简单模型剖析Spring管理Bean的原理

 package com.wxhx.mock;import java.io.InputStream;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import org.dom4j.Document;import org.dom4j.Element;import org.dom4j.XPath;import org.dom4j.io.SAXReader;import com.wxhx.bean.BeanDefinition;public class ClassPathXMLApplicationContextMock{private List<BeanDefinition> beanDefines = new ArrayList<BeanDefinition>();private Map<String, Object> singletons = new HashMap<String, Object>();public ClassPathXMLApplicationContextMock(String fileName){readXML(fileName);}private void instanceBeans(){for (BeanDefinition bean : beanDefines){try{if (bean.getClassName() != null && !"".equals(bean.getClassName().trim())){String id = bean.getId();String className = bean.getClassName();Object instance = Class.forName(className).newInstance();singletons.put(id, instance);}}catch (Exception e){// TODO Auto-generated catch blocke.printStackTrace();}}}private void readXML(String fileName){SAXReader saxReader = new SAXReader();Document document = null;InputStream stream = null;try{stream = this.getClass().getClassLoader().getResourceAsStream(fileName);Map<String, String> nsMap = new HashMap<String, String>();nsMap.put("ns", "http://www.springframework.org/schema/beans");saxReader.getDocumentFactory().setXPathNamespaceURIs(nsMap);document = saxReader.read(stream);XPath path = document.createXPath("//ns:beans/ns:bean");// path.setNamespaceURIs(nsMap);List<Element> beans = path.selectNodes(document);for (Element element : beans){String id = element.attributeValue("id");String className = element.attributeValue("class");BeanDefinition beanDefinition = new BeanDefinition();beanDefinition.setId(id);beanDefinition.setClassName(className);beanDefines.add(beanDefinition);}}catch (Exception e){e.printStackTrace();}}public Object getBean(String id){return singletons.get(id);}public static void main(String[] args){ClassPathXMLApplicationContextMock aa = new ClassPathXMLApplicationContextMock("applicationContext.xml");Object obj = aa.getBean("aaa");System.out.println(obj);}}

请导入dom4j的jar包。