spring自定义bean工厂模式解耦

在resources下创建bean.properties

accountService=cn.flypig666.service.impl.AccountServiceImpl
accountDao=cn.flypig666.dao.impl.AccountDaoImpl

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创建工厂：BeanFactory.java

创建单例对象效果更好

创建Map<String,Object>类型的容器beans

 //定义一个Properties对象
     private static Properties props;

     //定义一个Map，用于存放我们要创建的对象，称之为容器
     private static Map<String,Object> beans;

     //使用静态代码块为Properties对象赋值
     static {
         try {
             //实例化对象
             props = new Properties();
             //获取properties文件的流对象,创建在resources文件夹下的properties文件会成为类根路径下的文件，不用写包名
             InputStream in = BeanFactory.class.getClassLoader().getResourceAsStream("bean.properties");
             props.load(in);
             //实例化容器
             beans = new HashMap<String, Object>();
             //取出配置文件中所有的 Key
             Enumeration  keys = props.keys();
             //遍历枚举
             while (keys.hasMoreElements()){
                 //取出每个key
                 String key = keys.nextElement().toString();
                 //根据key获取value
                 String beanPath = props.getProperty(key);
                 //反射创建对象
                 Object value = Class.forName(beanPath).newInstance();
                 //把key和value存入容器中
                 beans.put(key,value);
             }
         } catch (Exception e) {
             throw new ExceptionInInitializerError("初始化properties失败");
         }
     }

     public static Object getBean(String beanName){
         return beans.get(beanName);
     }

     /**
      * 根据Bean的名称获取bean对象
      * @param beanName
      * @return
      */
     public static Object getBean(String beanName){
         Object bean = null;
         try{
             String beanPath = props.getProperty(beanName);
             System.out.println(beanPath);
             bean = Class.forName(beanPath).newInstance();
         }catch (Exception e){
             e.printStackTrace();
         }
         return bean;
     }

 }

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通过反射获取对象

/**
 * 账户业务层实现类
 */
public class AccountServiceImpl implements IAccountService {

    //private IAccountDao accountDao = new AccountDaoImpl();
    private IAccountDao accountDao = (IAccountDao) BeanFactory.getBean("accountDao");

    public void saveAccount(){
        accountDao.saveAccount();
    }
}

/**
 * 模拟一个表现层，用于调用业务层
 */
public class Client {

    public static void main(String[] args) {
//        IAccountService accountService = new AccountServiceImpl();
        IAccountService accountService = (IAccountService) BeanFactory.getBean("accountService");
        accountService.saveAccount();
    }
}