Do minor improvements to how we use field validators

bson/src/main/org/bson/AbstractBsonWriter.java

@@ -47,7 +47,7 @@ public abstract class AbstractBsonWriter implements BsonWriter, Closeable {
      * @param settings The writer settings.
      */
     protected AbstractBsonWriter(final BsonWriterSettings settings) {
-        this(settings, new NoOpFieldNameValidator());
+        this(settings, NoOpFieldNameValidator.INSTANCE);
     }
 
     /**

bson/src/main/org/bson/BsonBinaryWriter.java

@@ -67,7 +67,7 @@ public BsonBinaryWriter(final BsonOutput bsonOutput) {
      */
     public BsonBinaryWriter(final BsonWriterSettings settings, final BsonBinaryWriterSettings binaryWriterSettings,
                             final BsonOutput bsonOutput) {
-        this(settings, binaryWriterSettings, bsonOutput, new NoOpFieldNameValidator());
+        this(settings, binaryWriterSettings, bsonOutput, NoOpFieldNameValidator.INSTANCE);
     }
 
     /**

bson/src/main/org/bson/NoOpFieldNameValidator.java

@@ -16,7 +16,12 @@
 
 package org.bson;
 
-class NoOpFieldNameValidator implements FieldNameValidator {
+final class NoOpFieldNameValidator implements FieldNameValidator {
+    static final NoOpFieldNameValidator INSTANCE = new NoOpFieldNameValidator();
+
+    private NoOpFieldNameValidator() {
+    }
+
     @Override
     public boolean validate(final String fieldName) {
         return true;

driver-core/src/main/com/mongodb/internal/connection/CommandHelper.java

@@ -105,7 +105,7 @@ private static CommandMessage getCommandMessage(final String database, final Bso
                                                     final InternalConnection internalConnection,
                                                     final ClusterConnectionMode clusterConnectionMode,
                                                     @Nullable final ServerApi serverApi) {
-        return new CommandMessage(new MongoNamespace(database, COMMAND_COLLECTION_NAME), command, new NoOpFieldNameValidator(), primary(),
+        return new CommandMessage(new MongoNamespace(database, COMMAND_COLLECTION_NAME), command, NoOpFieldNameValidator.INSTANCE, primary(),
                 MessageSettings
                         .builder()
                          // Note: server version will be 0.0 at this point when called from InternalConnectionInitializer,

driver-core/src/main/com/mongodb/internal/connection/DefaultServerMonitor.java

@@ -308,7 +308,7 @@ private boolean shouldStreamResponses(final ServerDescription currentServerDescr
         private CommandMessage createCommandMessage(final BsonDocument command, final InternalConnection connection,
                 final ServerDescription currentServerDescription) {
             return new CommandMessage(new MongoNamespace("admin", COMMAND_COLLECTION_NAME), command,
-                    new NoOpFieldNameValidator(), primary(),
+                    NoOpFieldNameValidator.INSTANCE, primary(),
                     MessageSettings.builder()
                             .maxWireVersion(connection.getDescription().getMaxWireVersion())
                             .build(),

