Spring Core 6.1.4 · org.springframework.util.function.SingletonSupplier

A java.util.function.Supplier decorator that caches a singleton result and makes it available from get() (nullable) and obtain() (null-safe).

A SingletonSupplier can be constructed via of factory methods or via constructors that provide a default supplier as a fallback. This is particularly useful for method reference suppliers, falling back to a default supplier for a method that returned null and caching the result.

Modifier and Type	Field and Description
private final Supplier<? extends T>	defaultSupplier
private final Supplier<? extends T>	instanceSupplier
private volatile T	singletonInstance
private final Lock	writeLock Guards access to write operations on the `singletonInstance` field.

Constructor Summary

Access	Constructor and Description
public	SingletonSupplier(T the singleton instance (potentially `null`) instance, Supplier<? extends T> the default supplier as a fallback defaultSupplier) Build a `SingletonSupplier` with the given singleton instance and a default supplier for the case when the instance is `null`.
public	SingletonSupplier(Supplier<? extends T> the immediate instance supplier instanceSupplier, Supplier<? extends T> the default supplier as a fallback defaultSupplier) Build a `SingletonSupplier` with the given instance supplier and a default supplier for the case when the instance is `null`.
private	SingletonSupplier(Supplier<? extends T> supplier)
private	SingletonSupplier(T singletonInstance)

Method Summary

Modifier and Type	Method and Description
public T	Returns: the singleton instance (or `null` if none) get() Implements java.util.function.Supplier.get. Get the shared singleton instance for this supplier.
public T	Returns: the singleton instance (never `null`) obtain() Obtain the shared singleton instance for this supplier.
public static <T> SingletonSupplier<T>	Returns: the singleton supplier (never `null`) of(T the singleton instance (never `null`) instance) Build a `SingletonSupplier` with the given singleton instance.
public static <T> SingletonSupplier<T>	Returns: the singleton supplier (never `null`) of(Supplier<T> the instance supplier (never `null`) supplier) Build a `SingletonSupplier` with the given supplier.
public static <T> SingletonSupplier<T>	Returns: the singleton supplier, or `null` if the instance was `null` ofNullable(T the singleton instance (potentially `null`) instance) Build a `SingletonSupplier` with the given singleton instance.
public static <T> SingletonSupplier<T>	Returns: the singleton supplier, or `null` if the instance supplier was `null` ofNullable(Supplier<T> the instance supplier (potentially `null`) supplier) Build a `SingletonSupplier` with the given supplier.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

defaultSupplier	back to summary
private final Supplier<? extends T> defaultSupplier Annotations @Nullable

instanceSupplier	back to summary
private final Supplier<? extends T> instanceSupplier Annotations @Nullable

singletonInstance	back to summary
private volatile T singletonInstance Annotations @Nullable

writeLock	back to summary
private final Lock writeLock Guards access to write operations on the `singletonInstance` field.

Constructor Detail

SingletonSupplier back to summary

SingletonSupplier	back to summary
public SingletonSupplier(T instance, Supplier<? extends T> defaultSupplier) Build a `SingletonSupplier` with the given singleton instance and a default supplier for the case when the instance is `null`. Parameters instance:T the singleton instance (potentially `null`) defaultSupplier:Supplier<? extends T> the default supplier as a fallback

public SingletonSupplier(T instance, Supplier<? extends T> defaultSupplier)

Build a SingletonSupplier with the given singleton instance and a default supplier for the case when the instance is null.

Parameters

instance:T: the singleton instance (potentially null)
defaultSupplier:Supplier<? extends T>: the default supplier as a fallback

SingletonSupplier back to summary

SingletonSupplier	back to summary
public SingletonSupplier(Supplier<? extends T> instanceSupplier, Supplier<? extends T> defaultSupplier) Build a `SingletonSupplier` with the given instance supplier and a default supplier for the case when the instance is `null`. Parameters instanceSupplier:Supplier<? extends T> the immediate instance supplier defaultSupplier:Supplier<? extends T> the default supplier as a fallback

public SingletonSupplier(Supplier<? extends T> instanceSupplier, Supplier<? extends T> defaultSupplier)

Build a SingletonSupplier with the given instance supplier and a default supplier for the case when the instance is null.

