Merge pull request #37119 from zpavloudis

* gh-37119:
  Polish "Support unwrapping in ValidatorAdapter"
  Support unwrapping in ValidatorAdapter

Closes 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 +154,13 @@ public class ValidatorAdapter implements SmartValidator, ApplicationContextAware
 		return validator;
 	}
 
+	@Override
+	@SuppressWarnings("unchecked")
+	public <T> T unwrap(Class<T> type) {
+		if (type.isInstance(this.target)) {
+			return (T) this.target;
+		}
+		return this.target.unwrap(type);
+	}
+
 }

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

@@ -18,7 +18,9 @@ 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.Test;
 
 import org.springframework.boot.test.context.FilteredClassLoader;
@@ -27,10 +29,13 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.io.ClassPathResource;
+import org.springframework.validation.Errors;
 import org.springframework.validation.MapBindingResult;
+import org.springframework.validation.SmartValidator;
 import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatRuntimeException;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.BDDMockito.then;
 import static org.mockito.Mockito.mock;
@@ -91,6 +96,30 @@ class ValidatorAdapterTests {
 			.run((context) -> ValidatorAdapter.get(context, null));
 	}
 
+	@Test
+	void unwrapToJakartaValidatorShouldReturnJakartaValidator() {
+		this.contextRunner.withUserConfiguration(LocalValidatorFactoryBeanConfig.class).run((context) -> {
+			ValidatorAdapter wrapper = context.getBean(ValidatorAdapter.class);
+			assertThat(wrapper.unwrap(Validator.class)).isInstanceOf(Validator.class);
+		});
+	}
+
+	@Test
+	void whenJakartaValidatorIsWrappedMultipleTimesUnwrapToJakartaValidatorShouldReturnJakartaValidator() {
+		this.contextRunner.withUserConfiguration(DoubleWrappedConfig.class).run((context) -> {
+			ValidatorAdapter wrapper = context.getBean(ValidatorAdapter.class);
+			assertThat(wrapper.unwrap(Validator.class)).isInstanceOf(Validator.class);
+		});
+	}
+
+	@Test
+	void unwrapToUnsupportedTypeShouldThrow() {
+		this.contextRunner.withUserConfiguration(LocalValidatorFactoryBeanConfig.class).run((context) -> {
+			ValidatorAdapter wrapper = context.getBean(ValidatorAdapter.class);
+			assertThatRuntimeException().isThrownBy(() -> wrapper.unwrap(HibernateValidator.class));
+		});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class LocalValidatorFactoryBeanConfig {
 
@@ -106,6 +135,55 @@ class ValidatorAdapterTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class DoubleWrappedConfig {
+
+		@Bean
+		LocalValidatorFactoryBean validator() {
+			return new LocalValidatorFactoryBean();
+		}
+
+		@Bean
+		ValidatorAdapter wrapper(LocalValidatorFactoryBean validator) {
+			return new ValidatorAdapter(new Wrapper(validator), true);
+		}
+
+		static class Wrapper implements SmartValidator {
+
+			private final SmartValidator delegate;
+
+			Wrapper(SmartValidator delegate) {
+				this.delegate = delegate;
+			}
+
+			@Override
+			public boolean supports(Class<?> clazz) {
+				return this.delegate.supports(clazz);
+			}
+
+			@Override
+			public void validate(Object target, Errors errors) {
+				this.delegate.validate(target, errors);
+			}
+
+			@Override
+			public void validate(Object target, Errors errors, Object... validationHints) {
+				this.delegate.validate(target, errors, validationHints);
+			}
+
+			@Override
+			@SuppressWarnings("unchecked")
+			public <T> T unwrap(Class<T> type) {
+				if (type.isInstance(this.delegate)) {
+					return (T) this.delegate;
+				}
+				return this.delegate.unwrap(type);
+			}
+
+		}
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class NonManagedBeanConfig {