driver-core/src/main/com/mongodb/internal/operation/AsyncCommandBatchCursor.java

@@ -37,6 +37,7 @@
 import com.mongodb.internal.connection.Connection;
 import com.mongodb.internal.connection.OperationContext;
 import com.mongodb.internal.operation.AsyncOperationHelper.AsyncCallableConnectionWithCallback;
+import com.mongodb.internal.validator.NoOpFieldNameValidator;
 import com.mongodb.lang.Nullable;
 import org.bson.BsonDocument;
 import org.bson.BsonTimestamp;
@@ -53,7 +54,6 @@
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.FIRST_BATCH;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.MESSAGE_IF_CLOSED_AS_CURSOR;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.NEXT_BATCH;
-import static com.mongodb.internal.operation.CommandBatchCursorHelper.NO_OP_FIELD_NAME_VALIDATOR;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.getKillCursorsCommand;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.getMoreCommandDocument;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.logCommandCursorResult;
@@ -177,7 +177,7 @@ private void getMoreLoop(final AsyncConnection connection, final ServerCursor se
             final SingleResultCallback<List<T>> callback) {
         connection.commandAsync(namespace.getDatabaseName(),
                 getMoreCommandDocument(serverCursor.getId(), connection.getDescription(), namespace, batchSize, comment),
-                NO_OP_FIELD_NAME_VALIDATOR, ReadPreference.primary(),
+                NoOpFieldNameValidator.INSTANCE, ReadPreference.primary(),
                 CommandResultDocumentCodec.create(decoder, NEXT_BATCH),
                 assertNotNull(resourceManager.getConnectionSource()).getOperationContext(),
                 (commandResult, t) -> {
@@ -334,7 +334,7 @@ private void killServerCursor(final MongoNamespace namespace, final ServerCursor
             timeoutContext.resetToDefaultMaxTime();
 
             localConnection.commandAsync(namespace.getDatabaseName(), getKillCursorsCommand(namespace, localServerCursor),
-                    NO_OP_FIELD_NAME_VALIDATOR, ReadPreference.primary(), new BsonDocumentCodec(),
+                    NoOpFieldNameValidator.INSTANCE, ReadPreference.primary(), new BsonDocumentCodec(),
                     operationContext, (r, t) -> callback.onResult(null, null));
         }
     }

driver-core/src/main/com/mongodb/internal/operation/AsyncOperationHelper.java

@@ -225,7 +225,7 @@ static <T> void executeCommandAsync(final AsyncWriteBinding binding,
         Assertions.notNull("binding", binding);
         SingleResultCallback<T> addingRetryableLabelCallback = addingRetryableLabelCallback(callback,
                 connection.getDescription().getMaxWireVersion());
-        connection.commandAsync(database, command, new NoOpFieldNameValidator(), ReadPreference.primary(), new BsonDocumentCodec(),
+        connection.commandAsync(database, command, NoOpFieldNameValidator.INSTANCE, ReadPreference.primary(), new BsonDocumentCodec(),
                 binding.getOperationContext(), transformingWriteCallback(transformer, connection, addingRetryableLabelCallback));
     }
 
@@ -306,7 +306,7 @@ static <D, T> void createReadCommandAndExecuteAsync(
             callback.onResult(null, e);
             return;
         }
-        connection.commandAsync(database, command, new NoOpFieldNameValidator(), source.getReadPreference(), decoder,
+        connection.commandAsync(database, command, NoOpFieldNameValidator.INSTANCE, source.getReadPreference(), decoder,
                 operationContext, transformingReadCallback(transformer, source, connection, callback));
     }
 

driver-core/src/main/com/mongodb/internal/operation/BulkWriteBatch.java

@@ -54,7 +54,6 @@
 import org.bson.codecs.configuration.CodecRegistry;
 
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -69,6 +68,7 @@
 import static com.mongodb.internal.operation.OperationHelper.LOGGER;
 import static com.mongodb.internal.operation.OperationHelper.isRetryableWrite;
 import static com.mongodb.internal.operation.WriteConcernHelper.createWriteConcernError;
+import static java.util.Collections.singletonMap;
 import static org.bson.codecs.configuration.CodecRegistries.fromProviders;
 
 /**
@@ -77,7 +77,6 @@
 public final class BulkWriteBatch {
     private static final CodecRegistry REGISTRY = fromProviders(new BsonValueCodecProvider());
     private static final Decoder<BsonDocument> DECODER = REGISTRY.get(BsonDocument.class);
-    private static final FieldNameValidator NO_OP_FIELD_NAME_VALIDATOR = new NoOpFieldNameValidator();
 
     private final MongoNamespace namespace;
     private final ConnectionDescription connectionDescription;
@@ -279,15 +278,15 @@ BulkWriteBatch getNextBatch() {
 
