Add ReadPreference annotation.

The annotation enables a declarative style of defining the ReadPreference to use for individual or all repository queries.

Closes: #2971
Original Pull Request: #4503

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/Query.java

@@ -33,6 +33,7 @@ import org.springframework.data.mongodb.core.annotation.Collation;
  * @author Thomas Darimont
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Jorge Rodríguez
  */
 @Collation
 @Retention(RetentionPolicy.RUNTIME)
@@ -40,6 +41,7 @@ import org.springframework.data.mongodb.core.annotation.Collation;
 @Documented
 @QueryAnnotation
 @Hint
+@ReadPreference
 public @interface Query {
 
 	/**
@@ -147,4 +149,21 @@ public @interface Query {
 	 */
 	@AliasFor(annotation = Hint.class, attribute = "indexName")
 	String hint() default "";
+
+	/**
+	 * The mode of the read preference to use. <br />
+	 * {@code @Query(value = "...", readPreference = "secondary")} can be used as shortcut for:
+	 *
+	 * <pre class="code">
+	 * &#64;Query(...)
+	 * &#64;ReadPreference("secondary")
+	 * List&lt;User&gt; findAllByLastname(String collation);
+	 * </pre>
+	 *
+	 * @return the index name.
+	 * @since 4.2
+	 * @see ReadPreference#value()
+	 */
+	@AliasFor(annotation = ReadPreference.class, attribute = "value")
+	String readPreference() default "";
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/ReadPreference.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2011-2023 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.repository;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation to declare read preference for repository and query.
+ *
+ * @author Jorge Rodríguez
+ * @since 4.2
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.TYPE, ElementType.METHOD, ElementType.ANNOTATION_TYPE })
+@Documented
+public @interface ReadPreference {
+
+	/**
+	 * Configure read preference mode
+	 * @return read preference mode
+	 */
+	String value() default "";
+
+	/**
+	 * Set read preference tags
+	 * @return read preference tags
+	 */
+	ReadPreferenceTag[] tags() default {};
+
+	/**
+	 * Set read preference maxStalenessSeconds
+	 * @return read preference maxStalenessSeconds
+	 */
+	long maxStalenessSeconds() default -1;
+}
+

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/ReadPreferenceTag.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2011-2023 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.repository;
+
+/**
+ * Annotation used by {@link ReadPreference} for define {@link com.mongodb.Tag}
+ *
+ * @author Jorge Rodríguez
+ * @since 4.2
+ */
+public @interface ReadPreferenceTag {
+
+	/**
+	 * Set the name of tag
+	 * @return name of tag
+	 */
+	String name();
+
+	/**
+	 * Set the value of tag
+	 * @return value of tag
+	 */
+	String value();
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AbstractMongoQuery.java

@@ -62,6 +62,7 @@ import com.mongodb.client.MongoDatabase;
  * @author Thomas Darimont
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Jorge Rodríguez
  */
 public abstract class AbstractMongoQuery implements RepositoryQuery {
 
@@ -137,6 +138,7 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 		query = applyAnnotatedDefaultSortIfPresent(query);
 		query = applyAnnotatedCollationIfPresent(query, accessor);
 		query = applyHintIfPresent(query);
+		query = applyAnnotatedReadPreferenceIfPresent(query);
 
 		FindWithQuery<?> find = typeToRead == null //
 				? executableFind //
@@ -145,6 +147,22 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 		return getExecution(accessor, find).execute(query);
 	}
 
+	/**
+	 * If present apply the {@link com.mongodb.ReadPreference} from the {@link org.springframework.data.mongodb.repository.ReadPreference} annotation.
+	 *
+	 * @param query must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 4.2
+	 */
+	private Query applyAnnotatedReadPreferenceIfPresent(Query query) {
+		
+		if (!method.hasAnnotatedReadPreference()) {
+			return query;
+		}
+		
+		return query.withReadPreference(method.getAnnotatedReadPreference());
+	}
+
 	private MongoQueryExecution getExecution(ConvertingParameterAccessor accessor, FindWithQuery<?> operation) {
 
 		if (isDeleteQuery()) {

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AbstractReactiveMongoQuery.java

