Using Policy Files

Policy files allow a user to configure where to search for updates to a feature when checking for updates.

Creating the Policy File

A sample policy file is shown below:

<?xml version="1.0" encoding="UTF-8"?>
<update-policy>
  <url-map pattern="feature.id" url="http://hostname/update/nightly/policy.xml"/>
</update-policy>

In this example, we save this to an XML file named "policy.xml". This is then placed next to the corresponding update site.xml. This effectively says "when I see feature with id x, instead go to update site y rather than the default". You can also use wildcards, such as feature.id.* if you have multiple features with the same prefix.

If you wanted to update from a non-standard update site, you could use a policy file to redirect from the default Update site to a secondary one. For example:

<?xml version="1.0" encoding="UTF-8"?>
<update-policy>
  <url-map pattern="*" url="http://download.eclipse.org/modeling/emf/updates/site-interim.xml"/>
</update-policy>

Using the Policy File

In Eclipse, navigate to Window > Preferences > Install/Update, and paste in the URL to the policy file and hit OK, eg:

http://download.eclipse.org/modeling/mdt/updates/policy.xml

or, for a local file:

file:///home/nickb/workspace2/modeling/mdt/updates/policy.xml

The next time you search for updates, Eclipse will use the URL specified in the policy file.

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An additional thought is to provide a preference page to allow the end user to choose which "release stream" they wish to subscribe to. In this case, there is a radio button that might specify "stable", "rc" and "nightly". Selecting one of these radio buttons would automatically set the policy file behind the scenes.