Table Gateway (DAO)

Gateways and Mappers are general patterns for hiding differences in data representation between two collaborating systems.

The idea of a table gateway is to provide a gateway class for each database table.

Here's a Java sketch of the find method in the CustomerGateway class:

class CustomerGateway extends Gateway {
   CustomerRecordSet find(Customer c) {
      CustomerRecordSet result = new CustomerRecordSet();
      String query = "select * from customer where ";
      if (c.ID != null) {
         query += ("customerID = " + c.getID());
      } else {
         // use c to add conditions to query
      }
      ResultSet res = execute(sql);
      // for each row in res add a customer object to result
      return result;
   }
   // etc.
}

A JDBC Gateway can be found in Gateway.java