File Upload and Download

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File Upload and Download

File Upload

Button, Toolbarbutton and Menuitem support file upload out-of-box. In other words, you just need to enable it with the steps below:

  1. Specify upload attribute with true to enable file upload
  2. Assign an onUpload event listener to the component [1]

For example:

	void upload(UploadEvent event) { media = event.getMedia();
		if (media instanceof org.zkoss.image.Image) {
			org.zkoss.zul.Image image = new org.zkoss.zul.Image();
			image.setContent( (org.zkoss.image.Image) media);
		} else {"Not an image: "+media, "Error", Messagebox.OK, Messagebox.ERROR);
	<button label="Upload" upload="true" onUpload="upload(event)"/>
	<vlayout id="pics" />

You can control the maximal allowed number of files, the maximal allowed size, and other options. Please refer to org.zkoss.zul.Button.setUpload().

    <menuitem label="Upload" upload="true,maxsize=-1,native"/>

  1. If you enabled the use of event threads, you could use Fileupload.get() and related. For more information, please refer to the Event Thread section.

Open File Upload Dialog

If you want the file upload on another component rather than those components above (Button, Toolbarbutton, Menu), you can call FileUpload.get() in an event listener.

Here is an example:

    <a iconSclass="z-icon-upload" ...

public class UploadComposer extends SelectorComposer {

    @Listen(Events.ON_CLICK + "= a")
    public void handleUpload(MouseEvent e) {
        Fileupload.get(1, new EventListener<UploadEvent>() {
            public void onEvent(UploadEvent event) throws Exception {
                Media[] medias = event.getMedias();
                System.out.println("upload " +  medias[0].getName());

File Download

Filedownload provides a set of utilities to prompt a user to download a file from the server to a local folder. For example,

<button label="Download a file" onClick='"~./zklogo.png", null);'/>


The file could be a static resource, an input stream, a file, a URL and others. Please refer to ZK Component Reference and Filedownload for more information.

File Download Link

Clicking a file download link terminates client engine to work, please refer to ZK_Component_Reference/Essential_Components/A#File_Download_Link for correct usages.

Last Update : 2024/02/06

Copyright © Potix Corporation. This article is licensed under GNU Free Documentation License.