com.google.cloud.datastore

Interface Datastore

All Superinterfaces:

DatastoreReader, DatastoreReaderWriter, DatastoreWriter, Service<DatastoreOptions>

public interface Datastore
extends Service<DatastoreOptions>, DatastoreReaderWriter

An interface for Google Cloud Datastore.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	Datastore.TransactionCallable<T> A callback for running with a transactional DatastoreReaderWriter.

Method Summary

Methods

Modifier and Type	Method and Description
List<Entity>	add(FullEntity<?>... entities) Datastore add operation: inserts the provided entities.
Entity	add(FullEntity<?> entity) Datastore add operation: inserts the provided entity.
List<Key>	allocateId(IncompleteKey... keys) Returns a list of keys using the allocated ids ordered by the input.
Key	allocateId(IncompleteKey key) Allocate a unique id for the given key.
void	delete(Key... keys) A datastore delete operation.
List<Entity>	fetch(Iterable<Key> keys, ReadOption... options) Returns a list with a value for each given key (ordered by input).
Iterator<Entity>	get(Iterable<Key> keys, ReadOption... options) Returns an Entity for each given Key that exists in the Datastore.
Entity	get(Key key, ReadOption... options) Returns an Entity for the given Key or null if it doesn't exist.
Batch	newBatch() Returns a new Batch for processing multiple write operations in one request.
KeyFactory	newKeyFactory() Returns a new KeyFactory for this service
Transaction	newTransaction() Returns a new Datastore transaction.
List<Entity>	put(FullEntity<?>... entities) A Datastore put (a.k.a upsert) operation: creates an entity if it does not exist, updates it otherwise.
Entity	put(FullEntity<?> entity) A Datastore put (a.k.a upsert) operation: inserts an entity if it does not exist, updates it otherwise.
<T> QueryResults<T>	run(Query<T> query, ReadOption... options) Submits a Query and returns its result.
<T> T	runInTransaction(Datastore.TransactionCallable<T> callable) Invokes the callback's Datastore.TransactionCallable.run(com.google.cloud.datastore.DatastoreReaderWriter) method with a DatastoreReaderWriter that is associated with a new transaction.
void	update(Entity... entities) A Datastore update operation.

Methods inherited from interface com.google.cloud.Service

getOptions, options

Methods inherited from interface com.google.cloud.datastore.DatastoreReader

fetch, get, get, run

Method Detail

newTransaction

Transaction newTransaction()

Returns a new Datastore transaction.

Throws:

DatastoreException - upon failure

runInTransaction

<T> T runInTransaction(Datastore.TransactionCallable<T> callable)

Invokes the callback's Datastore.TransactionCallable.run(com.google.cloud.datastore.DatastoreReaderWriter) method with a DatastoreReaderWriter that is associated with a new transaction. The transaction will be committed upon successful invocation. Any thrown exception will cause the transaction to rollback and will be propagated as a DatastoreException with the original exception as its root cause.

Example of running in a transaction.

 String callableResult = "my_callable_result";
 TransactionCallable<String> callable = new TransactionCallable<String>() {
   public String run(DatastoreReaderWriter readerWriter) {
     // use readerWriter to run in transaction
     return callableResult;
   }
 };
 String result = datastore.runInTransaction(callable);
 

Parameters:

callable - the callback to call with a newly created transactional readerWriter

Throws:

DatastoreException - upon failure

newBatch

Batch newBatch()

Returns a new Batch for processing multiple write operations in one request.

Example of starting a new batch.

 String keyName1 = "my_key_name_1";
 String keyName2 = "my_key_name_2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 Batch batch = datastore.newBatch();
 Entity entity1 = Entity.newBuilder(key1).set("name", "John").build();
 Entity entity2 = Entity.newBuilder(key2).set("title", "title").build();
 batch.add(entity1);
 batch.add(entity2);
 batch.submit();
 

allocateId

Key allocateId(IncompleteKey key)

Allocate a unique id for the given key. The returned key will have the same information (projectId, kind, namespace and ancestors) as the given key and will have a newly assigned id.

Example of allocating an id.

 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 IncompleteKey incompleteKey = keyFactory.newKey();
 
 // let cloud datastore automatically assign an id
 Key key = datastore.allocateId(incompleteKey);
 

Throws:

DatastoreException - upon failure

allocateId

List<Key> allocateId(IncompleteKey... keys)

Returns a list of keys using the allocated ids ordered by the input.

Example of allocating multiple ids in a single batch.

