Check @RegisterReflectionForBinding specifies at least one class

Closes gh-29346

Author: sdeleuze

spring-core/src/main/java/org/springframework/aot/hint/annotation/RegisterReflectionForBindingProcessor.java

@@ -21,6 +21,7 @@
 import org.springframework.aot.hint.BindingReflectionHintsRegistrar;
 import org.springframework.aot.hint.ReflectionHints;
 import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.util.Assert;
 
 /**
  * A {@link ReflectiveProcessor} implementation that registers reflection hints
@@ -38,7 +39,10 @@ public class RegisterReflectionForBindingProcessor implements ReflectiveProcesso
 	public void registerReflectionHints(ReflectionHints hints, AnnotatedElement element) {
 		RegisterReflectionForBinding registerReflection = AnnotationUtils.getAnnotation(element, RegisterReflectionForBinding.class);
 		if (registerReflection != null) {
-			for (Class<?> type : registerReflection.classes()) {
+			Class<?>[] classes = registerReflection.classes();
+			Assert.state(classes.length != 0, "A least one class should be specified in" +
+					" @RegisterReflectionForBinding attributes and none was provided on " + element);
+			for (Class<?> type : classes) {
 				this.bindingRegistrar.registerReflectionHints(hints, type);
 			}
 		}

spring-core/src/test/java/org/springframework/aot/hint/annotation/RegisterReflectionForBindingProcessorTests.java

@@ -22,6 +22,7 @@
 import org.springframework.aot.hint.predicate.RuntimeHintsPredicates;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 /**
  * Tests for {@link RegisterReflectionForBindingProcessor}.
@@ -50,6 +51,21 @@ void registerReflectionForBindingOnMethod() throws NoSuchMethodException {
 		assertThat(RuntimeHintsPredicates.reflection().onMethod(SampleClassWithGetter.class, "getName")).accepts(hints);
 	}
 
+	@Test
+	void throwExceptionWithoutAnnotationAttributeOnClass() {
+		assertThatThrownBy(() -> processor.registerReflectionHints(hints.reflection(),
+				SampleClassWithoutAnnotationAttribute.class))
+				.isInstanceOf(IllegalStateException.class);
+	}
+
+	@Test
+	void throwExceptionWithoutAnnotationAttributeOnMethod() throws NoSuchMethodException {
+		assertThatThrownBy(() -> processor.registerReflectionHints(hints.reflection(),
+				SampleClassWithoutMethodLevelAnnotationAttribute.class.getMethod("method")))
+				.isInstanceOf(IllegalStateException.class);
+	}
+
+
 	@RegisterReflectionForBinding(SampleClassWithGetter.class)
 	static class ClassLevelAnnotatedBean {
 	}
@@ -66,7 +82,17 @@ static class SampleClassWithGetter {
 		public String getName() {
 			return null;
 		}
+	}
+
+	@RegisterReflectionForBinding
+	static class SampleClassWithoutAnnotationAttribute {
+	}
 
+	static class SampleClassWithoutMethodLevelAnnotationAttribute {
+
+		@RegisterReflectionForBinding
+		public void method() {
+		}
 	}
 
 }