模拟Spring容器管理bean
package com.spring;import java.io.IOException;import java.net.URL;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import org.jdom.Document;import org.jdom.Element;import org.jdom.JDOMException;import org.jdom.input.SAXBuilder;import org.jdom.xpath.XPath;import com.vo.BeanDefinition;/** * 简单模拟spring的ClassPathXmlApplicationContext spring容器管理bean * */@SuppressWarnings("unchecked")public class MyApplicationContext{ private List<BeanDefinition> list = new ArrayList<BeanDefinition>(); private Map<String, Object> sigletons = new HashMap<String, Object>(); public MyApplicationContext(String fileName) { this.readXML(fileName); try { instanceBeans(); } catch (Exception e) { e.printStackTrace(); } } /** * 实例化所有bean * * @throws InstantiationException * @throws IllegalAccessException * @throws ClassNotFoundException */ private void instanceBeans() throws InstantiationException, IllegalAccessException, ClassNotFoundException { for (BeanDefinition bean : list) { if (null != bean.getClassName() && bean.getClassName().length() > 0) sigletons.put(bean.getId(), Class.forName(bean.getClassName()) .newInstance()); } } /** * 读取xml配置 * * @param fileName */ public void readXML(String fileName) { SAXBuilder builder = new SAXBuilder(); URL url = this.getClass().getClassLoader().getResource(fileName); try { Document doc = builder.build(url); XPath xpath = XPath.newInstance("//ns:beans/ns:bean"); xpath.addNamespace("ns", "http://www.springframework.org/schema/beans"); List<Element> beans = xpath.selectNodes(doc); for (Element bean : beans) { String id = bean.getAttributeValue("id"); String className = bean.getAttributeValue("class"); BeanDefinition beanDefinition = new BeanDefinition(id, className); list.add(beanDefinition); } } catch (JDOMException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } /** * 得到指定id的bean * * @param id * @return */ public Object getBean(String id) { return sigletons.get(id); }} 测试：@Test public void testMyUserService() { MyApplicationContext ctx = new MyApplicationContext("beans.xml"); UserService us = (UserService) ctx.getBean("userService"); us.print(); }?