Scannable.Attr (reactor-3)

java.lang.Object
- reactor.core.Scannable.Attr<T>

类型参数:

T - the type of data associated with an attribute

封闭接口:

Scannable
```
public static class Scannable.Attr<T>
extends java.lang.Object
```
Base class for Scannable attributes, which all can define a meaningful default.

嵌套类概要

嵌套类
限定符和类型	类和说明
`static class`	`Scannable.Attr.RunStyle` An `Enum` enumerating the different styles an operator can run : their `Enum.ordinal()` reflects the level of confidence in their running mode

字段概要

字段
限定符和类型	字段和说明
`static Scannable.Attr<Scannable>`	`ACTUAL` The direct dependent component downstream reference if any.
`static Scannable.Attr<java.lang.Boolean>`	`ACTUAL_METADATA` Indicate that for some purposes a `Scannable` should be used as additional source of information about a contiguous `Scannable` in the chain.
`static Scannable.Attr<java.lang.Integer>`	`BUFFERED` A `Integer` attribute implemented by components with a backlog capacity.
`static Scannable.Attr<java.lang.Boolean>`	`CANCELLED` A `Boolean` attribute indicating whether or not a downstream component has interrupted consuming this scanned component, e.g., a cancelled subscription.
`static Scannable.Attr<java.lang.Integer>`	`CAPACITY` Return an an `Integer` capacity when no `PREFETCH` is defined or when an arbitrary maximum limit is applied to the backlog capacity of the scanned component.
`static Scannable.Attr<java.lang.Boolean>`	`DELAY_ERROR` Delay_Error exposes a `Boolean` whether the scanned component actively supports error delaying if it manages a backlog instead of fast error-passing which might drop pending backlog.
`static Scannable.Attr<java.lang.Throwable>`	`ERROR` a `Throwable` attribute which indicate an error state if the scanned component keeps track of it.
`static Scannable.Attr<java.lang.Long>`	`LARGE_BUFFERED` Similar to `BUFFERED`, but reserved for operators that can hold a backlog of items that can grow beyond Integer.MAX_VALUE.
`static Scannable.Attr<java.lang.String>`	`LIFTER` LIFTER attribute exposes name of the lifter function.
`static Scannable.Attr<java.lang.String>`	`NAME` An arbitrary name given to the operator component.
`static Scannable.Attr<Scannable>`	`PARENT` Parent key exposes the direct upstream relationship of the scanned component.
`static Scannable.Attr<java.lang.Integer>`	`PREFETCH` Prefetch is an `Integer` attribute defining the rate of processing in a component which has capacity to request and hold a backlog of data.
`static Scannable.Attr<java.lang.Long>`	`REQUESTED_FROM_DOWNSTREAM` A `Long` attribute exposing the current pending demand of a downstream component.
`static Scannable.Attr<Scannable>`	`RUN_ON` A key that links a `Scannable` to another `Scannable` it runs on.
`static Scannable.Attr<Scannable.Attr.RunStyle>`	`RUN_STYLE` An `Scannable.Attr.RunStyle` enum attribute indicating whether or not an operator continues to operate on the same thread.
`static Scannable.Attr<java.util.stream.Stream<Tuple2<java.lang.String,java.lang.String>>>`	`TAGS` A `Stream` of `Tuple2` representing key/value pairs for tagged components.
`static Scannable.Attr<java.lang.Boolean>`	`TERMINATED` A `Boolean` attribute indicating whether or not an upstream component terminated this scanned component. e.g. a post onComplete/onError subscriber.

方法概要

所有方法实例方法具体方法
限定符和类型	方法和说明
`T`	`defaultValue()` Meaningful and always applicable default value for the attribute, returned instead of null when a specific value hasn't been defined for a component.

