简单模拟Spring管理Bean对象

1: 首先我们要利用dom4j进行xml的解析，将所有的bean的配置读取出来。

2：利用java的反射机制进行对象的实例化。

3： 直接获得对象

 

package cn.Junit.test;



import java.net.URL;

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 org.springframework.beans.factory.config.BeanDefinition;



public class MyClassPathXmlApplicationContext {

	private String filemame;

	private List<DefBean> list = new ArrayList<DefBean>();

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



	public MyClassPathXmlApplicationContext() {

		super();

		// TODO Auto-generated constructor stub

	}



	public MyClassPathXmlApplicationContext(String filemame) {

		//1. 读取XML配置文件

		this.readXML(filemame);

		//2.实例化对象

		this.instanceBean();

	}



	private void instanceBean() {

		for (DefBean bean : list) {

			try {

				singletons.put(bean.getId(), Class.forName(bean.getClassName()).newInstance());

			} catch (Exception e) {

				// TODO Auto-generated catch block

				e.printStackTrace();

			}

		}

	}



	private void readXML(String filemame) {

		SAXReader saxReader = new SAXReader();

		Document document = null;

		try {

			URL xmlpath = this.getClass().getClassLoader()

					.getResource(filemame);

			document = saxReader.read(xmlpath);

			

			Map<String, String> nsMap = new HashMap<String, String>();

			nsMap.put("ns", "http://www.springframework.org/schema/beans");// 加入命名空间

			XPath xsub = document.createXPath("//ns:beans/ns:bean");// 创建beans/bean查询路径

			xsub.setNamespaceURIs(nsMap);// 设置命名空间

			List<Element> beans = xsub.selectNodes(document);// 获取文档下所有bean节点

			for (Element element : beans) {

				String id = element.attributeValue("id");// 获取id属性值

				String clazz = element.attributeValue("class"); // 获取class属性值

				DefBean bean = new DefBean(id, clazz);

				list.add(bean);

			}

		} catch (Exception e) {

			e.printStackTrace();

		}

	}

	//3. 获得bean对象

	public Object getBean(String key) {

		return singletons.get(key);

	}



}