DATAMONGO-2188 - Expose IndexResolver.

We now provide IndexResolver to resolve and derive index definitions from Mongo entities.

MongoMappingContext mappingContext = new MongoMappingContext();
IndexResolver indexResolver = IndexResolver.create(mappingContext);
Iterable<? extends IndexDefinitionHolder> definitions = indexResolver.resolveIndexFor(MyEntity.class);

Original Pull Request: #636

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

@@ -16,16 +16,33 @@
 package org.springframework.data.mongodb.core.index;
 
 import org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexResolver.IndexDefinitionHolder;
+import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
+import org.springframework.data.util.ClassTypeInformation;
 import org.springframework.data.util.TypeInformation;
+import org.springframework.util.Assert;
 
 /**
  * {@link IndexResolver} finds those {@link IndexDefinition}s to be created for a given class.
  *
  * @author Christoph Strobl
  * @author Thomas Darimont
+ * @author Mark Paluch
  * @since 1.5
  */
-interface IndexResolver {
+public interface IndexResolver {
+
+	/**
+	 * Creates a new {@link IndexResolver} given {@link MongoMappingContext}.
+	 *
+	 * @param mappingContext must not be {@literal null}.
+	 * @return the new {@link IndexResolver}.
+	 */
+	static IndexResolver create(MongoMappingContext mappingContext) {
+
+		Assert.notNull(mappingContext, "MongoMappingContext must not be null!");
+
+		return new MongoPersistentEntityIndexResolver(mappingContext);
+	}
 
 	/**
 	 * Find and create {@link IndexDefinition}s for properties of given {@link TypeInformation}. {@link IndexDefinition}s
@@ -36,4 +53,16 @@ interface IndexResolver {
 	 */
 	Iterable<? extends IndexDefinitionHolder> resolveIndexFor(TypeInformation<?> typeInformation);
 
+	/**
+	 * Find and create {@link IndexDefinition}s for properties of given {@link TypeInformation}. {@link IndexDefinition}s
+	 * are created for properties and types with {@link Indexed}, {@link CompoundIndexes} or {@link GeoSpatialIndexed}.
+	 *
+	 * @param entityType
+	 * @return Empty {@link Iterable} in case no {@link IndexDefinition} could be resolved for type.
+	 * @see 2.2
+	 */
+	default Iterable<? extends IndexDefinitionHolder> resolveIndexFor(Class<?> entityType) {
+		return resolveIndexFor(ClassTypeInformation.from(entityType));
+	}
+
 }

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

@@ -69,7 +69,7 @@ public class MongoPersistentEntityIndexCreator implements ApplicationListener<Ma
 	 */
 	public MongoPersistentEntityIndexCreator(MongoMappingContext mappingContext,
 			IndexOperationsProvider indexOperationsProvider) {
-		this(mappingContext, indexOperationsProvider, new MongoPersistentEntityIndexResolver(mappingContext));
+		this(mappingContext, indexOperationsProvider, IndexResolver.create(mappingContext));
 	}
 
 	/**

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

@@ -63,7 +63,7 @@ public class ReactiveMongoPersistentEntityIndexCreator {
 	 */
 	public ReactiveMongoPersistentEntityIndexCreator(MongoMappingContext mappingContext,
 			ReactiveIndexOperationsProvider operationsProvider) {
-		this(mappingContext, operationsProvider, new MongoPersistentEntityIndexResolver(mappingContext));
+		this(mappingContext, operationsProvider, IndexResolver.create(mappingContext));
 	}
 
 	/**

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

@@ -64,6 +64,7 @@ public class MongoPersistentEntityIndexResolverUnitTests {
 	 * Test resolution of {@link Indexed}.
 	 *
 	 * @author Christoph Strobl
+	 * @author Mark Paluch
 	 */
 	public static class IndexResolutionTests {
 
@@ -87,7 +88,17 @@ public class MongoPersistentEntityIndexResolverUnitTests {
 		}
 
 		@Test // DATAMONGO-899
-		public void depplyNestedIndexPathIsResolvedCorrectly() {
+		public void shouldResolveIndexViaClass() {
+
+			MongoMappingContext mappingContext = new MongoMappingContext();
+			IndexResolver indexResolver = IndexResolver.create(mappingContext);
+			Iterable<? extends IndexDefinitionHolder> definitions = indexResolver.resolveIndexFor(IndexOnLevelOne.class);
+
+			assertThat(definitions.iterator().hasNext(), is(true));
+		}
+
+		@Test // DATAMONGO-899
+		public void deeplyNestedIndexPathIsResolvedCorrectly() {
 
 			List<IndexDefinitionHolder> indexDefinitions = prepareMappingContextAndResolveIndexForType(IndexOnLevelTwo.class);