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Context Class

  • Reference
Package:
com.azure.core.util
Maven Artifact:
com.azure:azure-core:1.54.1
  • java.lang.Object
    • com.azure.core.util.Context

public class Context

Context offers a means of passing arbitrary data (key-value pairs) to pipeline policies. Most applications do not need to pass arbitrary data to the pipeline and can pass Context.NONE or null.

Each context object is immutable. The addData(Object key, Object value) method creates a new Context object that refers to its parent, forming a linked list.

Field Summary

Modifier and Type Field and Description
static final Context NONE

Signifies that no data needs to be passed to the pipeline.

Constructor Summary

Constructor Description
Context(Object key, Object value)

Constructs a new Context object.

Method Summary

Modifier and Type Method and Description
Context addData(Object key, Object value)

Adds a new immutable Context object with the specified key-value pair to the existing Context chain.
Optional<Object> getData(Object key)

Scans the linked-list of Context objects looking for one with the specified key.
Map<Object,Object> getValues()

Scans the linked-list of Context objects populating a Map with the values of the context.
static Context of(Map<Object,Object> keyValues)

Creates a new immutable Context object with all the keys and values provided by the input Map.

Methods inherited from java.lang.Object

clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Details

NONE

public static final Context NONE

Signifies that no data needs to be passed to the pipeline.

Constructor Details

Context

public Context(Object key, Object value)

Constructs a new Context object.

Code samples

// Create an empty context having no data
 Context emptyContext = Context.NONE;

 // OpenTelemetry context can be optionally passed using PARENT_TRACE_CONTEXT_KEY
 // when OpenTelemetry context is not provided explicitly, ambient
 // io.opentelemetry.context.Context.current() is used

 // Context contextWithSpan = new Context(PARENT_TRACE_CONTEXT_KEY, openTelemetryContext);

Parameters:

key - The key with which the specified value should be associated.
value - The value to be associated with the specified key.

Method Details

addData

public Context addData(Object key, Object value)

Adds a new immutable Context object with the specified key-value pair to the existing Context chain.

Code samples

// Users can pass parent trace context information and additional metadata to attach to spans created by SDKs
 // using the com.azure.core.util.Context object.
 final String hostNameValue = "host-name-value";
 final String entityPathValue = "entity-path-value";

 // TraceContext represents a tracing solution context type - io.opentelemetry.context.Context for OpenTelemetry.
 final TraceContext parentContext = TraceContext.root();
 Context parentSpanContext = new Context(PARENT_TRACE_CONTEXT_KEY, parentContext);

 // Add a new key value pair to the existing context object.
 Context updatedContext = parentSpanContext.addData(HOST_NAME_KEY, hostNameValue)
     .addData(ENTITY_PATH_KEY, entityPathValue);

 // Both key values found on the same updated context object
 System.out.printf("Hostname value: %s%n", updatedContext.getData(HOST_NAME_KEY).get());
 System.out.printf("Entity Path value: %s%n", updatedContext.getData(ENTITY_PATH_KEY).get());

Parameters:

key - The key with which the specified value should be associated.
value - The value to be associated with the specified key.

Returns:

the new Context object containing the specified pair added to the set of pairs.

getData

public Optional getData(Object key)

Scans the linked-list of Context objects looking for one with the specified key. Note that the first key found, i.e. the most recently added, will be returned.

Code samples

final String key1 = "Key1";
 final String value1 = "first-value";

 // Create a context object with given key and value
 Context context = new Context(key1, value1);

 // Look for the specified key in the returned context object
 Optional<Object> optionalObject = context.getData(key1);
 if (optionalObject.isPresent()) {
     System.out.printf("Key1 value: %s%n", optionalObject.get());
 } else {
     System.out.println("Key1 does not exist or have data.");
 }

Parameters:

key - The key to search for.

Returns:

The value of the specified key if it exists.

getValues

public Map getValues()

Scans the linked-list of Context objects populating a Map with the values of the context.

Code samples

final String key1 = "Key1";
 final String value1 = "first-value";
 final String key2 = "Key2";
 final String value2 = "second-value";

 Context context = new Context(key1, value1)
     .addData(key2, value2);

 Map<Object, Object> contextValues = context.getValues();
 if (contextValues.containsKey(key1)) {
     System.out.printf("Key1 value: %s%n", contextValues.get(key1));
 } else {
     System.out.println("Key1 does not exist.");
 }

 if (contextValues.containsKey(key2)) {
     System.out.printf("Key2 value: %s%n", contextValues.get(key2));
 } else {
     System.out.println("Key2 does not exist.");
 }

Returns:

A map containing all values of the context linked-list.

of

public static Context of(Map keyValues)

Creates a new immutable Context object with all the keys and values provided by the input Map.

Code samples

final String key1 = "Key1";
 final String value1 = "first-value";
 Map<Object, Object> keyValueMap = new HashMap<>();
 keyValueMap.put(key1, value1);

 // Create a context using the provided key value pair map
 Context keyValueContext = Context.of(keyValueMap);
 System.out.printf("Key1 value %s%n", keyValueContext.getData(key1).get());

Parameters:

keyValues - The input key value pairs that will be added to this context.

Returns:

Context object containing all the key-value pairs in the input map.

Applies to