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
Context	delete(Object key) Return a new Context that will resolve all existing keys except the removed one, key.
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 that exists within the Context, or throw a NoSuchElementException if the key is not present.
default <T> T	getOrDefault(Object key, T defaultValue) Resolve a value given a key within the Context.
default <T> Optional<T>	getOrEmpty(Object key) Resolve a value given a key within the Context.
boolean	hasKey(Object key) Return true if a value is resolvable given a key within the Context.
default boolean	isEmpty() Return true if Context is empty.
static Context	of(Object key, Object value) Create a Context pre-initialized with one key-value pair.
static Context	of(Object key1, Object value1, Object key2, Object value2) Create a Context pre-initialized with two key-value pairs.
static Context	of(Object key1, Object value1, Object key2, Object value2, Object key3, Object value3) Create a Context pre-initialized with three key-value pairs.
static Context	of(Object key1, Object value1, Object key2, Object value2, Object key3, Object value3, Object key4, Object value4) Create a Context pre-initialized with four key-value pairs.
static Context	of(Object key1, Object value1, Object key2, Object value2, Object key3, Object value3, Object key4, Object value4, Object key5, Object value5) Create a Context pre-initialized with five key-value pairs.
Context	put(Object key, Object value) Inject a key/value pair in a new Context inheriting current state.
default Context	putAll(Context other) Create a new Context by merging the content of this context and a given Context.
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

of

static Context of(Object key,
                  Object value)

Create a Context pre-initialized with one key-value pair.

Parameters:

key - the key to initialize.

value - the value for the key.

Returns:

a Context with a single entry.

of

static Context of(Object key1,
                  Object value1,
                  Object key2,
                  Object value2)

Create a Context pre-initialized with two key-value pairs.

Parameters:

key1 - the first key to initialize.

value1 - the value for the first key.

key2 - the second key to initialize.

value2 - the value for the second key.

Returns:

a Context with two entries.

of

static Context of(Object key1,
                  Object value1,
                  Object key2,
                  Object value2,
                  Object key3,
                  Object value3)

Create a Context pre-initialized with three key-value pairs.

Parameters:

key1 - the first key to initialize.

value1 - the value for the first key.

key2 - the second key to initialize.

value2 - the value for the second key.

key3 - the third key to initialize.

value3 - the value for the third key.

Returns:

a Context with three entries.

of

static Context of(Object key1,
                  Object value1,
                  Object key2,
                  Object value2,
                  Object key3,
                  Object value3,
                  Object key4,
                  Object value4)

Create a Context pre-initialized with four key-value pairs.

Parameters:

key1 - the first key to initialize.

value1 - the value for the first key.

key2 - the second key to initialize.

value2 - the value for the second key.

key3 - the third key to initialize.

value3 - the value for the third key.

key4 - the fourth key to initialize.

value4 - the value for the fourth key.

Returns:

a Context with four entries.

of

static Context of(Object key1,
                  Object value1,
                  Object key2,
                  Object value2,
                  Object key3,
                  Object value3,
                  Object key4,
                  Object value4,
                  Object key5,
                  Object value5)

Create a Context pre-initialized with five key-value pairs.

Parameters:

key1 - the first key to initialize.

value1 - the value for the first key.

key2 - the second key to initialize.

value2 - the value for the second key.

key3 - the third key to initialize.

value3 - the value for the third key.

key4 - the fourth key to initialize.

value4 - the value for the fourth key.

key5 - the fifth key to initialize.

value5 - the value for the fifth key.

Returns:

a Context with five entries.

get

<T> T get(Object key)

Resolve a value given a key that exists within the Context, or throw a NoSuchElementException if the key is not present.

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 value resolved for this key (throws if key not found)

Throws:

NoSuchElementException - when the given key is not present

See Also:

getOrDefault(Object, Object), hasKey(Object)

get

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 value resolved for this type key (throws if key not found)

Throws:

NoSuchElementException - when the given type key is not present

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

getOrEmpty

default <T> Optional<T> getOrEmpty(Object key)

Resolve a value given a key within the Context.

Parameters:

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

Returns:

an eventual value or the default passed

hasKey

boolean hasKey(Object key)

Return true if a value is resolvable given a key within the Context.

Parameters:

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

Returns:

true if this context contains the passed key

isEmpty

default boolean isEmpty()

Return true if Context is empty.

Returns:

true if Context is empty.

put

Context put(Object key,
            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

delete

Context delete(Object key)

Return a new Context that will resolve all existing keys except the removed one, key.

Note that if this Context doesn't contain the key, this method simply returns this same instance.

Parameters:

key - the key to remove.

Returns:

a new Context that doesn't include the provided key

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

putAll

default Context putAll(Context other)

Create a new Context by merging the content of this context and a given Context. If the other context is empty, the same Context instance is returned.

Parameters:

other - the other Context to get values from

Returns:

a new Context with a merge of the entries from this context and the given context.