设计模式-抽象工厂模式

今天来介绍一下另一个复杂一点的抽象工厂模式。

1.UML类图

IUser和IDepartment是想要创建的产品的抽象接口，而SqlserverUser、AccessUser和SqlserverDepartment、AccessDepartment分别是其两种不同的具体产品实现类。IFactory是抽象工厂，其中定义了创建两种产品的接口，其具体实现类实现这两个方法根据需求创建不同的IUser和IDepartment实现类。

2.示例代码

IUser接口以及其对应的两个实现类

public interface IUser {
    void insert(User user);

    User getUser(Integer id);
}

public class SqlServerUser implements IUser {
    @Override
    public void insert(User user) {
        System.out.println("在sql server中给user表添加一条记录");
    }

    @Override
    public User getUser(Integer id) {
        System.out.println("在sql server中根据id得到user表一条记录");
        return null;
    }
}

public class AccessUser implements IUser {
    @Override
    public void insert(User user) {
        System.out.println("在access中给user表添加一条记录");
    }

    @Override
    public User getUser(Integer id) {
        System.out.println("在access中根据id得到user表一条记录");
        return null;
    }
}

IDepartment接口以及其对应的实现类

public interface IDepartment {
    void insert(Department department);
    Department getDepartment(Integer id);
}

public class SqlServerDepartment implements IDepartment {
    @Override
    public void insert(Department department) {
        System.out.println("在sql server中给department表添加一条记录");
    }

    @Override
    public Department getDepartment(Integer id) {
        System.out.println("在sql server中根据id得到department表一条记录");
        return null;
    }
}

public class AccessDepartment implements IDepartment {
    @Override
    public void insert(Department department) {
        System.out.println("在access中给department表添加一条记录");
    }

    @Override
    public Department getDepartment(Integer id) {
        System.out.println("在access中根据id得到department表一条记录");
        return null;
    }
}

IFactory抽象工厂以及其对应的两个具体实现工厂，相应的具体工厂中定义了创建User和Department的方法

public interface IFactory {
    IUser createUser();

    IDepartment createDepartment();
}

public class AccessFactory implements IFactory {
    @Override
    public IUser createUser() {
        return new AccessUser();
    }

    @Override
    public IDepartment createDepartment() {
        return new AccessDepartment();
    }
}

public class SqlServerFactory implements IFactory {
    @Override
    public IUser createUser() {
        return new SqlServerUser();
    }

    @Override
    public IDepartment createDepartment() {
        return new SqlServerDepartment();
    }
}

public class Client {
    public static void main(String[] args) {
        User user = new User();
        Department department = new Department();

        IFactory factory = new SqlServerFactory();
        IUser iu = factory.createUser();
        iu.insert(user);
        iu.getUser(2);
    }
}

3.特点

抽象工厂提供一个创建一系列相关类或相互依赖对象的接口，而无需指定它们具体的类。它使得改变一个应用的具体工厂变得非常容易，它让具体的创建实例的过程与客户端分离，客户端是通过它们的抽象接口操纵实例，产品的具体类名也被具体工厂的实现分离，不会出现在客户端代码中。