九调用工厂方法实现Bean

以你之姓@ 2022-06-17 02:14 151阅读 0赞

1.静态工厂方法:

调用静态工厂方法创建 Bean是将对象创建的过程封装到静态方法中.

当客户端需要对象时, 只需要简单地调用静态方法, 而不同关心创建对象的细节.要声明通过静态方法创建的 Bean,

需要在 Bean 的 class 属性里指定拥有该工厂的方法的类, 同时在 factory-method 属性里指定工厂方法的名称.

最后, 使用 <constrctor-arg> 元素为该方法传递方法参数.  
ex:

首先创建一个静态工厂类:

public class StaticCarFactory {
        private static Map<String,Car> cars=new HashMap<>();
        static {
            cars.put("audi",new Car("audi",30000));
            cars.put("ford",new Car("ford",40000));
        }
        public static Car getCar(String name){
    
            return cars.get(name);
        }
    }

同样的需要配置bean:

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
        <bean id="cars" class="beansfactory.StaticCarFactory"
              factory-method="getCar">
            <constructor-arg value="audi"></constructor-arg>
        </bean>
    </beans>

在主程序中进行输出:

public class Main {
        public static void main(String[] args){
            ApplicationContext ctx=new ClassPathXmlApplicationContext("beans-factory.xml");
    
            Car test= (Car) ctx.getBean("cars");
            System.out.println(test);
    
        }
    }

![Center][]

2.调用实例工厂方法实现Bean:

首先创建一个实例工厂类：

public class InstanceCarFactory {
        private Map<String,Car> cars=null;
        public InstanceCarFactory(){
            cars=new HashMap<String,Car>();
            cars.put("audi",new Car("audi",30000));
            cars.put("ford",new Car("ford",40000));
    
        }
        public Car getCar(String brand){
            return cars.get(brand);
        }
    }

同样的创建配置文件:

<bean id="carFactory" class="beansfactory.InstanceCarFactory"></bean>
        
        <bean id="car2" factory-bean="carFactory" factory-method="getCar">
            <constructor-arg value="ford"></constructor-arg>
        </bean>

在主程序中进行调用:

public class Main {
        public static void main(String[] args){
            ApplicationContext ctx=new ClassPathXmlApplicationContext("beans-factory.xml");
    
            Car test= (Car) ctx.getBean("car2");
            System.out.println(test);
    
        }
    }

输出结果:

![Center 1][]

[Center]: /images/20220617/a21a7b90a1c249fc971b106ab0c1ee8f.png
[Center 1]: /images/20220617/2758250db3d742459f08499dcd0bfc39.png