From version < 8.1 >
edited by Sergiu Dumitriu
on 2011/11/21
To version < 9.1 >
edited by Denis Gervalle
on 2011/11/21
Change comment: Adding notes about Disposable interface, Component registration events and Entity reference immutability



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1 -XWiki.Sergiu
1 +XWiki.dgervalle
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35 35  * You wish to lazily get a component instance (instead of it getting injected when your Component is looked up the first time)
36 36  * You wish to control how you return the instance you're providing for. For example you may wish to read the Component Hint from a configuration file and return the instance of the Component matching that Hint dynamically
37 37  
38 +== Component registration and unregistration event are now properly paired ==
39 +
40 +The registration and unregistration event triggered by a component manager is now perfectly paired. Registering an existing component role and hint now trigger the unregistration event before registering the new component.
41 +
42 +== New Disposable interface for singleton components ==
43 +
44 +To prepare the future uninstallation feature of the Extension Manager, singleton components could now implements the Disposable interface. This interface require a single dispose() methods that will be call when a singleton component is unregistered from its component manager. When a singleton component has been created, this could happen in three cases:
45 + * the component role and hints is explicitly unregistered
46 + * another component role with same hints is registered and therefore replace the existing component
47 + * the component instance is explicitly released calling the release function in the manager
48 +
49 +Components that require a singleton component should be aware that the instance provided is now subject release and should prevent from accessing a component that have been released. This could be done by observing the registration events of the component manager. The Unregister Event is always triggered when a component is released.
50 +
38 38  == Upgrades ==
39 39  
40 40  The following dependencies have been upgraded:
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98 98  Always make sure you compare your ##xwiki.cfg## and ##xwiki.properties## files with the newest version since some configuration parameters were added. Note that you should add ##xwiki.store.migration=1## so that XWiki will attempt to automatically migrate your current database to the new schema. Make sure you backup your Database before doing anything.
99 99  {{/warning}}
100 100  
114 +== Entity references are now immutable ==
115 +
116 +EntityReference (and derived classes, DocumentReference...) has been refactored and are now immutable. This change has been introduced to prevent dangerous issues where a reference hold by an object could be changed by another one. This have a lot of consequences on the reference API and this break the backward compatibility. The following change should be noticed:
117 + * all setters on EntityReference is now protected and could not be used anymore by any public code. Deriving a reference to render it mutable is hardly discouraged.
118 + * EntityReference#getChild() has been removed, since a single entity may have more than one child. A EntityReference#getReversedParentChain() method has been added to allow easy iteration from the root entity to their children in a given parent chain.
119 + * EntityReference#clone() has been removed, a copy-construtor is still available, but is useless since an entity is immutable, there is no need to clone it
120 + * EntityReference#replaceParent(oldParent,newParent) allow creating a new entity with one of the parent in the parent chain replaced
121 + * EntityReference#appendParent() allow creating a new entity with an appended root parent, this one is useless on any derived class since the parent chain could not appended in them.
122 +
101 101  == Issues specific to <projet> <version> ==
102 102  
103 103  <issues specific to the project>

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