Getting 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.

As an example, this getFileEntries method contains all the above parameters except fileEntryTypeId (it contains mimeTypes instead):

List<FileEntry> getFileEntries(
        long repositoryId, 
        long folderId, 
        String[] mimeTypes, 
        int start, 
        int end, 
        OrderByComparator<FileEntry> obc
)

Follow these steps to use this method to get a list of files. Note that the example in these steps gets all the PNG images from the root folder of a Site’s default repository, sorted by title:

1. Get a reference to DLAppService:

   @Reference
   private DLAppService _dlAppService;
   

   For more information on this, see the section on getting a service reference in the getting started tutorial.

2. Get the data needed to populate the method’s arguments. You can do this any way you wish. As the next step describes, Liferay DXP provides constants and a comparator for all the arguments this example needs besides the group ID. This example gets the group ID by using ParamUtil with the request (javax.portlet.ActionRequest):

   long groupId = ParamUtil.getLong(actionRequest, "groupId");
   

   It’s also possible to get the group ID via the ThemeDisplay. Calling the ThemeDisplay method getScopeGroupId() gets the ID of your app’s current site (group):

   ThemeDisplay themeDisplay = (ThemeDisplay) request.getAttribute(WebKeys.THEME_DISPLAY);
   long groupId = themeDisplay.getScopeGroupId();
   

   For more information, see the Data Scopes tutorial.

3. Use the data from the previous step to call the service reference method you want to use to get the files. This example calls the above getFileEntries method with the group ID from the previous step, and constants and a comparator for the remaining arguments:

   List<FileEntry> fileEntries = 
           _dlAppService.getFileEntries(
                   groupId, 
                   DLFolderConstants.DEFAULT_PARENT_FOLDER_ID, 
                   new String[] {ContentTypes.IMAGE_PNG}, 
                   QueryUtil.ALL_POS, 
                   QueryUtil.ALL_POS, 
                   new RepositoryModelTitleComparator<>()
           );
   

   Here’s a description of the arguments used in this example:

   • groupId: Using the group ID as the repository ID specifies that the operation takes place in the default site repository.
   • DLFolderConstants.DEFAULT_PARENT_FOLDER_ID: Uses the DLFolderConstants constant DEFAULT_PARENT_FOLDER_ID to specify the repository’s root folder.
   • new String[] {ContentTypes.IMAGE_PNG}: Uses the ContentTypes constant IMAGE_PNG to specify PNG images.
   • QueryUtil.ALL_POS: Uses the QueryUtil constant ALL_POS for the start and end positions in the results. This specifies all results, bypassing pagination.
   • new RepositoryModelTitleComparator<>(): Creates a new RepositoryModelTitleComparator, which sorts the results by title.

Remember, this is just one of many getFileEntries and getGroupFileEntries methods. To see all such methods, see the DLAppService Javadoc.

Related Topics

Getting Started with the Documents and Media API

Getting Folders

Getting Multiple Entity Types

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