ej.storage.fs

Class StorageFs

java.lang.Object

ej.storage.fs.StorageFs

All Implemented Interfaces:

Storage

public class StorageFs
extends Object
implements Storage

Implementation of persistent storage on file system.

Constructor Summary

Constructors

Constructor and Description
StorageFs() Creates a storage on file system.
StorageFs(String root) Creates a storage on file system specifying the root folder where the files will be created.

Method Summary

Modifier and Type	Method and Description
OutputStream	append(String id) Appends some data to an entry referenced with an ID.
boolean	exists(String id) Tests whether an entry exists for this ID.
protected File	getFile(String id) Returns the file associated to the given storage id.
String[]	getIds() Returns all IDs of the stored entries.
protected static String	getRootFolderPropertyOrDefault() Gets the root folder set with ej.storage.fs.StorageFs.root or if none.
long	getSize(String id) Returns the size of the entry stored with an ID.
InputStream	load(String id) Loads the data stored with a specific ID or null if there is none.
OutputStream	modify(String id, int offset) Modifies the entry that is referenced by an ID.
void	move(String sourceId, String destinationId) Changes the ID of an entry.
void	remove(String id) Removes the entry stored with an ID.
OutputStream	store(String id) Stores data that will be referenced with an ID.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

StorageFs

public StorageFs()
          throws IOException

Creates a storage on file system.

The root folder where the files will be created can be specified with the property ej.storage.fs.StorageFs.root. If not set, will be used.

Throws:

IOException - if the specified root already exists and is not a directory.

IOException - if the specified root cannot be created.

StorageFs

public StorageFs(String root)
          throws IOException

Creates a storage on file system specifying the root folder where the files will be created.

Parameters:

root - the root.

Throws:

IOException - if the specified root already exists and is not a directory.

IOException - if the specified root cannot be created.

Method Detail

append

public OutputStream append(String id)
                    throws IOException

Description copied from interface: Storage

Appends some data to an entry referenced with an ID.

If an entry is already stored with this ID, its existing data is not removed and the given data will be added to the existing entry. Otherwise, a new entry is created.

This operation may block the current thread depending on the implementation.

The returned output stream must be flushed or closed to ensure that the data is available. Example of usage:

 try(OutputStream outputStream = append(id)) {
        outputStream.write(…);
        outputStream.write(…);
 }
 

Specified by:

append in interface Storage

Parameters:

id - the ID of the stored entry.

Returns:

the output stream to write data.

Throws:

IOException - if an I/O error occurs.

exists

public boolean exists(String id)
               throws IOException

Description copied from interface: Storage

Tests whether an entry exists for this ID.

Specified by:

exists in interface Storage

Parameters:

id - the ID to check.

Returns:

true if the given ID exists, false otherwise

Throws:

IOException - if an I/O error occurs.

getFile

protected File getFile(String id)

Returns the file associated to the given storage id.

Parameters:

id - the storage identifier.

Returns:

the file associated to the given storage id.

getIds

public String[] getIds()
                throws IOException

Description copied from interface: Storage

Returns all IDs of the stored entries.

Specified by:

getIds in interface Storage

Returns:

an array of all IDs.

Throws:

IOException - if an I/O error occurs.

getRootFolderPropertyOrDefault

protected static String getRootFolderPropertyOrDefault()

Gets the root folder set with ej.storage.fs.StorageFs.root or if none.

Returns:

the root folder.

getSize

public long getSize(String id)
             throws IOException

Description copied from interface: Storage

Returns the size of the entry stored with an ID.

Specified by:

getSize in interface Storage

Parameters:

id - the ID of the entry.

Returns:

the size of the entry.

Throws:

IOException - if an I/O error occurs.

load

@Nullable
public InputStream load(String id)
                            throws IOException

Description copied from interface: Storage

Loads the data stored with a specific ID or null if there is none.

The returned input stream must be closed by the caller.

This operation may block the current thread depending on the implementation.

Specified by:

load in interface Storage

Parameters:

id - the ID of the entry to be returned.

Returns:

the data of the entry stored with the given ID or null.

Throws:

IOException - if an I/O error occurs.

modify

public OutputStream modify(String id,
                           int offset)
                    throws IOException

Description copied from interface: Storage

Modifies the entry that is referenced by an ID.

If an entry is already stored with this ID, its existing data is not removed and only the targeted bytes will be overwritten. Otherwise, a new entry is created.

This operation may block the current thread depending on the implementation.

The returned output stream must be flushed or closed to ensure that the data is available.

Specified by:

modify in interface Storage

Parameters:

id - the ID of the stored entry.

offset - the offset at which to write data.

Returns:

the output stream to write data.

Throws:

IOException - if an I/O error occurs.

move

public void move(String sourceId,
                 String destinationId)
          throws IOException

Description copied from interface: Storage

Changes the ID of an entry.

If an entry is already stored with the destination ID, it is overwritten.

This operation may block the current thread depending on the implementation.

Specified by:

move in interface Storage

Parameters:

sourceId - the old ID of the entry.

destinationId - the new ID of the entry.

Throws:

IOException - if an I/O error occurs.

remove

public void remove(String id)
            throws IOException

Description copied from interface: Storage

Removes the entry stored with an ID.

This operation may block the current thread depending on the implementation.

Specified by:

remove in interface Storage

Parameters:

id - the ID of the entry to remove.

Throws:

IOException - if an I/O error occurs.

store

public OutputStream store(String id)
                   throws IOException

Description copied from interface: Storage

Stores data that will be referenced with an ID.

If an entry is already stored with this ID, its existing data is fully removed and replaced by the given data. Otherwise, a new entry is created.

This operation may block the current thread depending on the implementation.

The returned output stream must be flushed or closed to ensure that the data is available. Example of usage:

 try(OutputStream outputStream = store(id)) {
        outputStream.write(…);
        outputStream.write(…);
 }
 

Specified by:

store in interface Storage

Parameters:

id - the ID of the stored entry.

Returns:

the output stream to write data.

Throws:

IOException - if an I/O error occurs.