dom4j解析xml文件生成bean對象的四個步驟

1.將xml文件轉換成Document對象
2.通過xpath找到某個Element對象
3.通過屬性名找到對應的屬性值
4.通過該屬性值反射出一個對象

依賴的類庫：dom4j.jar及其依賴的xpath庫jaxen.jar.

package com.life.util;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class BeanFactory {
    public static Object getBean(String id){
        try { 
            SAXReader reader = new SAXReader();
            Document document = reader.read(BeanFactory.class.getClassLoader().getResourceAsStream("beans.xml"));
            //下面這兩個獲取document的方式也可以
            //Document document = reader.read(BeanFactory.class.getResourceAsStream("/beans.xml"));
            //Document document = reader.read(BeanFactory.class.getResourceAsStream("../../../beans.xml"));
            Element element = (Element)document.selectSingleNode("//bean[@id='"+id+"']");
            String value = element.attributeValue("class");
            Class<?> clz = Class.forName(value);
            return clz.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException();
        }
    }
}