Support different routing for each id in multiget.

src/main/java/org/springframework/data/elasticsearch/core/DocumentOperations.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.elasticsearch.core;
 
+import java.util.Collection;
 import java.util.List;
 
 import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
@@ -121,6 +122,8 @@ public interface DocumentOperations {
 	 * @param query the query defining the ids of the objects to get
 	 * @param clazz the type of the object to be returned
 	 * @return list of {@link MultiGetItem}s
+	 * @see Query#multiGetQuery(Collection)
+	 * @see Query#multiGetQueryWithRouting(List)
 	 * @since 4.1
 	 */
 	<T> List<MultiGetItem<T>> multiGet(Query query, Class<T> clazz);
@@ -132,6 +135,8 @@ public interface DocumentOperations {
 	 * @param clazz the type of the object to be returned
 	 * @param index the index(es) from which the objects are read.
 	 * @return list of {@link MultiGetItem}s
+	 * @see Query#multiGetQuery(Collection)
+	 * @see Query#multiGetQueryWithRouting(List)
 	 */
 	<T> List<MultiGetItem<T>> multiGet(Query query, Class<T> clazz, IndexCoordinates index);
 
@@ -283,7 +288,7 @@ default void bulkUpdate(List<UpdateQuery> queries, IndexCoordinates index) {
 
 	/**
 	 * Delete all records matching the query.
-	 * 
+	 *
 	 * @param query query defining the objects
 	 * @param clazz The entity class, must be annotated with
 	 *          {@link org.springframework.data.elasticsearch.annotations.Document}

src/main/java/org/springframework/data/elasticsearch/core/ElasticsearchRestTemplate.java

@@ -182,7 +182,6 @@ public <T> T get(String id, Class<T> clazz, IndexCoordinates index) {
 	public <T> List<MultiGetItem<T>> multiGet(Query query, Class<T> clazz, IndexCoordinates index) {
 
 		Assert.notNull(index, "index must not be null");
-		Assert.notEmpty(query.getIds(), "No Id defined for Query");
 
 		MultiGetRequest request = requestFactory.multiGetRequest(query, clazz, index);
 		MultiGetResponse result = execute(client -> client.mget(request, RequestOptions.DEFAULT));

src/main/java/org/springframework/data/elasticsearch/core/ElasticsearchTemplate.java

@@ -205,7 +205,6 @@ public <T> T get(String id, Class<T> clazz, IndexCoordinates index) {
 	public <T> List<MultiGetItem<T>> multiGet(Query query, Class<T> clazz, IndexCoordinates index) {
 
 		Assert.notNull(index, "index must not be null");
-		Assert.notEmpty(query.getIds(), "No Ids defined for Query");
 
 		MultiGetRequestBuilder builder = requestFactory.multiGetRequestBuilder(client, query, clazz, index);
 

src/main/java/org/springframework/data/elasticsearch/core/ReactiveDocumentOperations.java

@@ -148,6 +148,8 @@ default <T> Flux<T> saveAll(Iterable<T> entities, IndexCoordinates index) {
 	 * @param query the query defining the ids of the objects to get
 	 * @param clazz the type of the object to be returned, used to determine the index
 	 * @return flux with list of {@link MultiGetItem}s that contain the entities
+	 * @see Query#multiGetQuery(Collection)
+	 * @see Query#multiGetQueryWithRouting(List)
 	 * @since 4.1
 	 */
 	<T> Flux<MultiGetItem<T>> multiGet(Query query, Class<T> clazz);
@@ -159,6 +161,8 @@ default <T> Flux<T> saveAll(Iterable<T> entities, IndexCoordinates index) {
 	 * @param clazz the type of the object to be returned
 	 * @param index the index(es) from which the objects are read.
 	 * @return flux with list of {@link MultiGetItem}s that contain the entities
+	 * @see Query#multiGetQuery(Collection)
+	 * @see Query#multiGetQueryWithRouting(List)
 	 * @since 4.0
 	 */
 	<T> Flux<MultiGetItem<T>> multiGet(Query query, Class<T> clazz, IndexCoordinates index);

src/main/java/org/springframework/data/elasticsearch/core/ReactiveElasticsearchTemplate.java

@@ -338,7 +338,6 @@ public <T> Flux<MultiGetItem<T>> multiGet(Query query, Class<T> clazz, IndexCoor
 		Assert.notNull(index, "Index must not be null");
 		Assert.notNull(clazz, "Class must not be null");
 		Assert.notNull(query, "Query must not be null");
-		Assert.notEmpty(query.getIds(), "No Id define for Query");
 
 		DocumentCallback<T> callback = new ReadDocumentCallback<>(converter, clazz, index);
 

src/main/java/org/springframework/data/elasticsearch/core/RequestFactory.java

@@ -677,13 +677,13 @@ private List<MultiGetRequest.Item> getMultiRequestItems(Query searchQuery, Class
 
