JDBC初始化驱动、连接

将加载驱动、创建连接设定为仅在程序运行初始进行一次，之后重复调用即可。

Product：商品信息;TradeRecord：交易记录。

2个接口供业务使用

public interface DAOFactory {

    public ProductDAO getProductDAO();

    public TradeRecordDAO getTradeRecordDAO();

}

将加载驱动写在构造函数中，并提供一个getInstance静态方法返回私有静态final成员INSTANCE，这个成员在new的同时进行了加载驱动：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public final class JDBCDAOFactory implements DAOFactory {
    
    private static final JDBCDAOFactory INSTANCE = new JDBCDAOFactory();
    
    private JDBCDAOFactory() {
        try {
            Class.forName("oracle.jdbc.driver.OracleDriver");
        } catch (ClassNotFoundException cnfe) {
            throw new LinkageError("JDBC加载失败", cnfe);
        }
    }

    public static JDBCDAOFactory getInstance() {
        return INSTANCE;
    }

    private ProductDAO productDAO = new ProductDAOImpl(this);
    private TradeRecordDAO tradeRecordDAO = new TradeRecordDaoImpl(this);

    @Override
    public ProductDAO getProductDAO() {
        return productDAO;
    }

    @Override
    public TradeRecordDAO getTradeRecordDAO() {
        return tradeRecordDAO;
    }

    Connection getConnection() throws SQLException {
        return DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:HelloWorld", "scott", "tiger");
    }

}

根据实际情况修改：

import java.sql.*;

public class ProductDAOImpl implements ProductDAO {

    private final JDBCDAOFactory FACTORY;

    ProductDAOImpl(JDBCDAOFactory factory) {
        FACTORY = factory;
    }

    @Override
    public ProductTO insertProduct(ProductTO productTO) throws DaoException {
        String sql = "";
        try {
            Connection conn = FACTORY.getConnection();
            try {
                PreparedStatement pstatement = conn.prepareStatement(sql);
                pstatement.executeUpdate();
                .
                .
                .
                conn.commit();
                return null;
            } catch (SQLException sqle) {
                conn.rollback();
                throw sqle;
            } finally {
                conn.close();
            }
        } catch (SQLException sqle) {
            throw new DaoException(sqle);
        }
    }

    @Override
    public void updateProduct(ProductTO productTO) throws DaoException {
    }

    @Override
    public void deleteProduct(ProductTO productTO) throws DaoException {
    }

    @Override
    public ProductTO getProductById(String id) throws DaoException {
        return null;
    }

}

最后在ProductManagerImpl里就可以：

DAOFactory jdbcdaoFactory = JDBCDAOFactory.getInstance();

jdbcdaoFactory.getProductDAO().insertProduct()......