Versioning

Magnolia versions pages, assets and contacts by default when they are published and unpublished. You can also configure versioning for any other content type.

Showing versions

The Show versions action provides access to versions. This action is available in the Pages, Assets and Contacts apps and opens a dialog containing a list of versions. If workflow is enabled, the workflow comment is appended for each version (second set of brackets).

To show a version, select the version and click Show. The selected page, asset or contact opens for viewing.  You cannot edit the item in the view mode.

Comparing versions

In the Pages app two additional actions are available:

• Compare to previous version compares the current to the previous version and opens the page in diff view that uses redlining: deletions are highlighted in red and insertions in green.
  
• Compare versions allows you to select the versions to be compared. Select a From and To version and click Compare to open the page in diff view.
  

Restoring versions

The Restore versions action allows you to revert to a previous version. It is available in the Pages, Assets and Contacts apps. Select the version and click Restore. A new version is created automatically prior to restore. After restoring you need to publish the restored item.

Versioning functionality is enabled by default in Magnolia in the Pages, Assets and Contacts apps. Versions are saved automatically and can be reverted to as necessary.

The versioning functionality is enhanced by the Diff module that adds diff and redlining capabilities.

By default, versions are created when pages, assets and contacts are published, unpublished and restored in the related apps. Versions are also created in these apps for the purpose of restoring items prior to deletion. For more information see Deleting and restoring.

Versioning can be enabled by configuration for any content app. 

Configuration

Enabling versioning in content apps

You can enable versioning in a content app by triggering the activate/deactivate command chains in the versions catalog instead of the activate/deactivate commands in the default catalog. Here is the process to enable versioning in the Categories app.

In the Configuration app > /modules/categorization/apps/categories/subApps/browser: 

1. Change the activate and deactivate action definitions. 
   In the /actions/activate and /deactivate nodes add a catalog property and set the value to versioned. This calls the chained version command configured in the activation module in modules/activation/commands/versioned/activate and /deactivate.

   Node name	Value
   modules
   categorization
   apps
   categories
   subApps
   browser
   actions
   activate
   availability
   catalog	versioned
   class	info.magnolia.ui.framework.action.ActivationActionDefinition
   command	activate
   icon	icon-publish
   recursive	true
   deactivate
   availability
   catalog	versioned
   class	info.magnolia.ui.framework.action.DeactivationActionDefinition
   command	deactivate
   icon	icon-unpublish

2. Add the Show versions action configuration. 

   In the /actions node add the /showVersions configuration as shown below. Alternatively, you can simply extend the configuration in another content app, for example the configuration in the Contacts app configured in  /modules/contacts/apps/contacts/subApps/browser/actions/showVersions .

   Node name	Value
   browser
   actions
   activate
   deactivate
   showVersions
   availability
   rules
   HasVersionsRule
   implementationClass	info.magnolia.ui.framework.availability.HasVersionsRule
   class	info.magnolia.ui.contentapp.browser.action.ShowVersionsActionDefinition
   icon	icon-show-versions

3. Add the Show versions action to the action bar. 
   In the /actionbar/sections/category/groups node, add the /versionsActions configuration shown below. Alternatively, you can simply extend the configuration in another content app, for example the configuration in the Contacts app configured in  /modules/contacts/apps/contacts/subApps/browser/actionbar/sections/contact/groups/versionsActions .

   Node name	Value
   browser
   actions
   actionbar
   sections
   root
   deletedFolder
   deletedCategory
   folder
   category
   groups
   addActions
   editActions
   activationActions
   importExportActions
   versionsActions
   items
   showVersions

4. In the Categories app, create a few versions by activating and deactivating an item and then execute the Show versions action to open the VERSIONS dialog.

Number of versions

The number of versions you can create depends on the Magnolia edition:

• In the Community Edition, the number of versions is set to 3 and this is not configurable.

• In the Enterprise Edition, the number of versions is unlimited and you can set it in configuration. By default, 10 versions are stored.

The number of versions is configured in /server/versions:

Properties:

• active  enables and disables versioning.
• maxVersionIndex  sets the number of versions to store.

