Polishing.

Add assertions and missing Override annotations. Avoid recursive self-call on getClassLoader. Extend documentation.

See #1627
Original pull request: #4389

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/gridfs/GridFsTemplate.java

@@ -58,10 +58,14 @@ import com.mongodb.client.gridfs.model.GridFSUploadOptions;
  */
 public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOperations, ResourcePatternResolver {
 
-	private Supplier<GridFSBucket> bucketSupplier;
+	private final Supplier<GridFSBucket> bucketSupplier;
 
 	/**
 	 * Creates a new {@link GridFsTemplate} using the given {@link MongoDatabaseFactory} and {@link MongoConverter}.
+	 * <p>
+	 * Note that the {@link GridFSBucket} is obtained only once from {@link MongoDatabaseFactory#getMongoDatabase()
+	 * MongoDatabase}. Use {@link #GridFsTemplate(MongoConverter, Supplier)} if you want to use different buckets from the
+	 * same Template instance.
 	 *
 	 * @param dbFactory must not be {@literal null}.
 	 * @param converter must not be {@literal null}.
@@ -72,6 +76,10 @@ public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOpe
 
 	/**
 	 * Creates a new {@link GridFsTemplate} using the given {@link MongoDatabaseFactory} and {@link MongoConverter}.
+	 * <p>
+	 * Note that the {@link GridFSBucket} is obtained only once from {@link MongoDatabaseFactory#getMongoDatabase()
+	 * MongoDatabase}. Use {@link #GridFsTemplate(MongoConverter, Supplier)} if you want to use different buckets from the
+	 * same Template instance.
 	 *
 	 * @param dbFactory must not be {@literal null}.
 	 * @param converter must not be {@literal null}.
@@ -93,14 +101,19 @@ public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOpe
 
 		super(converter);
 
+		Assert.notNull(gridFSBucket, "GridFSBucket supplier must not be null");
+
 		this.bucketSupplier = gridFSBucket;
 	}
 
+	@Override
 	public ObjectId store(InputStream content, @Nullable String filename, @Nullable String contentType,
 			@Nullable Object metadata) {
 		return store(content, filename, contentType, toDocument(metadata));
 	}
 
+	@Override
+	@SuppressWarnings("unchecked")
 	public <T> T store(GridFsObject<T, InputStream> upload) {
 
 		GridFSUploadOptions uploadOptions = computeUploadOptionsFor(upload.getOptions().getContentType(),
@@ -119,6 +132,7 @@ public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOpe
 		return upload.getFileId();
 	}
 
+	@Override
 	public GridFSFindIterable find(Query query) {
 
 		Assert.notNull(query, "Query must not be null");
@@ -139,10 +153,12 @@ public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOpe
 		return iterable;
 	}
 
+	@Override
 	public GridFSFile findOne(Query query) {
 		return find(query).first();
 	}
 
+	@Override
 	public void delete(Query query) {
 
 		for (GridFSFile gridFSFile : find(query)) {
@@ -150,10 +166,12 @@ public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOpe
 		}
 	}
 
+	@Override
 	public ClassLoader getClassLoader() {
-		return this.getClassLoader();
+		return null;
 	}
 
+	@Override
 	public GridFsResource getResource(String location) {
 
 		return Optional.ofNullable(findOne(query(whereFilename().is(location)))) //
@@ -161,6 +179,7 @@ public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOpe
 				.orElseGet(() -> GridFsResource.absent(location));
 	}
 
+	@Override
 	public GridFsResource getResource(GridFSFile file) {
 
 		Assert.notNull(file, "GridFSFile must not be null");
@@ -168,6 +187,7 @@ public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOpe
 		return new GridFsResource(file, getGridFs().openDownloadStream(file.getId()));
 	}
 
+	@Override
 	public GridFsResource[] getResources(String locationPattern) {
 
 		if (!StringUtils.hasText(locationPattern)) {
@@ -191,12 +211,14 @@ public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOpe
 		return new GridFsResource[] { getResource(locationPattern) };
 	}
 
-	GridFSBucket getGridFs() {
+	private GridFSBucket getGridFs() {
 		return this.bucketSupplier.get();
 	}
 
 	private static GridFSBucket getGridFs(MongoDatabaseFactory dbFactory, @Nullable String bucket) {
 
+		Assert.notNull(dbFactory, "MongoDatabaseFactory must not be null");
+
 		MongoDatabase db = dbFactory.getMongoDatabase();
 		return bucket == null ? GridFSBuckets.create(db) : GridFSBuckets.create(db, bucket);
 	}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/gridfs/ReactiveGridFsTemplate.java

