java 反射机制的应用

import java.util.HashMap;
import java.util.Map;

import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

/**

获取资源文件 然后找到xml文件进行遍历 通过反射机制 实例化

*/

public final class BeanFactory {
private static Map<String,Object> map = null;
static {
   load();
}
public static Object getBean(String beanName) {
   return map.get(beanName);
}
public static void load() {
   map = new HashMap<String,Object>();
   try {
    Document doc = DocumentBuilderFactory.newInstance().newDocumentBuilder()  
    .parse(Thread.currentThread().getContextClassLoader().getResource("beanfactory.xml").getPath());
    NodeList daos = doc.getElementsByTagName("bean");
    Element e=null;
    int length=daos.getLength();
    for (int i = 0; i < length; i++) {
     e = (Element) daos.item(i);
     map.put(e.getAttribute("name"), Class.forName(e.getAttribute("class")).newInstance());
    }
    e=null;
    daos=null;
    doc=null;
   } catch (Exception ex) {
    ex.printStackTrace();
   }
}
}