 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 IncompleteKey incompleteKey1 = keyFactory.newKey();
 IncompleteKey incompleteKey2 = keyFactory.newKey();
 
 // let cloud datastore automatically assign the ids
 List<Key> keys = datastore.allocateId(incompleteKey1, incompleteKey2);
 

Throws:

DatastoreException - upon failure

See Also:

allocateId(IncompleteKey)

add

Entity add(FullEntity<?> entity)

Datastore add operation: inserts the provided entity. This method will automatically allocate an id if necessary.

If an entity for entity.getKey() does not exists, entity is inserted. Otherwise, a DatastoreException is thrown with BaseServiceException.getReason() equal to "ALREADY_EXISTS".

Example of adding a single entity.

 String keyName = "my_key_name";
 Key key = datastore.newKeyFactory().setKind("MyKind").newKey(keyName);
 Entity.Builder entityBuilder = Entity.newBuilder(key);
 entityBuilder.set("propertyName", "value");
 Entity entity = entityBuilder.build();
 try {
   datastore.add(entity);
 } catch (DatastoreException ex) {
   if ("ALREADY_EXISTS".equals(ex.getReason())) {
     // entity.getKey() already exists
   }
 }
 

Specified by:

add in interface DatastoreWriter

Parameters:

entity - the entity to add

Returns:

an Entity with the same properties and a key that is either newly allocated or the same one if key is already complete

Throws:

DatastoreException - upon failure or if an entity for entity.getKey() already exists

add

List<Entity> add(FullEntity<?>... entities)

Datastore add operation: inserts the provided entities. This method will automatically allocate id for any entity with an incomplete key.

If none of entities' keys exist, all entities are inserted. If any of entities' keys already exists the method throws a DatastoreException with BaseServiceException.getReason() equal to "ALREADY_EXISTS". All entities in entities whose key did not exist are inserted. To achieve a transactional behavior, use Transaction.

Example of adding multiple entities.

 String keyName1 = "my_key_name1";
 String keyName2 = "my_key_name2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Entity.Builder entityBuilder1 = Entity.newBuilder(key1);
 entityBuilder1.set("propertyName", "value1");
 Entity entity1 = entityBuilder1.build();
 
 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 Entity.Builder entityBuilder2 = Entity.newBuilder(key2);
 entityBuilder2.set("propertyName", "value2");
 Entity entity2 = entityBuilder2.build();
 
 try {
   datastore.add(entity1, entity2);
 } catch (DatastoreException ex) {
   if ("ALREADY_EXISTS".equals(ex.getReason())) {
     // at least one of entity1.getKey() and entity2.getKey() already exists
   }
 }
 

Specified by:

add in interface DatastoreWriter

Returns:

a list of Entity ordered by input with the same properties and a key that is either newly allocated or the same one if was already complete

Throws:

DatastoreException - upon failure or if any of entities' keys already exists

See Also:

DatastoreWriter.add(FullEntity)

update

void update(Entity... entities)

A Datastore update operation. The operation will fail if an entity with the same key does not already exist.

Example of updating multiple entities.

 String keyName1 = "my_key_name_1";
 String keyName2 = "my_key_name_2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Entity.Builder entityBuilder1 = Entity.newBuilder(key1);
 entityBuilder1.set("propertyName", "updatedValue1");
 Entity entity1 = entityBuilder1.build();
 
 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 Entity.Builder entityBuilder2 = Entity.newBuilder(key2);
 entityBuilder2.set("propertyName", "updatedValue2");
 Entity entity2 = entityBuilder2.build();
 
 datastore.update(entity1, entity2);
 

Specified by:

update in interface DatastoreWriter

Throws:

DatastoreException - upon failure

put

Entity put(FullEntity<?> entity)

A Datastore put (a.k.a upsert) operation: inserts an entity if it does not exist, updates it otherwise. This method will automatically allocate an id if necessary.

Example of putting a single entity.

 String keyName = "my_key_name";
 Key key = datastore.newKeyFactory().setKind("MyKind").newKey(keyName);
 Entity.Builder entityBuilder = Entity.newBuilder(key);
 entityBuilder.set("propertyName", "value");
 Entity entity = entityBuilder.build();
 datastore.put(entity);
 

Specified by:

put in interface DatastoreWriter

Parameters:

entity - the entity to put

Returns:

an Entity with the same properties and a key that is either newly allocated or the same one if key is already complete

Throws:

DatastoreException - upon failure

put

List<Entity> put(FullEntity<?>... entities)

A Datastore put (a.k.a upsert) operation: creates an entity if it does not exist, updates it otherwise. This method will automatically allocate id for any entity with an incomplete key.