@@ -62,11 +62,16 @@ import com.mongodb.reactivestreams.client.gridfs.GridFSUploadPublisher;
 public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements ReactiveGridFsOperations {
 
 	private final DataBufferFactory dataBufferFactory;
-	private Mono<GridFSBucket> bucketSupplier;
+	private final Mono<GridFSBucket> bucketSupplier;
 
 	/**
 	 * Creates a new {@link ReactiveGridFsTemplate} using the given {@link ReactiveMongoDatabaseFactory} and
 	 * {@link MongoConverter}.
+	 * <p>
+	 * Note that the {@link GridFSBucket} is obtained only once from
+	 * {@link ReactiveMongoDatabaseFactory#getMongoDatabase() MongoDatabase}. Use
+	 * {@link #ReactiveGridFsTemplate(MongoConverter, Mono, DataBufferFactory)} if you want to use different buckets from
+	 * the same Template instance.
 	 *
 	 * @param dbFactory must not be {@literal null}.
 	 * @param converter must not be {@literal null}.
@@ -78,10 +83,15 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 	/**
 	 * Creates a new {@link ReactiveGridFsTemplate} using the given {@link ReactiveMongoDatabaseFactory} and
 	 * {@link MongoConverter}.
+	 * <p>
+	 * Note that the {@link GridFSBucket} is obtained only once from
+	 * {@link ReactiveMongoDatabaseFactory#getMongoDatabase() MongoDatabase}. Use
+	 * {@link #ReactiveGridFsTemplate(MongoConverter, Mono, DataBufferFactory)} if you want to use different buckets from
+	 * the same Template instance.
 	 *
 	 * @param dbFactory must not be {@literal null}.
 	 * @param converter must not be {@literal null}.
-	 * @param bucket
+	 * @param bucket can be {@literal null}.
 	 */
 	public ReactiveGridFsTemplate(ReactiveMongoDatabaseFactory dbFactory, MongoConverter converter,
 			@Nullable String bucket) {
@@ -91,11 +101,16 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 	/**
 	 * Creates a new {@link ReactiveGridFsTemplate} using the given {@link DataBufferFactory},
 	 * {@link ReactiveMongoDatabaseFactory} and {@link MongoConverter}.
+	 * <p>
+	 * Note that the {@link GridFSBucket} is obtained only once from
+	 * {@link ReactiveMongoDatabaseFactory#getMongoDatabase() MongoDatabase}. Use
+	 * {@link #ReactiveGridFsTemplate(MongoConverter, Mono, DataBufferFactory)} if you want to use different buckets from
+	 * the same Template instance.
 	 *
 	 * @param dataBufferFactory must not be {@literal null}.
 	 * @param dbFactory must not be {@literal null}.
 	 * @param converter must not be {@literal null}.
-	 * @param bucket
+	 * @param bucket can be {@literal null}.
 	 */
 	public ReactiveGridFsTemplate(DataBufferFactory dataBufferFactory, ReactiveMongoDatabaseFactory dbFactory,
 			MongoConverter converter, @Nullable String bucket) {
@@ -105,7 +120,7 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 	/**
 	 * Creates a new {@link ReactiveGridFsTemplate} using the given {@link MongoConverter}, {@link Mono} emitting a
 	 * {@link ReactiveMongoDatabaseFactory} and {@link DataBufferFactory}.
-	 * 
+	 *
 	 * @param converter must not be {@literal null}.
 	 * @param gridFSBucket must not be {@literal null}.
 	 * @param dataBufferFactory must not be {@literal null}.
@@ -116,6 +131,7 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 
 		super(converter);
 
+		Assert.notNull(gridFSBucket, "GridFSBucket Mono must not be null");
 		Assert.notNull(dataBufferFactory, "DataBufferFactory must not be null");
 
 		this.bucketSupplier = gridFSBucket;
@@ -128,6 +144,8 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 		return store(content, filename, contentType, toDocument(metadata));
 	}
 
+	@Override
+	@SuppressWarnings("unchecked")
 	public <T> Mono<T> store(GridFsObject<T, Publisher<DataBuffer>> upload) {
 
 		GridFSUploadOptions uploadOptions = computeUploadOptionsFor(upload.getOptions().getContentType(),
@@ -258,15 +276,18 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 		return doGetBucket().flatMapMany(callback::doInBucket);
 	}
 
-	static Mono<GridFSBucket> doGetBucket(ReactiveMongoDatabaseFactory dbFactory, @Nullable String bucket) {
-		return dbFactory.getMongoDatabase()
-				.map(db -> bucket == null ? GridFSBuckets.create(db) : GridFSBuckets.create(db, bucket));
-	}
-
 	protected Mono<GridFSBucket> doGetBucket() {
 		return bucketSupplier;
 	}
 