Parameters

instanceSupplier:Supplier<? extends T>: the immediate instance supplier
defaultSupplier:Supplier<? extends T>: the default supplier as a fallback

SingletonSupplier	back to summary
private SingletonSupplier(Supplier<? extends T> supplier)

SingletonSupplier	back to summary
private SingletonSupplier(T singletonInstance)

Method Detail

get back to summary

get	back to summary
public T get() Implements java.util.function.Supplier.get. Get the shared singleton instance for this supplier. Returns:T the singleton instance (or `null` if none) Annotations @Override @Nullable

public T get()

Implements java.util.function.Supplier.get.

Get the shared singleton instance for this supplier.

Returns:T

the singleton instance (or null if none)

Annotations

@Override
@Nullable

obtain back to summary

obtain	back to summary
public T obtain() Obtain the shared singleton instance for this supplier. Returns:T the singleton instance (never `null`) Exceptions IllegalStateException: in case of no instance

public T obtain()

Obtain the shared singleton instance for this supplier.

Returns:T

the singleton instance (never null)

Exceptions

IllegalStateException:: in case of no instance

of back to summary

of	back to summary
public static <T> SingletonSupplier<T> of(T instance) Build a `SingletonSupplier` with the given singleton instance. Parameters instance:T the singleton instance (never `null`) Returns:SingletonSupplier<T> the singleton supplier (never `null`)

public static <T> SingletonSupplier<T> of(T instance)

Build a SingletonSupplier with the given singleton instance.

Parameters

instance:T: the singleton instance (never null)

Returns:SingletonSupplier<T>

the singleton supplier (never null)

of back to summary

of	back to summary
public static <T> SingletonSupplier<T> of(Supplier<T> supplier) Build a `SingletonSupplier` with the given supplier. Parameters supplier:Supplier<T> the instance supplier (never `null`) Returns:SingletonSupplier<T> the singleton supplier (never `null`)

public static <T> SingletonSupplier<T> of(Supplier<T> supplier)

Build a SingletonSupplier with the given supplier.

Parameters

supplier:Supplier<T>: the instance supplier (never null)

Returns:SingletonSupplier<T>

the singleton supplier (never null)

ofNullable back to summary

ofNullable	back to summary
public static <T> SingletonSupplier<T> ofNullable(T instance) Build a `SingletonSupplier` with the given singleton instance. Parameters instance:T the singleton instance (potentially `null`) Returns:SingletonSupplier<T> the singleton supplier, or `null` if the instance was `null` Annotations @Nullable

public static <T> SingletonSupplier<T> ofNullable(T instance)

Build a SingletonSupplier with the given singleton instance.

Parameters

instance:T: the singleton instance (potentially null)

Returns:SingletonSupplier<T>

the singleton supplier, or null if the instance was null

Annotations

@Nullable

ofNullable back to summary

ofNullable	back to summary
public static <T> SingletonSupplier<T> ofNullable(Supplier<T> supplier) Build a `SingletonSupplier` with the given supplier. Parameters supplier:Supplier<T> the instance supplier (potentially `null`) Returns:SingletonSupplier<T> the singleton supplier, or `null` if the instance supplier was `null` Annotations @Nullable

public static <T> SingletonSupplier<T> ofNullable(Supplier<T> supplier)

Build a SingletonSupplier with the given supplier.

Parameters

supplier:Supplier<T>: the instance supplier (potentially null)

Returns:SingletonSupplier<T>

the singleton supplier, or null if the instance supplier was null

Annotations

@Nullable

public Class SingletonSupplier<T>

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail