Introduce `ValidatingEntityCallback`.

Closes #4901
Original pull request: #4910

Signed-off-by: felgentraeger <rene.felgentraeger@gvl.de>

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/event/ValidatingEntityCallback.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2012-2025 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.data.mongodb.core.mapping.event;
+
+import jakarta.validation.ConstraintViolation;
+import jakarta.validation.ConstraintViolationException;
+import jakarta.validation.Validator;
+import java.util.Set;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.bson.Document;
+import org.springframework.core.Ordered;
+import org.springframework.util.Assert;
+
+/**
+ * JSR-303 dependant entities validator.
+ * <p>
+ * When it is registered as Spring component its automatically invoked after any {@link AbstractMongoEventListener} and
+ * before entities are saved in database.
+ *
+ * @author original authors of {@link ValidatingMongoEventListener}
+ * @author Rene Felgenträger
+ * @see {@link ValidatingMongoEventListener}
+ */
+public class ValidatingEntityCallback implements BeforeSaveCallback<Object>, Ordered {
+
+	private static final Log LOG = LogFactory.getLog(ValidatingEntityCallback.class);
+
+	// TODO: create a validation handler (similar to "AuditingHandler") an reference it from "ValidatingMongoEventListener" and "ValidatingMongoEventListener"
+	private final Validator validator;
+
+	/**
+	 * Creates a new {@link ValidatingEntityCallback} using the given {@link Validator}.
+	 *
+	 * @param validator must not be {@literal null}.
+	 */
+	public ValidatingEntityCallback(Validator validator) {
+		Assert.notNull(validator, "Validator must not be null");
+		this.validator = validator;
+	}
+
+	// TODO: alternatively implement the "BeforeConvertCallback" interface and set the order to highest value ?
+	@Override
+	public Object onBeforeSave(Object entity, Document document, String collection) {
+
+		if (LOG.isDebugEnabled()) {
+			LOG.debug(String.format("Validating object: %s", entity));
+		}
+		Set<ConstraintViolation<Object>> violations = validator.validate(entity);
+
+		if (!violations.isEmpty()) {
+			if (LOG.isDebugEnabled()) {
+				LOG.info(String.format("During object: %s validation violations found: %s", entity, violations));
+			}
+			throw new ConstraintViolationException(violations);
+		}
+		return entity;
+	}
+
+	@Override
+	public int getOrder() {
+		return 100;
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/event/ValidatingMongoEventListener.java

@@ -32,6 +32,8 @@ import org.springframework.util.Assert;
  * @author Maciej Walkowiak
  * @author Oliver Gierke
  * @author Christoph Strobl
+ *
+ * @see {@link ValidatingEntityCallback}
  */
 public class ValidatingMongoEventListener extends AbstractMongoEventListener<Object> {
 

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/mapping/event/ValidatingEntityCallbackUnitTests.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2012-2025 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.data.mongodb.core.mapping.event;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+import jakarta.validation.ConstraintViolationException;
+import jakarta.validation.Validation;
+import jakarta.validation.ValidatorFactory;
+import jakarta.validation.constraints.Min;
+import jakarta.validation.constraints.NotNull;
+import org.bson.Document;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit test for {@link ValidatingEntityCallback}.
+ *
+ * @author Rene Felgenträger
+ */
+class ValidatingEntityCallbackUnitTests {
+
+	private ValidatingEntityCallback callback;
+
+	@BeforeEach
+	public void setUp() {
+		try (ValidatorFactory factory = Validation.buildDefaultValidatorFactory()) {
+			callback = new ValidatingEntityCallback(factory.getValidator());
+		}
+	}
+
+	@Test
+		// GH-4910
+	void invalidModel_throwsException() {
+		Coordinates coordinates = new Coordinates(-1, -1);
+
+		assertThatExceptionOfType(ConstraintViolationException.class).isThrownBy(
+						() -> callback.onBeforeSave(coordinates, coordinates.toDocument(), "coordinates"))
+				.satisfies(e -> assertThat(e.getConstraintViolations()).hasSize(2));
+	}
+
+	@Test
+		// GH-4910
+	void validModel_noExceptionThrown() {
+		Coordinates coordinates = new Coordinates(0, 0);
+		Object entity = callback.onBeforeSave(coordinates, coordinates.toDocument(), "coordinates");
+		assertThat(entity).isEqualTo(coordinates);
+	}
+
+	record Coordinates(@NotNull @Min(0) Integer x, @NotNull @Min(0) Integer y) {
+
+		Document toDocument() {
+			return Document.parse("""
+					{
+					  "x": %d,
+					  "y": %d
+					}
+					""".formatted(x, y));
+		}
+	}
+}