org.apache.flink.statefun.sdk.state

Class PersistedValue<T>

java.lang.Object

org.apache.flink.statefun.sdk.state.PersistedValue<T>

Type Parameters:

T - type of the state.

public final class PersistedValue<T>
extends java.lang.Object

A PersistedValue is a value registered within StatefulFunctions and is persisted and maintained by the system for fault-tolerance.

Created persisted values must be registered by using the Persisted annotation. Please see the class-level Javadoc of StatefulFunction for an example on how to do that.

See Also:

StatefulFunction

Method Summary

Modifier and Type	Method and Description
void	clear() Clears the persisted value.
Expiration	expiration()
T	get() Returns the persisted value.
T	getOrDefault(java.util.function.Supplier<T> defaultSupplier) Attempts to get the persisted value.
T	getOrDefault(T orElse) Attempts to get the persisted value.
java.lang.String	name() Returns the unique name of the persisted value.
static <T> PersistedValue<T>	of(java.lang.String name, java.lang.Class<T> type) Creates a PersistedValue instance that may be used to access persisted state managed by the system.
static <T> PersistedValue<T>	of(java.lang.String name, java.lang.Class<T> type, Expiration expiration) Creates a PersistedValue instance that may be used to access persisted state managed by the system.
void	set(T value) Updates the persisted value.
java.lang.String	toString()
java.lang.Class<T>	type() Returns the type of the persisted values.
T	updateAndGet(java.util.function.Function<T,T> update) Updates the persisted value and returns it, in a single operation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

of

public static <T> PersistedValue<T> of(java.lang.String name,
                                       java.lang.Class<T> type)

Creates a PersistedValue instance that may be used to access persisted state managed by the system. Access to the persisted value is identified by an unique name and type of the value. These may not change across multiple executions of the application.

Type Parameters:

T - the type of the state values.

Parameters:

name - the unique name of the persisted state.

type - the type of the state values of this PersistedValue.

Returns:

a PersistedValue instance.

of

public static <T> PersistedValue<T> of(java.lang.String name,
                                       java.lang.Class<T> type,
                                       Expiration expiration)

Creates a PersistedValue instance that may be used to access persisted state managed by the system. Access to the persisted value is identified by an unique name and type of the value. These may not change across multiple executions of the application.

Type Parameters:

T - the type of the state values.

Parameters:

name - the unique name of the persisted state.

type - the type of the state values of this PersistedValue.

expiration - state expiration configuration.

Returns:

a PersistedValue instance.

name

public java.lang.String name()

Returns the unique name of the persisted value.

Returns:

unique name of the persisted value.

type

public java.lang.Class<T> type()

Returns the type of the persisted values.

Returns:

the type of the persisted values.

expiration

public Expiration expiration()

get

public T get()

Returns the persisted value.

Returns:

the persisted value.

set

public void set(T value)

Updates the persisted value.

Parameters:

value - the new value.

clear

public void clear()

Clears the persisted value. After being cleared, the value would be null.

updateAndGet

public T updateAndGet(java.util.function.Function<T,T> update)

Updates the persisted value and returns it, in a single operation.

Parameters:

update - function to process the previous value to obtain the new value.

Returns:

the new updated value.

getOrDefault

public T getOrDefault(T orElse)

Attempts to get the persisted value. If the current value is null, then a specified default is returned instead.

Parameters:

orElse - the default value to return if the current value is not present.

Returns:

the persisted value, or the provided default if it isn't present.

getOrDefault

public T getOrDefault(java.util.function.Supplier<T> defaultSupplier)

Attempts to get the persisted value. If the current value is null, then a default value obtained from a specified supplier is returned instead.

Parameters:

defaultSupplier - supplier for a default value to be used if the current value is not present.

Returns:

the persisted value, or a default value if it isn't present.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object