org.apache.wiki
Class ReferenceManager

java.lang.Object
  org.apache.wiki.api.filters.BasicPageFilter
      org.apache.wiki.ReferenceManager

All Implemented Interfaces:

EventListener, PageFilter, WikiEventListener, InternalModule

public class ReferenceManager
extends BasicPageFilter
implements InternalModule, WikiEventListener

Keeps track of wikipage references:

• What pages a given page refers to
• What pages refer to a given page

This is a quick'n'dirty approach without any finesse in storage and searching algorithms; we trust java.util.*.

This class contains two HashMaps, m_refersTo and m_referredBy. The first is indexed by WikiPage names and contains a Collection of all WikiPages the page refers to. (Multiple references are not counted, naturally.) The second is indexed by WikiPage names and contains a Set of all pages that refer to the indexing page. (Notice - the keys of both Maps should be kept in sync.)

When a page is added or edited, its references are parsed, a Collection is received, and we crudely replace anything previous with this new Collection. We then check each referenced page name and make sure they know they are referred to by the new page.

Based on this information, we can perform non-optimal searches for e.g. unreferenced pages, top ten lists, etc.

The owning class must take responsibility of filling in any pre-existing information, probably by loading each and every WikiPage and calling this class to update the references when created.

Since:

1.6.1

Constructor Summary

ReferenceManager(WikiEngine engine)
Builds a new ReferenceManager.

Method Summary

void	actionPerformed(WikiEvent event) Fired when a WikiEvent is triggered by an event source.
void	clearPageEntries(String pagename) Clears the references to a certain page so it's no longer in the map.
int	deepHashCode() This 'deepHashCode' can be used to determine if there were any modifications made to the underlying to and by maps of the ReferenceManager.
Set	findCreated() Returns a list of all pages that the ReferenceManager knows about.
Set	findReferredBy(String pageName) Returns all pages that refer to this page.
Collection	findReferrers(String pagename) Find all pages that refer to this page.
Collection	findRefersTo(String pageName) Returns all pages that this page refers to.
Collection	findUncreated() Finds all references to non-existant pages.
Collection	findUnreferenced() Finds all unreferenced pages.
protected Map	getReferredBy() Returns the referred-by list.
protected Map	getRefersTo() Returns the refers-to list.
void	initialize(Collection pages) Initializes the entire reference manager with the initial set of pages from the collection.
void	pageRemoved(WikiPage page) Updates the m_referedTo and m_referredBy hashmaps when a page has been deleted.
void	postSave(WikiContext context, String content) After the page has been saved, updates the reference lists.
void	updateReferences(String page, Collection<String> references) Updates the referred pages of a new or edited WikiPage.

Methods inherited from class org.apache.wiki.api.filters.BasicPageFilter

destroy, initialize, postTranslate, preSave, preTranslate

Methods inherited from class java.lang.Object

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

Constructor Detail

ReferenceManager

public ReferenceManager(WikiEngine engine)

Builds a new ReferenceManager.

Parameters:

engine - The WikiEngine to which this is managing references to.

Method Detail

initialize

public void initialize(Collection pages)
                throws ProviderException

Initializes the entire reference manager with the initial set of pages from the collection.

Parameters:

pages - A collection of all pages you want to be included in the reference count.

Throws:

ProviderException - If reading of pages fail.

Since:

2.2

postSave

public void postSave(WikiContext context,
                     String content)

After the page has been saved, updates the reference lists.

Specified by:

postSave in interface PageFilter

Overrides:

postSave in class BasicPageFilter

Parameters:

context - The WikiContext

content - The content which was just stored.

pageRemoved

public void pageRemoved(WikiPage page)

Updates the m_referedTo and m_referredBy hashmaps when a page has been deleted.

Within the m_refersTo map the pagename is a key. The whole key-value-set has to be removed to keep the map clean. Within the m_referredBy map the name is stored as a value. Since a key can have more than one value we have to delete just the key-value-pair referring page:deleted page.

