question: @ Override public synchronized Extension install ( URL url ) throws InvalidConfigException { Preconditions . checkNotNull ( url ) ; try { File tmpFile = download ( url ) ; Extension extension = loadFromFile ( tmpFile ) ; finishInstall ( tmpFile , extension ) ; return extension ; } catch ( InvalidConfigException e ) { throw e ; } catch ( Exception e ) { String msg = baseAction . getText ( "admin.extension.install.error" , new String [ ] { url . toString ( ) } ) ; log . error ( msg , e ) ; throw new InvalidConfigException ( TYPE . INVALID_EXTENSION , msg , e ) ; } }
target:  Download and install an extension into local file. The final filename is based on the extension's rowType.