I get this error: class file has wrong version 50.0, should be 49.0
That sounds like you're using a library that is compiled for use with
Java 6, while you're using Java 5. Either recompile the library to work with Java 5 (assuming that's possible, but chances are that it is), or find another library that works with java 5 out of the box, or upgrade your JDK to Java 6.
even though, again, json.jar is in its proper place, and proper directive is in JSP to import JSON classes
By "proper place" you mean your web app's WEB-INF/lib directory, right? Post the JSP directive.
where does JSONValuecome from, I don't see JSONValue here ... he imports org.json.simple, where does he get THAT from, there's no class SIMPLE in org.json..
The
footnote on that page tells you where to get the required files.
But in general, note this paragraph under "JSON parsers -> on the server-side", which I take to mean that
you should adapt the code to whatever JSON library you happen to use:
Decode the incoming JSON string and convert the result to an object using a JSON parser for the language of your choice. At http://www.json.org, you'll find JSON parsers for many modern programming languages. The methods available depend upon which parser you are using. See the parser's documentation for details.