java实现解耦小案例

简单地说，软件工程中对象之间的耦合度就是对象之间的依赖性。指导使用和维护对象的主要问题是对象之间的多重依赖性。对象之间的耦合越高，维护成本越高。因此对象的设计应使类和构件之间的耦合最小。

文件结构

Dao

public interface IAccountDao {
    void saveAccount();
}

DaoImpl

public class AccountDaoImpl implements IAccountDao {
    public void saveAccount() {
        System.out.println("账户保存实现了");
    }
}

Service

public interface IAccountService {
    void saveAccount();
}

ServiceImpl

public class AccountServiceImpl implements IAccountService {
    //private IAccountDao accountDao = new AccountDaoImpl();
    //使用反射方式,替代直接调用AccountDaoImpl
    private IAccountDao accountDao = (IAccountDao) BeanFactory.getBean("accountDao");
    public void saveAccount() {
        accountDao.saveAccount();
    }
}

表现层Client

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

工厂BeanFactory

public class BeanFactory {
    //读取配置文件
    private static Properties properties;

    //定义一个容器map,用于存放我们要创建的对象
    //单例模式
    private static Map<String, Object> beans;

    static {
        try {
            properties = new Properties();
            InputStream in = BeanFactory.class.getClassLoader().getResourceAsStream("bean.properties");
            properties.load(in);

            /* 单例模式 */
            //实例化容器
            beans = new HashMap<String, Object>();
            Enumeration<Object> keys = properties.keys();
            //遍历枚举
            while (keys.hasMoreElements()) {
                //取出每一个key
                String key = keys.nextElement().toString();
                //通过key获取value(全限定类名)
                String beanPath = properties.getProperty(key);
                //反射创建对象
                Object value = Class.forName(beanPath).newInstance();
                //存入容器map
                beans.put(key, value);
            }
        } catch (Exception e) {
            throw new ExceptionInInitializerError("初始化properties失败!");
        }
    }

    /**
     * 根据Bean的名称获取bean对象
     * 单例模式
     * @param beanName
     * @return
     */
    public static Object getBean(String beanName) {

        return beans.get(beanName);
    }



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

配置文件bean.properties

accountService=com.ouyang.service.impl.AccountServiceImpl
accountDao=com.ouyang.dao.impl.AccountDaoImpl