reactor.util.context

Interface Context

public interface Context

A key/value store that is propagated between components such as operators via the context protocol. Contexts are ideal to transport orthogonal infos such as tracing or security tokens.

Context implementations are thread-safe put(Object, Object) will usually return a safe new Context object.

Note that contexts are optimized for single key/value storage, and a user might want to represent his own context instead of using more costly put(java.lang.Object, java.lang.Object). Past one user key/value pair, the context will use a copy-on-write Context backed by a new Map on each put(java.lang.Object, java.lang.Object).

Author:

Stephane Maldini

Method Summary

Modifier and Type	Method and Description
static Context	empty() Return an empty Context
default <T> T	get(Class<T> key) Resolve a value given a type key within the Context.
<T> T	get(Object key) Resolve a value given a key within the Context.
default <T> T	getOrDefault(Object key, T defaultValue) Resolve a value given a key within the Context.
default boolean	isEmpty() Return true if Context is empty.
Context	put(Object key, Object value) Inject a key/value pair in a new Context inheriting current state.
Stream<Map.Entry<Object,Object>>	stream() Stream key/value pairs from this Context

Method Detail

empty

static Context empty()

Return an empty Context

Returns:

an empty Context

put

Context put(Object key,
            @Nullable
            Object value)

Inject a key/value pair in a new Context inheriting current state. The returned Context will resolve the new key/value pair and any existing key/value pair.

Parameters:

key - a lookup key to reuse later for value resolution

value - the target object to store in the new Context

Returns:

a new Context including the user-provided key/value

get

@Nullable
<T> T get(Object key)

Resolve a value given a key within the Context.

Type Parameters:

T - an unchecked casted generic for fluent typing convenience

Parameters:

key - a lookup key to resolve the value within the context

Returns:

the eventual value resolved by this key or null

get

@Nullable
default <T> T get(Class<T> key)

Resolve a value given a type key within the Context.

Type Parameters:

T - an unchecked casted generic for fluent typing convenience

Parameters:

key - a type key to resolve the value within the context

Returns:

the eventual value resolved by this type key or null

getOrDefault

@Nullable
default <T> T getOrDefault(Object key,
                                     @Nullable
                                     T defaultValue)

Resolve a value given a key within the Context. If unresolved return the passed default value.

Parameters:

key - a lookup key to resolve the value within the context

defaultValue - a fallback value if key doesn't resolve

Returns:

an eventual value or the default passed

isEmpty

default boolean isEmpty()

Return true if Context is empty.

Returns:

true if Context is empty.

stream

Stream<Map.Entry<Object,Object>> stream()

Stream key/value pairs from this Context

Returns:

a Stream of key/value pairs held by this context