     FieldNameValidator getFieldNameValidator() {
         if (batchType == UPDATE || batchType == REPLACE) {
-            Map<String, FieldNameValidator> rootMap = new HashMap<>();
+            Map<String, FieldNameValidator> rootMap;
             if (batchType == REPLACE) {
-                rootMap.put("u", new ReplacingDocumentFieldNameValidator());
+                rootMap = singletonMap("u", ReplacingDocumentFieldNameValidator.INSTANCE);
             } else {
-                rootMap.put("u", new UpdateFieldNameValidator());
+                rootMap = singletonMap("u", new UpdateFieldNameValidator());
             }
-            return new MappedFieldNameValidator(NO_OP_FIELD_NAME_VALIDATOR, rootMap);
+            return new MappedFieldNameValidator(NoOpFieldNameValidator.INSTANCE, rootMap);
         } else {
-            return NO_OP_FIELD_NAME_VALIDATOR;
+            return NoOpFieldNameValidator.INSTANCE;
         }
     }
 

driver-core/src/main/com/mongodb/internal/operation/CommandBatchCursor.java

@@ -33,6 +33,7 @@
 import com.mongodb.internal.binding.ConnectionSource;
 import com.mongodb.internal.connection.Connection;
 import com.mongodb.internal.connection.OperationContext;
+import com.mongodb.internal.validator.NoOpFieldNameValidator;
 import com.mongodb.lang.Nullable;
 import org.bson.BsonDocument;
 import org.bson.BsonTimestamp;
@@ -52,7 +53,6 @@
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.MESSAGE_IF_CLOSED_AS_CURSOR;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.MESSAGE_IF_CLOSED_AS_ITERATOR;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.NEXT_BATCH;
-import static com.mongodb.internal.operation.CommandBatchCursorHelper.NO_OP_FIELD_NAME_VALIDATOR;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.getKillCursorsCommand;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.getMoreCommandDocument;
 import static com.mongodb.internal.operation.CommandBatchCursorHelper.logCommandCursorResult;
@@ -237,7 +237,7 @@ private void getMore() {
                         assertNotNull(
                             connection.command(namespace.getDatabaseName(),
                                  getMoreCommandDocument(serverCursor.getId(), connection.getDescription(), namespace, batchSize, comment),
-                                 NO_OP_FIELD_NAME_VALIDATOR,
+                                 NoOpFieldNameValidator.INSTANCE,
                                  ReadPreference.primary(),
                                  CommandResultDocumentCodec.create(decoder, NEXT_BATCH),
                                  assertNotNull(resourceManager.getConnectionSource()).getOperationContext())));
@@ -374,7 +374,7 @@ private void killServerCursor(final MongoNamespace namespace, final ServerCursor
             timeoutContext.resetToDefaultMaxTime();
 
             localConnection.command(namespace.getDatabaseName(), getKillCursorsCommand(namespace, localServerCursor),
-                    NO_OP_FIELD_NAME_VALIDATOR, ReadPreference.primary(), new BsonDocumentCodec(), operationContext);
+                    NoOpFieldNameValidator.INSTANCE, ReadPreference.primary(), new BsonDocumentCodec(), operationContext);
         }
     }
 }

driver-core/src/main/com/mongodb/internal/operation/CommandBatchCursorHelper.java

@@ -22,15 +22,13 @@
 import com.mongodb.MongoQueryException;
 import com.mongodb.ServerCursor;
 import com.mongodb.connection.ConnectionDescription;
-import com.mongodb.internal.validator.NoOpFieldNameValidator;
 import com.mongodb.lang.Nullable;
 import org.bson.BsonArray;
 import org.bson.BsonDocument;
 import org.bson.BsonInt32;
 import org.bson.BsonInt64;
 import org.bson.BsonString;
 import org.bson.BsonValue;
-import org.bson.FieldNameValidator;
 
 import static com.mongodb.internal.operation.DocumentHelper.putIfNotNull;
 import static com.mongodb.internal.operation.OperationHelper.LOGGER;
@@ -42,7 +40,6 @@ final class CommandBatchCursorHelper {
 