@@ -66,6 +66,7 @@ import com.mongodb.MongoClientSettings;
  *
  * @author Mark Paluch
  * @author Christoph Strobl
+ * @author Jorge Rodríguez
  * @since 2.0
  */
 public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
@@ -161,6 +162,8 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 			query = applyAnnotatedDefaultSortIfPresent(query);
 			query = applyAnnotatedCollationIfPresent(query, accessor);
 			query = applyHintIfPresent(query);
+			query = applyAnnotatedReadPreferenceIfPresent(query);
+
 
 			FindWithQuery<?> find = typeToRead == null //
 					? findOperationWithProjection //
@@ -229,6 +232,7 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 		return method.getTailableAnnotation() != null;
 	}
 
+
 	Query applyQueryMetaAttributesWhenPresent(Query query) {
 
 		if (method.hasQueryMetaAttributes()) {
@@ -286,6 +290,22 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 		return query.withHint(method.getAnnotatedHint());
 	}
 
+	/**
+	 * If present apply the {@link com.mongodb.ReadPreference} from the {@link org.springframework.data.mongodb.repository.ReadPreference} annotation.
+	 *
+	 * @param query must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 4.2
+	 */
+	private Query applyAnnotatedReadPreferenceIfPresent(Query query) {
+
+		if (!method.hasAnnotatedReadPreference()) {
+			return query;
+		}
+
+		return query.withReadPreference(method.getAnnotatedReadPreference());
+	}
+
 	/**
 	 * Creates a {@link Query} instance using the given {@link ConvertingParameterAccessor}. Will delegate to
 	 * {@link #createQuery(ConvertingParameterAccessor)} by default but allows customization of the count query to be

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/MongoQueryMethod.java

@@ -22,7 +22,11 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
 
+import com.mongodb.Tag;
+import com.mongodb.TagSet;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.data.geo.GeoPage;
 import org.springframework.data.geo.GeoResult;
@@ -36,6 +40,7 @@ import org.springframework.data.mongodb.repository.Aggregation;
 import org.springframework.data.mongodb.repository.Hint;
 import org.springframework.data.mongodb.repository.Meta;
 import org.springframework.data.mongodb.repository.Query;
+import org.springframework.data.mongodb.repository.ReadPreference;
 import org.springframework.data.mongodb.repository.Tailable;
 import org.springframework.data.mongodb.repository.Update;
 import org.springframework.data.projection.ProjectionFactory;
@@ -57,6 +62,7 @@ import org.springframework.util.StringUtils;
  * @author Oliver Gierke
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Jorge Rodríguez
  */
 public class MongoQueryMethod extends QueryMethod {
 
@@ -314,6 +320,58 @@ public class MongoQueryMethod extends QueryMethod {
 				"Expected to find @Query annotation but did not; Make sure to check hasAnnotatedSort() before."));
 	}
 
