persiste ( long text & special chars ) in app engine from GWT and get the result from appengine as json

now i have GWT application ( front end ) and java GAE ( back end ) i need some help at this item :

1 - how to store text in appengine and retrieve it as json format.

2 - how to validate that special character can store correctly in app engine and retr开发者_JAVA技巧ieve correctly in json format.

If you're using JDO or JPA under GAE, you shouldn't have to worry too much about special characters, so long as you pass String values via API calls to set parameters rather than directly trying to insert them into queries. As far as marshalling them across the wire via JSON, is there any cause for concern using GWT's JSON support?