文件上传：MultipartConfig
http://www.codejava.net/java-ee/servlet/multipartconfig-annotation-examples
https://github.com/antonio2306/joy-demo/blob/master/src/main/java/cn/joy/demo/external/upload/Servlet3FileUpload.java
原文：http://www.cnblogs.com/mada0/p/4792884.html