工厂方法模式（Factory Method)

factory method 提供了一种延迟创建类的方式，使用这个方式可以在运行期由子类判断创建哪一个类的实例。其次，创建一个对象似乎是一个最简单的是object=new ClassName(),但面对大型软件或不同运行环境时就存在问题： 1、简单的创建方式造成硬编码，在不同的运行环境中就需要复杂的逻辑实例化不同的实例。 2、为了使用于不同的运行环境，通常我们需要定义抽象的接口，在不同的环境中实现不同的子类实例 效果： 根据不同的配置及上下文环境加载具有相同抽象类的不同实现实例，实现可配置，动态的创建

#include <iostream> using namespace std; namespace Occ{ /** * 职业 */ class Occupation { public: virtual void learn()=0; virtual void write()=0; virtual void read()=0; }; class Student: public Occupation { public: void learn() { cout << "学生学习..." << endl; } void write() { cout << "学生写作..." << endl; } void read() { cout << "学生读文章..." << endl; } }; class Teacher: public Occupation { public: void learn() { cout << "老师学习..." << endl; } void write() { cout << "老师写作..." << endl; } void read() { cout << "老师读文章..." << endl; } }; } namespace IFac{ class IFactory { public: virtual Occ::Occupation *createOccupation()=0; }; class StudentFactory: public IFactory { Occ::Occupation *createOccupation(){ return new Occ::Student(); } }; class TeacherFactory: public IFactory { Occ::Occupation *createOccupation(){ return new Occ::Teacher(); } }; } int main() { //需要创建学生时 IFac::IFactory * ifctory =new IFac::StudentFactory(); Occ::Occupation * occupation=ifctory->createOccupation(); occupation->learn(); occupation->write(); occupation->read(); //需要创建老师时 IFac::IFactory * ifctory1 =new IFac::TeacherFactory(); Occ::Occupation * occupation1=ifctory1->createOccupation(); occupation1->learn(); occupation1->write(); occupation1->read(); cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!! return 0; }

Spring 通过工厂方法来配置bean

bean.xml <bean id="ifctory " class="com.dpicadev.factoryMethod.IFactory "> ...... </bean> <bean id="occupation" factory-bean="ifctory" factory-method="createOccupation"> ..... </bean> <bean id="occupation1" factory-bean="ifctory" factory-method="createOccupation"> ..... </bean> java: ApplicationContext ctx = new ClassPathXmlApplicationContext("bean.xml"); Occupation occupation= (Occupation ) ctx.getBean("occupation"); System.out.println(occupation->learn()); Occupation occupation1= (Occupation ) ctx.getBean("occupation1"); System.out.println(occupation1->learn());