+
+	/**
+	 * Check if the query method is decorated with an non empty {@link Query#collation()}.
+	 *
+	 * @return true if method annotated with {@link Query} or {@link Aggregation} having a non-empty collation attribute.
+	 * @since 4.2
+	 */
+	public boolean hasAnnotatedReadPreference() {
+		return doFindReadPreferenceAnnotation().map(ReadPreference::value).filter(StringUtils::hasText).isPresent();
+	}
+
+	/**
+	 * Get the {@link com.mongodb.ReadPreference} extracted from the {@link ReadPreference} annotation.
+	 *
+	 * @return the {@link ReadPreference()}.
+	 * @throws IllegalStateException if method not annotated with {@link Query}. Make sure to check
+	 *                               {@link #hasAnnotatedQuery()} first.
+	 * @since 4.2
+	 */
+	public com.mongodb.ReadPreference getAnnotatedReadPreference() {
+
+		return doFindReadPreferenceAnnotation().map(annotationReadPreference -> {
+
+			com.mongodb.ReadPreference readPreference = com.mongodb.ReadPreference.valueOf(annotationReadPreference.value());
+
+			if (annotationReadPreference.tags().length > 0) {
+				List<Tag> tags = Arrays.stream(annotationReadPreference.tags())
+						.map(tag -> new Tag(tag.name(), tag.value()))
+						.collect(Collectors.toList());
+				readPreference = readPreference.withTagSet(new TagSet(tags));
+			}
+			
+			if (annotationReadPreference.maxStalenessSeconds() > 0) {
+				readPreference = readPreference.withMaxStalenessMS(annotationReadPreference.maxStalenessSeconds(), TimeUnit.SECONDS);
+			}
+			
+			return readPreference;
+		}).orElseThrow(() -> new IllegalStateException(
+						"Expected to find @ReadPreference annotation but did not; Make sure to check hasAnnotatedReadPreference() before."));
+	}
+
+	/**
+	 * Get {@link com.mongodb.ReadPreference} from query. First check if the method is annotated. If not, check if the class is annotated.
+	 * So if the method and the class are annotated with @ReadPreference, the method annotation takes precedence.
+	 * @return the {@link com.mongodb.ReadPreference}
+	 * @since 4.2
+	 */
+	private Optional<ReadPreference> doFindReadPreferenceAnnotation() {
+		return doFindAnnotation(ReadPreference.class).or(() -> doFindAnnotationInClass(ReadPreference.class));
+	}
+
+
 	/**
 	 * Check if the query method is decorated with an non empty {@link Query#collation()} or or
 	 * {@link Aggregation#collation()}.
@@ -401,10 +459,20 @@ public class MongoQueryMethod extends QueryMethod {
 	@SuppressWarnings("unchecked")
 	private <A extends Annotation> Optional<A> doFindAnnotation(Class<A> annotationType) {
 		
+
 		return (Optional<A>) this.annotationCache.computeIfAbsent(annotationType,
 				it -> Optional.ofNullable(AnnotatedElementUtils.findMergedAnnotation(method, it)));
 	}
 
+	@SuppressWarnings("unchecked")
+	private <A extends Annotation> Optional<A>  doFindAnnotationInClass(Class<A> annotationType) {
+
+		Optional<Annotation> mergedAnnotation = Optional.ofNullable(AnnotatedElementUtils.findMergedAnnotation(method.getDeclaringClass(), annotationType));
+		annotationCache.put(annotationType, mergedAnnotation);
+
+		return (Optional<A>) mergedAnnotation;
+	}
+
 	@Override
 	public boolean isModifyingQuery() {
 		return isModifying.get();

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/query/AbstractMongoQueryUnitTests.java

@@ -23,7 +23,11 @@ import java.lang.reflect.Method;
 import java.util.List;
 import java.util.Locale;
 import java.util.Optional;
+import java.util.concurrent.TimeUnit;
 
+import com.mongodb.Tag;
+import com.mongodb.TagSet;
+import com.mongodb.TaggableReadPreference;
 import org.bson.Document;
 import org.bson.codecs.configuration.CodecRegistry;
 import org.bson.types.ObjectId;
@@ -65,6 +69,8 @@ import org.springframework.data.mongodb.core.query.UpdateDefinition;
 import org.springframework.data.mongodb.repository.Hint;
 import org.springframework.data.mongodb.repository.Meta;
 import org.springframework.data.mongodb.repository.MongoRepository;
+import org.springframework.data.mongodb.repository.ReadPreference;
+import org.springframework.data.mongodb.repository.ReadPreferenceTag;
 import org.springframework.data.mongodb.repository.Update;
 import org.springframework.data.projection.ProjectionFactory;
 import org.springframework.data.projection.SpelAwareProxyProjectionFactory;
@@ -84,6 +90,7 @@ import com.mongodb.client.result.UpdateResult;
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Mark Paluch
+ * @author Jorge Rodríguez
  */
 @ExtendWith(MockitoExtension.class)
 @MockitoSettings(strictness = Strictness.LENIENT)
@@ -518,6 +525,33 @@ class AbstractMongoQueryUnitTests {
 		assertThat(captor.getValue().getSortObject()).isEqualTo(new Document("fn", 1));
 	}
 