+	private static Mono<GridFSBucket> doGetBucket(ReactiveMongoDatabaseFactory dbFactory, @Nullable String bucket) {
+
+		Assert.notNull(dbFactory, "ReactiveMongoDatabaseFactory must not be null");
+
+		return dbFactory.getMongoDatabase()
+				.map(db -> bucket == null ? GridFSBuckets.create(db) : GridFSBuckets.create(db, bucket));
+	}
+
 	/**
 	 * @param <T>
 	 * @author Mathieu Ouellet
@@ -289,6 +310,7 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 			this.sortObject = sortObject;
 		}
 
+		@Override
 		public GridFSFindPublisher doInBucket(GridFSBucket bucket) {
 
 			GridFSFindPublisher findPublisher = bucket.find(queryObject).sort(sortObject);
@@ -326,21 +348,8 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 		}
 	}
 
-	private static class UploadCallback implements ReactiveBucketCallback<Void> {
-
-		private final BsonValue fileId;
-		private final String filename;
-		private final Publisher<ByteBuffer> source;
-		private final GridFSUploadOptions uploadOptions;
-
-		public UploadCallback(BsonValue fileId, String filename, Publisher<ByteBuffer> source,
-				GridFSUploadOptions uploadOptions) {
-
-			this.fileId = fileId;
-			this.filename = filename;
-			this.source = source;
-			this.uploadOptions = uploadOptions;
-		}
+	private record UploadCallback(BsonValue fileId, String filename, Publisher<ByteBuffer> source,
+			GridFSUploadOptions uploadOptions) implements ReactiveBucketCallback<Void> {
 
 		@Override
 		public GridFSUploadPublisher<Void> doInBucket(GridFSBucket bucket) {
@@ -348,19 +357,8 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 		}
 	}
 
-	private static class AutoIdCreatingUploadCallback implements ReactiveBucketCallback<ObjectId> {
-
-		private final String filename;
-		private final Publisher<ByteBuffer> source;
-		private final GridFSUploadOptions uploadOptions;
-
-		public AutoIdCreatingUploadCallback(String filename, Publisher<ByteBuffer> source,
-				GridFSUploadOptions uploadOptions) {
-
-			this.filename = filename;
-			this.source = source;
-			this.uploadOptions = uploadOptions;
-		}
+	private record AutoIdCreatingUploadCallback(String filename, Publisher<ByteBuffer> source,
+			GridFSUploadOptions uploadOptions) implements ReactiveBucketCallback<ObjectId> {
 
 		@Override
 		public GridFSUploadPublisher<ObjectId> doInBucket(GridFSBucket bucket) {
@@ -368,13 +366,7 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 		}
 	}
 
-	private static class DeleteCallback implements ReactiveBucketCallback<Void> {
-
-		private final BsonValue id;
-
-		public DeleteCallback(BsonValue id) {
-			this.id = id;
-		}
+	private record DeleteCallback(BsonValue id) implements ReactiveBucketCallback<Void> {
 
 		@Override
 		public Publisher<Void> doInBucket(GridFSBucket bucket) {

src/main/asciidoc/reference/gridfs.adoc

@@ -3,7 +3,6 @@
 
 MongoDB supports storing binary files inside its filesystem, GridFS. Spring Data MongoDB provides a `GridFsOperations` interface as well as the corresponding implementation, `GridFsTemplate`, to let you interact with the filesystem. You can set up a `GridFsTemplate` instance by handing it a `MongoDatabaseFactory` as well as a `MongoConverter`, as the following example shows:
 
-
 ====
 .Java
 [source,java,role="primary"]
@@ -82,7 +81,7 @@ class GridFsClient {
 
   @Test
   public void findFilesInGridFs() {
-    GridFSFindIterable result = operations.find(query(whereFilename().is("filename.txt")))
+    GridFSFindIterable result = operations.find(query(whereFilename().is("filename.txt")));
   }
 }
 ----
@@ -110,3 +109,7 @@ class GridFsClient {
 ====
 
 `GridFsOperations` extends `ResourcePatternResolver` and lets the `GridFsTemplate` (for example) to be plugged into an `ApplicationContext` to read Spring Config files from MongoDB database.
+
+NOTE: By default, `GridFsTemplate` obtains `GridFSBucket` once upon the first GridFS interaction.
+After that, the Template instance reuses the cached bucket.
+To use different buckets, from the same Template instance use the constructor accepting `Supplier<GridFSBucket>`.