实现 FactoryBean 接口在 Spring IOC 容器中配置 Bean
- Spring 中有两种类型的 Bean, 一种是普通Bean, 另一种是工厂Bean, 即FactoryBean.
- 工厂 Bean 跟普通Bean不同, 其返回的对象不是指定类的一个实例, 其返回的是该工厂 Bean 的 getObject 方法所返回的对象
package com.atguigu.spring.beans.factorybean; public class Car { private String brand; private double price; public String getBrand() { return brand; } public void setBrand(String brand) { this.brand = brand; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } @Override public String toString() { return "Car [brand=" + brand + ", price=" + price + "]"; } public Car(String brand, double price) { super(); this.brand = brand; this.price = price; } public Car() { System.out.println("car的构造器"); } }
package com.atguigu.spring.beans.factorybean; import org.springframework.beans.factory.FactoryBean; //自定义的FactoryBean需要实现FactoryBean接口 public class CarFactoryBean implements FactoryBean<Car> { private String brand; public String getBrand() { return brand; } public void setBrand(String brand) { this.brand = brand; } //还回bean对象 @Override public Car getObject() throws Exception { return new Car(brand,600000); } //还回bean的类型 @Override public Class<?> getObjectType() { return Car.class; } @Override public boolean isSingleton() { return true; } }
<?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"> <!-- 通过FactoryBean来配置Bean的实例 class:指向FactoryBean的全类名 property:配置FactoryBean的属性 但实际还回的实例确实FactoryBean的getObject()方法还回的实例 --> <bean id="car" class="com.atguigu.spring.beans.factorybean.CarFactoryBean"> <property name="brand" value="宝马"></property> </bean> </beans>
package com.atguigu.spring.beans.factorybean; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Main { public static void main(String[] args) { ApplicationContext apl = new ClassPathXmlApplicationContext("beans-beanfactory.xml"); Car car = (Car) apl.getBean("car"); System.out.println(car); } }
结果:
六月 13, 2018 2:18:44 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh 信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@6193b845: startup date [Wed Jun 13 14:18:44 CST 2018]; root of context hierarchy 六月 13, 2018 2:18:44 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions 信息: Loading XML bean definitions from class path resource [beans-beanfactory.xml] Car [brand=宝马, price=600000.0]