Support unwrapping in ValidatorAdapter

See gh-37119

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/validation/ValidatorAdapter.java

@@ -39,6 +39,7 @@ import org.springframework.validation.beanvalidation.SpringValidatorAdapter;
  *
  * @author Stephane Nicoll
  * @author Phillip Webb
+ * @author Zisis Pavloudis
  * @since 2.0.0
  */
 public class ValidatorAdapter implements SmartValidator, ApplicationContextAware, InitializingBean, DisposableBean {
@@ -153,4 +154,17 @@ public class ValidatorAdapter implements SmartValidator, ApplicationContextAware
 		return validator;
 	}
 
+	@Override
+	@SuppressWarnings("unchecked")
+	public <T> T unwrap(Class<T> type) {
+		if (type.isAssignableFrom(this.target.getClass())) {
+			if (this.target instanceof SpringValidatorAdapter adapter) {
+				return adapter.unwrap(type);
+			}
+			return (T) this.target;
+		}
+
+		throw new IllegalArgumentException("Cannot unwrap " + this.target + " to " + type.getName());
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/validation/ValidatorAdapterTests.java

@@ -18,7 +18,10 @@ package org.springframework.boot.autoconfigure.validation;
 
 import java.util.HashMap;
 
+import jakarta.validation.Validator;
 import jakarta.validation.constraints.Min;
+import org.hibernate.validator.HibernateValidator;
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.test.context.FilteredClassLoader;
@@ -91,6 +94,15 @@ class ValidatorAdapterTests {
 			.run((context) -> ValidatorAdapter.get(context, null));
 	}
 
+	@Test
+	void unwrapValidatorInstanceOfJakartaTypeAndExceptionThrownWhenTypeNotSupported() {
+		this.contextRunner.withUserConfiguration(LocalValidatorFactoryBeanConfig.class).run((context) -> {
+			ValidatorAdapter wrapper = context.getBean(ValidatorAdapter.class);
+			assertThat(wrapper.unwrap(Validator.class)).isInstanceOf(Validator.class);
+			Assertions.assertThrows(IllegalArgumentException.class, () -> wrapper.unwrap(HibernateValidator.class));
+		});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class LocalValidatorFactoryBeanConfig {