CMS Preview: Component Variant-selection does not Work

Issue:

When in the Experience Manager, after selecting a component, a side-bar for component configuration opens up at the right side. When we select a "variant" from the variant-dropdown, the whole side-bar "breaks" and the message "failed to edit component" is displayed.

Possible Reasons

The CMS URL contains [] characters, which are not accepted in the tomcat versions (since 8.5). 

Cause:

Nginx decodes the URL and sends the [] in decoded form to the Tomcat instance. Nginx has encoded the URL incorrectly and forwarded the URL, triggering an error in the backend.

Solution

• A possible fix is to change the tomcat connector setting to accept certain characters: (related parts relaxedPathChars and relaxedQueryChars). You can also refer to this article for more information.

• If there is proxy_pass expression like: proxy_pass http://host.docker.internal:8080/. The slash at the end of the URL would cause the URL to get decoded before it was passed to the backend, which causes the 500 Error. After removing the slash from the end and avoiding decoding the URL, the issue can be fixed. For more information, you can refer to this article.

Related Resources: 

• Apahe Tomcat 9 Configuration Reference
• How to allow ^ characters in URL in Tomcat 8.5
• Disabling URL decoding in n ginx proxy