计算类

Question

我们最近开始使用servlet，到目前为止一直很好。我们能够完成大部分工作，但在尝试计算价格时遇到问题，请参阅下文

    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
}

可以在此处找到RetrievePrice：

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;
}

}

它产生了以下错误：

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)

我们需要访问数据库并提取实际窗口类型的价格！有线索吗？