org.apache.flink.api.common.state

Class StateDescriptor<S extends State,T>

java.lang.Object

org.apache.flink.api.common.state.StateDescriptor<S,T>

Type Parameters:

S - The type of the State objects created from this StateDescriptor.

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

FoldingStateDescriptor, ListStateDescriptor, ReducingStateDescriptor, ValueStateDescriptor

@PublicEvolving
public abstract class StateDescriptor<S extends State,T>
extends Object
implements Serializable

Base class for state descriptors. A StateDescriptor is used for creating partitioned State in stateful operations. This contains the name and can create an actual state object given a StateBackend using bind(StateBackend).

Subclasses must correctly implement equals(Object) and hashCode().

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected T	defaultValue The default value returned by the state when no other value is bound to a key
protected String	name Name that uniquely identifies state created from this StateDescriptor.
protected TypeSerializer<T>	serializer The serializer for the type.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	StateDescriptor(String name, Class<T> type, T defaultValue) Create a new StateDescriptor with the given name and the given type information.
protected	StateDescriptor(String name, TypeInformation<T> typeInfo, T defaultValue) Create a new StateDescriptor with the given name and the given type information.
protected	StateDescriptor(String name, TypeSerializer<T> serializer, T defaultValue) Create a new StateDescriptor with the given name and the given type serializer.

Method Summary

Modifier and Type	Method and Description
abstract S	bind(StateBackend stateBackend) Creates a new State on the given StateBackend.
abstract boolean	equals(Object o)
T	getDefaultValue() Returns the default value.
String	getName() Returns the name of this StateDescriptor.
TypeSerializer<T>	getSerializer() Returns the TypeSerializer that can be used to serialize the value in the state.
abstract int	hashCode()
void	initializeSerializerUnlessSet(ExecutionConfig executionConfig) Initializes the serializer, unless it has been initialized before.
boolean	isSerializerInitialized() Checks whether the serializer has been initialized.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

name

protected final String name

Name that uniquely identifies state created from this StateDescriptor.

serializer

protected TypeSerializer<T> serializer

The serializer for the type. May be eagerly initialized in the constructor, or lazily once the type is serialized or an ExecutionConfig is provided.

defaultValue

protected transient T defaultValue

The default value returned by the state when no other value is bound to a key

Constructor Detail

StateDescriptor

protected StateDescriptor(String name,
                          TypeSerializer<T> serializer,
                          T defaultValue)

Create a new StateDescriptor with the given name and the given type serializer.

Parameters:

name - The name of the StateDescriptor.

serializer - The type serializer for the values in the state.

defaultValue - The default value that will be set when requesting state without setting a value before.

StateDescriptor

protected StateDescriptor(String name,
                          TypeInformation<T> typeInfo,
                          T defaultValue)

Create a new StateDescriptor with the given name and the given type information.

Parameters:

name - The name of the StateDescriptor.

typeInfo - The type information for the values in the state.

defaultValue - The default value that will be set when requesting state without setting a value before.

StateDescriptor

protected StateDescriptor(String name,
                          Class<T> type,
                          T defaultValue)

Create a new StateDescriptor with the given name and the given type information.

If this constructor fails (because it is not possible to describe the type via a class), consider using the StateDescriptor(String, TypeInformation, Object) constructor.

Parameters:

name - The name of the StateDescriptor.

type - The class of the type of values in the state.

defaultValue - The default value that will be set when requesting state without setting a value before.

Method Detail

getName

public String getName()

Returns the name of this StateDescriptor.

getDefaultValue

public T getDefaultValue()

Returns the default value.

getSerializer

public TypeSerializer<T> getSerializer()

Returns the TypeSerializer that can be used to serialize the value in the state. Note that the serializer may initialized lazily and is only guaranteed to exist after calling initializeSerializerUnlessSet(ExecutionConfig).

bind

public abstract S bind(StateBackend stateBackend)
                throws Exception

Creates a new State on the given StateBackend.

Parameters:

stateBackend - The StateBackend on which to create the State.

Throws:

Exception

isSerializerInitialized

public boolean isSerializerInitialized()

Checks whether the serializer has been initialized. Serializer initialization is lazy, to allow parametrization of serializers with an ExecutionConfig via initializeSerializerUnlessSet(ExecutionConfig).

Returns:

True if the serializers have been initialized, false otherwise.

initializeSerializerUnlessSet

public void initializeSerializerUnlessSet(ExecutionConfig executionConfig)

Initializes the serializer, unless it has been initialized before.

Parameters:

executionConfig - The execution config to use when creating the serializer.

hashCode

public abstract int hashCode()

Overrides:

hashCode in class Object

equals

public abstract boolean equals(Object o)

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object