I was able to reproduce the error on a different server in Windows when i created a  new user using the command  db.addUser( "guest", "pass", { readOnly: true } )

OK, I'll fix the ClassCastException, but I think that in your scenario the readOnly parameter is wrongly fed to the addUser() method. The MongoDB documentation for this method mentions the legacy version of it:

Parameters:

• user (string) – Specifies the username.
• password (string) – Specifies the corresponding password.
• readOnly (boolean) – Optional. Defaults to false. Grants users a restricted privilege set that only allows the user to read the this database.

db.addUser( "<username>", "<password>", { readOnly: <boolean> } )

The readOnly parameter is not a JSON object, but a boolean one. I think the curly braces have in this case the sense of "optional parameter".

The JavaScript definition of this method (you can see it by calling > db.<functionName> under MongoShell without the round braces) proves my statement:

> db.addUser
function () {
if (arguments.length == 0) {
throw Error("No arguments provided to addUser");
}
if (typeof arguments[0] == "object") {
this._addUser.apply(this, arguments);
} else {
this._addUserV22.apply(this, arguments);
}
}
> db._addUserV22
function ( username , pass, readOnly, replicatedTo, timeout ) {
if ( pass == null || pass.length == 0 )
throw "password can't be empty";

readOnly = readOnly || false;             // <---- evaluated as boolean parameter
var c = this.getCollection( "system.users" );
var u = c.findOne({user : username, userSource:null}) || { user : username };
u.readOnly = readOnly;
u.pwd = _hashPassword(username, pass);

this._createUser(u, replicatedTo, timeout);
}

Compare it with the newer (2.4.x) version of this function, whose first argument is a JSON object:

> db._addUser
function (userObj, replicatedTo, timeout) {
var roles = userObj['roles'];     // <-------- userObj argument evaluated as JSON object ( associative array )
var oldPwd;

....

Therefore, your call should be:

> db.addUser( "guest", "pass", true)

The ClassCastException has been fixed on nosql-jdbc v1.1.1 .

Fixed in 14.0-dev-38