 		FetchSourceContext fetchSourceContext = getFetchSourceContext(searchQuery);
 
-		if (!isEmpty(searchQuery.getIds())) {
+		if (!isEmpty(searchQuery.getIdsWithRouting())) {
 			String indexName = index.getIndexName();
-			for (String id : searchQuery.getIds()) {
-				MultiGetRequest.Item item = new MultiGetRequest.Item(indexName, id);
 
-				if (searchQuery.getRoute() != null) {
-					item = item.routing(searchQuery.getRoute());
+			for (Query.IdWithRouting idWithRouting : searchQuery.getIdsWithRouting()) {
+				MultiGetRequest.Item item = new MultiGetRequest.Item(indexName, idWithRouting.getId());
+				if (idWithRouting.getRouting() != null) {
+					item = item.routing(idWithRouting.getRouting());
 				}
 
 				// note: multiGet does not have fields, need to set sourceContext to filter

src/main/java/org/springframework/data/elasticsearch/core/query/AbstractQuery.java → src/main/java/org/springframework/data/elasticsearch/core/query/BaseQuery.java

@@ -16,20 +16,23 @@
 package org.springframework.data.elasticsearch.core.query;
 
 import static java.util.Collections.*;
+import static org.springframework.util.CollectionUtils.*;
 
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
- * AbstractQuery
+ * BaseQuery
  *
  * @author Rizwan Idrees
  * @author Mohsin Husen
@@ -40,7 +43,7 @@
  * @author Peter-Josef Meisch
  * @author Peer Mueller
  */
-abstract class AbstractQuery implements Query {
+public class BaseQuery implements Query {
 
 	protected Pageable pageable = DEFAULT_PAGE;
 	@Nullable protected Sort sort;
@@ -63,6 +66,7 @@ abstract class AbstractQuery implements Query {
 	@Nullable private List<Object> searchAfter;
 	protected List<RescorerQuery> rescorerQueries = new ArrayList<>();
 	@Nullable protected Boolean requestCache;
+	private List<IdWithRouting> idsWithRouting = Collections.emptyList();
 
 	@Override
 	@Nullable
@@ -81,7 +85,7 @@ public final <T extends Query> T setPageable(Pageable pageable) {
 		Assert.notNull(pageable, "Pageable must not be null!");
 
 		this.pageable = pageable;
-		return (T) this.addSort(pageable.getSort());
+		return this.addSort(pageable.getSort());
 	}
 
 	@Override
@@ -116,7 +120,7 @@ public SourceFilter getSourceFilter() {
 
 	@Override
 	@SuppressWarnings("unchecked")
-	public final <T extends Query> T addSort(Sort sort) {
+	public final <T extends Query> T addSort(@Nullable Sort sort) {
 		if (sort == null) {
 			return (T) this;
 		}
@@ -139,14 +143,46 @@ public void setMinScore(float minScore) {
 		this.minScore = minScore;
 	}
 
-	@Nullable
+	/**
+	 * Set Ids for a multi-get request with on this query.
+	 *
+	 * @param ids list of id values
+	 */
+	public void setIds(@Nullable Collection<String> ids) {
+		this.ids = ids;
+	}
+
 	@Override
+	@Nullable
 	public Collection<String> getIds() {
 		return ids;
 	}
 
-	public void setIds(Collection<String> ids) {
-		this.ids = ids;
+	@Override
+	public List<IdWithRouting> getIdsWithRouting() {
+
+		if (!isEmpty(idsWithRouting)) {
+			return Collections.unmodifiableList(idsWithRouting);
+		}
+
+		if (!isEmpty(ids)) {
+			return ids.stream().map(id -> new IdWithRouting(id, route)).collect(Collectors.toList());
+		}
+
+		return Collections.emptyList();
+	}
+
+	/**
+	 * Set Ids with routing values for a multi-get request set on this query.
+	 *
+	 * @param idsWithRouting list of id values, must not be {@literal null}
+	 * @since 4.3
+	 */
+	public void setIdsWithRouting(List<IdWithRouting> idsWithRouting) {
+
+		Assert.notNull(idsWithRouting, "idsWithRouting must not be null");
+
+		this.idsWithRouting = idsWithRouting;
 	}
 
 	@Nullable
@@ -337,4 +373,5 @@ public void setRequestCache(@Nullable Boolean value) {
 	public Boolean getRequestCache() {
 		return this.requestCache;
 	}
+
 }

src/main/java/org/springframework/data/elasticsearch/core/query/CriteriaQuery.java

@@ -26,7 +26,7 @@
  * @author Mark Paluch
  * @author Peter-Josef Meisch
  */
-public class CriteriaQuery extends AbstractQuery {
+public class CriteriaQuery extends BaseQuery {
 
 	private Criteria criteria;
 

src/main/java/org/springframework/data/elasticsearch/core/query/MoreLikeThisQuery.java

