com.planetj.taste.impl.model.file
Class FileDataModel

java.lang.Object
  com.planetj.taste.impl.model.file.FileDataModel

All Implemented Interfaces:

Refreshable, DataModel

public class FileDataModel
extends java.lang.Object
implements DataModel

A DataModel backed by a comma-delimited file. This class assumes that each line of the file contains a user ID, followed by item ID, followed by preferences value, separated by commas. The preference value is assumed to be parseable as a double. The user and item IDs are ready literally as Strings and treated as such in the API. Note that this means that whitespace matters in the data file; they will be treated as part of the ID values.

This class is not intended for use with very large amounts of data (over, say, a million rows). For that, MySQLJDBCDataModel and a database are more appropriate. The file will be periodically reloaded if a change is detected.

Author:

Sean Owen

Constructor Summary

FileDataModel(java.io.File dataFile)

Method Summary

protected Item	buildItem(java.lang.String id) Subclasses may override to return a different Item implementation.
protected Preference	buildPreference(User user, Item item, double value) Subclasses may override to return a different Preference implementation.
protected User	buildUser(java.lang.String id, java.util.List<Preference> prefs) Subclasses may override to return a different User implementation.
Item	getItem(java.lang.Object id)
java.lang.Iterable<? extends Item>	getItems()
int	getNumItems()
int	getNumUsers()
java.lang.Iterable<? extends Preference>	getPreferencesForItem(java.lang.Object itemID)
Preference[]	getPreferencesForItemAsArray(java.lang.Object itemID)
User	getUser(java.lang.Object id)
java.lang.Iterable<? extends User>	getUsers()
void	refresh() Triggers "refresh" -- whatever that means -- of the implementation.
protected void	reload()
void	removePreference(java.lang.Object userID, java.lang.Object itemID) Removes a particular preference for a user.
void	setPreference(java.lang.Object userID, java.lang.Object itemID, double value) Sets a particular preference (item plus rating) for a user.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

FileDataModel

public FileDataModel(java.io.File dataFile)
              throws java.io.FileNotFoundException

Parameters:

dataFile - file containing preferences data

Throws:

java.io.FileNotFoundException - if dataFile does not exist

Method Detail

reload

protected void reload()
               throws java.io.IOException

Throws:

java.io.IOException

getUsers

@NotNull
public java.lang.Iterable<? extends User> getUsers()
                                            throws TasteException

Specified by:

getUsers in interface DataModel

Returns:

a List of all Users in the model, ordered by User

Throws:

TasteException - if an error occurs while accessing the data

getUser

@NotNull
public User getUser(java.lang.Object id)
             throws TasteException

Specified by:

getUser in interface DataModel

Parameters:

id - user ID

Returns:

User who has that ID

Throws:

java.util.NoSuchElementException - if there is no such user

TasteException - if an error occurs while accessing the data

getItems

@NotNull
public java.lang.Iterable<? extends Item> getItems()
                                            throws TasteException

Specified by:

getItems in interface DataModel

Returns:

a List of all Items in the model, order by Item

Throws:

TasteException - if an error occurs while accessing the data

getItem

@NotNull
public Item getItem(java.lang.Object id)
             throws TasteException

Specified by:

getItem in interface DataModel

Parameters:

id - item ID

Returns:

Item that has that ID

Throws:

TasteException - if an error occurs while accessing the data

getPreferencesForItem

@NotNull
public java.lang.Iterable<? extends Preference> getPreferencesForItem(java.lang.Object itemID)
                                                               throws TasteException

Specified by:

getPreferencesForItem in interface DataModel

Parameters:

itemID - item ID

Returns:

all existing Preferences expressed for that item, ordered by User

Throws:

TasteException - if an error occurs while accessing the data

getPreferencesForItemAsArray

@NotNull
public Preference[] getPreferencesForItemAsArray(java.lang.Object itemID)
                                          throws TasteException

Specified by:

getPreferencesForItemAsArray in interface DataModel

Parameters:

itemID - item ID

Returns:

all existing Preferences expressed for that item, ordered by User, as an array

Throws:

TasteException - if an error occurs while accessing the data

getNumItems

public int getNumItems()
                throws TasteException

Specified by:

getNumItems in interface DataModel

Returns:

total number of Items known to the model. This is generally the union of all Items preferred by at least one User but could include more.

Throws:

TasteException - if an error occurs while accessing the data

getNumUsers

public int getNumUsers()
                throws TasteException

Specified by:

getNumUsers in interface DataModel

Returns:

total number of Users known to the model.

Throws:

TasteException - if an error occurs while accessing the data

setPreference

public void setPreference(java.lang.Object userID,
                          java.lang.Object itemID,
                          double value)

Description copied from interface: DataModel

Sets a particular preference (item plus rating) for a user.

Specified by:

setPreference in interface DataModel

Parameters:

userID - user to set preference for

itemID - item to set preference for

value - preference value

Throws:

java.lang.UnsupportedOperationException

removePreference

public void removePreference(java.lang.Object userID,
                             java.lang.Object itemID)

Description copied from interface: DataModel

Removes a particular preference for a user.

Specified by:

removePreference in interface DataModel

Parameters:

userID - user from which to remove preference

itemID - item to remove preference for

Throws:

java.lang.UnsupportedOperationException

refresh

public void refresh()

Triggers "refresh" -- whatever that means -- of the implementation. The general contract is that any Refreshable should always leave itself in a consistent, operational state, and that the refresh atomically updates internal state from old to new.

Specified by:

refresh in interface Refreshable

buildUser

@NotNull
protected User buildUser(java.lang.String id,
                                 java.util.List<Preference> prefs)

Subclasses may override to return a different User implementation.

Parameters:

id - user ID

prefs - user preferences

Returns:

GenericUser by default

buildItem

@NotNull
protected Item buildItem(java.lang.String id)

Subclasses may override to return a different Item implementation.

Parameters:

id - item ID

Returns:

GenericItem by default

buildPreference

@NotNull
protected Preference buildPreference(User user,
                                             Item item,
                                             double value)

Subclasses may override to return a different Preference implementation.

Parameters:

user - User who expresses the preference

item - preferred Item

value - preference value

Returns:

GenericPreference by default

toString

@NotNull
public java.lang.String toString()

Overrides:

toString in class java.lang.Object