Reinstate support for placeholders in @EntityScan

Fixes gh-25436

Author: wilkinsona

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/domain/EntityScanPackages.java

@@ -32,6 +32,7 @@
 import org.springframework.beans.factory.support.GenericBeanDefinition;
 import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
 import org.springframework.core.annotation.AnnotationAttributes;
+import org.springframework.core.env.Environment;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -124,6 +125,12 @@ public static void register(BeanDefinitionRegistry registry, Collection<String>
 	 */
 	static class Registrar implements ImportBeanDefinitionRegistrar {
 
+		private final Environment environment;
+
+		Registrar(Environment environment) {
+			this.environment = environment;
+		}
+
 		@Override
 		public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
 			register(registry, getPackagesToScan(metadata));
@@ -132,11 +139,12 @@ public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionR
 		private Set<String> getPackagesToScan(AnnotationMetadata metadata) {
 			AnnotationAttributes attributes = AnnotationAttributes
 					.fromMap(metadata.getAnnotationAttributes(EntityScan.class.getName()));
-			String[] basePackages = attributes.getStringArray("basePackages");
-			Class<?>[] basePackageClasses = attributes.getClassArray("basePackageClasses");
-			Set<String> packagesToScan = new LinkedHashSet<>(Arrays.asList(basePackages));
-			for (Class<?> basePackageClass : basePackageClasses) {
-				packagesToScan.add(ClassUtils.getPackageName(basePackageClass));
+			Set<String> packagesToScan = new LinkedHashSet<>();
+			for (String basePackage : attributes.getStringArray("basePackages")) {
+				addResolvedPackage(basePackage, packagesToScan);
+			}
+			for (Class<?> basePackageClass : attributes.getClassArray("basePackageClasses")) {
+				addResolvedPackage(ClassUtils.getPackageName(basePackageClass), packagesToScan);
 			}
 			if (packagesToScan.isEmpty()) {
 				String packageName = ClassUtils.getPackageName(metadata.getClassName());
@@ -146,6 +154,10 @@ private Set<String> getPackagesToScan(AnnotationMetadata metadata) {
 			return packagesToScan;
 		}
 
+		private void addResolvedPackage(String packageName, Set<String> packagesToScan) {
+			packagesToScan.add(this.environment.resolvePlaceholders(packageName));
+		}
+
 	}
 
 	static class EntityScanPackagesBeanDefinition extends GenericBeanDefinition {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/domain/EntityScannerTests.java

@@ -31,6 +31,7 @@
 import org.springframework.boot.autoconfigure.domain.scan.b.EntityB;
 import org.springframework.boot.autoconfigure.domain.scan.c.EmbeddableC;
 import org.springframework.boot.autoconfigure.domain.scan.c.EntityC;
+import org.springframework.boot.test.util.TestPropertyValues;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
@@ -66,6 +67,19 @@ void scanShouldScanFromSinglePackage() throws Exception {
 		context.close();
 	}
 
+	@Test
+	void scanShouldScanFromResolvedPlaceholderPackage() throws Exception {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		TestPropertyValues.of("com.example.entity-package=org.springframework.boot.autoconfigure.domain.scan")
+				.applyTo(context);
+		context.register(ScanPlaceholderConfig.class);
+		context.refresh();
+		EntityScanner scanner = new EntityScanner(context);
+		Set<Class<?>> scanned = scanner.scan(Entity.class);
+		assertThat(scanned).containsOnly(EntityA.class, EntityB.class, EntityC.class);
+		context.close();
+	}
+
 	@Test
 	void scanShouldScanFromMultiplePackages() throws Exception {
 		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ScanAConfig.class,
@@ -141,4 +155,10 @@ static class ScanBConfig {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@EntityScan("${com.example.entity-package}")
+	static class ScanPlaceholderConfig {
+
+	}
+
 }