In JSF 2.3 the ExternalContext is available as an implicit object

JSF provides several objects related to the current request and environment. EL exposes these objects (known as implicit objects) that can be accessed at runtime in a Facelet, servlets, or backing bean—these objects are accessible through value expressions and are managed by the container. Beside the JSF 2.2 implicit objects, JSF 2.3 will allow developers to access the ExternalContext via an implicit object. Basically, we have:

JSF 2.2 - access ExternalContext via static method

ExternalContext externalContext = FacesContext.getCurrentInstance().getExternalContext();

OmniFaces static shortcut for ExternalContext

ExternalContext externalContext = Faces.getExternalContext();

JSF 2.3 - ExternalContext implicit object

#{externalContext}

JSF 2.3 CDI producer method for ExternalContext:

@Inject

private ExternalContext externalContext;

Check out the entire list of JSF 2.3 CDI producer methods:

http://arjan-tijms.omnifaces.org/p/jsf-23.html

http://omnifaces-fans.org/2015/09/jsf-23-injection-and-el-resolving-of.html