Support validation non PersistentEntity types

spring-data-rest-core/src/main/java/org/springframework/data/rest/core/ValidationErrors.java

@@ -18,6 +18,7 @@
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
+import java.util.Optional;
 
 import org.springframework.beans.BeansException;
 import org.springframework.beans.ConfigurablePropertyAccessor;
@@ -39,6 +40,7 @@
  *
  * @author Jon Brisbin
  * @author Oliver Gierke
+ * @author Florian Cramer
  */
 public class ValidationErrors extends AbstractPropertyBindingResult {
 
@@ -92,7 +94,12 @@ public Object getPropertyValue(String propertyName) throws BeansException {
 			 */
 			private Object lookupValueOn(Object value, String segment) {
 
-				PersistentProperty<?> property = entities.getPersistentEntity(value.getClass()) //
+				Optional<PersistentEntity<?, ? extends PersistentProperty<?>>> entity = entities.getPersistentEntity(value.getClass());
+				if (!entity.isPresent()) {
+					return new DirectFieldAccessor(value).getPropertyValue(segment);
+				}
+
+				PersistentProperty<?> property = entity //
 						.map(it -> it.getPersistentProperty(PropertyAccessorUtils.getPropertyName(segment))) //
 						.orElseThrow(() -> new NotReadablePropertyException(value.getClass(), segment));
 

spring-data-rest-core/src/test/java/org/springframework/data/rest/core/ValidationErrorsUnitTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2022 original author or authors.
+ * Copyright 2016-2023 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.
@@ -24,14 +24,18 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.NotReadablePropertyException;
+import org.springframework.data.keyvalue.core.mapping.KeyValuePersistentEntity;
+import org.springframework.data.keyvalue.core.mapping.KeyValuePersistentProperty;
 import org.springframework.data.keyvalue.core.mapping.context.KeyValueMappingContext;
 import org.springframework.data.mapping.context.PersistentEntities;
+import org.springframework.data.util.TypeInformation;
 import org.springframework.validation.Errors;
 
 /**
  * Unit tests for {@link ValidationErrors}.
  *
  * @author Oliver Gierke
+ * @author Florian Cramer
  */
 class ValidationErrorsUnitTests {
 
@@ -40,7 +44,7 @@ class ValidationErrorsUnitTests {
 	@BeforeEach
 	void setUp() {
 
-		KeyValueMappingContext<?, ?> context = new KeyValueMappingContext<>();
+		KeyValueMappingContext<?, ?> context = new TestKeyValueMappingContext<>();
 		context.getPersistentEntity(Foo.class);
 
 		this.entities = new PersistentEntities(Arrays.asList(context));
@@ -71,6 +75,14 @@ void returnsNullForPropertyValue() {
 		assertThat(errors.getFieldValue("bar")).isNull();
 	}
 
+	@Test // GH-2252
+	void getsTheNestedFieldsValueForNonPersistentEntity() {
+
+		ValidationErrors errors = new ValidationErrors(new Foo(), entities);
+
+		assertThat(errors.getFieldValue("qux.field")).isEqualTo("World");
+	}
+
 	private static void expectedErrorBehavior(Errors errors) {
 
 		assertThat(errors.getFieldValue("bars")).isNotNull();
@@ -88,9 +100,22 @@ private static void expectedErrorBehavior(Errors errors) {
 	static class Foo {
 		List<Bar> bars = Collections.singletonList(new Bar());
 		Bar bar = null;
+		Qux qux = new Qux();
 	}
 
 	static class Bar {
 		String field = "Hello";
 	}
+
+	static class Qux {
+		String field = "World";
+	}
+
+	static class TestKeyValueMappingContext<E extends KeyValuePersistentEntity<?, P>, P extends KeyValuePersistentProperty<P>> extends KeyValueMappingContext<E, P> {
+
+		@Override
+		protected boolean shouldCreatePersistentEntityFor(TypeInformation<?> type) {
+			return Qux.class != type.getType() && super.shouldCreatePersistentEntityFor(type);
+		}
+	}
 }