01spring spring的简单模拟

spring的设计是面向接口(抽象)的好处：灵活，可以更换不同的实现模拟spring读取xml配置文件beans.xml//可以看成是一个大的容器<beans><bean id="u" class="com.dao.impl.UserDAOImpl"/><bean id="userService" class="com.service.UserService"><property name="userDAO" bean="u"/>//把userDAO装配(注入)到userService中</bean></beans>public interface BeanFactory{public Object getBean(String name);}public class ClassPathXmlApplicationContext implements BeanFactory{private Map<String,Object> beans = new HashMap<String,Object>();public ClassPathXmlApplicationContext() throws Exception{SAXBuilder builder = new SAXBuilder();Document doc = builder.build(Sample.class.getClassLoader().getResourceAsStream("beans.xml"));//构造文档对象Element root = doc.getRootElement();//获取根元素List list = root.getChildren("bean");//取名字为bean的所有元素for(int i=0;i<list.size();i++){Element element = (Element)list.get(i);String id = element.getAttributeValue("id");String clazz = element.getChildText("class");System.out.println(id+":"+clazz);Object o = Class.forName(clazz).newInstance();beans.put(id,o);for(Element propertyElement:(List<Element>)element.getChild("property")){String name = propertyElement.getAttributeValue("name");//userDAOString bean = propertyElement.getAttributeValue("bean");//uObject beanObject = beans.get(bean);//UserDAOImpl instanceString methodName = "set"+name.substring(0,1).toUpperCase()+name.substring(1);System.out.println("method name = "+methodName);Method m = o.getClass().getMethod(methodName,beanObject.getClass().getInterfaces()[0]);//根据方法名和参数获取方法(因为可能存在重载)//参数是userDAOImpl实现的接口中的一个m.invoke(o,beanObject);//调用o对象的m方法，传入参数beanObject}}}public Object getBean(String name){return beans.get(name);}}public class UserServiceTest{@Testpublic void testAdd() throws Exception{BeanFactory factory = new ClassPathXmlApplicationContext();UserService service = new UserService();//UserDAO userDAO = (UserDAO)factory.getBean("u");//service.setUserDAO(userDAO);User u = new User();service.add(u);}}