Allow common messages to be specified for message sources

Extend message source configuration properties and auto-configuration to
support common messages.

See gh-42472

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/context/MessageSourceAutoConfiguration.java

@@ -16,7 +16,10 @@
 
 package org.springframework.boot.autoconfigure.context;
 
+import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.time.Duration;
+import java.util.Properties;
 
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
@@ -41,6 +44,7 @@ import org.springframework.context.support.ResourceBundleMessageSource;
 import org.springframework.core.Ordered;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
+import org.springframework.core.io.support.PropertiesLoaderUtils;
 import org.springframework.core.type.AnnotatedTypeMetadata;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.ConcurrentReferenceHashMap;
@@ -81,6 +85,19 @@ public class MessageSourceAutoConfiguration {
 		}
 		messageSource.setAlwaysUseMessageFormat(properties.isAlwaysUseMessageFormat());
 		messageSource.setUseCodeAsDefaultMessage(properties.isUseCodeAsDefaultMessage());
+
+		try {
+			if (properties.getCommonMessages() != null) {
+				Properties commonProperties = new Properties();
+				for (Resource commonResource : properties.getCommonMessages()) {
+					PropertiesLoaderUtils.fillProperties(commonProperties, commonResource);
+				}
+				messageSource.setCommonMessages(commonProperties);
+			}
+		}
+		catch (IOException ex) {
+			throw new UncheckedIOException("Failed to load common messages", ex);
+		}
 		return messageSource;
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/context/MessageSourceProperties.java

@@ -25,6 +25,7 @@ import java.util.List;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.convert.DurationUnit;
+import org.springframework.core.io.Resource;
 
 /**
  * Configuration properties for Message Source.
@@ -44,6 +45,11 @@ public class MessageSourceProperties {
 	 */
 	private List<String> basename = new ArrayList<>(List.of("messages"));
 
+	/**
+	 * Comma-separated list of locale-independent common messages.
+	 */
+	private List<Resource> commonMessages;
+
 	/**
 	 * Message bundles encoding.
 	 */
@@ -123,4 +129,12 @@ public class MessageSourceProperties {
 		this.useCodeAsDefaultMessage = useCodeAsDefaultMessage;
 	}
 
+	public List<Resource> getCommonMessages() {
+		return this.commonMessages;
+	}
+
+	public void setCommonMessages(List<Resource> commonMessages) {
+		this.commonMessages = commonMessages;
+	}
+
 }

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

@@ -116,6 +116,14 @@ class MessageSourceAutoConfigurationTests {
 			.run((context) -> assertThat(context.getMessage("foo", null, "Foo message", Locale.UK)).isEqualTo("bar"));
 	}
 
+	@Test
+	void testCommonMessages() {
+		this.contextRunner
+			.withPropertyValues("spring.messages.basename:test/messages",
+					"spring.messages.common-messages:test/common-messages")
+			.run((context) -> assertThat(context.getMessage("hello", null, "Hello!", Locale.UK)).isEqualTo("world"));
+	}
+
 	@Test
 	void testFallbackDefault() {
 		this.contextRunner.withPropertyValues("spring.messages.basename:test/messages")

spring-boot-project/spring-boot-autoconfigure/src/test/resources/test/common-messages.properties

@@ -0,0 +1 @@
+hello=world