TextMapGetter (OpenTelemetry Context (Incubator))

Type Parameters:

C - carrier of propagation fields, such as an http request.
```
public interface TextMapGetter<C>
```
Interface that allows a TextMapPropagator to read propagated fields from a carrier.
Getter is stateless and allows to be saved as a constant to avoid runtime allocations.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`String`	`get(C carrier, String key)`	Returns the first value of the given propagation `key` or returns `null`.
`Iterable<String>`	`keys(C carrier)`	Returns all the keys in the given carrier.

- Method Detail
  - keys
```
Iterable<String> keys(C carrier)
```
    Returns all the keys in the given carrier.
    
    Parameters:
    
    carrier - carrier of propagation fields, such as an http request.
    
    Since:
    
    0.10.0
  - get
```
@Nullable
String get(@Nullable
           C carrier,
           String key)
```
    Returns the first value of the given propagation key or returns null.
    
    Parameters:
    
    carrier - carrier of propagation fields, such as an http request.
    
    key - the key of the field.
    
    Returns:
    
    the first value of the given propagation key or returns null.