reactor.core

Interface Scannable

All Known Implementing Classes:

DirectProcessor, EmitterProcessor, FluxProcessor, FluxSource, MonoSource, Operators.DeferredSubscription, ReplayProcessor, TopicProcessor, UnicastProcessor, WorkQueueProcessor

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface Scannable

A Scannable component exposes state in a non strictly memory consistent way and results should be understood as best-effort hint of the underlying state. This is useful to retro-engineer a component graph such as a flux operator chain via Stream queries from actuals(), parents() and inners(). This allows for visiting patterns and possibly enable serviceability features.

Scannable is also a useful tool for the advanced user eager to learn which kind of state we usually manage in the package-scope schedulers or operators implementations.

Author:

Stephane Maldini

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	Scannable.Attr A list of reserved keys for component state scanning

Method Summary

Modifier and Type	Method and Description
default Stream<? extends Scannable>	actuals() Return a Stream navigating the Subscriber chain (downward).
static Scannable	from(Object o) Return the casted Scannable, null or a constant Scannable that return false on isScanAvailable().
default Stream<? extends Scannable>	inners() Return a Stream of referenced inners (flatmap, multicast etc)
default boolean	isScanAvailable() Return true whether the component is available for scan(Attr) resolution.
default Stream<? extends Scannable>	parents() Return a Stream navigating the Subscription chain (upward).
Object	scan(Scannable.Attr key) Return an eventual value or null for a given component state Scannable.Attr
default <T> T	scan(Scannable.Attr key, Class<T> type) Resolve a value given an Scannable.Attr within the Scannable.
default <T> T	scanOrDefault(Scannable.Attr key, T defaultValue) Resolve a value given an Scannable.Attr within the Scannable.

Method Detail

from

static Scannable from(Object o)

Return the casted Scannable, null or a constant Scannable that return false on isScanAvailable().

Parameters:

o - a reference to cast

Returns:

the casted Scannable, null or Scannable.Attr.UNAVAILABLE_SCAN

actuals

default Stream<? extends Scannable> actuals()

Return a Stream navigating the Subscriber chain (downward).

Returns:

a Stream navigating the Subscriber chain (downward)

inners

default Stream<? extends Scannable> inners()

Return a Stream of referenced inners (flatmap, multicast etc)

Returns:

a Stream of referenced inners (flatmap, multicast etc)

isScanAvailable

default boolean isScanAvailable()

Return true whether the component is available for scan(Attr) resolution.

Returns:

true whether the component is available for scan(Attr) resolution.

parents

default Stream<? extends Scannable> parents()

Return a Stream navigating the Subscription chain (upward).

Returns:

a Stream navigating the Subscription chain (upward)

scan

Object scan(Scannable.Attr key)

Return an eventual value or null for a given component state Scannable.Attr

Parameters:

key - an Scannable.Attr to get the operator state

Returns:

an eventual value or null

scan

default <T> T scan(Scannable.Attr key,
                   Class<T> type)

Resolve a value given an Scannable.Attr within the Scannable. If unresolved return the passed default value.

Parameters:

key - a Scannable.Attr to resolve the value within the context

type - the attribute type

Returns:

an eventual value or null if unmatched or unresolved

scanOrDefault

default <T> T scanOrDefault(Scannable.Attr key,
                            T defaultValue)

Resolve a value given an Scannable.Attr within the Scannable. If unresolved return the passed default value.

Parameters:

key - a Scannable.Attr to resolve the value within the context

defaultValue - a fallback value if key doesn't resolve

Returns:

an eventual value or the default passed