     static final String FIRST_BATCH = "firstBatch";
     static final String NEXT_BATCH = "nextBatch";
-    static final FieldNameValidator NO_OP_FIELD_NAME_VALIDATOR = new NoOpFieldNameValidator();
     static final String MESSAGE_IF_CLOSED_AS_CURSOR = "Cursor has been closed";
     static final String MESSAGE_IF_CLOSED_AS_ITERATOR = "Iterator has been closed";
 

driver-core/src/main/com/mongodb/internal/operation/FindAndDeleteOperation.java

@@ -89,7 +89,7 @@ public FindAndDeleteOperation<T> let(@Nullable final BsonDocument variables) {
     }
 
     protected FieldNameValidator getFieldNameValidator() {
-        return new NoOpFieldNameValidator();
+        return NoOpFieldNameValidator.INSTANCE;
     }
 
     protected void specializeCommand(final BsonDocument commandDocument, final ConnectionDescription connectionDescription) {

driver-core/src/main/com/mongodb/internal/operation/FindAndReplaceOperation.java

@@ -30,11 +30,9 @@
 import org.bson.FieldNameValidator;
 import org.bson.codecs.Decoder;
 
-import java.util.HashMap;
-import java.util.Map;
-
 import static com.mongodb.assertions.Assertions.notNull;
 import static com.mongodb.internal.operation.DocumentHelper.putIfTrue;
+import static java.util.Collections.singletonMap;
 
 /**
  * An operation that atomically finds and replaces a single document.
@@ -133,9 +131,9 @@ public FindAndReplaceOperation<T> let(@Nullable final BsonDocument variables) {
     }
 
     protected FieldNameValidator getFieldNameValidator() {
-        Map<String, FieldNameValidator> map = new HashMap<>();
-        map.put("update", new ReplacingDocumentFieldNameValidator());
-        return new MappedFieldNameValidator(new NoOpFieldNameValidator(), map);
+        return new MappedFieldNameValidator(
+                NoOpFieldNameValidator.INSTANCE,
+                singletonMap("update", ReplacingDocumentFieldNameValidator.INSTANCE));
     }
 
     protected void specializeCommand(final BsonDocument commandDocument, final ConnectionDescription connectionDescription) {

driver-core/src/main/com/mongodb/internal/operation/FindAndUpdateOperation.java

@@ -31,13 +31,12 @@
 import org.bson.FieldNameValidator;
 import org.bson.codecs.Decoder;
 
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 
 import static com.mongodb.assertions.Assertions.notNull;
 import static com.mongodb.internal.operation.DocumentHelper.putIfNotNull;
 import static com.mongodb.internal.operation.DocumentHelper.putIfTrue;
+import static java.util.Collections.singletonMap;
 
 /**
  * An operation that atomically finds and updates a single document.
@@ -161,9 +160,7 @@ public FindAndUpdateOperation<T> let(@Nullable final BsonDocument variables) {
     }
 
     protected FieldNameValidator getFieldNameValidator() {
-        Map<String, FieldNameValidator> map = new HashMap<>();
-        map.put("update", new UpdateFieldNameValidator());
-        return new MappedFieldNameValidator(new NoOpFieldNameValidator(), map);
+        return new MappedFieldNameValidator(NoOpFieldNameValidator.INSTANCE, singletonMap("update", new UpdateFieldNameValidator()));
     }
 
     protected void specializeCommand(final BsonDocument commandDocument, final ConnectionDescription connectionDescription) {

driver-core/src/main/com/mongodb/internal/operation/MixedBulkWriteOperation.java

@@ -47,7 +47,6 @@
 import org.bson.BsonDocument;
 import org.bson.BsonString;
 import org.bson.BsonValue;
-import org.bson.FieldNameValidator;
 
 import java.util.List;
 import java.util.Optional;
@@ -77,7 +76,6 @@
  * <p>This class is not part of the public API and may be removed or changed at any time</p>
  */
 public class MixedBulkWriteOperation implements AsyncWriteOperation<BulkWriteResult>, WriteOperation<BulkWriteResult> {
-    private static final FieldNameValidator NO_OP_FIELD_NAME_VALIDATOR = new NoOpFieldNameValidator();
     private final MongoNamespace namespace;
     private final List<? extends WriteRequest> writeRequests;
     private final boolean ordered;
@@ -408,14 +406,14 @@ private boolean handleMongoWriteConcernWithResponseExceptionAsync(final RetrySta
 
