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.

T - The type of the value of the state object described by this state descriptor.

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

AggregatingStateDescriptor, FoldingStateDescriptor, ListStateDescriptor, MapStateDescriptor, 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 StateBinder using bind(StateBinder).

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

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	StateDescriptor.Type An enumeration of the types of supported states.

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(StateBinder stateBinder) Creates a new State on the given StateBinder.
boolean	equals(Object o)
T	getDefaultValue() Returns the default value.
String	getName() Returns the name of this StateDescriptor.
String	getQueryableStateName() Returns the queryable state name.
TypeSerializer<T>	getSerializer() Returns the TypeSerializer that can be used to serialize the value in the state.
abstract StateDescriptor.Type	getType()
int	hashCode()
void	initializeSerializerUnlessSet(ExecutionConfig executionConfig) Initializes the serializer, unless it has been initialized before.
boolean	isQueryable() Returns whether the state created from this descriptor is queryable.
boolean	isSerializerInitialized() Checks whether the serializer has been initialized.
void	setQueryable(String queryableStateName) Sets the name for queries of state created from this descriptor.
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

@Nullable
protected TypeSerializer<T> serializer

The serializer for the type. May be eagerly initialized in the constructor, or lazily once the initializeSerializerUnlessSet(ExecutionConfig) method is called.

defaultValue

@Nullable
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,
                          @Nullable
                          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,
                          @Nullable
                          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,
                          @Nullable
                          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).

setQueryable

public void setQueryable(String queryableStateName)

Sets the name for queries of state created from this descriptor.

If a name is set, the created state will be published for queries during runtime. The name needs to be unique per job. If there is another state instance published under the same name, the job will fail during runtime.

Parameters:

queryableStateName - State name for queries (unique name per job)

Throws:

IllegalStateException - If queryable state name already set

getQueryableStateName

@Nullable
public String getQueryableStateName()

Returns the queryable state name.

Returns:

Queryable state name or null if not set.

isQueryable

public boolean isQueryable()

Returns whether the state created from this descriptor is queryable.

Returns:

true if state is queryable, false otherwise.

bind

public abstract S bind(StateBinder stateBinder)
                throws Exception

Creates a new State on the given StateBinder.

Parameters:

stateBinder - 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 final int hashCode()

Overrides:

hashCode in class Object

equals

public final boolean equals(Object o)

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object

getType

public abstract StateDescriptor.Type getType()