+	@Test // GH-2971
+	void findShouldApplyReadPreference() {
+
+		createQueryForMethod("findWithReadPreferenceByFirstname", String.class).execute(new Object[] { "Jasna" });
+
+		ArgumentCaptor<Query> captor = ArgumentCaptor.forClass(Query.class);
+		verify(withQueryMock).matching(captor.capture());
+		assertThat(captor.getValue().getReadPreference().getName()).isEqualTo("secondaryPreferred");
+		assertThat(((TaggableReadPreference)captor.getValue().getReadPreference()).getTagSetList())
+				.containsExactly(new TagSet(List.of(new Tag("local", "east"), new Tag("pre", "west"))));
+		assertThat(((TaggableReadPreference)captor.getValue().getReadPreference()).getMaxStaleness(TimeUnit.SECONDS)).isEqualTo(99);
+	}
+
+	@Test // GH-2971
+	void findShouldApplyReadPreferenceAtRepository() {
+
+		createQueryForMethod("findWithLimit", String.class, Limit.class).execute(new Object[] { "dalinar", Limit.of(42) });
+
+		ArgumentCaptor<Query> captor = ArgumentCaptor.forClass(Query.class);
+		verify(withQueryMock).matching(captor.capture());
+		assertThat(captor.getValue().getReadPreference().getName()).isEqualTo("primaryPreferred");
+		assertThat(((TaggableReadPreference)captor.getValue().getReadPreference()).getTagSetList())
+						.containsExactly(new TagSet(List.of(new Tag("primary-local", "east"), new Tag("primary-pre", "west"))));
+		assertThat(((TaggableReadPreference)captor.getValue().getReadPreference()).getMaxStaleness(TimeUnit.SECONDS)).isEqualTo(20);
+	}
+
+
 	private MongoQueryFake createQueryForMethod(String methodName, Class<?>... paramTypes) {
 		return createQueryForMethod(Repo.class, methodName, paramTypes);
 	}
@@ -588,6 +622,11 @@ class AbstractMongoQueryUnitTests {
 		}
 	}
 
+	@ReadPreference(
+			value = "primaryPreferred",
+			tags = { @ReadPreferenceTag(name = "primary-local", value = "east"), @ReadPreferenceTag(name = "primary-pre", value = "west") },
+			maxStalenessSeconds = 20
+	)
 	private interface Repo extends MongoRepository<Person, Long> {
 
 		List<Person> deleteByLastname(String lastname);
@@ -643,6 +682,13 @@ class AbstractMongoQueryUnitTests {
 		List<Person> findWithLimit(String firstname, Limit limit);
 
 		List<Person> findWithSortAndLimit(String firstname, Sort sort, Limit limit);
+
+		@ReadPreference(
+				value = "secondaryPreferred", 
+				tags = { @ReadPreferenceTag(name = "local", value = "east"), @ReadPreferenceTag(name = "pre", value = "west") },
+				maxStalenessSeconds = 99
+		)
+		List<Person> findWithReadPreferenceByFirstname(String firstname);
 	}
 
 	// DATAMONGO-1872

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/query/AbstractReactiveMongoQueryUnitTests.java

@@ -19,6 +19,9 @@ import static org.assertj.core.api.Assertions.*;
 import static org.mockito.Mockito.*;
 
 import com.mongodb.MongoClientSettings;
+import com.mongodb.Tag;
+import com.mongodb.TagSet;
+import com.mongodb.TaggableReadPreference;
 import com.mongodb.client.result.UpdateResult;
 import org.bson.codecs.configuration.CodecRegistry;
 import org.springframework.data.mongodb.core.ReactiveUpdateOperation.TerminatingUpdate;
@@ -26,6 +29,8 @@ import org.springframework.data.mongodb.core.ReactiveUpdateOperation.ReactiveUpd
 import org.springframework.data.mongodb.core.ReactiveUpdateOperation.UpdateWithQuery;
 import org.springframework.data.mongodb.core.query.UpdateDefinition;
 import org.springframework.data.mongodb.repository.Hint;
+import org.springframework.data.mongodb.repository.ReadPreference;
+import org.springframework.data.mongodb.repository.ReadPreferenceTag;
 import org.springframework.data.mongodb.repository.Update;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -33,6 +38,7 @@ import reactor.core.publisher.Mono;
 import java.lang.reflect.Method;
 import java.util.List;
 import java.util.Locale;
+import java.util.concurrent.TimeUnit;
 
