Provide ConfigFileApplicationListener replacement

Deprecate `ConfigFileApplicationListener` and provide a replacement
mechanism that supports arbitrary config data imports.

This commit updates the following areas:

- Extract `EnvironmentPostProcessor` invocation logic from the
  `ConfigFileApplicationListener` to new dedicated listener. Also
  providing support for `Log` injection.

- Extract `RandomPropertySource` adding logic from the
  `ConfigFileApplicationListener` to a dedicated class.

- Migrate to the recently introduced `DefaultPropertiesPropertySource`
  class when moving the defaultProperties `PropertySource`

- Replace processing logic with a phased approach to ensure that
  profile enablement happens in a distinct phase and that profiles
  can no longer be activated on an ad-hoc basis.

- Provide a more predictable and logical import order for processing
  `application.properties` and `application.yml` files.

- Add support for a `spring.config.import` property which can be used
  to import additional config data. Also provide a pluggable API
  allowing third-parties to resolve and load locations themselves.

- Add `spring.config.activate.on-profile` support which replaces the
  existing `spring.profiles` property.

- Add `spring.config.activate.on-cloud-platform` support which allows
  a config data document to be active only on a given cloud platform.

- Support a `spring.config.use-legacy-processing` property allowing the
  previous processing logic to be used.

Closes gh-22497

Co-authored-by: Madhura Bhave <mbhave@vmware.com>

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/ConfigDataApplicationContextInitializer.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2012-2020 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.test.context;
+
+import java.util.function.Supplier;
+
+import org.springframework.boot.context.config.ConfigData;
+import org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor;
+import org.springframework.boot.env.DefaultPropertiesPropertySource;
+import org.springframework.boot.env.RandomValuePropertySource;
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.io.ResourceLoader;
+import org.springframework.test.context.ContextConfiguration;
+
+/**
+ * {@link ApplicationContextInitializer} that can be used with the
+ * {@link ContextConfiguration#initializers()} to trigger loading of {@link ConfigData}
+ * such as {@literal application.properties}.
+ *
+ * @author Phillip Webb
+ * @since 2.4.0
+ * @see ConfigDataEnvironmentPostProcessor
+ */
+public class ConfigDataApplicationContextInitializer
+		implements ApplicationContextInitializer<ConfigurableApplicationContext> {
+
+	@Override
+	public void initialize(ConfigurableApplicationContext applicationContext) {
+		ConfigurableEnvironment environment = applicationContext.getEnvironment();
+		RandomValuePropertySource.addToEnvironment(environment);
+		new ConfigDataProcessor().addPropertySources(environment, applicationContext);
+		DefaultPropertiesPropertySource.moveToEnd(environment);
+	}
+
+	private static class ConfigDataProcessor extends ConfigDataEnvironmentPostProcessor {
+
+		ConfigDataProcessor() {
+			super(Supplier::get);
+		}
+
+		void addPropertySources(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
+			addPropertySources(environment, resourceLoader, null);
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/ConfigFileApplicationContextInitializer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -16,7 +16,6 @@
 
 package org.springframework.boot.test.context;
 
-import org.springframework.boot.context.config.ConfigFileApplicationListener;
 import org.springframework.context.ApplicationContextInitializer;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.test.context.ContextConfiguration;
@@ -28,14 +27,16 @@ import org.springframework.test.context.ContextConfiguration;
  *
  * @author Phillip Webb
  * @since 1.4.0
- * @see ConfigFileApplicationListener
+ * @see org.springframework.boot.context.config.ConfigFileApplicationListener
+ * @deprecated since 2.4.0 in favor of {@link ConfigDataApplicationContextInitializer}
  */
+@Deprecated
 public class ConfigFileApplicationContextInitializer
 		implements ApplicationContextInitializer<ConfigurableApplicationContext> {
 
 	@Override
 	public void initialize(ConfigurableApplicationContext applicationContext) {
-		new ConfigFileApplicationListener() {
+		new org.springframework.boot.context.config.ConfigFileApplicationListener() {
 			public void apply() {
 				addPropertySources(applicationContext.getEnvironment(), applicationContext);
 				addPostProcessors(applicationContext);

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

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2012-2020 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.test.context;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.env.Environment;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ConfigDataApplicationContextInitializer}.
+ *
+ * @author Phillip Webb
+ */
+@ExtendWith(SpringExtension.class)
+@DirtiesContext
+@ContextConfiguration(classes = ConfigDataApplicationContextInitializerTests.Config.class,
+		initializers = ConfigDataApplicationContextInitializer.class)
+class ConfigDataApplicationContextInitializerTests {
+
+	@Autowired
+	private Environment environment;
+
+	@Test
+	void initializerPopulatesEnvironment() {
+		assertThat(this.environment.getProperty("foo")).isEqualTo("bucket");
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class Config {
+
+	}
+
+}

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

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2012-2020 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.test.context;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.env.Environment;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.TestPropertySource;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ConfigDataApplicationContextInitializer}.
+ *
+ * @author Phillip Webb
+ */
+@ExtendWith(SpringExtension.class)
+@DirtiesContext
+@TestPropertySource(properties = "spring.config.use-legacy-processing=true")
+@ContextConfiguration(classes = ConfigDataApplicationContextInitializerWithLegacySwitchTests.Config.class,
+		initializers = ConfigDataApplicationContextInitializer.class)
+class ConfigDataApplicationContextInitializerWithLegacySwitchTests {
+
+	@Autowired
+	private Environment environment;
+
+	@Test
+	void initializerPopulatesEnvironment() {
+		assertThat(this.environment.getProperty("foo")).isEqualTo("bucket");
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class Config {
+
+	}
+
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -33,6 +33,8 @@ import static org.assertj.core.api.Assertions.assertThat;
  *
  * @author Phillip Webb
  */
+@Deprecated
+@SuppressWarnings("deprecation")
 @ExtendWith(SpringExtension.class)
 @DirtiesContext
 @ContextConfiguration(classes = ConfigFileApplicationContextInitializerTests.Config.class,