Register ProtocolResolvers with the application context by default

Any ProtocolResolvers that are registered in a spring.factories file
will be added to the application context using an
ApplicationContextInitializer.

Closes gh-41433

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

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2012-2024 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.util.List;
+
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.core.io.ProtocolResolver;
+import org.springframework.core.io.support.SpringFactoriesLoader;
+
+/**
+ * {@link ApplicationContextInitializer} that adds all {@link ProtocolResolver}s
+ * registered in a {@code spring.factories} file.
+ *
+ * @author Scott Frederick
+ */
+class ProtocolResolverApplicationContextInitializer
+		implements ApplicationContextInitializer<ConfigurableApplicationContext> {
+
+	@Override
+	public void initialize(ConfigurableApplicationContext applicationContext) {
+		SpringFactoriesLoader loader = SpringFactoriesLoader
+			.forDefaultResourceLocation(applicationContext.getClassLoader());
+		List<ProtocolResolver> protocolResolvers = loader.load(ProtocolResolver.class);
+		protocolResolvers.forEach(applicationContext::addProtocolResolver);
+	}
+
+}

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

@@ -36,6 +36,7 @@ org.springframework.boot.diagnostics.FailureAnalyzers
 org.springframework.context.ApplicationContextInitializer=\
 org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\
 org.springframework.boot.context.ContextIdApplicationContextInitializer,\
+org.springframework.boot.io.ProtocolResolverApplicationContextInitializer,\
 org.springframework.boot.rsocket.context.RSocketPortInfoApplicationContextInitializer,\
 org.springframework.boot.web.context.ServerPortInfoApplicationContextInitializer
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/builder/SpringApplicationBuilderTests.java

@@ -265,7 +265,7 @@ class SpringApplicationBuilderTests {
 		SpringApplicationBuilder application = new SpringApplicationBuilder(ExampleConfig.class)
 			.web(WebApplicationType.NONE);
 		this.context = application.run();
-		assertThat(application.application().getInitializers()).hasSize(4);
+		assertThat(application.application().getInitializers()).hasSize(5);
 	}
 
 	@Test
@@ -274,7 +274,7 @@ class SpringApplicationBuilderTests {
 			.child(ChildConfig.class)
 			.web(WebApplicationType.NONE);
 		this.context = application.run();
-		assertThat(application.application().getInitializers()).hasSize(5);
+		assertThat(application.application().getInitializers()).hasSize(6);
 	}
 
 	@Test
@@ -284,7 +284,7 @@ class SpringApplicationBuilderTests {
 			.initializers((ConfigurableApplicationContext applicationContext) -> {
 			});
 		this.context = application.run();
-		assertThat(application.application().getInitializers()).hasSize(5);
+		assertThat(application.application().getInitializers()).hasSize(6);
 	}
 
 	@Test

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

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2012-2024 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.IOException;
+import java.nio.charset.Charset;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.WebApplicationType;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.io.Resource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for resolving configuration properties using
+ * {@code ProtocolResolver}s.
+ *
+ * @author Scott Frederick
+ */
+class ProtocolResolverApplicationContextInitializerIntegrationTests {
+
+	@Test
+	void base64ResourceResolves() throws IOException {
+		SpringApplication application = new SpringApplication(TestConfiguration.class);
+		application.setDefaultProperties(Map.of("test.resource", "base64:dGVzdC12YWx1ZQ=="));
+		application.setWebApplicationType(WebApplicationType.NONE);
+		ConfigurableApplicationContext context = application.run();
+		TestProperties propertiesBean = context.getBean(TestProperties.class);
+		Resource resource = propertiesBean.getResource();
+		assertThat(resource).isNotNull();
+		assertThat(resource.exists()).isTrue();
+		assertThat(resource.getContentAsString(Charset.defaultCharset())).isEqualTo("test-value");
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@EnableConfigurationProperties(TestProperties.class)
+	static class TestConfiguration {
+
+	}
+
+	@ConfigurationProperties(prefix = "test")
+	static class TestProperties {
+
+		Resource resource;
+
+		Resource getResource() {
+			return this.resource;
+		}
+
+		void setResource(Resource resource) {
+			this.resource = resource;
+		}
+
+	}
+
+}

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

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2012-2024 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.util.Collection;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.core.io.DefaultResourceLoader;
+import org.springframework.core.io.ProtocolResolver;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ProtocolResolverApplicationContextInitializer}.
+ *
+ * @author Scott Frederick
+ */
+class ProtocolResolverApplicationContextInitializerTests {
+
+	@Test
+	void initializeAddsProtocolResolversToApplicationContext() {
+		try (ConfigurableApplicationContext context = new AnnotationConfigApplicationContext()) {
+			ProtocolResolverApplicationContextInitializer initializer = new ProtocolResolverApplicationContextInitializer();
+			initializer.initialize(context);
+			assertThat(context).isInstanceOf(DefaultResourceLoader.class);
+			Collection<ProtocolResolver> protocolResolvers = ((DefaultResourceLoader) context).getProtocolResolvers();
+			assertThat(protocolResolvers).hasExactlyElementsOfTypes(Base64ProtocolResolver.class);
+		}
+	}
+
+}