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();
    }
}