从类继承的方法 java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 字段详细资料
  - ACTUAL
```
public static final Scannable.Attr<Scannable> ACTUAL
```
    The direct dependent component downstream reference if any. Operators in Flux/Mono for instance delegate to a target Subscriber, which is going to be the actual chain navigated with this reference key. Subscribers are not always Scannable, but this attribute will convert these raw results to an unavailable scan object in this case.
    A reference chain downstream can be navigated via Scannable.actuals().
  - ACTUAL_METADATA
```
public static final Scannable.Attr<java.lang.Boolean> ACTUAL_METADATA
```
    Indicate that for some purposes a Scannable should be used as additional source of information about a contiguous Scannable in the chain.
    For example Scannable.steps() uses this to collate the stepName of an assembly trace to its wrapped operator (the one before it in the assembly chain).
  - BUFFERED
```
public static final Scannable.Attr<java.lang.Integer> BUFFERED
```
    A Integer attribute implemented by components with a backlog capacity. It will expose current queue size or similar related to user-provided held data. Note that some operators and processors CAN keep a backlog larger than Integer.MAX_VALUE, in which case the Attr LARGE_BUFFERED should be used instead. Such operators will attempt to serve a BUFFERED query but will return Integer.MIN_VALUE when actual buffer size is oversized for int.
  - CAPACITY
```
public static final Scannable.Attr<java.lang.Integer> CAPACITY
```
    Return an an Integer capacity when no PREFETCH is defined or when an arbitrary maximum limit is applied to the backlog capacity of the scanned component. Integer.MAX_VALUE signal unlimited capacity.
    Note: This attribute usually resolves to a constant value.
  - CANCELLED
```
public static final Scannable.Attr<java.lang.Boolean> CANCELLED
```
    A Boolean attribute indicating whether or not a downstream component has interrupted consuming this scanned component, e.g., a cancelled subscription. Note that it differs from TERMINATED which is intended for "normal" shutdown cycles.
  - DELAY_ERROR
```
public static final Scannable.Attr<java.lang.Boolean> DELAY_ERROR
```
    Delay_Error exposes a Boolean whether the scanned component actively supports error delaying if it manages a backlog instead of fast error-passing which might drop pending backlog.
    Note: This attribute usually resolves to a constant value.
  - ERROR
```
public static final Scannable.Attr<java.lang.Throwable> ERROR
```
    a Throwable attribute which indicate an error state if the scanned component keeps track of it.
  - LARGE_BUFFERED
```
public static final Scannable.Attr<java.lang.Long> LARGE_BUFFERED
```
    Similar to BUFFERED, but reserved for operators that can hold a backlog of items that can grow beyond Integer.MAX_VALUE. These operators will also answer to a BUFFERED query up to the point where their buffer is actually too large, at which point they'll return Integer.MIN_VALUE, which serves as a signal that this attribute should be used instead. Defaults to null.
    Flux.flatMap, Flux.filterWhen and Flux.window (with overlap) are known to use this attribute.
  - NAME
```
public static final Scannable.Attr<java.lang.String> NAME
```
    An arbitrary name given to the operator component. Defaults to null.
  - PARENT
```
public static final Scannable.Attr<Scannable> PARENT
```
    Parent key exposes the direct upstream relationship of the scanned component. It can be a Publisher source to an operator, a Subscription to a Subscriber (main flow if ambiguous with inner Subscriptions like flatMap), a Scheduler to a Worker. These types are not always Scannable, but this attribute will convert such raw results to an unavailable scan object in this case.
    Scannable.parents() can be used to navigate the parent chain.
  - RUN_ON
```
public static final Scannable.Attr<Scannable> RUN_ON
```
    A key that links a Scannable to another Scannable it runs on. Usually exposes a link between an operator/subscriber and its Scheduler.Worker or Scheduler, provided these are Scannable. Will return UNAVAILABLE_SCAN if the supporting execution is not Scannable or NULL_SCAN if the operator doesn't define a specific runtime.
  - PREFETCH
```
public static final Scannable.Attr<java.lang.Integer> PREFETCH
```
    Prefetch is an Integer attribute defining the rate of processing in a component which has capacity to request and hold a backlog of data. It usually maps to a component capacity when no arbitrary CAPACITY is set. Integer.MAX_VALUE signal unlimited capacity and therefore unbounded demand.
    Note: This attribute usually resolves to a constant value.
  - REQUESTED_FROM_DOWNSTREAM
```
public static final Scannable.Attr<java.lang.Long> REQUESTED_FROM_DOWNSTREAM
```
    A Long attribute exposing the current pending demand of a downstream component. Note that Long.MAX_VALUE indicates an unbounded (push-style) demand as specified in Subscription.request(long).
  - TERMINATED
```
public static final Scannable.Attr<java.lang.Boolean> TERMINATED
```
    A Boolean attribute indicating whether or not an upstream component terminated this scanned component. e.g. a post onComplete/onError subscriber. By opposition to CANCELLED which determines if a downstream component interrupted this scanned component.
  - TAGS
```
public static final Scannable.Attr<java.util.stream.Stream<Tuple2<java.lang.String,java.lang.String>>> TAGS
```
    A Stream of Tuple2 representing key/value pairs for tagged components. Defaults to null.
  - RUN_STYLE
```
public static final Scannable.Attr<Scannable.Attr.RunStyle> RUN_STYLE
```
    An Scannable.Attr.RunStyle enum attribute indicating whether or not an operator continues to operate on the same thread. Each value provides a different degree of guarantee from weakest Scannable.Attr.RunStyle.UNKNOWN to strongest Scannable.Attr.RunStyle.SYNC. Defaults to Scannable.Attr.RunStyle.UNKNOWN.
  - LIFTER
```
public static final Scannable.Attr<java.lang.String> LIFTER
```
    LIFTER attribute exposes name of the lifter function. It is calculated as Object.toString() of a function passed to the Operators.lift(java.util.function.BiFunction<reactor.core.Scannable, ? super reactor.core.CoreSubscriber<? super O>, ? extends reactor.core.CoreSubscriber<? super I>>) or Operators.liftPublisher(java.util.function.BiFunction<org.reactivestreams.Publisher, ? super reactor.core.CoreSubscriber<? super O>, ? extends reactor.core.CoreSubscriber<? super I>>). Defaults to null.
- 方法详细资料
  - defaultValue
```
@Nullable
public T defaultValue()
```
    Meaningful and always applicable default value for the attribute, returned instead of null when a specific value hasn't been defined for a component. null if no sensible generic default is available.
    
    返回:
    
    the default value applicable to all components or null if none.

类 Scannable.Attr<T>

嵌套类概要

字段概要

方法概要

从类继承的方法 java.lang.Object

字段详细资料

ACTUAL

ACTUAL_METADATA

BUFFERED

CAPACITY

CANCELLED

DELAY_ERROR

ERROR

LARGE_BUFFERED

NAME

PARENT

RUN_ON

PREFETCH

REQUESTED_FROM_DOWNSTREAM

TERMINATED

TAGS

RUN_STYLE

LIFTER

方法详细资料

defaultValue