commons-fileupload源码分析

public void doPost(HttpServletRequest req, HttpServletResponse res) {   DiskFileItemFactory factory = new DiskFileItemFactory();   // maximum size that will be stored in memory   factory.setSizeThreshold(4096);   // the location for saving data that is larger than getSizeThreshold()   factory.setRepository(new File("/tmp"));   ServletFileUpload upload = new ServletFileUpload(factory);   // maximum size before a FileUploadException will be thrown   upload.setSizeMax(1000000);   List fileItems = upload.parseRequest(req);   // assume we know there are two files. The first file is a small   // text file, the second is unknown and is written to a file on   // the server   Iterator i = fileItems.iterator();   String comment = ((FileItem)i.next()).getString();   FileItem fi = (FileItem)i.next();   // filename on the client   String fileName = fi.getName();   // save comment and filename to database   ...   // write the file   fi.write(new File("/www/uploads/", fileName)); }

以上代码为apache官网的一段commons-fileupload的demo。其中主要分为两个部分

1、创建DiskFileItemFactory

2、创建SerletFileUpload

（1）DiskFileItemFactory实现了FileItemFactory接口createItem，在里面指定了默认的阀值。同时声明一个FileCleaningTracker去跟踪是否超过阀值。