Before you start using the Documents and Media API, you must learn these things:
- Key Interfaces: The interfaces you’ll use most while using the API.
- Getting a Service Reference: How to get a service reference that lets you call the API’s services.
- Specifying Repositories: How to specify which Documents and Media repository you want.
- Specifying Folders: How to specify which folder you want.
Key Interfaces
The Documents and Media API contains several key interfaces:
-
Documents and Media Services: These interfaces expose all the available Documents and Media functionality:
DLAppLocalService: The local service.DLAppService: The remote service. This service wraps the local service methods in permission checks.
Note that Liferay used Service Builder to create these services. Because the remote service contains permission checks, it’s a best practice to call it instead of the local service. See the section below for instructions on getting a service reference.
-
Entity Interfaces: These interfaces represent entities in the Documents and Media library. Here are the primary ones you’ll use:
FileEntry: Represents a file.Folder: Represents a folder.FileShortcut: Represents a shortcut to a file.
Getting a Service Reference
Before you can do anything with the Documents and Media API, you must get
a service reference. If you’re using OSGi modules, use the @Reference
annotation to
get a service reference in an OSGi component via Declarative Services.
For example, this code gets a reference to DLAppService:
@Reference
private DLAppService _dlAppService;
If you’re using a standard web module (WAR file), use a Service Tracker to get a reference to the service instead.
Getting the reference this way ensures that you leverage OSGi’s
dependency management
features. If you must use the Documents and Media services outside of an OSGi
component (e.g., in a JSP), then you can use the services’ static *Util
classes:
Specifying Repositories
Many methods in the Documents and Media API contain a repositoryId parameter
that identifies the Documents and Media repository where the operation is
performed. A Site (group) can have multiple repositories, but only one can be
accessed via the portal UI. This is called the Site (group) repository, which is
effectively a Site’s default repository. To access this repository via the API,
provide the group ID as the repositoryId.
You can also get the repositoryId via file (FileEntry), folder (Folder),
and file shortcut (FileShortcut) entities. Each of these entities has
a getRepositoryId method that gets the ID of its repository. For example, this
code gets the repository ID of the FileEntry object fileEntry:
long repositoryId = fileEntry.getRepositoryId();
There may also be cases that require a Repository object. You can get one by
creating a RepositoryProvider reference and passing the repository ID to its
getRepository method:
@Reference
private RepositoryProvider repositoryProvider;
Repository repository = repositoryProvider.getRepository(repositoryId);
Even if you only have an entity ID (e.g., a file ID or folder ID), you can still
use RepositoryProvider to get a Repository object. To do so, call the
RepositoryProvider method for the entity type with the entity ID as its
argument. For example, this code gets a folder’s Repository by calling the
RepositoryProvider method getFolderRepository with the folder’s ID:
Repository repository = repositoryProvider.getFolderRepository(folderId);
See the
RepositoryProvider Javadoc
for a list of the methods for other entity types.
Note that there are ways to create repositories programmatically, including repositories private to specific apps. For simplicity, however, the tutorials here access the default site repository.
Specifying Folders
Many API methods require the ID of a folder that they perform operations in or
on. For example, such methods may contain parameters like folderId or
parentFolderId. Also note that you can use the constant
DLFolderConstants.DEFAULT_PARENT_FOLDER_ID to specify the root folder of your
current repository.
Related Topics
OSGi Services and Dependency Injection with Declarative Services