app.put("/api/students/:studentId", function(req, res) {

    var updateDoc = req.body;
    delete updateDoc._id;

    db.collection(STUDENTS_COLLECTION).findOne({
        studentId: parseInt(req.params.studentId)
    }, function(err, doc) {
        if (err) {
            handleError(res, err.message, "No student with id " + req.params.studentId);
        } else {
            if (doc) {
                updateDoc.studentId = doc.studentId
                db.collection(STUDENTS_COLLECTION).updateOne({
                    studentId: doc.studentId
                }, updateDoc, function(err, finalDoc) {
                    if (err) {
                        handleError(res, err.message, "Failed to update student");
                    } else {
                        res.status(200).json(finalDoc);
                    }
                });
            } else {
                handleError(res, "Invalid user input", "No student with id " + req.params.studentId);
            }
        }
    });

});