Spring的IOC机制，利用了java的反射机制，通过读取配置文件，动态生成所需要的类。

public static void main(String[] args) {        // TODO Auto-generated method stub        Resource rs = new FileSystemResource("helloMessage.xml");        BeanFactory bf = new XmlBeanFactory(rs);        Person person = (Person)bf.getBean("person");        String s = person.sayHello();        System.out.println("The person is currently saying " + s);            }

源码

　　https://git.oschina.net/zkzk945/Spring.git