spring （学习记录）通过factorybean配置bean

小咪咪 2022-04-01 12:42 230阅读 0赞

之前学了，配置bean可以用普通全类名配置、用工厂方法配置，FactoryBean又是什么呢

有时候配置bean要用到，IOC其他Bean，这时，用FactoryBean配置最合适。

FactoryBean是一个接口，要用的话就要实现它。他有三个方法：

getObject() //返回bean对象

getObjectType() //返回bean的类型

isSingleton() //是否单例

看例子：  
Car类：

package com.beans.factorybean;
    
    public class Car {
            public String brand;
            public double price;
    		public String getBrand() {
    			return brand;
    		}
    		public Car() {
    			super();
    			// TODO Auto-generated constructor stub
    			System.out.println("Car's constructor....");
    		}
    		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;
    		}
            
    }

CarFactoryBean类：

package com.beans.factorybean;
    
    import org.springframework.beans.factory.FactoryBean;
    
    public class CarFactoryBean implements FactoryBean<Car>{
    	private String brand;
    	
       
    	public void setBrand(String brand) {
    		this.brand = brand;
    	}
    	//返回bean的对象
    	@Override
    	public Car getObject() throws Exception {
    		// TODO Auto-generated method stub
    		return new Car("BMW",2000000);
    	
    	}
        //返回bean的类型
    	@Override
    	public Class<?> getObjectType() {
    		// TODO Auto-generated method stub
    		return Car.class;
    	}
    	
    	@Override   
    	public boolean isSingleton() {
    		
    		return true;
    	}
    	
    }

配置文件xml

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
    	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xmlns:util="http://www.springframework.org/schema/util"
    	xmlns:p="http://www.springframework.org/schema/p"
    	xsi:schemaLocation="http://www.springframework.org/schema/beans 
    	http://www.springframework.org/schema/beans/spring-beans.xsd
    	 http://www.springframework.org/schema/util
         http://www.springframework.org/schema/util/spring-util.xsd
    	"
    	>
        
        <bean id="car" class="com.beans.factorybean.CarFactoryBean">
             <property name="brand" value="BMW"></property>
        </bean>
    	                                                                                                                                           
    </beans>

运行主类：

package com.beans.factorybean;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class main {
            public static void main(String[] args) {
    			ApplicationContext ctx=new ClassPathXmlApplicationContext("factorybean.xml");
    			Car car=(Car) ctx.getBean("car");
    			System.out.println(car);
    		}
    }

貌似和以前的类名配置一样，  
**注意：返回的实例确是factorybean的getObject（）方法返回的实例！还有这里的BeanFactory和FactoryBean并不是同一件东西**