English version:
constants：static constants of setting parameters
CodeConstants: static constants of error codes.
Config: configuration class of reading files.
HttpConstants: some static constants of http.
QMonitorConstants: constants of monitor that is used for logging client's type.
StorageConfig: configuration class of saving, it's maily used for reading storage path and initialziing storage of file.
controller：interfaces
NewDownloadController：The interface of downloading which a key, the unique identifier of the file, is required to request it. The transmission of download is based on blocks with size of 64k.
UploadController: It's the interface for client to make sure whether file exists in server, this interface is called before uploading file.
resolveException: The class of global exception resolve.
MonitorInterceptor：Monitors for logging client's type.
model: Common tools
servlet: Class of servlet
UploadV2Servlet：The class of interfaces of uploading which a unique identification of file, usually the md5 result of the file's name, is required to request it.
utils: Common utils.
DownloadUtils：It's for making download link of files and defining the link's format.
InputStreamWrapper：It's for customizing of pictures' inputstream, mainly used for adding buffer.
ImgTypeUtils: It's for getting real type of pictures, you can get it from the first 12 bytes of inputStreamWrapper.
中文版本:
constants：提供常静态常量配置参数
CodeConstants:静态常量 主要是错误码
Config:配置文件读取类
HttpConstants: 关于http的一些静态常量
QMonitorConstants: 监控的常量，用于客户端类型的记录
StorageConfig:存储的配置类，主要功读取文件存储位置的配置参数以及初始化文件存储位置
controller：接口
NewDownloadController：文件下载接口，必传的请求参数为文件的key，文件的唯一标识。采取分块传输,块大小64K
UploadController: 客户端查询文件是否存在接口，上传时会先验证文件是否存在。
resolveException:全局异常解析类
MonitorInterceptor：拦截器记录客户端类型
model: 常用工具类
servlet:servlet类
UploadV2Servlet：文件上传的servlet接口类，必传参数key，文件的唯一标识。一般是客户端将文件进行MD5后的值防止文件key重名导致的覆盖
utils:常用工具类
DownloadUtils：定义下载链接的格式，获取到文件的下载链接。可自定义
InputStreamWrapper：自定义图片inputstream,主要是增加buffer
ImgTypeUtils:获取图片的真是类型，通过inputStreamWrapper的前12个字节即可确认真实类型