Multiparthttpservletrequest implementation of file uploads in spring

Multiparthttpservletrequest implementation of file uploads in spring

Posted from: http://my.oschina.net/nyniuch/blog/185266

Implement image upload
Users must be able to upload images, so the ability to upload files is required. The more common file upload components are commons FileUpload (http://jakarta.apache.org/commons/fileupload/a>) and Cos FileUpload (HTTP/ Www.servlets.com/cos), Spring has fully integrated both of these components, and here we choose commons FileUpload.
Because post a form that contains file uploads is sent to the server as a multipart/form-data request, you must explicitly tell Dispatcherservlet how to handle the multipartrequest. First declare a multipartresolver in Dispatcher-servlet.xml:

XML code

1. <bean id= "Multipartresolver"
2. class= "Org.springframework.web.multipart.commons.CommonsMultipartResolver" >
3. <!--set the maximum size of the upload file to 1MB
4. <property name= "Maxuploadsize" >
5. <value>1048576</value>
6. </property>
7. </bean>

So once a request is a multipartrequest, it is first processed by Multipartresolver and then forwarded to the appropriate controller.
In Uploadimagecontroller, HttpServletRequest is transformed into Multiparthttpservletrequest, which makes it easy to get file names and file contents:

Java code

2. Public Modelandview HandleRequest (HttpServletRequest request,
4. HttpServletResponse response) throws Exception {
6. Transition to Multiparthttprequest:
8. Multiparthttpservletrequest multipartrequest = (multiparthttpservletrequest) request;
10. Get the file:
12. Multipartfile file = multipartrequest.getfile ("file");
14. Get file name:
16. String filename = File.getoriginalfilename ();
18. Get input stream:
20. InputStream input = File.getinputstream ();
22. Write file
26. Or:
28. File Source = new file (localfilename.tostring ());
30. Multipartfile.transferto (source);
32. }

Generate thumbnails (Table of contents)
When a user uploads a picture, a thumbnail must be generated so that the user can quickly navigate. We don't need third-party software, and the JDK standard library contains an API for image processing. We scaled a picture proportionally to the 120x120 size, and here's the key code:

Java code

2. Public Static void createpreviewimage (string srcfile, String destfile) {
4. Try {
6. File fi = new file (srcfile); Src
8. File fo = new file (destfile); Dest
10. BufferedImage bis = imageio.read (FI);
14. int w = bis.getwidth ();
16. int h = bis.getheight ();
18. Double scale = (double) w/h;
20. int NW = image_size; Final int image_size = 120;
22. int nh = (NW * h)/w;
24. if (NH > Image_size) {
26. NH = image_size;
28. NW = (NH * w)/h;
30. }
32. Double sx = (double) nw/w;
34. double sy = (double) nh/h;
38. Transform.settoscale (SX, SY);
40. Affinetransformop ato = new affinetransformop (transform, null);
42. BufferedImage bid = new bufferedimage (NW, NH,
44. BUFFEREDIMAGE.TYPE_3BYTE_BGR);
46. Ato.filter (bis, Bid);
48. Imageio.write (BID, "jpeg", FO);
50. } catch (Exception e) {
52. E.printstacktrace ();
54. Throw New RuntimeException (
56. "Failed in Create preview image. Error: "
58. + e.getmessage ());
60. }
62. }

Multiparthttpservletrequest implementation of file uploads in spring