     @Nullable
     private BsonDocument executeCommand(final OperationContext operationContext, final Connection connection, final BulkWriteBatch batch) {
-        return connection.command(namespace.getDatabaseName(), batch.getCommand(), NO_OP_FIELD_NAME_VALIDATOR, null, batch.getDecoder(),
+        return connection.command(namespace.getDatabaseName(), batch.getCommand(), NoOpFieldNameValidator.INSTANCE, null, batch.getDecoder(),
                 operationContext, shouldAcknowledge(batch, operationContext.getSessionContext()),
                 batch.getPayload(), batch.getFieldNameValidator());
     }
 
     private void executeCommandAsync(final OperationContext operationContext, final AsyncConnection connection, final BulkWriteBatch batch,
             final SingleResultCallback<BsonDocument> callback) {
-        connection.commandAsync(namespace.getDatabaseName(), batch.getCommand(), NO_OP_FIELD_NAME_VALIDATOR, null, batch.getDecoder(),
+        connection.commandAsync(namespace.getDatabaseName(), batch.getCommand(), NoOpFieldNameValidator.INSTANCE, null, batch.getDecoder(),
                 operationContext, shouldAcknowledge(batch, operationContext.getSessionContext()),
                 batch.getPayload(), batch.getFieldNameValidator(), callback);
     }

driver-core/src/main/com/mongodb/internal/operation/SyncOperationHelper.java

@@ -210,7 +210,7 @@ static <T> T executeCommand(final WriteBinding binding, final String database, f
                                 commandCreator.create(binding.getOperationContext(),
                                         source.getServerDescription(),
                                         connection.getDescription()),
-                                new NoOpFieldNameValidator(), primary(), BSON_DOCUMENT_CODEC, binding.getOperationContext())),
+                                NoOpFieldNameValidator.INSTANCE, primary(), BSON_DOCUMENT_CODEC, binding.getOperationContext())),
                         connection));
     }
 
@@ -219,7 +219,7 @@ static <D, T> T executeCommand(final WriteBinding binding, final String database
                                    final Decoder<D> decoder, final CommandWriteTransformer<D, T> transformer) {
         return withSourceAndConnection(binding::getWriteConnectionSource, false, (source, connection) ->
                 transformer.apply(assertNotNull(
-                        connection.command(database, command, new NoOpFieldNameValidator(), primary(), decoder,
+                        connection.command(database, command, NoOpFieldNameValidator.INSTANCE, primary(), decoder,
                                 binding.getOperationContext())), connection));
     }
 
@@ -228,7 +228,7 @@ static <T> T executeCommand(final WriteBinding binding, final String database, f
                                 final Connection connection, final CommandWriteTransformer<BsonDocument, T> transformer) {
         notNull("binding", binding);
         return transformer.apply(assertNotNull(
-                connection.command(database, command, new NoOpFieldNameValidator(), primary(), BSON_DOCUMENT_CODEC,
+                connection.command(database, command, NoOpFieldNameValidator.INSTANCE, primary(), BSON_DOCUMENT_CODEC,
                         binding.getOperationContext())),
                 connection);
     }
@@ -295,7 +295,7 @@ static <D, T> T createReadCommandAndExecute(
         BsonDocument command = commandCreator.create(operationContext, source.getServerDescription(),
                 connection.getDescription());
         retryState.attach(AttachmentKeys.commandDescriptionSupplier(), command::getFirstKey, false);
-        return transformer.apply(assertNotNull(connection.command(database, command, new NoOpFieldNameValidator(),
+        return transformer.apply(assertNotNull(connection.command(database, command, NoOpFieldNameValidator.INSTANCE,
                 source.getReadPreference(), decoder, operationContext)), source, connection);
     }