Add collation for an index via @CompoundIndex and @Index annotations.

Closes #3002, closes #4130

Original Pull Request: #4131

Author: StefanTirea

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/CompoundIndex.java

@@ -46,6 +46,7 @@
  * @author Johno Crawford
  * @author Christoph Strobl
  * @author Dave Perryman
+ * @author Stefan Tirea
  */
 @Target({ ElementType.TYPE })
 @Documented
@@ -163,4 +164,19 @@
 	 * @since 3.1
 	 */
 	String partialFilter() default "";
+
+	/**
+	 * The actual collation definition in JSON format or a {@link org.springframework.expression.spel.standard.SpelExpression
+	 * template expression} resolving to either a JSON String or a {@link org.bson.Document}. The keys of the JSON
+	 * document are configuration options for the collation (language-specific rules for string comparison).
+	 * <br><br>
+	 * TODO write code documentation & example!!!
+	 * <br>
+	 *
+	 * @return empty String by default.
+	 * @see <a href=
+	 * "https://www.mongodb.com/docs/manual/reference/collation/">https://www.mongodb.com/docs/manual/reference/collation/</a>
+	 * @since 3.4
+	 */
+	String collation() default "";
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/Indexed.java

@@ -31,6 +31,7 @@
  * @author Christoph Strobl
  * @author Jordi Llach
  * @author Mark Paluch
+ * @author Stefan Tirea
  */
 @Target({ ElementType.ANNOTATION_TYPE, ElementType.FIELD })
 @Retention(RetentionPolicy.RUNTIME)
@@ -173,4 +174,14 @@
 	 * @since 3.1
 	 */
 	String partialFilter() default "";
+
+	/**
+	 * Apply collation configuration for field <br />
+	 *
+	 * @return empty by default.
+	 * @see <a href=
+	 *      "https://www.mongodb.com/docs/manual/reference/collation/">https://www.mongodb.com/docs/manual/reference/collation//</a>
+	 * @since 3.1
+	 */
+	String collation() default "";
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/MongoPersistentEntityIndexResolver.java

@@ -74,6 +74,7 @@
  * @author Martin Macko
  * @author Mark Paluch
  * @author Dave Perryman
+ * @author Stefan Tirea
  * @since 1.5
  */
 public class MongoPersistentEntityIndexResolver implements IndexResolver {
@@ -453,6 +454,10 @@ protected IndexDefinitionHolder createCompoundIndexDefinition(String dotPath, St
 			indexDefinition.partial(evaluatePartialFilter(index.partialFilter(), entity));
 		}
 
+		if (StringUtils.hasText(index.collation())) {
+			indexDefinition.collation(Collation.parse(index.collation()));
+		}
+
 		return new IndexDefinitionHolder(dotPath, indexDefinition, collection);
 	}
 
@@ -572,6 +577,10 @@ protected IndexDefinitionHolder createIndexDefinition(String dotPath, String col
 			indexDefinition.partial(evaluatePartialFilter(index.partialFilter(), persistentProperty.getOwner()));
 		}
 
+		if (StringUtils.hasText(index.collation())) {
+			indexDefinition.collation(Collation.parse(index.collation()));
+		}
+
 		return new IndexDefinitionHolder(dotPath, indexDefinition, collection);
 	}
 

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/index/IndexInfoUnitTests.java

@@ -29,6 +29,7 @@
  *
  * @author Oliver Gierke
  * @author Christoph Strobl
+ * @author Stefan Tirea
  */
 public class IndexInfoUnitTests {
 
@@ -37,6 +38,7 @@ public class IndexInfoUnitTests {
 	static final String INDEX_WITH_EXPIRATION_TIME = "{ \"v\" : 2, \"key\" : { \"lastModifiedDate\" : 1 },\"name\" : \"expire-after-last-modified\", \"ns\" : \"db.collectio\", \"expireAfterSeconds\" : 3600 }";
 	static final String HASHED_INDEX = "{ \"v\" : 2, \"key\" : { \"score\" : \"hashed\" }, \"name\" : \"score_hashed\", \"ns\" : \"db.collection\" }";
 	static final String WILDCARD_INDEX = "{ \"v\" : 2, \"key\" : { \"$**\" : 1 }, \"name\" : \"$**_1\", \"wildcardProjection\" : { \"fieldA\" : 0, \"fieldB.fieldC\" : 0 } }";
+	static final String INDEX_WITH_COLLATION = "{ \"v\" : 2, \"key\" : { \"_id\" : 1 }, \"name\" : \"projectName\", \"collation\": { \"locale\": \"en_US\", \"strength\": 2 } }";
 
