// 抽象类：DAO工厂
						public abstract class DAOFactory {
						// 工厂所支持的DAO类型列表
						public static final int CLOUDSCAPE = 1;
						public static final int ORACLE = 2;
						public static final int SYBASE = 3;
						...
						// 对于每一中所支持的DAO，都有一个方法与之对应。 
						// 实体工厂必须实现这类方法。
						public abstract CustomerDAO getCustomerDAO();
						public abstract AccountDAO getAccountDAO();
						public abstract OrderDAO getOrderDAO();
						...
						public static DAOFactory getDAOFactory(
						int whichFactory) {
						switch (whichFactory) {
						case CLOUDSCAPE: 
						return new CloudscapeDAOFactory();
						case ORACLE    : 
						return new OracleDAOFactory();      
						case SYBASE    : 
						return new SybaseDAOFactory();
						...
						default           : 
						return null;
						}
						}
						}
						

						// Cloudscape concrete DAO Factory implementation
						import java.sql.*;
						public class CloudscapeDAOFactory extends DAOFactory {
						public static final String DRIVER=
						"COM.cloudscape.core.RmiJdbcDriver";
						public static final String DBURL=
						"jdbc:cloudscape:rmi://localhost:1099/CoreJ2EEDB";
						// method to create Cloudscape connections
						public static Connection createConnection() {
						// Use DRIVER and DBURL to create a connection
						// Recommend connection pool implementation/usage
						}
						public CustomerDAO getCustomerDAO() {
						// CloudscapeCustomerDAO implements CustomerDAO
						return new CloudscapeCustomerDAO();
						}
						public AccountDAO getAccountDAO() {
						// CloudscapeAccountDAO implements AccountDAO
						return new CloudscapeAccountDAO();
						}
						public OrderDAO getOrderDAO() {
						// CloudscapeOrderDAO implements OrderDAO
						return new CloudscapeOrderDAO();
						}
						...
						}
						

						// Interface that all CustomerDAOs must support
						public interface CustomerDAO {
						public int insertCustomer(...);
						public boolean deleteCustomer(...);
						public Customer findCustomer(...);
						public boolean updateCustomer(...);
						public RowSet selectCustomersRS(...);
						public Collection selectCustomersTO(...);
						...
						}
						

						// CloudscapeCustomerDAO implementation of the 
						// CustomerDAO interface. This class can contain all
						// Cloudscape specific code and SQL statements. 
						// The client is thus shielded from knowing 
						// these implementation details.
						import java.sql.*;
						public class CloudscapeCustomerDAO implements 
						CustomerDAO {
						public CloudscapeCustomerDAO() {
						// initialization 
						}
						// The following methods can use
						// CloudscapeDAOFactory.createConnection() 
						// to get a connection as required
						public int insertCustomer(...) {
						// Implement insert customer here.
						// Return newly created customer number
						// or a -1 on error
						}
						public boolean deleteCustomer(...) {
						// Implement delete customer here
						// Return true on success, false on failure
						}
						public Customer findCustomer(...) {
						// Implement find a customer here using supplied
						// argument values as search criteria
						// Return a Transfer Object if found,
						// return null on error or if not found
						}
						public boolean updateCustomer(...) {
						// implement update record here using data
						// from the customerData Transfer Object
						// Return true on success, false on failure or
						// error
						}
						public RowSet selectCustomersRS(...) {
						// implement search customers here using the
						// supplied criteria.
						// Return a RowSet. 
						}
						public Collection selectCustomersTO(...) {
						// implement search customers here using the
						// supplied criteria.
						// Alternatively, implement to return a Collection 
						// of Transfer Objects.
						}
						...
						}
						

						public class Customer implements java.io.Serializable {
						// member variables
						int CustomerNumber;
						String name;
						String streetAddress;
						String city;
						...
						// getter and setter methods...
						...
						}
						

						...
						// create the required DAO Factory
						DAOFactory cloudscapeFactory =   
						DAOFactory.getDAOFactory(DAOFactory.DAOCLOUDSCAPE);
						// Create a DAO
						CustomerDAO custDAO = 
						cloudscapeFactory.getCustomerDAO();
						// create a new customer
						int newCustNo = custDAO.insertCustomer(...);
						// Find a customer object. Get the Transfer Object.
						Customer cust = custDAO.findCustomer(...);
						// modify the values in the Transfer Object.
						cust.setAddress(...);
						cust.setEmail(...);
						// update the customer object using the DAO
						custDAO.updateCustomer(cust);
						// delete a customer object
						custDAO.deleteCustomer(...);
						// select all customers in the same city 
						Customer criteria=new Customer();
						criteria.setCity("New York");
						Collection customersList = 
						custDAO.selectCustomersTO(criteria);
						// returns customersList - collection of Customer
						// Transfer Objects. iterate through this collection to
						// get values.
						...