 import org.bson.Document;
 import org.junit.jupiter.api.BeforeEach;
@@ -68,7 +74,7 @@ import org.springframework.expression.spel.standard.SpelExpressionParser;
  *
  * @author Christoph Strobl
  * @author Mark Paluch
- * @currentRead Way of Kings - Brandon Sanderson
+ * @author Jorge Rodríguez
  */
 @ExtendWith(MockitoExtension.class)
 @MockitoSettings(strictness = Strictness.LENIENT)
@@ -263,6 +269,19 @@ class AbstractReactiveMongoQueryUnitTests {
 		assertThat(captor.getValue().getHint()).isEqualTo("idx-ln");
 	}
 
+	@Test // GH-2971
+	void findShouldApplyReadPreference() {
+
+		createQueryForMethod("findWithReadPreferenceByFirstname", String.class).executeBlocking(new Object[] { "Jasna" });
+
+		ArgumentCaptor<Query> captor = ArgumentCaptor.forClass(Query.class);
+		verify(withQueryMock).matching(captor.capture());
+		assertThat(captor.getValue().getReadPreference().getName()).isEqualTo("secondaryPreferred");
+		assertThat(((TaggableReadPreference)captor.getValue().getReadPreference()).getTagSetList())
+				.containsExactly(new TagSet(List.of(new Tag("local", "east"), new Tag("pre", "west"))));
+		assertThat(((TaggableReadPreference)captor.getValue().getReadPreference()).getMaxStaleness(TimeUnit.SECONDS)).isEqualTo(99);
+	}
+
 	private ReactiveMongoQueryFake createQueryForMethod(String methodName, Class<?>... paramTypes) {
 		return createQueryForMethod(Repo.class, methodName, paramTypes);
 	}
@@ -367,5 +386,12 @@ class AbstractReactiveMongoQueryUnitTests {
 
 		@Hint("idx-fn")
 		void findWithHintByFirstname(String firstname);
+
+		@ReadPreference(
+				value = "secondaryPreferred",
+				tags = { @ReadPreferenceTag(name = "local", value = "east"), @ReadPreferenceTag(name = "pre", value = "west") },
+				maxStalenessSeconds = 99
+		)
+		Flux<Person> findWithReadPreferenceByFirstname(String firstname);
 	}
 }

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/query/MongoQueryMethodUnitTests.java

@@ -41,6 +41,7 @@ import org.springframework.data.mongodb.repository.Contact;
 import org.springframework.data.mongodb.repository.Meta;
 import org.springframework.data.mongodb.repository.Person;
 import org.springframework.data.mongodb.repository.Query;
+import org.springframework.data.mongodb.repository.ReadPreference;
 import org.springframework.data.projection.ProjectionFactory;
 import org.springframework.data.projection.SpelAwareProxyProjectionFactory;
 import org.springframework.data.repository.Repository;
@@ -52,6 +53,7 @@ import org.springframework.data.repository.core.support.DefaultRepositoryMetadat
  * @author Oliver Gierke
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Jorge Rodríguez
  */
 public class MongoQueryMethodUnitTests {
 
@@ -311,6 +313,43 @@ public class MongoQueryMethodUnitTests {
 		assertThat(method.getAnnotatedCollation()).isEqualTo("de_AT");
 	}
 
