question: private static < T > int migrateAll ( Migration < T > migration ) throws Exception { int migrated = 0 ; for ( T entity : migration . getAllEntities ( ) ) { try { if ( migration . isMigrated ( entity ) ) continue ; } catch ( Exception x ) { LOG . error ( "Couldn't check if the entity '{}' is migrated due to occurred error" , entity ) ; throw x ; } try { migration . migrate ( entity ) ; } catch ( Exception x ) { LOG . error ( "Error migrating the entity '{}" , entity ) ; throw x ; } migrated ++ ; } return migrated ; }
target:  Migrates entities and skips those which are already migrated.