Hello, I spend a lot of time in search how to use the rest api, but only i find information to use the rest api with oAuth, but in dont want to use oauth, i want to type the username and password in the code and this is all, i want to make an app where the client dont see any rest api comunication, I mean execute the apex code in background.

I find a code in http://208.69.57.141/index.php/2011/05/using-the-salesforce-rest-api-with-javascript-and-jquery-in-visualforce-pages-using-apex/#comments

But show me a error [{"message":"Session expired or invalid","errorCode":"INVALID_SESSION_ID"}]

Thanks