Interface Datastore (2.11.4)

public interface Datastore extends Service<DatastoreOptions>, DatastoreReaderWriter

An interface for Google Cloud Datastore.

Implements

com.google.cloud.Service<com.google.cloud.datastore.DatastoreOptions>, DatastoreReaderWriter

Methods

<T>run(Query<T> query, ReadOption[] options)

public abstract QueryResults<T> <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);
 }

Parameters

Name	Description
query	`Query<T>`
options	`ReadOption[]`

Returns

Type	Description
QueryResults<T>

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

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

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);

Parameter

Name	Description
callable	`TransactionCallable<T>` the callback to call with a newly created transactional readerWriter

Returns

Type	Description
T

<T>runInTransaction(Datastore.TransactionCallable<T> callable, TransactionOptions options)

public abstract T <T>runInTransaction(Datastore.TransactionCallable<T> callable, TransactionOptions options)

Invokes the callback's Datastore.TransactionCallable#run 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. If TransactionOptions is set to read-write mode, previous transaction Id in the options will be automatically populated each time a transaction is retried.

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;
   }
 };

 TransactionOptions options = TransactionOptions.newBuilder()
     .setReadWrite(TransactionOptions.ReadWrite
         .getDefaultInstance())
     .build();

 String result = datastore.runInTransaction(callable, options);

Parameters

Name	Description
callable	`TransactionCallable<T>` the callback to call with a newly created transactional readerWriter
options	`TransactionOptions` the Transaction options indicating whether the transaction mode is Read-only or Read-Write

Returns

Type	Description
T

add(FullEntity<?> entity)

public abstract 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 exist, entity is inserted. Otherwise, a DatastoreException is thrown with DatastoreException#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
   }
 }

Parameter

Name	Description
entity	`FullEntity<?>`

Returns

Type	Description
Entity

add(FullEntity<?>[] entities)

public abstract 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 DatastoreException#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
   }
 }

Parameter

Name	Description
entities	`FullEntity<?>[]`

Returns

Type	Description
List<Entity>

allocateId(IncompleteKey key)

public abstract 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);

Parameter

Name	Description
key	`IncompleteKey`

Returns

Type	Description
Key

allocateId(IncompleteKey[] keys)

public abstract 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);

delete(Key[] keys)

public abstract 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);

Parameter

Name	Description
keys	`Key[]`

fetch(Iterable<Key> keys, ReadOption[] options)

public abstract 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 #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
 }

Parameters

Name	Description
keys	`Iterable<Key>`
options	`ReadOption[]`

Returns

Type	Description
List<Entity>

get(Key key, ReadOption[] options)

public abstract 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

Parameters

Name	Description
key	`Key`
options	`ReadOption[]`

Returns

Type	Description
Entity

get(Iterable<Key> keys, ReadOption[] options)

public abstract 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);
 }

newBatch()

public abstract 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();

Returns

Type	Description
Batch

newKeyFactory()

public abstract KeyFactory newKeyFactory()

Returns a new KeyFactory for this service

Example of creating a KeyFactory.


 KeyFactory keyFactory = datastore.newKeyFactory();

Returns

Type	Description
KeyFactory

newTransaction()

public abstract Transaction newTransaction()

Returns a new Datastore transaction.

Returns

Type	Description
Transaction

newTransaction(TransactionOptions options)

public abstract Transaction newTransaction(TransactionOptions options)

Returns a new Datastore transaction.

Parameter

Name	Description
options	`TransactionOptions` a transaction option indicating the mode of the transaction (read-only or read-write)

Returns

Type	Description
Transaction

put(FullEntity<?> entity)

public abstract 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);

Parameter

Name	Description
entity	`FullEntity<?>`

Returns

Type	Description
Entity

put(FullEntity<?>[] entities)

public abstract 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);

Parameter

Name	Description
entities	`FullEntity<?>[]`

Returns

Type	Description
List<Entity>

reserveIds(Key[] keys)

public abstract List<Key> reserveIds(Key[] keys)

Reserve one or more keys, preventing them from being automatically allocated by Datastore.

Example of reserving multiple ids in a single batch.


 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 Key key1 = keyFactory.newKey(10);
 Key key2 = keyFactory.newKey("name");
 List<Key> keys = datastore.reserveIds(key1, key2);

Parameter

Name	Description
keys	`Key[]`

Returns

Type	Description
List<Key>

update(Entity[] entities)

public abstract 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);

Parameter

Name	Description
entities	`Entity[]`