Templates are used at various points in AEM:
- When creating a page you need to select a template; this will be used as the base for the new page. The template defines the structure of the resultant page, any initial content and the components that can be used (design properties).
- When creating a Content Fragment you also need to select a template. This template defines the structure, initial elements and variations.
When using a template to create a new page there is no visible difference (to the page author) and no indication of the type of template being used.
- Can be created and edited by your authors.
- Have been introduced to allow you to define the following for any pages created with the template:
- the structure
- the initial content
- content policies
- After the new page is created a dynamic connection is maintained between the page and the template; this means that changes to the template structure will be reflected on any pages created with that template (changes to the initial content will not be reflected).
- Uses content policies (edited from the template editor) to persist the design properties (does not use Design mode within the page editor).
- Are stored under /conf
- See Editable Templates for further information.
- Must be defined and configured by your developers.
- These templates have been available for several versions of AEM.
- A static template is a hierarchy of nodes that has the same structure as the page to be created, but without any actual content.
- Are copied to create the new page, no dynamic connection exists after this.
- Uses Design Mode to persist design properties.
- Are stored under /apps
- See Static Templates for further information.
AEM offers multiple properties to control the templates allowed under Sites. However, combining them can lead to very complex rules that are difficult to track and manage.
Therefore, Adobe recommends that you start simple, by defining:
- only the cq:allowedTemplates property
- only on the site root
For an example, see We.Retail: /content/we-retail/jcr:content
The properties allowedPaths, allowedParents, and allowedChildren can also be placed on the templates to define more sophisticated rules. However, when possible, it is much simpler to define further cq:allowedTemplates properties on sub-sections of the site if there is a need to further restrict the allowed templates.
An additional advantage is that the cq:allowedTemplates properties can be updated by an author in the Advanced tab of the Page Properties. The other template properties cannot be updated using the (standard) UI, so would need a developer to maintain the rules and a code deployment for every change.
When creating a new page in the site admin interface, the list of available templates depends on the location of the new page and the restrictions on placement specified in each template.
The following properties determine whether a template T is allowed to be used for a new page to be placed as a child of page P. Each of these properties is a multi-value string holding zero or more Regular Expressions that are used for matching with paths:
- The cq:allowedTemplates property of the jcr:content subnode of P or an ancestor of P.
- The allowedPaths property of T.
- The allowedParents property of T.
- The allowedChildren property of the template of P.
The evaluation works as follows:
- The first non-empty cq:allowedTemplates property found while ascending the page hierarchy starting with P is matched against the path of T. If none of the values match, T is rejected.
- If T has a non-empty allowedPaths property, but none of the values match the path of P, T is rejected.
- If both of the above properties are either empty or non-existent, T is rejected unless it belongs to the same application as P. T belongs to the same application as P if and only if the name of the second level of the path of T is the same as the name of the second level of the path of P. For example, the template /apps/geometrixx/templates/foo belongs to the same application as the page /content/geometrixx.
- If T has an non-empty allowedParents property, but none of the values match the path of P, T is rejected.
- If the template of P has a non-empty allowedChildren property, but none of the values match the path of T, T is rejected.
- In all other cases, T is allowed.
The following diagram depicts the template evaluation process:
To limit what templates can be used to create child pages under a given page, use the cq:allowedTemplates property of jcr:content node of the page to specify the list of templates to be allowed as child pages. Each value in the list must be an absolute path to a template for an allowed child page, for example /apps/geometrixx/templates/contentpage.
You can use the cq:allowedTemplates property on the template's jcr:content node to have this configuration applied to all newly created pages that use this template.
If you want to add more constraints, for example regarding the template hierarchy, you can use the allowedParents/allowedChildren properties on the template. You can then explicitly specify that pages created from a template T have to be parents/children of pages created from a template T.
See Content Fragment Templates for full information.