Spring中通过FactoryBean来配置bean

Spring中通过FactoryBean来配置bean

一、说在前面

实现 FactoryBean 接口在 Spring IOC 容器中配置 Bean
1、Spring 中有两种类型的 Bean, 一种是普通Bean, 另一种是工厂Bean, 即FactoryBean。
2、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。

二、实例演示

Car类：

package com.at.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;
	}
}

CarFactoryBean类：

package com.at.beans.factorybean;

import org.springframework.beans.factory.FactoryBean;
//自定义的CarFactoryBean需要实现FactoryBean接口
public class CarFactoryBean implements FactoryBean<Car>{

	private String brand;
	public void setBrand(String brand) {
		this.brand = brand;
	}
	//返回bean的对象
	public Car getObject() throws Exception {
		return new Car(brand,500000);
	}
	//返回bean的类型
	public Class<?> getObjectType() {
		return Car.class;
	}
	//是不是单实例的
	public boolean isSingleton() {
		return true;
	}

}

bean配置：

<?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实例
		class：指向FactoryBean的全类名
		property:配置FactoryBean的属性
		
		但是实际上返回的实例确实FactoryBean的getObject()方法返回的实例
	 -->
	<bean id="car" class="com.at.beans.factorybean.CarFactoryBean">
		<property name="brand" value="Audi"></property>
	</bean>
</beans>

测试函数：

		ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-factorybean.xml");
		Car car = (Car) ctx.getBean("car");
		System.out.println(car);	

返回结果：

六月 01, 2017 5:07:34 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@1c49094: startup date [Thu Jun 01 17:07:34 CST 2017]; root of context hierarchy
六月 01, 2017 5:07:35 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [beans-factorybean.xml]
Car [brand=Audi, price=500000.0]

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