Explanation

While it's technically possible to install extensions by importing XAR files, this is not the recommended method. Importing extension Pages is not enough to have the extensions working because extensions need their dependencies. It is always better to use the Extension Manager for installing extensions, as this ensures all dependencies are properly handled. 

Some extensions can be packaged as XAR files. When importing XWiki Pages (a XAR), the import process analyzes the information defined in the package.xml file contained in the XAR archive. If the package.xml file contains an extensionId value (which represents an Extension ID), the Importer will check whether this Extension exists in the configured XWiki Extension Repositories. The configuration of these repositories is defined in: xwiki.properties, using the keys: extension.repositories.

If the Extension is found in one of the configured repositories, the Importer will register the Extension as installed in the current XWiki instance. The Extension will be visible in the Extension Manager, under "Installed extensions". 

FAQ

What is the recommended method to import Pages from extensions or to install extensions ?

• It’s recommended to use the Extension Manager to import Pages from extensions or to install extensions. Importing extension Pages on top of a different version of the same extension may break the extension because of API incompatibilities.