reactor.util.context

Interface Context

All Superinterfaces:

ContextView

public interface Context
extends ContextView

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

Context implementations are thread-safe and immutable: mutative operations like put(Object, Object) will in fact return a new Context instance.

Note that contexts are optimized for low cardinality key/value storage, and a user might want to associate a dedicated mutable structure to a single key to represent his own context instead of using multiple put(java.lang.Object, java.lang.Object), which could be more costly. Past five user key/value pair, the Context will use a copy-on-write implementation 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
static Context	of(ContextView contextView) Create a Context out of a ContextView, enabling write API on top of the read-only view.
static Context	of(Map<?,?> map) Create a Context out of a Map.
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) Create a new Context that contains all current key/value pairs plus the given key/value pair.
default Context	putAll(Context context) Deprecated. will be removed in 3.5, kept for backward compatibility with 3.3
default Context	putAll(ContextView other) Create a new Context by merging the content of this context and a given ContextView.
default Context	putNonNull(Object key, Object valueOrNull) Create a new Context that contains all current key/value pairs plus the given key/value pair only if the value is not null.
default ContextView	readOnly() Switch to the ContextView interface, which only allows reading from the context.

Methods inherited from interface reactor.util.context.ContextView

get, get, getOrDefault, getOrEmpty, hasKey, isEmpty, size, stream

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.

Throws:

NullPointerException - if either key or value are null

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.

Throws:

NullPointerException - if any key or value is null

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.

Throws:

NullPointerException - if any key or value is null

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.

Throws:

NullPointerException - if any key or value is null

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.

Throws:

NullPointerException - if any key or value is null

of

static Context of(Map<?,?> map)

Create a Context out of a Map. Prefer this method if you're somehow incapable of checking keys are all distinct in other of(Object, Object, Object, Object, Object, Object, Object, Object) implementations.

Implementation Note:

this method compacts smaller maps into a relevant fields-based implementation when map size is less than 6.

of

static Context of(ContextView contextView)

Create a Context out of a ContextView, enabling write API on top of the read-only view. If the ContextView is already a Context, return the same instance.

Parameters:

contextView - the ContextView to convert (or cast) to Context

Returns:

the converted Context for further modifications

readOnly

default ContextView readOnly()

Switch to the ContextView interface, which only allows reading from the context.

Returns:

the ContextView of this context

put

Context put(Object key,
            Object value)

Create a new Context that contains all current key/value pairs plus the given key/value pair. If that key existed in the current Context, its associated value is replaced in the resulting Context.

Parameters:

key - the key to add/update in the new Context

value - the value to associate to the key in the new Context

Returns:

a new Context including the provided key/value

Throws:

NullPointerException - if either the key or value are null

putNonNull

default Context putNonNull(Object key,
                           @Nullable
                           Object valueOrNull)

Create a new Context that contains all current key/value pairs plus the given key/value pair only if the value is not null. If that key existed in the current Context, its associated value is replaced in the resulting Context.

Parameters:

key - the key to add/update in the new Context

valueOrNull - the value to associate to the key in the new Context, null to ignore the operation

Returns:

a new Context including the provided key/value, or the same Context if value is null

Throws:

NullPointerException - if the key is null

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

putAll

default Context putAll(ContextView other)

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

Parameters:

other - the other ContextView from which to copy entries

Returns:

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

putAll

@Deprecated
default Context putAll(Context context)

Deprecated. will be removed in 3.5, kept for backward compatibility with 3.3

See putAll(ContextView).

Parameters:

context - the Context from which to copy entries

Returns:

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