Package nl.knaw.dans.layerstore

Interface Layer

public interface Layer

This interface represents a layer in the layered item store. A layer can be in the following states:

#	open/closed	archived	staged?	when?
1	open	niet archived	ja	beginsituatie van elke top layer
2	closed	niet archived	ja (met .closed suffix)	op het moment voordat de top layer gearchiveerd wordt
3	closed	archived	nee	archivering gelukt
4	open	archived	ja	reopened
5	closed	archived	ja (met .closed suffix)	close van een heropende layer

Method Summary

Modifier and Type	Method	Description
void	archive()	Turns the layer into an archive file.
void	close()	Changes the state of the layer to 'closed'.
void	createDirectory(String path)	Creates a directory at the given path.
void	deleteDirectory(String path)	Deletes the directory at the given path, including all its contents.
void	deleteFiles(List<String> paths)	Deletes the files pointed to by paths.
boolean	fileExists(String path)	Returns whether a file exists at the given path in this layer.
long	getId()	Returns the id of the layer.
long	getSizeInBytes()	Returns the size of the layer in bytes.
boolean	isArchived()	Returns whether the layer is archived.
boolean	isOpen()	Returns whether the layer is open.
Iterator<Item>	listAllItems()	Lists the items in this layer.
void	moveDirectoryInternal(String source, String destination)	Moves the directory at source to destination, where both paths are relative to the root of the layer.
void	moveDirectoryInto(Path source, String destination)	Moves the directory at source into the directory at destination.
InputStream	readFile(String path)	Reads the file at the given path.
void	reopen()	Changes the state of the layer to open.
void	writeFile(String filePath, InputStream content)	Writes the content of the given input stream to the file at the given path.

Method Details

getId

long getId()

Returns the id of the layer.

Returns:

the id of the layer

close

void close()

Changes the state of the layer to 'closed'.

Throws:

IllegalStateException - if the layer is already closed

reopen

void reopen()
     throws IOException

Changes the state of the layer to open. It also stages the archive file in the staging directory. This operation is not allowed when the layer is not closed or not yet archived.

Throws:

IOException

isOpen

boolean isOpen()

Returns whether the layer is open.

Returns:

whether the layer is open

archive

void archive()

Turns the layer into an archive file.

isArchived

boolean isArchived()

Returns whether the layer is archived.

Returns:

whether the layer is archived

createDirectory

void createDirectory(String path)
              throws IOException

Creates a directory at the given path. Not allowed when the layer is closed.

Parameters:

path - the path of the directory relative to the storage root

Throws:

IOException - if the directory cannot be created

deleteDirectory

void deleteDirectory(String path)
              throws IOException

Deletes the directory at the given path, including all its contents. Not allowed when the layer is closed.

Parameters:

path - the path of the directory relative to the storage root

Throws:

IOException - if the directory cannot be deleted

fileExists

boolean fileExists(String path)
            throws IOException

Returns whether a file exists at the given path in this layer.

Parameters:

path - the path of the file relative to the storage root

Returns:

whether the file exists

Throws:

IOException - if the existence of the file cannot be determined

readFile

InputStream readFile(String path)
              throws IOException

Reads the file at the given path. Note, that this may take a long time if the layer is archived, especially when the archive is stored on tape.

Parameters:

path - the path of the file relative to the storage root

Returns:

an input stream for reading the file; the caller is responsible for closing the stream

Throws:

IOException - if the file cannot be read

writeFile

void writeFile(String filePath,
 InputStream content)
        throws IOException

Writes the content of the given input stream to the file at the given path. Not allowed when the layer is closed. If the file already exists, it is overwritten.

Parameters:

filePath - the path of the file relative to the storage root

content - the content of the file

Throws:

IOException - if the file cannot be written

deleteFiles

void deleteFiles(List<String> paths)
          throws IOException

Deletes the files pointed to by paths. Not allowed when the layer is closed.

Parameters:

paths - the paths of the files to be deleted

Throws:

IOException - if the files cannot be deleted

moveDirectoryInto

void moveDirectoryInto(Path source,
 String destination)
                throws IOException

Moves the directory at source into the directory at destination. Not allowed when the layer is closed.

Parameters:

source - the path of the directory to be moved; must be an existing directory

destination - the path of the directory to move into; the directory is created if it does not exist yet

Throws:

IOException - if the directory cannot be moved

moveDirectoryInternal

void moveDirectoryInternal(String source,
 String destination)
                    throws IOException

Moves the directory at source to destination, where both paths are relative to the root of the layer.

Parameters:

source - the path of the directory to be moved; must be an existing directory

destination - the path of the destination directory; must not exist yet

Throws:

IOException - if the directory cannot be moved

getSizeInBytes

long getSizeInBytes()
             throws IOException

Returns the size of the layer in bytes. If the layer is archived, this may take a long time, especially when the archive is stored on tape.

Returns:

the size of the layer in bytes

Throws:

IOException - if the size cannot be determined

listAllItems

Iterator<Item> listAllItems()
                     throws IOException

Lists the items in this layer.

Returns:

the items in this layer

Throws:

IOException - if the items cannot be listed