利用工厂模式实现Dao层和Service的解耦

dao.properties的文件内容

UpfileDao=cn.itcast.dao.impl.UpfileDaoImpl

DaoFactory的实现

public class DaoFactory {

    private static Properties daoconfig = new Properties();
    static{
        try {
            daoconfig.load(DaoFactory.class.getClassLoader().getResourceAsStream("dao.properties"));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    private DaoFactory(){}
    private static final DaoFactory instance = new DaoFactory();
    public static DaoFactory getInstance(){
        return instance;
    }
    
    public <T> T createDao(Class<T> interfaceClass){
        String name = interfaceClass.getSimpleName();
        String daoClassname = daoconfig.getProperty(name);
        try {
            return (T) Class.forName(daoClassname).newInstance();
        } catch (Exception e) {
            throw new RuntimeException(e);
        } 
    }
    
}

BusinessServiceImpl利用DaoFactory进行解耦

private UpfileDao dao = DaoFactory.getInstance().createDao(UpfileDao.class);