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
*
* @author examda
*
*/
@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();
}
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