Infer hints for custom constraint validators

This commit introduces a BeanValidationBeanRegistrationAotProcessor
which adds reflection hints for custom ConstraintValidator discovered
on beans constructors, methods and properties.

Closes gh-29823

spring-context/src/main/java/org/springframework/validation/beanvalidation/BeanValidationBeanRegistrationAotProcessor.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2002-2023 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.validation.beanvalidation;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+import jakarta.validation.ConstraintValidator;
+import jakarta.validation.Validation;
+import jakarta.validation.Validator;
+import jakarta.validation.metadata.BeanDescriptor;
+import jakarta.validation.metadata.ConstraintDescriptor;
+import jakarta.validation.metadata.ConstructorDescriptor;
+import jakarta.validation.metadata.MethodDescriptor;
+import jakarta.validation.metadata.MethodType;
+import jakarta.validation.metadata.ParameterDescriptor;
+import jakarta.validation.metadata.PropertyDescriptor;
+
+import org.springframework.aot.generate.GenerationContext;
+import org.springframework.aot.hint.MemberCategory;
+import org.springframework.beans.factory.aot.BeanRegistrationAotContribution;
+import org.springframework.beans.factory.aot.BeanRegistrationAotProcessor;
+import org.springframework.beans.factory.aot.BeanRegistrationCode;
+import org.springframework.beans.factory.support.RegisteredBean;
+import org.springframework.lang.Nullable;
+import org.springframework.util.ClassUtils;
+
+/**
+ * AOT {@code BeanRegistrationAotProcessor} that adds additional hints
+ * required for {@link ConstraintValidator}s.
+ *
+ * @author Sebastien Deleuze
+ * @since 6.0.5
+ */
+class BeanValidationBeanRegistrationAotProcessor implements BeanRegistrationAotProcessor {
+
+	private static final boolean isBeanValidationPresent = ClassUtils.isPresent(
+			"jakarta.validation.Validation", BeanValidationBeanRegistrationAotProcessor.class.getClassLoader());
+
+	@Nullable
+	@Override
+	public BeanRegistrationAotContribution processAheadOfTime(RegisteredBean registeredBean) {
+		if (isBeanValidationPresent) {
+			return BeanValidationDelegate.processAheadOfTime(registeredBean);
+		}
+		return null;
+	}
+
+	private static class BeanValidationDelegate {
+
+		private static Validator validator = Validation.buildDefaultValidatorFactory().getValidator();
+
+		@Nullable
+		public static BeanRegistrationAotContribution processAheadOfTime(RegisteredBean registeredBean) {
+			BeanDescriptor descriptor = validator.getConstraintsForClass(registeredBean.getBeanClass());
+			Set<ConstraintDescriptor<?>> constraintDescriptors = new HashSet<>();
+			for (MethodDescriptor methodDescriptor : descriptor.getConstrainedMethods(MethodType.NON_GETTER, MethodType.GETTER)) {
+				for (ParameterDescriptor parameterDescriptor : methodDescriptor.getParameterDescriptors()) {
+					constraintDescriptors.addAll(parameterDescriptor.getConstraintDescriptors());
+				}
+			}
+			for (ConstructorDescriptor constructorDescriptor : descriptor.getConstrainedConstructors()) {
+				for (ParameterDescriptor parameterDescriptor : constructorDescriptor.getParameterDescriptors()) {
+					constraintDescriptors.addAll(parameterDescriptor.getConstraintDescriptors());
+				}
+			}
+			for (PropertyDescriptor propertyDescriptor : descriptor.getConstrainedProperties()) {
+				constraintDescriptors.addAll(propertyDescriptor.getConstraintDescriptors());
+			}
+			if (!constraintDescriptors.isEmpty()) {
+				return new BeanValidationBeanRegistrationAotContribution(constraintDescriptors);
+			}
+			return null;
+		}
+
+	}
+
+	private static class BeanValidationBeanRegistrationAotContribution implements BeanRegistrationAotContribution {
+
+		private final Collection<ConstraintDescriptor<?>> constraintDescriptors;
+
+		public BeanValidationBeanRegistrationAotContribution(Collection<ConstraintDescriptor<?>> constraintDescriptors) {
+			this.constraintDescriptors = constraintDescriptors;
+		}
+
+		@Override
+		public void applyTo(GenerationContext generationContext, BeanRegistrationCode beanRegistrationCode) {
+			for (ConstraintDescriptor<?> constraintDescriptor : this.constraintDescriptors) {
+				for (Class<?> constraintValidatorClass : constraintDescriptor.getConstraintValidatorClasses()) {
+					generationContext.getRuntimeHints().reflection().registerType(constraintValidatorClass,
+							MemberCategory.INVOKE_DECLARED_CONSTRUCTORS);
+				}
+			}
+		}
+	}
+
+}