Parameters:

page - Name of the page to remove from the maps.

updateReferences

public void updateReferences(String page,
                             Collection<String> references)

Updates the referred pages of a new or edited WikiPage. If a refersTo entry for this page already exists, it is removed and a new one is built from scratch. Also calls updateReferredBy() for each referenced page.

This is the method to call when a new page has been created and we want to a) set up its references and b) notify the referred pages of the references. Use this method during run-time.

Parameters:

page - Name of the page to update.

references - A Collection of Strings, each one pointing to a page this page references.

getRefersTo

protected Map getRefersTo()

Returns the refers-to list. For debugging.

Returns:

The refers-to list.

getReferredBy

protected Map getReferredBy()

Returns the referred-by list. For debugging.

Returns:

Referred-by lists.

clearPageEntries

public void clearPageEntries(String pagename)

Clears the references to a certain page so it's no longer in the map.

Parameters:

pagename - Name of the page to clear references for.

findUnreferenced

public Collection findUnreferenced()

Finds all unreferenced pages. This requires a linear scan through m_referredBy to locate keys with null or empty values.

Returns:

The Collection of Strings

findUncreated

public Collection findUncreated()

Finds all references to non-existant pages. This requires a linear scan through m_refersTo values; each value must have a corresponding key entry in the reference Maps, otherwise such a page has never been created.

Returns a Collection containing Strings of unreferenced page names. Each non-existant page name is shown only once - we don't return information on who referred to it.

Returns:

A Collection of Strings

findReferrers

public Collection findReferrers(String pagename)

Find all pages that refer to this page. Returns null if the page does not exist or is not referenced at all, otherwise returns a collection containing page names (String) that refer to this one.

Parameters:

pagename - The page to find referrers for.

Returns:

A Collection of Strings. (This is, in fact, a Set, and is likely to change at some point to a Set). May return null, if the page does not exist, or if it has no references.

findReferredBy

public Set findReferredBy(String pageName)

Returns all pages that refer to this page. Note that this method returns an unmodifiable Map, which may be abruptly changed. So any access to any iterator may result in a ConcurrentModificationException.

The advantages of using this method over findReferrers() is that it is very fast, as it does not create a new object. The disadvantages are that it does not do any mapping between plural names, and you may end up getting a ConcurrentModificationException.

Parameters:

pageName - Page name to query.

Returns:

A Set of Strings containing the names of all the pages that refer to this page. May return null, if the page does not exist or has not been indexed yet.

Since:

2.2.33

findRefersTo

public Collection findRefersTo(String pageName)

Returns all pages that this page refers to. You can use this as a quick way of getting the links from a page, but note that it does not link any InterWiki, image, or external links. It does contain attachments, though.

The Collection returned is unmutable, so you cannot change it. It does reflect the current status and thus is a live object. So, if you are using any kind of an iterator on it, be prepared for ConcurrentModificationExceptions.

The returned value is a Collection, because a page may refer to another page multiple times.

Parameters:

pageName - Page name to query

Returns:

A Collection of Strings containing the names of the pages that this page refers to. May return null, if the page does not exist or has not been indexed yet.

Since:

2.2.33

deepHashCode

public int deepHashCode()

This 'deepHashCode' can be used to determine if there were any modifications made to the underlying to and by maps of the ReferenceManager. The maps of the ReferenceManager are not synchronized, so someone could add/remove entries in them while the hashCode is being computed.

Returns:

Sum of the hashCodes for the to and by maps of the ReferenceManager

Since:

2.3.24

findCreated

public Set findCreated()

Returns a list of all pages that the ReferenceManager knows about. This should be roughly equivalent to PageManager.getAllPages(), but without the potential disk access overhead. Note that this method is not guaranteed to return a Set of really all pages (especially during startup), but it is very fast.

Returns:

A Set of all defined page names that ReferenceManager knows about.

Since:

2.3.24

actionPerformed

public void actionPerformed(WikiEvent event)

Fired when a WikiEvent is triggered by an event source.

Specified by:

actionPerformed in interface WikiEventListener

Parameters:

event - a WikiEvent object