When ColdFusion or Tomcat throws a 500 server error, it returns a response code to IIS of 500. By default, IIS intercepts this status code and presents a "friendly" IIS error page instead of returning the actual generated error page. But in development this isn't very helpful since it doesn't show the underlying error message.
You can override this behavior and display the CF-generated error instead with these steps:
- Open IIS Manager and either select your server root or the individual web site.
- In the Features view, scroll down to the Management section and open Configuration Editor.
- In the Sections dropdown, select and expand system.webServer, then select httpErrors.
- The existingResponse value will be set to Auto. Click the dropdown and select PassThrough instead.
- On the right side menu, click the Apply button to save the changes
You'll now see the appropriate ColdFusion error message.