（层与层之间的解耦）面向接口的编程

package com.itheima.utils;

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

public class BeanFactory {

public static Object getBean(String id){

//生产对象---根据清单生产----配置文件----将每一个bean对象的生产的细节配到配置文件中
//使用dom4j的xml解析技术

try {
//1、创建解析器
SAXReader reader = new SAXReader();
//2、解析文档---bean.xml在src下
String path = BeanFactory.class.getClassLoader().getResource("bean.xml").getPath();
Document doc = reader.read(path);
//3、获得元素---参数是xpath规则
Element element = (Element) doc.selectSingleNode("//bean[@id='"+id+"']");
//<bean id="adminService" class="com.itheima.service.impl.AdminServiceImpl"></bean>
String className = element.attributeValue("class");
//com.itheima.service.impl.AdminServiceImpl
//使用反射创建对象
Class clazz = Class.forName(className);
Object object = clazz.newInstance();

return object;

} catch (Exception e) {
e.printStackTrace();
}

return null;
}

}

<?xml version="1.0" encoding="UTF-8"?>
<beans>
<!-- 配置AdminServiceImpl的清单 -->
<bean id="adminService" class="com.itheima.service.impl.AdminServiceImpl"></bean>
<!-- <bean id="adminService" class="com.itheima.service.impl.AdminServiceImpl2"></bean> -->

<bean id="adminDao" class="com.itheima.dao.impl.AdminDaoImplMySql"></bean>
<!-- <bean id="adminDao" class="com.itheima.dao.impl.AdminDaoImplOracle"></bean> -->

</beans>