@@ -16,7 +16,7 @@
 package org.springframework.data.elasticsearch.core.query;
 
 import static java.util.Collections.*;
-import static org.springframework.data.elasticsearch.core.query.AbstractQuery.*;
+import static org.springframework.data.elasticsearch.core.query.BaseQuery.*;
 
 import java.util.ArrayList;
 import java.util.List;

src/main/java/org/springframework/data/elasticsearch/core/query/NativeSearchQuery.java

@@ -42,7 +42,7 @@
  * @author Martin Choraine
  * @author Peter-Josef Meisch
  */
-public class NativeSearchQuery extends AbstractQuery {
+public class NativeSearchQuery extends BaseQuery {
 
 	@Nullable private final QueryBuilder query;
 	@Nullable private QueryBuilder filter;

src/main/java/org/springframework/data/elasticsearch/core/query/Query.java

@@ -26,6 +26,7 @@
 import org.springframework.data.domain.Sort;
 import org.springframework.data.elasticsearch.core.SearchHit;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 
 /**
  * Query
@@ -76,7 +77,7 @@ static Query findAll() {
 	 * @param sort
 	 * @return
 	 */
-	<T extends Query> T addSort(Sort sort);
+	<T extends Query> T addSort(@Nullable Sort sort);
 
 	/**
 	 * @return null if not set
@@ -137,13 +138,48 @@ static Query findAll() {
 	boolean getTrackScores();
 
 	/**
-	 * Get Ids
-	 *
-	 * @return
+	 * @return Get ids set on this query.
 	 */
 	@Nullable
 	Collection<String> getIds();
 
+	/**
+	 * @return Ids with routing values used in a multi-get request.
+	 * @see #multiGetQueryWithRouting(List)
+	 * @since 4.3
+	 */
+	List<IdWithRouting> getIdsWithRouting();
+
+	/**
+	 * Utility method to get a query for a multiget request
+	 *
+	 * @param idsWithRouting Ids with routing values used in a multi-get request.
+	 * @return Query instance
+	 */
+	static Query multiGetQueryWithRouting(List<IdWithRouting> idsWithRouting) {
+
+		Assert.notNull(idsWithRouting, "idsWithRouting must not be null");
+
+		BaseQuery query = new BaseQuery();
+		query.setIdsWithRouting(idsWithRouting);
+		return query;
+	}
+
+	/**
+	 * Utility method to get a query for a multiget request
+	 *
+	 * @param ids Ids used in a multi-get request.
+	 * @return Query instance
+	 */
+	static Query multiGetQuery(Collection<String> ids) {
+
+		Assert.notNull(ids, "ids must not be null");
+
+		BaseQuery query = new BaseQuery();
+		query.setIds(ids);
+		return query;
+	}
+
 	/**
 	 * Get route
 	 *
@@ -362,4 +398,31 @@ default List<RescorerQuery> getRescorerQueries() {
 	enum SearchType {
 		QUERY_THEN_FETCH, DFS_QUERY_THEN_FETCH
 	}
+
+	/**
+	 * Value class combining an id with a routing value. Used in multi-get requests.
+	 *
+	 * @since 4.3
+	 */
+	final class IdWithRouting {
+		private final String id;
+		@Nullable private final String routing;
+
+		public IdWithRouting(String id, @Nullable String routing) {
+
+			Assert.notNull(id, "id must not be null");
+
+			this.id = id;
+			this.routing = routing;
+		}
+
+		public String getId() {
+			return id;
+		}
+
+		@Nullable
+		public String getRouting() {
+			return routing;
+		}
+	}
 }

src/main/java/org/springframework/data/elasticsearch/core/query/StringQuery.java

@@ -24,7 +24,7 @@
  * @author Rizwan Idrees
  * @author Mohsin Husen
  */
-public class StringQuery extends AbstractQuery {
+public class StringQuery extends BaseQuery {
 
 	private String source;
 

src/main/java/org/springframework/data/elasticsearch/repository/support/SimpleElasticsearchRepository.java

@@ -16,6 +16,7 @@
 package org.springframework.data.elasticsearch.repository.support;
 
 import static org.elasticsearch.index.query.QueryBuilders.*;
+import static org.springframework.util.CollectionUtils.*;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -50,7 +51,6 @@
 import org.springframework.data.util.Streamable;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
-import org.springframework.util.CollectionUtils;
 
 /**
  * Elasticsearch specific repository implementation. Likely to be used as target within
@@ -149,7 +149,7 @@ public Iterable<T> findAllById(Iterable<ID> ids) {
 
 		List<T> result = new ArrayList<>();
 		Query idQuery = getIdQuery(ids);
-		if (CollectionUtils.isEmpty(idQuery.getIds())) {
+		if (isEmpty(idQuery.getIds())) {
 			return result;
 		}