Java/Servlet error with calculation class

Question

We've recently started to work with servlets and so far so good. We're able to make most work, yet we encounter an issue when attempting to calculate a price, see below

    public int retrievePrice(int type, int height, int width) throws Exception{
    this.type = type;
    this.height = height;
    this.width = width;

    int sum = 0;
    try {

        DataAccessObject data = new DataAccessObject();

        int priceOfGlass = 300; // Price of glass per m2.
        int priceOfFrame = 0;

        int glassInSqMeters = height * width;
        int glassPrice = glassInSqMeters * priceOfGlass;

        priceOfFrame = data.retrievePrice(type);
        int framePrice = (priceOfFrame * height) + (priceOfFrame * width);

        sum = framePrice + glassPrice;
        return sum;
    } catch (Exception e) {
        e.printStackTrace();
    }
    return 45; // debugging
}

The RetrievePrice can be found here:

public class DataAccessObject  {

public int retrievePrice(int frameType) throws Exception{
    int price = 0;
    try{
        DBConnector con = new DBConnector();
        ResultSet res = con.doQuery("SELECT * FROM pricing WHERE type = "+frameType+"");
        if (res.next()) {
            price = res.getInt("price");
        }
    } catch(SQLException | ClassNotFoundException e) {
        throw new RuntimeException(e);
    }

    return price;
}

}

It's producing the following errors:

java.lang.RuntimeException: java.lang.ClassNotFoundException:     com.mysql.jdbc.Driver
at Glazier.DataAccessObject.retrievePrice(DataAccessObject.java:22)
at Calculations.retrievePrice(Calculations.java:37)
at Servlet.doGet(Servlet.java:53)

We need to access the database and pull the price of the actual window type! Any clues?