文件上传说白了就是利用form表单request域中上传数据，后台到Action中解析request域进行文件获取和文件类型以及后缀解析，过程比较繁琐，不过这些公共的繁琐步骤是struts框架已经为我们做好了，只需要按照其规则进行页面绘制和后台属性注入即可。(Upload file upload namely using form form request field data, the background to the Action of parsing the request domain for file access and file types and suffix parsing, process is tedious, but the public is cumbersome steps the struts framework has prepared for us, only need according to the rules page rendering attributes can be injected and the background.)