org.mycore.datamodel.ifs2
Class MCRStore

java.lang.Object
  org.mycore.datamodel.ifs2.MCRStore

Direct Known Subclasses:

MCRFileStore, MCRMetadataStore

public abstract class MCRStore
extends Object

Stores metadata files or file collections containing files and directories in a persistent store implemented using a local filesystem. For better filesystem performance, the store can build slot subdirectories (containing other subdirectories and so on) so that not all objects are stored in the same filesystem directory. Directories containing a very large number of files typically show bad performance. The slot layout of the store defines the usage of subdirectories within the base directory. A layout of "8" would mean no subdirectories will be used, the maximum ID size is 8 digits, and therefore up to 99999999 objects can be stored all in the same base directory. A layout of "2-2-4" would mean data is stored using two levels of subdirectories, where the first subdirectory contains up to 100 (00-99) subdirectories, the second subdirectory level below contains up to 100 subdirectories, too, and below the data is stored, with up to 10000 data objects in the subdirectory. Using this slot layout, the data of ID 10485 would be stored in the file object "/00/01/00010485", for example. Using layout "4-2-2", data would be stored in "/0001/04/00010485", and so on. The slot file name itself may optionally have a prefix and suffix. With prefix "derivate-", the slot name would be "derivate-00010485". With prefix "DocPortal_document_" and suffix ".xml", the slot name would be "DocPortal_document_00010485.xml" for example. MCR.IFS2.Store.ID.Class=org.mycore.datamodel.ifs2.MCRFileStore MCR.IFS2.Store.ID.BaseDir=/foo/bar MCR.IFS2.Store.ID.SlotLayout=4-2-2

Author:

Frank Lützenkirchen

Field Summary

static boolean	ASCENDING Indicates ascending order when listing IDs
static boolean	DESCENDING Indicates descending order when listing IDs
protected File	dir The base directory containing the stored data
protected String	id The ID of the store
protected int	idLength The maximum length of IDs
protected int	lastID The last ID assigned by this store.
protected int	offset Offset to add to the maximum ID found in the store to build the new ID.
protected String	prefix The prefix of slot names
protected int[]	slotLength The slot subdirectory layout, which is the number of digits used at each subdirectory level to build the filename.
protected static HashMap<String,MCRStore>	stores Map of defined stores, where store ID is the map key.
protected String	suffix The suffix of slot names

Constructor Summary

MCRStore()

Method Summary

(package private) void	delete(org.apache.commons.vfs.FileObject fo) Deletes the data stored in the given file object from the store
void	delete(int id) Deletes the data stored under the given ID from the store
boolean	exists(int id) Returns true if data for the given ID is existing in the store.
(package private) String	getBaseDir() Returns the absolute path of the local base directory
int	getHighestStoredID()
String	getID() Returns the ID of this store
int	getNextFreeID() Returns the next free ID that can be used to store data.
(package private) org.apache.commons.vfs.FileObject	getSlot(int ID) Returns the slot file object used to store data for the given ID.
(package private) String	getSlotPath(int ID) Returns the relative path used to store data for the given ID within the store base directory
(package private) String[]	getSlotPaths(int ID) Returns the paths of all subdirectories and the slot itself used to store data for the given ID relative to the store base directory
protected static MCRStore	getStore(String ID) Returns the store with the given ID
protected void	init(String id) Initializes a new store instance
Iterator<Integer>	listIDs(boolean order) Lists all IDs currently used in the store, in ascending or descending order

Methods inherited from class java.lang.Object

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

Field Detail

stores

protected static HashMap<String,MCRStore> stores

Map of defined stores, where store ID is the map key.

id

protected String id

The ID of the store

dir

protected File dir

The base directory containing the stored data

idLength

protected int idLength

The maximum length of IDs

slotLength

protected int[] slotLength

The slot subdirectory layout, which is the number of digits used at each subdirectory level to build the filename.

prefix

protected String prefix

The prefix of slot names

suffix

protected String suffix

The suffix of slot names

offset

protected int offset

Offset to add to the maximum ID found in the store to build the new ID. This is normally 1, but initially higher to avoid reassigning the same ID after system restarts. Consider the following example: 1) User creates new document, ID assigned is 10. 2) User deletes document 10. 3) Web application is restarted. 4) User creates new document, ID assigned is 20. If offset would always be 1, ID assigned would have been 10 again, and that is not nice, because we can not distinguish the two creates easily.

lastID

protected int lastID

The last ID assigned by this store.

ASCENDING

public static final boolean ASCENDING

Indicates ascending order when listing IDs

See Also:

Constant Field Values

DESCENDING

public static final boolean DESCENDING

Indicates descending order when listing IDs

See Also:

Constant Field Values

Constructor Detail

MCRStore

public MCRStore()

Method Detail

getStore

protected static MCRStore getStore(String ID)

Returns the store with the given ID

Parameters:

ID - the ID of the store

init

protected void init(String id)

Initializes a new store instance

getID

public String getID()

Returns the ID of this store

getBaseDir

String getBaseDir()

Returns the absolute path of the local base directory

Returns:

the base directory storing the data

getSlot

org.apache.commons.vfs.FileObject getSlot(int ID)
                                    throws Exception

Returns the slot file object used to store data for the given ID. This may be a file or directory, depending on the subclass of MCRStore that is used.

Parameters:

ID - the ID of the data

Returns:

the file object storing that data

Throws:

Exception

getSlotPath

String getSlotPath(int ID)

Returns the relative path used to store data for the given ID within the store base directory

Parameters:

ID - the ID of the data

Returns:

the relative path storing that data

getSlotPaths

String[] getSlotPaths(int ID)

Returns the paths of all subdirectories and the slot itself used to store data for the given ID relative to the store base directory

Parameters:

ID - the ID of the data

Returns:

the directory and file names of the relative path storing that data

exists

public boolean exists(int id)
               throws Exception

Returns true if data for the given ID is existing in the store.

Parameters:

id - the ID of the data

Returns:

true, if data for the given ID is existing in the store.

Throws:

Exception

getNextFreeID

public int getNextFreeID()

Returns the next free ID that can be used to store data. Call as late as possible to avoid that another process, for example from batch import, in the meantime already used that ID.

Returns:

the next free ID that can be used to store data

getHighestStoredID

public int getHighestStoredID()

listIDs

public Iterator<Integer> listIDs(boolean order)

Lists all IDs currently used in the store, in ascending or descending order

Parameters:

order - the order in which IDs should be returned.

Returns:

all IDs currently used in the store

See Also:

ASCENDING, DESCENDING

delete

public void delete(int id)
            throws Exception

Deletes the data stored under the given ID from the store

Parameters:

id - the ID of the document to be deleted

Throws:

Exception

delete

void delete(org.apache.commons.vfs.FileObject fo)
      throws Exception

Deletes the data stored in the given file object from the store

Parameters:

fo - the file object to be deleted

Throws:

Exception