An object that implements this interface contains the information needed to act as source input (XML source or transformation instructions).
Get the system identifier that was set with setSystemId.
Return
The system identifier that was set with setSystemId, or null if setSystemId was not called.
Set the system identifier for this Source.

The system identifier is optional if the source does not get its data from a URL, but it may still be useful to provide one. The application can use a system identifier, for example, to resolve relative URIs and to include in error messages and warnings.

Parameters
systemIdThe system identifier as a URL string.