Example of putting multiple entities.

 String keyName1 = "my_key_name1";
 String keyName2 = "my_key_name2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Entity.Builder entityBuilder1 = Entity.newBuilder(key1);
 entityBuilder1.set("propertyName", "value1");
 Entity entity1 = entityBuilder1.build();
 
 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 Entity.Builder entityBuilder2 = Entity.newBuilder(key2);
 entityBuilder2.set("propertyName", "value2");
 Entity entity2 = entityBuilder2.build();
 
 datastore.put(entity1, entity2);
 

Specified by:

put in interface DatastoreWriter

Returns:

a list of updated or inserted Entity, ordered by input. Returned keys are either newly allocated or the same one if was already complete.

Throws:

DatastoreException - upon failure

delete

void delete(Key... keys)

A datastore delete operation. It is OK to request the deletion of a non-existing key.

Example of deleting multiple entities.

 String keyName1 = "my_key_name1";
 String keyName2 = "my_key_name2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 datastore.delete(key1, key2);
 

Specified by:

delete in interface DatastoreWriter

Throws:

DatastoreException - upon failure

newKeyFactory

KeyFactory newKeyFactory()

Returns a new KeyFactory for this service

Example of creating a KeyFactory.

 KeyFactory keyFactory = datastore.newKeyFactory();
 

get

Entity get(Key key,
         ReadOption... options)

Returns an Entity for the given Key or null if it doesn't exist. ReadOptions can be specified if desired.

Example of getting an entity.

 String keyName = "my_key_name";
 Key key = datastore.newKeyFactory().setKind("MyKind").newKey(keyName);
 Entity entity = datastore.get(key);
 // Do something with the entity
 

Throws:

DatastoreException - upon failure

get

Iterator<Entity> get(Iterable<Key> keys,
                   ReadOption... options)

Returns an Entity for each given Key that exists in the Datastore. The order of the result is unspecified. Results are loaded lazily, so it is possible to get a DatastoreException from the returned Iterator's hasNext or next methods. ReadOptions can be specified if desired.

Example of getting multiple entity objects.

 String firstKeyName = "my_first_key_name";
 String secondKeyName = "my_second_key_name";
 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 Key firstKey = keyFactory.newKey(firstKeyName);
 Key secondKey = keyFactory.newKey(secondKeyName);
 Iterator<Entity> entitiesIterator = datastore.get(Lists.newArrayList(firstKey, secondKey));
 List<Entity> entities = Lists.newArrayList();
 while (entitiesIterator.hasNext()) {
   Entity entity = entitiesIterator.next();
   // do something with the entity
   entities.add(entity);
 }
 

Throws:

DatastoreException - upon failure

See Also:

DatastoreReader.get(Key)

fetch

List<Entity> fetch(Iterable<Key> keys,
                 ReadOption... options)

Returns a list with a value for each given key (ordered by input). null values are returned for nonexistent keys. When possible prefer using DatastoreReader.get(Key...) to avoid eagerly loading the results. ReadOptions can be specified if desired.

Example of fetching a list of Entity objects.

 String firstKeyName = "my_first_key_name";
 String secondKeyName = "my_second_key_name";
 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 Key firstKey = keyFactory.newKey(firstKeyName);
 Key secondKey = keyFactory.newKey(secondKeyName);
 List<Entity> entities = datastore.fetch(Lists.newArrayList(firstKey, secondKey));
 for (Entity entity : entities) {
   // do something with the entity
 }
 

run

<T> QueryResults<T> run(Query<T> query,
                      ReadOption... options)

Submits a Query and returns its result. ReadOptions can be specified if desired.

Example of running a query to find all entities of one kind.

 String kind = "my_kind";
 StructuredQuery<Entity> query = Query.newEntityQueryBuilder()
     .setKind(kind)
     .build();
 QueryResults<Entity> results = datastore.run(query);
 List<Entity> entities = Lists.newArrayList();
 while (results.hasNext()) {
   Entity result = results.next();
   // do something with result
   entities.add(result);
 }
 

Example of running a query to find all entities with a matching property value.

 String kind = "my_kind";
 String property = "my_property";
 String value = "my_value";
 StructuredQuery<Entity> query = Query.newEntityQueryBuilder()
     .setKind(kind)
     .setFilter(PropertyFilter.eq(property, value))
     .build();
 QueryResults<Entity> results = datastore.run(query);
 List<Entity> entities = Lists.newArrayList();
 while (results.hasNext()) {
   Entity result = results.next();
   // do something with result
   entities.add(result);
 }
 

Throws:

DatastoreException - upon failure