+	@Test // GH-2971
+	void readsReadPreferenceAtQueryAnnotation() throws Exception {
+
+		MongoQueryMethod method = queryMethod(PersonRepository.class, "findWithReadPreferenceFromAtReadPreferenceByFirstname", String.class);
+
+		assertThat(method.hasAnnotatedReadPreference()).isTrue();
+		assertThat(method.getAnnotatedReadPreference().getName()).isEqualTo("secondaryPreferred");
+	}
+
+	@Test // GH-2971
+	void readsReadPreferenceFromAtQueryAnnotation() throws Exception {
+
+		MongoQueryMethod method = queryMethod(PersonRepository.class, "findWithReadPreferenceFromAtQueryByFirstname", String.class);
+
+		assertThat(method.hasAnnotatedReadPreference()).isTrue();
+		assertThat(method.getAnnotatedReadPreference().getName()).isEqualTo("secondaryPreferred");
+	}
+
+	@Test // GH-2971
+	void annotatedReadPreferenceClashSelectsAtReadPreferenceAnnotationValue() throws Exception {
+
+		MongoQueryMethod method = queryMethod(PersonRepository.class, "findWithMultipleReadPreferencesFromAtQueryAndAtReadPreferenceByFirstname", String.class);
+
+		assertThat(method.hasAnnotatedReadPreference()).isTrue();
+		assertThat(method.getAnnotatedReadPreference().getName()).isEqualTo("secondaryPreferred");
+		
+	}
+
+	@Test // GH-2971
+	void readsReadPreferenceAtRepositoryAnnotation() throws Exception {
+
+		MongoQueryMethod method = queryMethod(PersonRepository.class, "deleteByUserName", String.class);
+
+		assertThat(method.hasAnnotatedReadPreference()).isTrue();
+		assertThat(method.getAnnotatedReadPreference().getName()).isEqualTo("primaryPreferred");
+	}
+
 	private MongoQueryMethod queryMethod(Class<?> repository, String name, Class<?>... parameters) throws Exception {
 
 		Method method = repository.getMethod(name, parameters);
@@ -318,6 +357,7 @@ public class MongoQueryMethodUnitTests {
 		return new MongoQueryMethod(method, new DefaultRepositoryMetadata(repository), factory, context);
 	}
 
+	@ReadPreference(value = "primaryPreferred")
 	interface PersonRepository extends Repository<User, Long> {
 
 		// Misses Pageable
@@ -381,6 +421,16 @@ public class MongoQueryMethodUnitTests {
 		@Collation("de_AT")
 		@Query(collation = "en_US")
 		List<User> findWithMultipleCollationsFromAtQueryAndAtCollationByFirstname(String firstname);
+
+		@ReadPreference("secondaryPreferred")
+		List<User> findWithReadPreferenceFromAtReadPreferenceByFirstname(String firstname);
+
+		@Query(readPreference = "secondaryPreferred")
+		List<User> findWithReadPreferenceFromAtQueryByFirstname(String firstname);
+
+		@ReadPreference("secondaryPreferred")
+		@Query(readPreference = "primaryPreferred")
+		List<User> findWithMultipleReadPreferencesFromAtQueryAndAtReadPreferenceByFirstname(String firstname);
 	}
 
 	interface SampleRepository extends Repository<Contact, Long> {

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/query/ReactiveMongoQueryMethodUnitTests.java

@@ -21,6 +21,7 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.data.mongodb.core.annotation.Collation;
 import org.springframework.data.mongodb.repository.Query;
+import org.springframework.data.mongodb.repository.ReadPreference;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -53,6 +54,7 @@ import org.springframework.data.repository.core.support.DefaultRepositoryMetadat
  *
  * @author Mark Paluch
  * @author Christoph Strobl
+ * @author Jorge Rodríguez
  */
 public class ReactiveMongoQueryMethodUnitTests {
 
@@ -226,6 +228,43 @@ public class ReactiveMongoQueryMethodUnitTests {
 		assertThat(method.getAnnotatedCollation()).isEqualTo("de_AT");
 	}
 
