DATAMONGO-1761 - Polishing.

Refactor MongoConverter.mapValueToTargetType to imperative method instead of returning a function for easier consumption. Adapt return types in Javadoc to the actual return type. Remove undocumented type parameters. Add overload using reified entity and return type generics. Slight documentation tweaks.

Original pull request: spring-projects#494.
Related pull request: spring-projects#514.

Author: mp911de

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/CodecRegistryProvider.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2018 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.
@@ -23,9 +23,13 @@
 import org.springframework.util.Assert;
 
 /**
+ * Provider interface to obtain {@link CodecRegistry} from the underlying MongoDB Java driver.
+ *
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 2.1
  */
+@FunctionalInterface
 public interface CodecRegistryProvider {
 
 	/**
@@ -50,7 +54,7 @@ default boolean hasCodecFor(Class<?> type) {
 	/**
 	 * Get the {@link Codec} registered for the given {@literal type} or an {@link Optional#empty() empty Optional}
 	 * instead.
-	 * 
+	 *
 	 * @param type must not be {@literal null}.
 	 * @param <T>
 	 * @return never {@literal null}.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/MongoDbFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2013 the original author or authors.
+ * Copyright 2011-2018 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.
@@ -25,23 +25,24 @@
 
 /**
  * Interface for factories creating {@link DB} instances.
- * 
+ *
  * @author Mark Pollack
  * @author Thomas Darimont
+ * @author Christoph Strobl
  */
 public interface MongoDbFactory extends CodecRegistryProvider {
 
 	/**
 	 * Creates a default {@link DB} instance.
-	 * 
+	 *
 	 * @return
 	 * @throws DataAccessException
 	 */
 	MongoDatabase getDb() throws DataAccessException;
 
 	/**
 	 * Creates a {@link DB} instance to access the database with the given name.
-	 * 
+	 *
 	 * @param dbName must not be {@literal null} or empty.
 	 * @return
 	 * @throws DataAccessException
@@ -50,13 +51,18 @@ public interface MongoDbFactory extends CodecRegistryProvider {
 
 	/**
 	 * Exposes a shared {@link MongoExceptionTranslator}.
-	 * 
+	 *
 	 * @return will never be {@literal null}.
 	 */
 	PersistenceExceptionTranslator getExceptionTranslator();
 
 	DB getLegacyDb();
 
+	/**
+	 * Get the underlying {@link CodecRegistry} used by the MongoDB Java driver.
+	 *
+	 * @return never {@literal null}.
+	 */
 	@Override
 	default CodecRegistry getCodecRegistry() {
 		return getDb().getCodecRegistry();

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/ReactiveMongoDatabaseFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2018 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.
@@ -56,6 +56,11 @@ public interface ReactiveMongoDatabaseFactory extends CodecRegistryProvider {
 	 */
 	PersistenceExceptionTranslator getExceptionTranslator();
 
+	/**
+	 * Get the underlying {@link CodecRegistry} used by the reactive MongoDB Java driver.
+	 *
+	 * @return never {@literal null}.
+	 */
 	@Override
 	default CodecRegistry getCodecRegistry() {
 		return getMongoDatabase().getCodecRegistry();

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2018 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.
@@ -258,7 +258,7 @@ interface DistinctWithProjection {
 		 * to obtain the domain type. <br />
 		 * Using {@link Object} also works for non strictly typed fields. Eg. a mixture different types like fields using
 		 * {@link String} in one {@link org.bson.Document} while {@link Long} in another.</dd>
-		 * <dt>Any Simple type like {@link String}, {@link Long}, ...</dt>
+		 * <dt>Any Simple type like {@link String} or {@link Long}.</dt>
 		 * <dd>The result is mapped directly by the MongoDB Java driver and the {@link org.bson.codecs.CodeCodec Codecs} in
 		 * place. This works only for results where all documents considered for the operation use the very same type for
 		 * the field.</dd>

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2018 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.
@@ -209,12 +209,13 @@ public boolean exists() {
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.ExecutableFindOperation.FindDistinct#distinct(java.lang.String)
 		 */
+		@SuppressWarnings("unchecked")
 		@Override
 		public TerminatingDistinct<Object> distinct(String field) {
 
 			Assert.notNull(field, "Field must not be null!");
 
-			return new DistinctOperationSupport<>(this, field);
+			return new DistinctOperationSupport(this, field);
 		}
 
 		private List<T> doFind(@Nullable CursorPreparer preparer) {
@@ -287,9 +288,9 @@ CursorPreparer limit(int limit) {
 	static class DistinctOperationSupport<T> implements TerminatingDistinct<T> {
 
 		private final String field;
-		private final ExecutableFindSupport delegate;
+		private final ExecutableFindSupport<T> delegate;
 
