spring4-2-bean配置-10-通过FactoryBean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
　　

1.1 创建bean:

package spring.demo_01.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;
    }
    public Car(String brand, double price) {
        super();
        this.brand = brand;
        this.price = price;
    }
    @Override
    public String toString() {
        return "Car [brand=" + brand + ", price=" + price + "]";
    }
}

1.2 创建MyFactoryBean 实现接口FactoryBean

package spring.demo_01.factorybean;

import org.springframework.beans.factory.FactoryBean;

public class MyFactoryBean implements FactoryBean<Car> {
    private String brand;

    public void setBrand(String brand) {
        this.brand = brand;
    }

    @Override
    public Car getObject() throws Exception {
        return new Car(brand,30000);
    }

    @Override
    public Class<?> getObjectType() {
        return Car.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }

}

1.3 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">

    <!--
        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

        实际返回的是 FactoryBean的getObject 方法获取的实例.
     -->

    <bean id="car" class="spring.demo_01.factorybean.MyFactoryBean">
        <property name="brand" value="BMW"></property>
    </bean>
</beans>

1.4 测试类:

package spring.demo_01.factorybean;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class App {
    @SuppressWarnings("resource")
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-factorybean.xml");
        Car car = ctx.getBean("car",Car.class);
        System.out.println(car);
    }
}