In an earlier post, I had written on performing file upload and download using Spring MVC. In that example I used commons-fileupload-1.2.2.jar. This is because Servlets did not have built in support for File upload operation. However Servlets 3.x provides support - as a part of the specs. So no need to include any additional jars. I decided to try an example of the same.
First step was to add an HTML form:
The enctype attribute indicates the encoding used. Its default value is application/x-www-form-urlencoded which is what we use in our simple forms. To process the form I created an upload servlet:
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On completion:
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The Multipart configuration can also be placed in the XML file - making it easier to increase/decrease
First step was to add an HTML form:
<html>The form accepts three files and a text field. The form type is multipart/form-data which indicates a form capable of sending simple data as well as files.
<head></head>
<body>
<form action="upload.upl" method="post"enctype="multipart/form-data">
Enter Player Name:
<input type="text" name="playerName"/><br/>
Select File(s) to Upload:
<inputtype="file" name="file1Name"><br/>
<input type="file" name="file2Name"><br/>
<input type="file" name="file3Name"><br/>
<input type="submit" value="Upload">
</form>
</body>
</html>
The enctype attribute indicates the encoding used. Its default value is application/x-www-form-urlencoded which is what we use in our simple forms. To process the form I created an upload servlet:
@SuppressWarnings("serial")The new annotation introduced here is the MultipartConfig.As described by Java docs:
@WebServlet(displayName = "FileUploadServlet",
description = "Servlet for FileUpload Operations", urlPatterns = { "*.upl" })
@MultipartConfig(fileSizeThreshold = 1024 * 1024 * 10, // 10 MB
maxFileSize = 1024 * 1024 * 25, // 25 MB
maxRequestSize = 1024 * 1024 * 50) // 50 MB
publicclass FileUploadServlet extends HttpServlet {
Annotation that may be specified on a Servlet class, indicating that instancesI added the code to process the post request of the form in the doPost method:
of the Servlet expect requests that conform to the multipart/form-data MIME type.
/**The code can be explained as below:
* Directory where uploaded files will be saved, its relative to the web
* application directory.
*/
privatestaticfinal File UPLOAD_DIRECTORY = new File("E:\\temp");
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// Get all the parts from request and write it to the file on server
// 1: Return a collection of all uploaded Parts.
Collection<Part> allUploadedParts = request.getParts();
int i = 0;
for (Part part : allUploadedParts) {
// Part: class represents a part as uploaded to the server as part of a
// multipart/form-data request body. The part may represent either an
// uploaded file or form data.
// 2: Retain only file parts and not any form parts
// Get name of File
String fileName = part.getSubmittedFileName();
if (fileName == null)
continue;
// 3: Write the file to the disk
// convenience method to write an uploaded part to disk.
part.write(UPLOAD_DIRECTORY + File.separator + fileName);
i++;
}
String playerName = request.getParameter("");
playerName = playerName != null&& !"".equals(playerName.trim())
? playerName.toUpperCase() : " UNKNOWN ";
response.getWriter()
.write(playerName + " has " + i + " File(s) uploaded successfully!");
response.getWriter().flush();
}
- The getParts method gets all the Part components of this request, provided that it is of type multipart/form-data. Parts include both files and form inputs.
- The getSubmittedFileName method of Part will be null for file fields.
- The last method I used here is the write method - which will write the file contents to the directory specified as a file.
On completion:
<servlet>
<description></description>
<display-name>WelcomeServlet</display-name>
<servlet-name>WelcomeServlet</servlet-name>
<servlet-class>com.servlets.WelcomeServlet</servlet-class>
<multipart-config>
<location>/tmp</location>
<max-file-size>208480</max-file-size>
<max-request-size>418841</max-request-size>
<file-size-threshold>1066476</file-size-threshold>
</multipart-config>
</servlet>