RFE: Directory- or page-specific 404 pages

hi ​@yoshida.mhx, 

To serve dedicated 404 pages for a very specific pages without affecting the rest of the website you can use either granular Apache Dispatcher routing or the ACS AEM Commons Error Page Handler.

Approach 1: Apache Dispatcher Location Directives

The most performant approach is to configure Apache to intercept errors and serve specific pages based on the exact requested URL path. This is done using <Location> or <LocationMatch> blocks within your Virtual Host configuration.​

To implement this, modify your site's .vhost file within the Dispatcher configuration:

1. Enable the Dispatcher to pass errors to Apache by setting DispatcherPassError 1.​

2. Define your global ErrorDocument fallback for the rest of the website.​

3. Add specific <Location> (for exact page paths) or <LocationMatch> (for regex-matched sets of pages) blocks below the global declaration to override the 404 behavior for your specific pages.

<VirtualHost *:80>
    # 1. Let Apache handle the errors instead of passing them directly
    <IfModule disp_apache2.c>
        DispatcherPassError 1
    </IfModule>

    # 2. General fallback for the whole website
    ErrorDocument 404 /content/mysite/us/en/errors/404.html

    # 3a. Override for a specific directory and its sub-pages
    <LocationMatch "^/content/mysite/us/en/special-campaign/.*">
        ErrorDocument 404 /content/mysite/us/en/special-campaign/404.html
    </LocationMatch>

    # 3b. Override for one exact specific page
    <Location "/content/mysite/us/en/highly-specific-page.html">
        ErrorDocument 404 /content/mysite/us/en/custom-isolated-404.html
    </Location>
</VirtualHost>

This approach requires a Cloud Manager deployment to update the paths, so it is best for paths that do not change frequently.

Approach 2: ACS AEM Commons Error Page Handler

If content authors need the flexibility to define specific 404 pages dynamically without developer intervention, the ACS AEM Commons package provides an authorable solution.​ While I haven’t personally tested it, it should function effectively.

Instead of hardcoding paths in Apache, this tool allows authors to set error pages directly via Page Properties.​

1. Install and enable the ACS AEM Commons Error Page Handler in your AEM environment.​

2. Navigate to the Page Properties of the specific page (or the parent page of the specific set).

3. Under the Advanced tab, locate the Error Pages field (which you have to add btw)

4. Browse and select the dedicated 404 page for that specific section.

When a 404 occurs, the script will traverse upward from the missing page's requested path. It will find the custom error page defined on that specific parent page and display it, while the rest of the site will naturally fall back to the site-wide configuration.