File previews help users browse and find media efficiently. To view a preview of a file, click the file’s name in the Document Library. If the file is an image, the image appears. If an app is installed that can render a preview of the file type, a representative image of the file appears (e.g., the opening frame of a video file or a presentation’s first slide). If there are no such preview apps for the file, a generic image based on the file type appears.
Whenever possible, Liferay DXP generates previews of documents added to the Document Library. Out of the box, Java-based APIs generate previews. The only tool available that is 100% Java and has a compatible license to be distributed with Liferay DXP is PDFBox. A separate thread generates a preview for PDFs when uploaded. This process may last only a few seconds for a small file. The larger the file, the longer it takes.
While PDFBox provides a default implementation of image generation for document previews and thumbnails, you must install and configure additional tools to harness the full power of document previews. These tools include:
OpenOffice or LibreOffice: Using one of these in server mode lets you generate thumbnails and previews for supported file types (
.odp, etc.), view documents in your browser, and convert documents.
Xuggler: Enables audio and video previews, lets you play audio and video files in your browser, and extracts thumbnails from video files.
After installing these tools, you can configure them via portal properties in
the Control Panel’s Server Administration screen, or in a
portal-ext.properties file. To learn how to use these tools, see
Configuring Liferay DXP.
With these tools installed and configured, a customized viewer displays Documents and Media content, depending on the content type. For example, you can view a document with a customized viewer that lets you navigate through the document’s pages. You can also view and play multimedia documents (audio or video). If the browser supports HTML5, the viewer uses the browser’s native player. Otherwise it falls back to a Flash player.
You can also manage a file from its preview. The bar above the preview contains these buttons:
Info (): Open/close the file’s info panel. This panel contains more detailed information about the file. For more information on this, see The Info Panel.
Share: Share the file with other users. For more information, see Sharing Files.
Download: Download the file.
Actions (): Opens a menu that lets you perform these actions on the file:
Edit: Modify the file’s name, description, document type, categorization, and related assets. You can even upload a new file to replace it. Note that modifying the file increments its version.
Edit with Image Editor: Edit the image in the Image Editor. The Image Editor is explained in Editing Images.
Checkout/Checkin: Checkout prevents others from editing the document while you are working on it. Other users can still view the current version of the document, if they have permission. You can check in the document when you’re done with it.
Move: Relocate the file to a different parent folder.
Permissions: Specify which actions each role can perform on the file.
Move to Recycle Bin: Move the file from the Documents and Media library to the Recycle Bin.
Also note that the Options menu () at the top-right of the screen contains the same actions as the Actions menu.
The comments area (below the preview area) lets you comment on and subscribe to comments on the file.
As mentioned above, clicking the Info icon () opens the info panel. The top of the info panel displays the file’s name, version, and workflow status. There are two tabs in the info panel: Details, and Versions. Details is selected by default and shows the following:
Owner: The file’s owner.
Download: A button to download the file.
Latest Version URL: A URL to access the newest version of the file.
WebDAV URL: A WebDAV URL for accessing the file via a desktop.
Document Type: The file’s document type.
Extension: The file’s extension (e.g., JPG, PDF, etc.).
Size: The file’s size on disk.
Modified: The user that last modified the file, and when it was last modified.
Created: The user that created the file, and when it was created.
Ratings: The file’s average user rating.
Automatically Extracted Metadata: Any and all metadata automatically extracted from the file. When adding new documents or viewing existing documents, a process is triggered automatically that extracts the file’s metadata. The library used by this process is TIKA and it’s included out of the box. Depending on your file’s type and the metadata written with the file, you can find out all kinds of details. In the case of audio or video files, the media’s duration is displayed.
To instead view the file’s version history, select the Versions tab near the top of the info panel. The info panel then changes to list the different versions of the file and lets you view, download, remove, and revert to specific file versions. File version history actions are explained in Checking Out and Editing Files.