Package io.opentelemetry.instrumentation.api.util

Class VirtualField<T,F>

java.lang.Object

io.opentelemetry.instrumentation.api.util.VirtualField<T,F>

Type Parameters:

T - The type that will contain the new virtual field.

F - The field type that'll be added to T.

public abstract class VirtualField<T,F>
extends Object

Represents a "virtual" field of type F that is added to type T in the runtime.

A virtual field has similar semantics to a weak-keys strong-values map: the value will be garbage collected when their owner instance is collected. It is discouraged to use a virtual field for keeping values that might reference their key, as it may cause memory leaks.

Constructor Summary

Constructors

Constructor	Description
VirtualField()

Method Summary

Modifier and Type	Method	Description
static <U extends T, V extends F, T, F> VirtualField<U,V>	find(Class<T> type, Class<F> fieldType)	Finds a VirtualField instance for given type and fieldType.
abstract F	get(T object)	Gets the value of this virtual field.
abstract void	set(T object, F fieldValue)	Sets the new value of this virtual field.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

VirtualField

public VirtualField()

Method Details

find

public static <U extends T,
V extends F,
T,
F>
VirtualField<U,V> find(Class<T> type,
 Class<F> fieldType)

Finds a VirtualField instance for given type and fieldType.

Conceptually this can be thought of as a map lookup to fetch a second level map given type.

In runtime, when using the javaagent, the calls to this method are rewritten to something more performant while injecting advice into a method.

When using this method outside of Advice method, the VirtualField should be looked up once and stored in a field to avoid repeatedly calling this method.

Parameters:

type - The type that will contain the new virtual field.

fieldType - The field type that will be added to type.

get

@Nullable
public abstract F get(T object)

Gets the value of this virtual field.

set

public abstract void set(T object,
 @Nullable
 F fieldValue)

Sets the new value of this virtual field.