Getting Entities

The Documents and Media API contains many methods for getting entities from a repository. Most methods in DLAppService get single entities (e.g., a file or folder), a collection of entities that match certain characteristics, or the number of such entities. Because there are so many similar methods for getting entities, they aren’t all described here. You can find full descriptions for all DLAppService methods in its reference documentation.

Here, you’ll learn about getting these entities:

• Files
• Folders
• Multiple Entity Types

Files

Getting files is one of the most common tasks you’ll perform with the Documents and Media API. There are two main method families for getting files:

getFileEntries: Gets files from a specific repository.

getGroupFileEntries: Gets files from a Site (group), regardless of repository.

Since these method families are common, their methods share many parameters:

repositoryId: The ID of the repository to get files from. To specify the default Site repository, use the groupId (Site ID).

folderId: The ID of the folder to get files from. Note that these methods don’t traverse the folder structure—they only get files directly from the specified folder. To specify the repository’s root folder, use the constant DLFolderConstants.DEFAULT_PARENT_FOLDER_ID.

start and end: Integers that specify the lower and upper bounds, respectively, of collection items to include in a page of results. If you don’t want to use pagination, use QueryUtil.ALL_POS for these parameters.

obc: The comparator to use to order collection items. Comparators are OrderByComparator implementations that sort collection items.

fileEntryTypeId: The ID of the file type to retrieve. Use this to retrieve files of a specific type.

mimeTypes: The MIME types of the files to retrieve. Use this to retrieve files of the specified MIME types. You can specify MIME types via the constants in ContentTypes.

Note that the obc parameter must be an implementation of OrderByComparator. Although you can implement your own comparators, Liferay DXP already contains a few useful implementations in the package com.liferay.document.library.kernel.util.comparator:

RepositoryModelCreateDateComparator: Sorts by creation date.

RepositoryModelModifiedDateComparator: Sorts by modification date.

RepositoryModelReadCountComparator: Sorts by number of views.

RepositoryModelSizeComparator: Sorts by file size.

RepositoryModelTitleComparator: Sorts by title.

See Getting Files for step-by-step instructions on using the above method families.

Folders

The Documents and Media API can get folders in a similar way to getting files. The main difference is that folder retrieval methods may have an additional argument to tell the system whether to include mount folders. Mount folders are mount points for external repositories (e.g. Alfresco or SharePoint) that appear as regular folders in a Site’s default repository. They let users navigate seamlessly between repositories. To account for this, some folder retrieval methods include the boolean parameter includeMountFolders. Setting this parameter to true includes mount folders in the results, while omitting it or setting it to false excludes them.

For example, to get a list of a parent folder’s subfolders from a repository, including any mount folders, use this getFolders method:

getFolders(long repositoryId, long parentFolderId, boolean includeMountFolders)

Note that there are several other getFolders methods in DLAppService. Use the one that best matches your use case. See Getting Folders for step-by-step instructions on using these getFolders methods.

Multiple Entity Types

There are also methods in the Documents and Media API that retrieve lists containing several entity types. These methods use many of the same parameters as those already described for retrieving files and folders. For example, the getFileEntriesAndFileShortcuts method gets files and shortcuts from a given repository and folder. Its status parameter specifies a workflow status. As before, the start and end parameters control pagination of the entities:

getFileEntriesAndFileShortcuts(long repositoryId, long folderId, int status, int start, int end)

For step-by-step instructions on calling this method and others like it, see Getting Multiple Entity Types. To see all such methods, see the DLAppService Javadoc.