-		public DistinctOperationSupport(ExecutableFindSupport delegate, String field) {
+		public DistinctOperationSupport(ExecutableFindSupport<T> delegate, String field) {
 
 			this.delegate = delegate;
 			this.field = field;
@@ -300,11 +301,12 @@ public DistinctOperationSupport(ExecutableFindSupport delegate, String field) {
 		 * @see org.springframework.data.mongodb.core.ExecutableFindOperation.DistinctWithProjection#as(java.lang.Class)
 		 */
 		@Override
+		@SuppressWarnings("unchecked")
 		public <R> TerminatingDistinct<R> as(Class<R> resultType) {
 
 			Assert.notNull(resultType, "ResultType must not be null!");
 
-			return new DistinctOperationSupport((ExecutableFindSupport) delegate.as(resultType), field);
+			return new DistinctOperationSupport<>((ExecutableFindSupport) delegate.as(resultType), field);
 		}
 
 		/*
@@ -316,7 +318,7 @@ public TerminatingDistinct<T> matching(Query query) {
 
 			Assert.notNull(query, "Query must not be null!");
 
-			return new DistinctOperationSupport((ExecutableFindSupport) delegate.matching(query), field);
+			return new DistinctOperationSupport<>((ExecutableFindSupport<T>) delegate.matching(query), field);
 		}
 
 		/*

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

@@ -761,7 +761,6 @@ <T> List<T> findDistinct(Query query, String field, String collectionName, Class
 	 * @param field the name of the field to inspect for distinct values. Must not be {@literal null}.
 	 * @param collection the explicit name of the actual {@link MongoCollection}. Must not be {@literal null}.
 	 * @param resultClass the result type. Must not be {@literal null}.
-	 * @param <T>
 	 * @return never {@literal null}.
 	 * @since 2.1
 	 */

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2017 the original author or authors.
+ * Copyright 2010-2018 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.
@@ -121,7 +121,6 @@
 import org.springframework.util.ResourceUtils;
 import org.springframework.util.StringUtils;
 
-import com.mongodb.Function;
 import com.mongodb.MongoClient;
 import com.mongodb.MongoException;
 import com.mongodb.ReadPreference;
@@ -803,7 +802,7 @@ public <T> T findById(Object id, Class<T> entityClass, String collectionName) {
 	}
 
 	/*
-	 * (non-Javadoc) 
+	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.MongoOperations#findDistinct(org.springframework.data.mongodb.core.query.Query, java.lang.String, java.lang.Class, java.lang.Class)
 	 */
 	@Override
@@ -816,6 +815,7 @@ public <T> List<T> findDistinct(Query query, String field, Class<?> entityClass,
 	 * @see org.springframework.data.mongodb.core.MongoOperations#findDistinct(org.springframework.data.mongodb.core.query.Query, java.lang.String, java.lang.String, java.lang.Class, java.lang.Class)
 	 */
 	@Override
+	@SuppressWarnings("unchecked")
 	public <T> List<T> findDistinct(Query query, String field, String collectionName, Class<?> entityClass,
 			Class<T> resultClass) {
 
@@ -830,20 +830,24 @@ public <T> List<T> findDistinct(Query query, String field, String collectionName
 		Document mappedQuery = queryMapper.getMappedObject(query.getQueryObject(), entity);
 		String mappedFieldName = queryMapper.getMappedFields(new Document(field, 1), entity).keySet().iterator().next();
 
-		Class<?> mongoDriverCompatibleType = getMongoDbFactory().getCodecFor(resultClass).map(Codec::getEncoderClass)
+		Class<T> mongoDriverCompatibleType = getMongoDbFactory().getCodecFor(resultClass).map(Codec::getEncoderClass)
 				.orElse((Class) BsonValue.class);
 
 		MongoIterable<?> result = execute((db) -> {
 
-			DistinctIterable<?> iterable = db.getCollection(collectionName).distinct(mappedFieldName, mappedQuery,
+			DistinctIterable<T> iterable = db.getCollection(collectionName).distinct(mappedFieldName, mappedQuery,
 					mongoDriverCompatibleType);
 
-			return query.getCollation().isPresent()
-					? iterable.collation(query.getCollation().map(Collation::toMongoCollation).get()) : iterable;
+			return query.getCollation().map(Collation::toMongoCollation).map(iterable::collation).orElse(iterable);
 		});
 
 		if (resultClass == Object.class || mongoDriverCompatibleType != resultClass) {
-			result = result.map(mapDistinctResult(getMostSpecificConversionTargetType(resultClass, entityClass, field)));
+
+			MongoConverter converter = getConverter();
+			DefaultDbRefResolver dbRefResolver = new DefaultDbRefResolver(mongoDbFactory);
+
+			result = result.map((source) -> converter.mapValueToTargetType(source,
+					getMostSpecificConversionTargetType(resultClass, entityClass, field), dbRefResolver));
 		}
 
 		try {
@@ -860,7 +864,7 @@ public <T> List<T> findDistinct(Query query, String field, String collectionName
 	 * @return the most specific conversion target type depending on user preference and domain type property.
 	 * @since 2.1
 	 */
-	private Class<?> getMostSpecificConversionTargetType(Class<?> userType, Class<?> domainType, String field) {
+	private static Class<?> getMostSpecificConversionTargetType(Class<?> userType, Class<?> domainType, String field) {
 
