Java-马士兵设计模式学习笔记-工厂模式-用Jdom模拟Spring

一、概述

1.目标：模拟Spring的Ioc

2.用到的知识点：利用jdom的xpath读取xml文件，反射

二、有如下文件：

1.applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans>
  <bean id="vehicle" class="com.tong.spring.factory.Car">
  </bean>
</beans>

　　

2.BeanFactory.java

public interface BeanFactory {
	Object getBean(String id);
}

　　

3.ClassPathXmlApplicationContext.java

public class ClassPathXmlApplicationContext implements BeanFactory{

	private Map<String, Object> container = new HashMap<String, Object>();

	public ClassPathXmlApplicationContext(String fileName) {

		//读取xml文件
		SAXBuilder sb = new SAXBuilder();
		Document doc;
		try {
			//doc = sb.build(fileName);
			//Test.java要改为BeanFactory factory = new ClassPathXmlApplicationContext("com/tong/spring/factory/applicationContext.xml");
			//否则付出现“java.net.MalformedURLException”
			doc = sb.build(this.getClass().getClassLoader().getResourceAsStream(fileName));
			Element root = doc.getRootElement();
			List list = XPath.selectNodes(root, "/beans/bean");

			for (int i = 0; i < list.size(); i++) {
				Element element = (Element) list.get(i);
				String id = element.getAttributeValue("id");
				String clazz = element.getAttributeValue("class");

				// 利用反射生成例,然后装进容器
				Object o = Class.forName(clazz).newInstance();
				container.put(id, o);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

	@Override
	public Object getBean(String id) {
		return container.get(id);
	}

}

　　

4.Movable.java

public interface Movable {
	void run();
}

　　

5.Car.java

public class Car implements Movable {

	public void run() {
		System.out.println("Car running...............");
	}

}

　

6.Test.java　

public class Test {

	@org.junit.Test
	public void test() {

		//BeanFactory factory = new ClassPathXmlApplicationContext("applicationContext.xml");
		BeanFactory factory = new ClassPathXmlApplicationContext("com/tong/spring/factory/applicationContext.xml");
		Object o = factory.getBean("vehicle");
		Movable m = (Movable)o;
		m.run();
	}
}

　　

　　

运行结果：