vaadin-framework/documentation/components/components-upload.asciidoc

---
title: Upload
order: 26
layout: page
---

[[components.upload]]
= [classname]#Upload#

ifdef::web[]
[.sampler]
image:{live-demo-image}[alt="Live Demo", link="http://demo.vaadin.com/sampler/#ui/data-input/other/upload"]
endif::web[]

The [classname]#Upload# component allows a user to upload files to the server.
It displays a file name entry box, a file selection button, and an upload submit
button. The user can either write the filename in the text area or click the
[guibutton]#Browse# button to select a file. After the file is selected, the
user sends the file by clicking the upload submit button.

Uploading requires a receiver that implements [interfacename]#Upload.Receiver#
to provide an output stream to which the upload is written by the server.

[source, java]
----
Upload upload = new Upload("Upload it here", receiver);
----

[[figure.ui.upload]]
.The [classname]#Upload# component
image::img/upload.png[width=60%, scaledwidth=80%]

You can set the text of the upload button with [methodname]#setButtonCaption()#.
Note that it is difficult to change the caption or look of the
[guibutton]#Browse# button. This is a security feature of web browsers. The
language of the [guibutton]#Browse# button is determined by the browser, so if
you wish to have the language of the [classname]#Upload# component consistent,
you will have to use the same language in your application.

[source, java]
----
upload.setButtonCaption("Upload Now");
----

You can also hide the upload button with [literal]#++.v-upload .v-button
{display: none}++# in theme, have custom logic for starting the upload, and call
[methodname]#startUpload()# to start it. If the upload component has
[methodname]#setImmediate(true)# enabled, uploading starts immediately after
choosing the file.

[[components.upload.receiving]]
== Receiving Upload Data

The uploaded files are typically stored as files in a file system, in a
database, or as temporary objects in memory. The upload component writes the
received data to an [classname]#java.io.OutputStream# so you have plenty of
freedom in how you can process the upload content.

To use the [classname]#Upload# component, you need to implement the
[classname]#Upload.Receiver# interface. The [methodname]#receiveUpload()# method
of the receiver is called when the user clicks the submit button. The method
must return an [classname]#OutputStream#. To do this, it typically creates a
file or a memory buffer to which the stream is written. The method gets the file
name and MIME type of the file, as reported by the browser.

While uploading, the upload progress can be monitored with an
[interfacename]#Upload.ProgressListener#. The [methodname]#updateProgress()#
method gets the number of read bytes and the content length as parameters. The
content length is reported by the browser, but the reported value is not
reliable, and can also be unknown, in which case the value is -1. It is
therefore recommended to follow the upload progress and check the allowed size
in a progress listener. Upload can be terminated by calling
[methodname]#interruptUpload()# on the upload component. You may want to use a
[classname]#ProgressBar# to visualize the progress, and in indeterminate mode if
the content length is not known.

When an upload is finished, successfully or unsuccessfully, the
[classname]#Upload# component will emit the [classname]#Upload.FinishedEvent#
event, which you can handle with an [classname]#Upload.FinishedListener# added
to the upload component. The event object will include the file name, MIME type,
and final length of the file. More specific [classname]#Upload.FailedEvent# and
[classname]#Upload.SucceededEvent# events will be called in the cases where the
upload failed or succeeded, respectively.

The following example uploads images to [filename]#/tmp/uploads# directory in
(UNIX) filesystem (the directory must exist or the upload fails). The component
displays the uploaded image in an [classname]#Image# component.

[source, java]
----
// Show uploaded file in this placeholder
final Embedded image = new Embedded("Uploaded Image");
image.setVisible(false);

// Implement both receiver that saves upload in a file and
// listener for successful upload
class ImageUploader implements Receiver, SucceededListener {
    public File file;

    public OutputStream receiveUpload(String filename,
                                      String mimeType) {
        // Create upload stream
        FileOutputStream fos = null; // Stream to write to
        try {
            // Open the file for writing.
            file = new File("/tmp/uploads/" + filename);
            fos = new FileOutputStream(file);
        } catch (final java.io.FileNotFoundException e) {
            new Notification("Could not open file<br/>",
                             e.getMessage(),
                             Notification.Type.ERROR_MESSAGE)
                .show(Page.getCurrent());
            return null;
        }
        return fos; // Return the output stream to write to
    }

    public void uploadSucceeded(SucceededEvent event) {
        // Show the uploaded file in the image viewer
        image.setVisible(true);
        image.setSource(new FileResource(file));
    }
};
ImageUploader receiver = new ImageUploader();

// Create the upload with a caption and set receiver later
Upload upload = new Upload("Upload Image Here", receiver);
upload.setButtonCaption("Start Upload");
upload.addSucceededListener(receiver);

// Put the components in a panel
Panel panel = new Panel("Cool Image Storage");
Layout panelContent = new VerticalLayout();
panelContent.addComponents(upload, image);
panel.setContent(panelContent);
----
See the http://demo.vaadin.com/book-examples-vaadin7/book#component.upload.basic[on-line example, window="_blank"].

Note that the example does not check the type of the uploaded files in any way,
which will cause an error if the content is anything else but an image. The
program also assumes that the MIME type of the file is resolved correctly based
on the file name extension. After uploading an image, the component will look as
shown in <<figure.ui.upload.example>>.

[[figure.ui.upload.example]]
.Image Upload Example
image::img/upload-example.png[width=60%, scaledwidth=80%]

[[components.upload.css]]
== CSS Style Rules


[source, css]
----
.v-upload { }
  .gwt-FileUpload { }
  .v-button { }
    .v-button-wrap { }
      .v-button-caption { }
----

The [classname]#Upload# component has an overall [literal]#++v-upload++# style.
The upload button has the same structure and style as a regular
[classname]#Button# component.