Upgrade Project Versions
Upgrade Parent Version
Change the version of your project's parent artifact (either hippo-cms7-release or hippo-cms7-enterprise-release) to the most recent available version in the 15.x range.
With this change in place, you will have to go through a series of additional steps before your project is ready again to build and start up successfully.
Upgrade Essentials Version
Even though Essentials has been designed primarily to scaffold new projects, there may be reasons for hanging on to Essentials in your to-be-upgraded project. If so, change the <essentials.version> property in your project's root pom.xml to the most recent available version in the 15.x range. If not, consider deleting the essentials module from your project.
Upgrade Dependency Versions
In the ideal case, all dependency versions are controlled - and upgraded - through the project's parent artifact, so you don't need to do anything. However, if your project contains version overrides of specific dependencies, investigate if these overrides are still applicable. Whenever possible, you should clean them up during the upgrade.
Your project may also contain dependencies on add-ons which are not managed through the project's parent artifact, such as community-supported Bloomreach Experience Manager add-ons from the Bloomreach Forge. For such dependencies, it is very likely that your upgraded project will require a new version. If that version is already available, use it. If not, you can choose to ask the community to provide a 15-compatible version of the add-on, or to upgrade the add-on yourself.