VirtualField (instrumentation-api 1.12.0-alpha API)

java.lang.Object
- io.opentelemetry.instrumentation.api.field.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

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
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 Detail
  - VirtualField
```
public VirtualField()
```
- Method Detail
  - 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.