FileManager Module

About the FileManagerModule

The FileManagerModule provides an abstraction layer for storing and retrieving files in an efficient way. Files are uniquely identified using a FileDescriptor and stored in a named FileRepository. Clients access all files and repositories through the central FileManager bean.

By default the FileManagerModule sets up local directory based file repositories and requires very little configuration.

.1. Artifact

<dependencies>
	<dependency>
		<groupId>com.foreach.across.modules</groupId>
		<artifactId>file-manager-module</artifactId>
		<version>0.0.3.RELEASE</version>
	</dependency>
</dependencies>

.2. Module dependencies

Table 1. Module dependencies
Module	Type	Description
`EntityModule`	optional	Enables the ability to render the fileUpload control.
`AcrossHibernateJpaModule`	optional	Enables the ability to persist the `FileReference` entity.
`PropertiesModule`	optional	Used to add properties to a file

For more information about what FileManagerModule has to offer when other modules are detected see the section Module relations.

.3. Core classes

.3.1. FileDescriptor

Files are identified by a unique FileDescriptor that determines in which backing FileRepository a file should be saved or from which it should be retrieved. A FileDescriptor has a URI property that is a globally unique String version of the descriptor. Any FileDescriptor can be serialized to and from its URI.

.3.2. FileRepository

A FileRepository is identified by a unique repository id. The first part of a FileDescriptor will always contain the repository id. How a FileRepository stores its files is implementation dependent. This could be disk-based storage, database backed or any form of cloud storage. The purpose of the FileManager, FileDescriptor and FileRepository interfaces is to provide a flexible way for modules to interact with files, without knowing how or where they are actually persisted.

.3.3. FileManager

The FileManager service bean (exposed) is the facade to access any FileRepository. It is the central interface that clients should use for accessing files. Using it is pretty straightforward, the interface methods are well-documented and fairly self-explanatory.

.4. Default configuration

The default configuration of the FileManagerModule will automatically create file based repositories in a single root folder (controller by the fileManagerModule.localRepositoriesRoot property). A new repository will be created when it is accessed for the first time. If no explicit repository id is specified for file access, default will be used.

Uploading files

FileManagerModule provides the FileReference entity to handle uploading and saving of files. The FileReference entity will handle the file persistence and it provides a link between your entity and the physical file.

Example of storing a file linked to an entity

@Entity
@Getter
@Setter
@NoArgsConstructor
public class Invoice extends SettableIdBasedEntity<Invoice> {
    private FileReference attachment;
}

You can find more information about multiple file uploads and moving files to another FileRepository while saving in the uploading and saving files section.

Amazon S3 support

FileManager has support build in to store files on a Amazon S3 bucket (https://aws.amazon.com/s3/) by using a AwsS3FileRepository.

Azure Blob Storage support

FileManager has support build in to store files on a Azure Blob Storage container (https://azure.microsoft.com/en-us/services/storage/blobs/) by using a AzureFileRepository.

Saving files form code

The creation and moving of files can by done by using the FileManager. The FileManager uses the provided FileRepository to handle to actual saving of the file. When no fileRepository is provided the default fileRepository LocalFileRepository is used.

The default pathGenerator used by the FileRepository is a DateFormatPathGenerator. This means by default files will be saved using the yyyy/MM/dd path.

Example storing a file

// Create a new temporary file
File tempFile = fileManager.createTempFile();
// Write data to the temporary file
writeUploadedImage( tempFile );
// Move the file into the 'images' repository (this deletes the temp file)
FileDescriptor fd = fileManager.moveInto( "images", tempFile );
// Store the unique file descriptor in database
imageRecord.setFileUri( fd.getUri() );

Because a FileRepository can have different types of implementations, modify operations on java.io.File instances might be limited. To ensure maximum compatibility intermediate stages (using temporary files) or the InputSteam/OutputStream based methods should be used. See the FileRepository javadoc for more details.

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