Previous versions are deleted when you change to a smaller number and create a version. It's OK to change the number. The index won't be affected until a new version is created. For example, if node ‘A' has 10 versions and you change the max version index to 2, you will still see all 10 versions until the next versioning occurs. Once node 'A' is versioned again, all previous 9 versions will be removed.

Version command

Versions are created when VersionCommand is triggered. A new version of the content is created and added to the version file. VersionCommand provides for standard and recursive versioning, and the addition of a version comment.

Command chains

Command definitions that call versionCommand are configured for the activate and deactivate command chains in the Activation module.

Here's the command definition in the activation module in the Configuration app > /modules/activation/commands/versioned/activate/version and /deactivate/version. 

The command chains are triggered when the Publish, Unpublish and Publish deletion actions are executed in the various apps that use them. Here's the action definition for the Publish action in the Assets app configured in the Configuration app > /modules/dam/apps/assets/subApps/browser/actions/activate.

Diff implementation

Version comparison relies on functionality provided by the Diff module. The module uses the daisydiff java library to compare HTML files. Diff is an Enterprise Edition feature.

Diff servlet

VersionDiffHtmlServlet is registered in the Magnolia filter chain in the Configuration app > /server/filters/servlets/VersionDiffHtmlServlet. The controller generates the diff view between two versions of a page by checking the toVersionNr and fromVersionNr request parameters.

Diff configuration

The default settings for headers, cookies, host and port can be set by configuration.

By default Magnolia is set to generate a JSESSIONID cookie. This is configured in the diff module in the Configuration app > /modules/diff/config/cookies. 

You can configure custom settings for:

• cookies: You can specify any number of custom session cookie names to forward.
• headers: The default value is none. By adding a  headers config node you can specify any number of headers to be sent to the diff servlet thereby automatically excluding any headers that are not specified.
• host and port : The default host and port is localhost and 8080. However, the Diff module will work even if you change the default Tomcat port. This means that you can use the diff functionality against another server.

 Headers and cookies are configured separately.

Diff HTML generator

VersionDiffHtmlGenerator compares two HTML files using  HTMLDiffer and returns HTML that highlights the differences between the compared pages:

• The comparison only includes the body of the HTML document.
• The differences are marked with span tags.
• The header is taken from the HTML of the page that is compared to.
• CSS is added.

Here's a snippet from diff.css (GIT) located in the mgnl-resources folder of the module jar

/*
 * Styles for the HTML Diff
 */
span.diff-html-added {
    font-size: 100%;
    background-color: #ccffcc; /* light green */
    cursor: pointer;
}
span.diff-html-removed {
    font-size: 100%;
    text-decoration: line-through;
    background-color: #fc6f6f; /* light red */
    cursor: pointer;
}
span.diff-html-changed {
    background-color: #95c6fd; /* light blue */
    cursor: pointer;
}
span.diff-html-selected {
    background-color: #FF8800; /* light orange */
    cursor: pointer;
}

Diff utility classes

Two utility classes are provided:

• DiffUtil provides the buildComparisonURL, buildComparisonURLToCurrent and buildComparisonURLToCurrentUnversioned methods.
• VersionComparisona POJO that gets and sets the versionFrom and versionTo methods.

Compare actions

The CompareVersionsAction and CompareToPreviousVersionAction open the diff subapp (see below) configured in the Pages app. The action definitions are configured in the Configuration app > /modules/pages/apps/pages/subApps/browser/actions.

Diff subapp

The diff view that opens when comparing different page versions is configured in the Pages app. This configuration is in the Configuration app > /modules/pages/apps/pages/subApps/diff.

• class : EmbeddedPageSubAppDescriptor embeds the page in an iframe. 
• label: Renders in the subapp tab.
• subAppClass: EmbeddedPageSubApp is the main tab in an embedded page app.

Here's the diff subapp for the /travel/about/what-we-believe  page. The URL is  http://localhost:8080/magnoliaAuthor/.magnolia/admincentral#app:pages:diff;/magnoliaAuthor/.magnolia/versionDiff?diffViewContentHandle=/travel/about/what-we-believe&fromVersionNr=1.2&toVersionNr=1.0  . Note the reference to the  diffViewContentHandle and VersionNr parameters