Unwrap SpringValidatorAdapter (e.g. CustomValidatorBean) to native Validator

Issue: SPR-15629
(cherry picked from commit 8330134)

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

@@ -378,6 +378,7 @@ public class LocalValidatorFactoryBean extends SpringValidatorAdapter
 	*/
 
 	@Override
+	@SuppressWarnings("unchecked")
 	public <T> T unwrap(@Nullable Class<T> type) {
 		if (type == null || !ValidatorFactory.class.isAssignableFrom(type)) {
 			try {
@@ -387,7 +388,16 @@ public class LocalValidatorFactoryBean extends SpringValidatorAdapter
 				// ignore - we'll try ValidatorFactory unwrapping next
 			}
 		}
-		return this.validatorFactory.unwrap(type);
+		try {
+			return this.validatorFactory.unwrap(type);
+		}
+		catch (ValidationException ex) {
+			// ignore if just being asked for ValidatorFactory
+			if (ValidatorFactory.class == type) {
+				return (T) this.validatorFactory;
+			}
+			throw ex;
+		}
 	}
 
 	public void close() {

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

@@ -83,9 +83,13 @@ public class MethodValidationPostProcessor extends AbstractBeanFactoryAwareAdvis
 	 * <p>Default is the default ValidatorFactory's default Validator.
 	 */
 	public void setValidator(Validator validator) {
+		// Unwrap to the native Validator with forExecutables support
 		if (validator instanceof LocalValidatorFactoryBean) {
 			this.validator = ((LocalValidatorFactoryBean) validator).getValidator();
 		}
+		else if (validator instanceof SpringValidatorAdapter) {
+			this.validator = validator.unwrap(Validator.class);
+		}
 		else {
 			this.validator = validator;
 		}

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

@@ -25,6 +25,7 @@ import java.util.Map;
 import java.util.Set;
 import java.util.TreeMap;
 import javax.validation.ConstraintViolation;
+import javax.validation.ValidationException;
 import javax.validation.executable.ExecutableValidator;
 import javax.validation.metadata.BeanDescriptor;
 import javax.validation.metadata.ConstraintDescriptor;
@@ -303,7 +304,16 @@ public class SpringValidatorAdapter implements SmartValidator, javax.validation.
 	@SuppressWarnings("unchecked")
 	public <T> T unwrap(@Nullable Class<T> type) {
 		Assert.state(this.targetValidator != null, "No target Validator set");
-		return (type != null ? this.targetValidator.unwrap(type) : (T) this.targetValidator);
+		try {
+			return (type != null ? this.targetValidator.unwrap(type) : (T) this.targetValidator);
+		}
+		catch (ValidationException ex) {
+			// ignore if just being asked for plain Validator
+			if (javax.validation.Validator.class == type) {
+				return (T) this.targetValidator;
+			}
+			throw ex;
+		}
 	}
 
 	@Override