+
+	@Test // GH-2971
+	void readsReadPreferenceAtQueryAnnotation() throws Exception {
+
+		MongoQueryMethod method = queryMethod(MongoQueryMethodUnitTests.PersonRepository.class, "findWithReadPreferenceFromAtReadPreferenceByFirstname", String.class);
+
+		assertThat(method.hasAnnotatedReadPreference()).isTrue();
+		assertThat(method.getAnnotatedReadPreference().getName()).isEqualTo("secondaryPreferred");
+	}
+
+	@Test // GH-2971
+	void readsReadPreferenceFromAtQueryAnnotation() throws Exception {
+
+		MongoQueryMethod method = queryMethod(MongoQueryMethodUnitTests.PersonRepository.class, "findWithReadPreferenceFromAtQueryByFirstname", String.class);
+
+		assertThat(method.hasAnnotatedReadPreference()).isTrue();
+		assertThat(method.getAnnotatedReadPreference().getName()).isEqualTo("secondaryPreferred");
+	}
+
+	@Test // GH-2971
+	void annotatedReadPreferenceClashSelectsAtReadPreferenceAnnotationValue() throws Exception {
+
+		MongoQueryMethod method = queryMethod(MongoQueryMethodUnitTests.PersonRepository.class, "findWithMultipleReadPreferencesFromAtQueryAndAtReadPreferenceByFirstname", String.class);
+
+		assertThat(method.hasAnnotatedReadPreference()).isTrue();
+		assertThat(method.getAnnotatedReadPreference().getName()).isEqualTo("secondaryPreferred");
+	}
+
+	@Test // GH-2971
+	void readsReadPreferenceAtRepositoryAnnotation() throws Exception {
+
+		MongoQueryMethod method = queryMethod(MongoQueryMethodUnitTests.PersonRepository.class, "deleteByUserName", String.class);
+
+		assertThat(method.hasAnnotatedReadPreference()).isTrue();
+		assertThat(method.getAnnotatedReadPreference().getName()).isEqualTo("primaryPreferred");
+	}
+
 	private ReactiveMongoQueryMethod queryMethod(Class<?> repository, String name, Class<?>... parameters)
 			throws Exception {
 
@@ -234,6 +273,7 @@ public class ReactiveMongoQueryMethodUnitTests {
 		return new ReactiveMongoQueryMethod(method, new DefaultRepositoryMetadata(repository), factory, context);
 	}
 
+	@ReadPreference(value = "primaryPreferred")
 	interface PersonRepository extends Repository<User, Long> {
 
 		Mono<Person> findMonoByLastname(String lastname, Pageable pageRequest);
@@ -277,6 +317,16 @@ public class ReactiveMongoQueryMethodUnitTests {
 		@Collation("de_AT")
 		@Query(collation = "en_US")
 		List<User> findWithMultipleCollationsFromAtQueryAndAtCollationByFirstname(String firstname);
+
+		@ReadPreference("secondaryPreferred")
+		Flux<User> findWithReadPreferenceFromAtReadPreferenceByFirstname(String firstname);
+
+		@Query(readPreference = "secondaryPreferred")
+		Flux<User> findWithReadPreferenceFromAtQueryByFirstname(String firstname);
+
+		@ReadPreference("secondaryPreferred")
+		@Query(readPreference = "primaryPreferred")
+		Flux<User> findWithMultipleReadPreferencesFromAtQueryAndAtReadPreferenceByFirstname(String firstname);
 	}
 
 	interface SampleRepository extends Repository<Contact, Long> {

src/main/antora/modules/ROOT/pages/mongodb/repositories/query-methods.adoc

@@ -824,3 +824,33 @@ interface GameRepository extends Repository<Game, String> {
 <2> Instead of `@Query(collation=...)`.
 <3> Favors `@Collation` over meta usage.
 ====
+
+== Read Preferences
+
+The `@ReadPreference` annotation allows you to configure MongoDB's ReadPreferences
+
+.Example of read preferences
+====
+[source,java]
+----
+
+@ReadPreference(
+        value = "primaryPreferred",
+        tags = {@ReadPreferenceTag(name = "local", value = "east"), @ReadPreferenceTag(name = "pre", value = "west")},
+        maxStalenessSeconds = 150
+) <1>
+public interface PersonRepository extends CrudRepository<Person, String> {
+
+    @ReadPreference(value = "secondaryPreferred") <2>
+    List<Person> findWithReadPreferenceAnnotationByLastname(String lastname);
+
+    @Query(readPreference = "nearest") <3>
+    List<Person> findWithReadPreferenceAtTagByFirstname(String firstname);
+
+    List<Person> findWithReadPreferenceAtTagByFirstname(String firstname); <4>
+----
+<1> Configure read preference for all repository operations that do not have a query-level definition. Therefore, in this case the read preference mode will be `primaryPreferred`
+<2> Use the read preference mode defined in annotation `ReadPreference`, in this case secondaryPreferred
+<3> The `@Query` annotation defines the `read preference mode` alias which is equivalent to adding the `@ReadPreference` annotation.
+<4> This query will use the read preference mode defined in the repository.
+====