Cygnus: Check special characters for filenames

[fgalan]

Moved from telefonicaid/fiware-livedemoapp#15:

As experienced with FINESCE people, if an entity or attribute name or type contains the "/" character then the persisted file for this entity-attribute pair will contain the "/" character. When creating thar file, WebHDFS/HttpFS understands a subdirectory must be created and then a file.

E.g. entity=mycar, entity_tpe=car, attribute_name=speed, attribute_type=km/h will be persisted as mycar-car-speed-km/h.txt, which in the end is the following directory /user/myuser/mystorage/mycar-car-speed-km containing a h.txt file.

Special characters usage must be checked before creating the file name.

[fgalan]

I think to remember that we had some similar issue with other special character in the past, such ":", that gets replaced by _. Probably it is just a matter of including "/" to the list of special characters to check and replace by _.

[frbattid]

You are right, the characters ':' and '-' are currently replaced by '_'. I would extend the list to any non alphanumeric character, I think using regular expressions this is quite easy:

s = s.replaceAll("[^a-zA-Z0-9]", "_");

[frbattid]

As being discussed by Skype, this is a very different thing than serializing the entity and attribute type and id/name. In this case, we must ensure the serialized characters don't break the Json parsing.

[frbattid]

Solved in PR telefonicaid/fiware-connectors#44