[jira] [Resolved] (JCR-5140) Improve support for generating namespace prefixes

["Julian Reschke (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/JCR-5140?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Reschke resolved JCR-5140.
---------------------------------
    Fix Version/s: 2.23.3
       Resolution: Fixed

> Improve support for generating namespace prefixes
> -------------------------------------------------
>
>                 Key: JCR-5140
>                 URL: https://issues.apache.org/jira/browse/JCR-5140
>             Project: Jackrabbit Content Repository
>          Issue Type: Task
>          Components: jackrabbit-jcr-commons
>            Reporter: Julian Reschke
>            Assignee: Julian Reschke
>            Priority: Major
>             Fix For: 2.23.3
>
>
> There are a few use cases where a new namespace prefix needs to be computed for a given namespace name (this list may not be exhaustive):
>  - when mapping expanded names to JCR names when the namespace name (URI) is not known in the repository (yet) - though that's a use case not supported in Oak, creating of new items with previously non-registered namespace is not possible
>  - when importing content where namespace names (URIs) are known, but prefixes may be not
>  - when looking up a name from the repository from a repo that persists names with prefixes, but the prefix is already locally mapped to a different namespace
> - when registering node types where the namespace name (such as defined in the CND) is new, but the "preferred" prefix is already in use) - note that this requires write access to the repository's namespace registry
> Automatically generating the prefixes has several commons problems:
>  - consistency: generating prefixes in different places and/or based on previous state of the registry (such as by incrementing counters until new non-conflicting prefix found) causes prefix inconsistency across systems for no good reason
>  - conciseness and readability: for certain namespaces, there are commonly used prefixes (such as in DC, XMPP etc), and it would be good to just use those when possible
> Proposal: have a single place that offers help for generating prefixes (this ticket is in JCR space as jackrabbit-jcr-commons already has NamespaceHelper, but of course the location can be discussed). -We may want to start in oak-commons, so that we can more quickly iterate in Oak, and then maybe later move this into JCR commons.-
> Blue print:
> {code:java}
> // Suggests a prefix for the given namespace, based on
> // well-known XML namespaces, or alternatively derived 
> // from the namespace name.
> public static String suggestPrefix(String namespace);
> // as above, but will take exisiting prefixes into account
> // this would be for the case where the prefix already exists
> // but is mapped to a different namespace name.
> // Lookup for existing prefix so that we can abstract out the 
> // actual JCR interface (to be discussed)
> public static String suggestPrefix(String namespace, Function<String, String> getNamespaceForPrefix);
> // maybe more helpers:
> public static boolean isValidNamespace(String namespace);
> public static Map.Entry<String, String> extractPrefixAndNamespace(String jcrName, Function<String, String> getNamespaceForPrefix);{code}
> We'd also need a hook to account for "internal", unless we want to hard-wire that into this.



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