If encoding of resource is passes as null and reader is InputStreamReader encoding taken from reader is overriden to null.
"this.encoding = encoding;" should be in else block in my opinion.

public ReaderResource(Reader reader, String encoding, ResourceType type ) {
if ( reader == null )

if ( encoding == null && reader instanceof InputStreamReader )

this.reader = reader;

this.encoding = encoding; <== encoding assigned to null

setResourceType( type );

this.timestamp = System.currentTimeMillis();
this.lastRead = this.timestamp;
}