.org.webcompere.systemstubs.SystemStubs
+			.withEnvironmentVariable("MY_CONFIG_BASE64_YAML", Base64.getEncoder().encodeToString("""
+					my:
+					  value: from-base64-yaml
+					""".getBytes(StandardCharsets.UTF_8)))
+			.execute(() -> this.application
+				.run("--spring.config.location=classpath:application-import-base64-yaml-from-environment.properties"));
+		assertThat(context.getEnvironment().getProperty("my.value")).isEqualTo("from-base64-yaml");
+	}
+
+	@Test
+	void runWhenImportPropertiesFromEnvironmentVariable() throws Exception {
+		ConfigurableApplicationContext context = uk.org.webcompere.systemstubs.SystemStubs
+			.withEnvironmentVariable("MY_CONFIG_PROPERTIES", """
+					my.value1: from-properties-1
+					my.value2: from-properties-2
+					""")
+			.execute(() -> this.application
+				.run("--spring.config.location=classpath:application-import-properties-from-environment.properties"));
+		assertThat(context.getEnvironment().getProperty("my.value1")).isEqualTo("from-properties-1");
+		assertThat(context.getEnvironment().getProperty("my.value2")).isEqualTo("from-properties-2");
+	}
+
 	@Test
 	void runWhenImportWithProfileVariantAndDirectProfileImportOrdersPropertySourcesCorrectly() {
 		this.application.setAdditionalProfiles("dev");

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/io/ProtocolResolverApplicationContextInitializerTests.java

@@ -41,7 +41,8 @@ void initializeAddsProtocolResolversToApplicationContext() {
 			initializer.initialize(context);
 			assertThat(context).isInstanceOf(DefaultResourceLoader.class);
 			Collection<ProtocolResolver> protocolResolvers = ((DefaultResourceLoader) context).getProtocolResolvers();
-			assertThat(protocolResolvers).hasExactlyElementsOfTypes(Base64ProtocolResolver.class);
+			assertThat(protocolResolvers).hasExactlyElementsOfTypes(Base64ProtocolResolver.class,
+					EnvironmentVariableProtocolResolver.class);
 		}
 	}
 

spring-boot-project/spring-boot/src/test/resources/application-import-base64-yaml-from-environment.properties

@@ -0,0 +1,2 @@
+my.value=application-import-base64-yaml-from-environment
+spring.config.import=env:base64:MY_CONFIG_BASE64_YAML[.yaml]