 		Class<?> conversionTargetType = userType;
 		try {
@@ -879,16 +883,6 @@ private Class<?> getMostSpecificConversionTargetType(Class<?> userType, Class<?>
 		return conversionTargetType;
 	}
 
-	/**
-	 * @param targetType the desired conversion target type.
-	 * @return new {@link Function} converting {@link BsonValue} into desired target type.
-	 * @since 2.1
-	 */
-	private <S, T> Function<S, T> mapDistinctResult(Class<T> targetType) {
-		return (source) -> getConverter().mapValueToTargetType(targetType, new DefaultDbRefResolver(mongoDbFactory))
-				.apply(source);
-	}
-
 	@Override
 	public <T> GeoResults<T> geoNear(NearQuery near, Class<T> entityClass) {
 		return geoNear(near, entityClass, determineCollectionName(entityClass));

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2018 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.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2018 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.
@@ -217,6 +217,7 @@ private Flux<T> doFind(@Nullable FindPublisherPreparer preparer) {
 					preparer != null ? preparer : getCursorPreparer(query));
 		}
 
+		@SuppressWarnings("unchecked")
 		private Flux<T> doFindDistinct(String field) {
 
 			return template.findDistinct(query, field, getCollectionName(), domainType,
@@ -259,19 +260,20 @@ public <R> TerminatingDistinct<R> as(Class<R> resultType) {
 
 				Assert.notNull(resultType, "ResultType must not be null!");
 
-				return new DistinctOperationSupport((ReactiveFindSupport) delegate.as(resultType), field);
+				return new DistinctOperationSupport<>((ReactiveFindSupport) delegate.as(resultType), field);
 			}
 
 			/*
 			 * (non-Javadoc)
 			 * @see org.springframework.data.mongodb.core.ReactiveFindOperation.DistinctWithQuery#matching(org.springframework.data.mongodb.core.query.Query)
 			 */
 			@Override
+			@SuppressWarnings("unchecked")
 			public TerminatingDistinct<T> matching(Query query) {
 
 				Assert.notNull(query, "Query must not be null!");
 
-				return new DistinctOperationSupport((ReactiveFindSupport) delegate.matching(query), field);
+				return new DistinctOperationSupport<>((ReactiveFindSupport<T>) delegate.matching(query), field);
 			}
 
 			/*

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

@@ -379,7 +379,7 @@ <T> Mono<MongoCollection<Document>> createCollection(Class<T> entityClass,
 
 	/**
 	 * Finds the distinct values for a specified {@literal field} across a single {@link MongoCollection} or view and
-	 * returns the results in a {@link List}.
+	 * returns the results in a {@link Flux}.
 	 *
 	 * @param field the name of the field to inspect for distinct values. Must not be {@literal null}.
 	 * @param entityClass the domain type used for determining the actual {@link MongoCollection}. Must not be
@@ -394,7 +394,7 @@ default <T> Flux<T> findDistinct(String field, Class<?> entityClass, Class<T> re
 
 	/**
 	 * Finds the distinct values for a specified {@literal field} across a single {@link MongoCollection} or view and
-	 * returns the results in a {@link List}.
+	 * returns the results in a {@link Flux}.
 	 *
 	 * @param query filter {@link Query} to restrict search. Must not be {@literal null}.
 	 * @param field the name of the field to inspect for distinct values. Must not be {@literal null}.
@@ -408,7 +408,7 @@ default <T> Flux<T> findDistinct(String field, Class<?> entityClass, Class<T> re
 
 	/**
 	 * Finds the distinct values for a specified {@literal field} across a single {@link MongoCollection} or view and
-	 * returns the results in a {@link List}.
+	 * returns the results in a {@link Flux}.
 	 *
 	 * @param query filter {@link Query} to restrict search. Must not be {@literal null}.
 	 * @param field the name of the field to inspect for distinct values. Must not be {@literal null}.
@@ -423,14 +423,13 @@ <T> Flux<T> findDistinct(Query query, String field, String collectionName, Class
 
 	/**
 	 * Finds the distinct values for a specified {@literal field} across a single {@link MongoCollection} or view and
-	 * returns the results in a {@link List}.
+	 * returns the results in a {@link Flux}.
 	 *
 	 * @param query filter {@link Query} to restrict search. Must not be {@literal null}.
 	 * @param field the name of the field to inspect for distinct values. Must not be {@literal null}.
 	 * @param collection the explicit name of the actual {@link MongoCollection}. Must not be {@literal null}.
 	 * @param resultClass the result type. Must not be {@literal null}.
-	 * @param <T>
-	 * @return
+	 * @return never {@literal null}.
 	 * @since 2.1
 	 */
 	default <T> Flux<T> findDistinct(Query query, String field, String collection, Class<T> resultClass) {