| ndCustomer()被调用时，CloudscapeCustomerDAO创建一个Customer值对象。
范例9-6是使用DAO的范例代码。
2.实现数据访问对象的工厂策略
1)使用工厂方法模式
2)使用抽象工厂模式
范例代码9-2是CloudscapeDAOFactory的范例代码。
范例代码9-3中的CustomerDAO接口为Customer持久性对象定义了DAO方法，这些接口是被所有具体DAO实现来实现的，比如CloudscapeCustomerDAO、OracleCustomerDAO、已经SybaseCustomerDAO。Account和OrederDAO接口也与此类似。
Example 9.1 Abstract DAOFactory Class
// Abstract class DAO Factory
public abstract class DAOFactory {
// List of DAO types supported by the factory
public static final int CLOUDSCAPE = 1;
public static final int ORACLE = 2;
public static final int SYBASE = 3;
...
// There will be a method for each DAO that can be
// created. The concrete factories will have to
// implement these methods.
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;
}
}
}
Java模式设计之数据访问对象模式(5)
时间:2010-12-06
Example 9.2 Concrete DAOFactory Implementation for Cloudscape
// 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();
}
...
}
Example 9.3 Base DAO Interface for Customer
// 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 selectCustomersVO(...);
...
}
Example 9.4 Cloudscape DAO Implementation for Customer
// CloudscapeCustomerDAO implementation of the
// CustomerDAO interface. This class can contain all
// Cloudscape specific code and SQL statements.
// The client is
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