Upload field on a lift screen

[Tareq Abedrabbo]

Hi all,

I'm wondering how to create a file upload field on a Lift Screen. I
can see that Lift Screen checks for upload fields and that Field has
an uploadField_? property but I'm not clear on whether a call to the
field method can render a file upload field and what the default value
would be in this case.
Thanks in advance for your help.

Tareq

[David Pollak]

You have to create a custom field.  Here's a Screen that does an upload:

import net.liftweb._

import http._

import common._

import scala.xml._

class UploadScreen extends LiftScreen {

  override protected def hasUploadField = true

  val name = field("Name", "")

  val file = makeField[Array[Byte], Nothing]("File", new Array[Byte](0),

    field => SHtml.fileUpload(fph => field.set(fph.file)),

    NothingOtherValueInitializer)

  def finish() {

    S.notice("Thanks for uploading a file of " + file.get.length + " bytes ")

  }

}

Here's a running example: https://github.com/dpp/starting_point/tree/screen_file_upload

--
Lift, the simply functional web framework: http://liftweb.net
Code: http://github.com/lift
Discussion: http://groups.google.com/group/liftweb
Stuck? Help us help you: https://www.assembla.com/wiki/show/liftweb/Posting_example_code

--
Lift, the simply functional web framework http://liftweb.net

Simply Lift http://simply.liftweb.net
Follow me: http://twitter.com/dpp
Blog: http://goodstuff.im

[Readman]

Hey David,

Thanks for posting this example.

However, what is the upload directory in this example? I can not see any file in folder, when i uploaded a file

Chenguang He

[Olek Swirski]

file goes to whatever is temp dir for your app,
which may quite possibly be /tmp
in that case, file may quickly be cleaned by OS,
so then you would need to keep reference
to FileParamHolder and move it elsewhere or
maybe setting tmp dir for your app to different
value with System.setProperty or by giving
command line arg to java

--

[Olek Swirski]

oh, I forgot. by default file will be loaded into the memory
and never appear on the hard drive. then fph is your
only handle to do something with it before it disappears.

to get on disk file you need to call this in your boot:
    /* store uploads as files on disk */
    LiftRules.handleMimeFile = OnDiskFileParamHolder.apply
you may also need these:
    /* set max total upload size */
    LiftRules.maxMimeSize = 1024 * 1024 * 32
    /* set max per-file upload size */
    LiftRules.maxMimeFileSize = 1024 * 1024 * 32;

also, that file will have some random name, because
otherwise there could easily be name clash if someone
uploads two same named files to your application. you
may restore original upload name from fph.fileName

[Chenguang He]

Uhm..

Sorry, i still don't know how to upload file to a  specific folder.

Does fph store the file or the location in memory?

   

Chenguang He

[Olek Swirski]

If you set up
LiftRules.handleMimeFile = OnDiskFileParamHolder.apply
then, the the file will be accessible as fph.localFile
if you use InMemFileParamHolder (which I think is default)
then, you get file bytes via
val file: Array[Byte]
and need to write them yourself somewhere, which can be
done with java.io or java.nio (you may need to read javadoc
for these, which are very comprehensive)

[Olek Swirski]

you need to have java 7 (not 6 or earlier) to use nio package
docs are here:
http://docs.oracle.com/javase/7/docs/api/java/io/package-summary.html
http://docs.oracle.com/javase/7/docs/api/java/nio/package-summary.html
there is a nice io tutorial here:
http://docs.oracle.com/javase/tutorial/essential/io/index.html

[Chenguang He]

Thank you.

It works!

Chenguang He