The Updater service in Eclipse is based on Equinox p2, the Equinox framework OSGi implementation.
The OSGi (Open Service Gateway initiative) specification describes a modular system and a service platform for the Java programming language that implements a complete and dynamic component model, something that does not exist in standalone Java/VM environments.
When you run Help > Check for Updates, the Updater checks for system and component (addin) updates according to a list of “Available Software Sites” – which are p2 repositories. p2 stand for “Provisioning”.
Preferences > Install/Update > Available Software Sites
In my experience, this mechanism is buggy. You have to manually tweak the list (by adding, deleting, and editing) the items in the list.
http://wiki.eclipse.org/Eclipse_Project_Update_Sites
Here’s a list of URLs that you can visit to find the latest Update URI for a particular component.
<?xml version=”1.0″ encoding=”UTF-8″?>
<bookmarks>
<site url=” https://dl-ssl.google.com/android/eclipse/” selected=”true” name=”ADT Plugin”/>
<site url=” http://download.eclipse.org/webtools/updates” selected=”true” name=”Eclipse Web Tools Platform Repository”/>
<site url=” https://sourceforge.net/projects/eclipsejsonedit/files/update” selected=”true” name=”eclipse-json-editor”/>
<site url=” http://e-p-i-c.sf.net/updates/” selected=”true” name=”EPIC – Perl Editor and IDE for Eclipse”/>
<site url=” http://nextinterfaces.com/http4e/install/” selected=”true” name=”HTTP4e”/>
<site url=” http://download.eclipse.org/mylyn/releases/luna” selected=”true” name=”Mylyn for Eclipse Luna”/>
<site url=” http://www.oxygenxml.com/InstData/Editor/Eclipse/site.xml” selected=”true” name=”oXygen XML Editor Install”/>
<site url=” http://pydev.org/updates/” selected=”true” name=”PyDev Update Site”/>
<site url=” http://resteditor.sourceforge.net/eclipse/” selected=”true” name=”ReST Editor Update Site”/>
<site url=” http://download.eclipse.org/releases/luna/” selected=”true” name=”The Eclipse 4.4 (Luna) Updates”/>
<site url=” http://download.eclipse.org/webtools/repository/luna” selected=”true” name=”The Eclipse Web Tools Platform (WTP) software repository”/>
<site url=”http://www.oxygenxml.com/InstData/Editor/Eclipse” selected=”true” name=”update site: http://www.oxygenxml.com/InstData/Editor/Eclipse“/>
</bookmarks>