javax.jcr.NamespaceException: Unknown namespace prefix error in AEM

This article offers a solution to the error "javax.jcr.NamespaceException: Unknown namespace prefix" in AEM.

Description

Environment
Adobe Experience Manager

Issue
If the error below appear in the logs:

javax.jcr.NamespaceException: Unknown namespace prefix: [ namespacename]
Could not Build Package "Unknown namespace prefix: [ namespacename]

Cause

This error usually shows up in environments where partial data migration was done using the crx2oak tool.
The crx2oak tool doesn’t support migrating namespaces with the data.

Resolution

Solution
To resolve this issue, follow these steps:

1. Register the missing namespaces via the CRX Explorer:

2. Go to http://hostname:port/crx/explorer/index.jsp and log in as admin user.

3. Click Node Type Administration in the CRX Explorer.

4. In the Node Type Administration window, click Namespaces, which is at far right of the toolbar.

   

5. At the bottom of the Namespaces window, click New.

6. Enter the URI and the Namespace mapping, then click OK.

7. Enter the prefix of the Namespace mapping, then click OK.