 	@Test
 	public void isIndexForFieldsCorrectly() {
@@ -87,7 +89,14 @@ public void identifiesWildcardIndexCorrectly() {
 
 	@Test // GH-3225
 	public void readsWildcardIndexProjectionCorrectly() {
-		assertThat(getIndexInfo(WILDCARD_INDEX).getWildcardProjection()).contains(new Document("fieldA", 0).append("fieldB.fieldC", 0));
+		assertThat(getIndexInfo(WILDCARD_INDEX).getWildcardProjection())
+				.contains(new Document("fieldA", 0).append("fieldB.fieldC", 0));
+	}
+
+	@Test // DATAMONGO-2133
+	public void collationParsedCorrectly() {
+		assertThat(getIndexInfo(INDEX_WITH_COLLATION).getCollation())
+				.contains(Document.parse("{ \"locale\": \"en_US\", \"strength\": 2 }"));
 	}
 
 	private static IndexInfo getIndexInfo(String documentJson) {

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/index/MongoPersistentEntityIndexResolverUnitTests.java

@@ -61,6 +61,7 @@
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author Dave Perryman
+ * @author Stefan Tirea
  */
 @RunWith(Suite.class)
 @SuiteClasses({ IndexResolutionTests.class, GeoSpatialIndexResolutionTests.class, CompoundIndexResolutionTests.class,
@@ -699,6 +700,19 @@ public void singleIndexWithPartialFilter() {
 					org.bson.Document.parse("{'value': {'$exists': true}}"));
 		}
 
+		@Test // DATAMONGO-2133
+		public void compoundIndexWithCollation() {
+
+			List<IndexDefinitionHolder> indexDefinitions = prepareMappingContextAndResolveIndexForType(
+					CompoundIndexWithCollation.class);
+
+			IndexDefinition indexDefinition = indexDefinitions.get(0).getIndexDefinition();
+			assertThat(indexDefinition.getIndexOptions())
+					.isEqualTo(new org.bson.Document().append("name", "compound_index_with_collation").append("collation",
+							new org.bson.Document().append("locale", "en_US").append("strength", 2)));
+			assertThat(indexDefinition.getIndexKeys()).isEqualTo(new org.bson.Document().append("foo", 1));
+		}
+
 		@Document("CompoundIndexOnLevelOne")
 		class CompoundIndexOnLevelOne {
 
@@ -774,6 +788,11 @@ class RepeatedCompoundIndex {}
 		@CompoundIndex(name = "compound_index_with_partial", def = "{'foo': 1, 'bar': -1}", background = true,
 				unique = true, partialFilter = "{'value': {'$exists': true}}")
 		class SingleCompoundIndexWithPartialFilter {}
+
+		@Document
+		@CompoundIndex(name = "compound_index_with_collation", def = "{'foo': 1}",
+				collation = "{'locale': 'en_US', 'strength': 2}")
+		class CompoundIndexWithCollation {}
 	}
 
 	public static class TextIndexedResolutionTests {
@@ -1400,6 +1419,18 @@ public void shouldSkipMapStructuresUnlessAnnotatedWithWildcardIndex() {
 			assertThat(indexDefinitions).hasSize(1);
 		}
 
+		@Test // DATAMONGO-2133
+		public void indexedWithCollation() {
+
+			List<IndexDefinitionHolder> indexDefinitions = prepareMappingContextAndResolveIndexForType(
+					IndexedWithCollation.class);
+
+			IndexDefinition indexDefinition = indexDefinitions.get(0).getIndexDefinition();
+			assertThat(indexDefinition.getIndexOptions()).isEqualTo(new org.bson.Document().append("name", "value")
+					.append("unique", true)
+					.append("collation", new org.bson.Document().append("locale", "en_US").append("strength", 2)));
+		}
+
 		@Document
 		class MixedIndexRoot {
 
@@ -1717,6 +1748,12 @@ class WithComposedHashedIndexAndIndex {
 			@ComposedHashIndexed(name = "idx-name") String value;
 		}
 
+		@Document
+		class IndexedWithCollation {
+			@Indexed(collation = "{'locale': 'en_US', 'strength': 2}", unique = true) //
+			private String value;
+		}
+
 		@HashIndexed
 		@Indexed
 		@Retention(RetentionPolicy.RUNTIME)