DAO API

CS636 Pizza1's DAO API, plus sample methods

Note how the domain objects pass through the DAO API
The DAO create domain objects, based on reading the database data, or inserts/updates/deletes based on given domain objects
The domain objects in memory can usually be thought of as "scratch copies" of the database data, but when a domain object is passed down to the DAO in a data-changing call, it forces the database to change to its version of the data.
Thus the service layer is really in charge of how the database changes over time.
The DAO layer is supposed to be a servant of the service layer, just doing what it's told, not making "business decisions."

DAO methods:

topcat$ grep public *DAO.java

      
AdminDAO.java:public class AdminDAO {
AdminDAO.java:  public AdminDAO(DbDAO db) throws SQLException {
AdminDAO.java:  public void advanceDay() throws SQLException
AdminDAO.java:  public int findCurrentDay() throws SQLException
DbDAO.java:public class DbDAO {
DbDAO.java:     public DbDAO(String dbUrl, String usr, String passwd) throws SQLException {
DbDAO.java:     public void close() throws SQLException {
DbDAO.java:     public void initializeDb() throws SQLException {
MenuDAO.java:public class MenuDAO {
MenuDAO.java:   public MenuDAO(DbDAO db) throws SQLException {
MenuDAO.java:   public MenuSize findMenuSize(String name) throws SQLException
MenuDAO.java:   public Set<MenuSize> findMenuSizes() throws SQLException
MenuDAO.java:   public MenuTopping findMenuTopping(String name) throws SQLException
MenuDAO.java:   public Set<MenuTopping> findMenuToppings() throws SQLException {
MenuDAO.java:   public void createMenuTopping(String toppingName) throws SQLException {
MenuDAO.java:   public void createMenuSize(String sizeName) throws SQLException {
MenuDAO.java:   public void deleteMenuTopping(String topping) throws SQLException
MenuDAO.java:   public void deleteMenuSize(String size) throws SQLException
PizzaOrderDAO.java:public class PizzaOrderDAO {
PizzaOrderDAO.java:     public PizzaOrderDAO(DbDAO db) throws SQLException {
PizzaOrderDAO.java:     public void insertOrder(PizzaOrder order) throws SQLException {
PizzaOrderDAO.java:     public List<PizzaOrder> findOrdersByRoom(int roomNumber, int day) throws SQLException
PizzaOrderDAO.java:     public int findFirstOrder(int status) throws SQLException
PizzaOrderDAO.java:     public void updateOrderStatus(int ordNo, int newStatus) throws SQLException
PizzaOrderDAO.java:     public List<PizzaOrder> findOrdersByDays(int day1, int day2) throws SQLException {

These throw SQLException on errors, but they first carefully close the statement in a finally clause.
They use a private connection object set up at the program start for reuse--typical client-server use of longer-lived connection.

Sample DAO method:

   // find all active toppings
   public Set<MenuTopping> findMenuToppings() throws SQLException {
      Set<MenuTopping> toppings = new TreeSet<MenuTopping>();

      Statement stmt = connection.createStatement();
      try {
            ResultSet set = stmt.executeQuery("select * from " + MENU_TOPPING_TABLE);
            while (set.next())
              toppings.add(new MenuTopping(set.getInt("id"), set.getString("topping_name")));
      } finally {
            stmt.close();
      }
      return toppings;
   }

Another DAO method, from AdminDAO.java:

   
   public void advanceDay() throws SQLException
   {
       Statement stmt = connection.createStatement();
       try {
           stmt.executeUpdate("update " + SYS_TABLE
                               + " set current_day = current_day + 1 ");
       } finally {
           stmt.close();
       }
   }