About Javin Paul
Uploading File to server using Servlet and JSP is a common task in Java web application. Before coding your Servlet or JSP to handle file upload request, you need to know little bit about File upload support in HTML and HTTP protocol. If you want your user to choose files from file system and upload to server than you need to use <input type=”file”/>. This will enable to choose any file form file system and upload to server. Next thing is that form method should be HTTP POST with enctype as multipart/form-data, which makes file data available in parts inside request body. Now in order to read those file parts and create a File inside Servlet can be done by using ServletOutputStream. It’s better to use Apache commons FileUpload, an open source library. Apache FileUpload handles all low details of parsing HTTP request which confirm to RFC 1867 or “Form based File upload in HTML”, when you set form method post and content type as “multipart/form-data”.
Important points:
- DiskFileItemFactory is default Factory class for FileItem. When Apache commons read multipart content and generates FileItem, this implementation keep file content either in memory or in disk as temporary file, depending upon threshold size. By default DiskFileItemFactory has threshold size of 10KB and generates temporary files in temp directory, returned by System.getProperty(“java.io.tmpdir”). Both of these values are configurable and it’s best to configure these for production usage. You may get permission issues if user account used for running Server doesn’t have sufficient permission to write files into temp directory.
Source : http://www.javacodegeeks.com/2013/08/file-upload-example-in-servlet-and-jsp.html
