There are several web applications available for modifying a Java Content Repository (JCR) repository, including:
Apache Jackrabbit WebDAV Library: Apache Jackrabbit includes a WebDAV library that allows you to access the content repository through a WebDAV interface. This interface can be used with any WebDAV client, including web-based clients such as Cyberduck and Mountain Duck.
Apache Sling: Apache Sling is a web framework that is built on top of the JCR standard. It provides a RESTful API for accessing content in the repository and includes a set of web applications for managing content, including a web-based console for browsing and editing content.
Magnolia CMS: Magnolia CMS includes a web-based content authoring environment that allows you to create and edit content directly in the repository. It includes a visual editor and a range of content management tools for organizing and publishing content.
Hippo CMS: Hippo CMS includes a web-based authoring environment that allows you to create and edit content directly in the repository. It includes a drag-and-drop interface and a range of content management tools for organizing and publishing content.
Adobe Experience Manager (AEM): AEM includes a web-based authoring environment that allows you to create and edit content directly in the repository. It includes a range of content management tools for organizing and publishing content, as well as a visual editor for creating and managing digital experiences.
These are just a few examples of web applications that are available for modifying a JCR repository. The specific tools and applications available may depend on the particular JCR implementation being used and the requirements of the content management system being built.