`TomcatService` doesn't work Spring Boot error handling

Hi, Armeria team.

I migrated a synchronous Spring Boot application with embedded Tomcat to use Armeria server. As I can’t migrate all synchronous code to asynchronous and reactive code, I used TomcatService to connect with Armeria and Tomcat. And I found that the TomcatService does not handle error handling describe in the Spring Boot’s document:

By default, Spring Boot provides an /error mapping that handles all errors in a sensible way, and it is registered as a “global” error page in the servlet container. For machine clients, it produces a JSON response with details of the error, the HTTP status, and the exception message. For browser clients, there is a “whitelabel” error view that renders the same data in HTML format (to customize it, add a View that resolves to error).

Similarly, @ControllerAdvice does not work well:

You can also define a class annotated with @ControllerAdvice to customize the JSON document to return for a particular controller and/or exception type, as shown in the following example: …

Any JSON response is not respond from the Armeria server. And I guess it’s because the “global” error page in the servlet container does not called.

I made an example in my repository. The example have two applications, one is a Spring Boot application with embedded Tomcat. And the other one is similar application but integrated with the Armeria. Tests in both applications describe expected behavior and the Armeria application’s test is failed because JSON response does not exist.

[heowc]

I am interested in this issue and have tried debugging it. 😎

As a result of doing this, the problematic parts are as follows. Each module in the example produces different results here.

https://github.com/apache/tomcat/blob/9747a3a6334369deb9b5bef1b17b1fe0ce774cdf/java/org/apache/catalina/core/StandardHostValve.java#L157-L165

https://github.com/apache/tomcat/blob/9747a3a6334369deb9b5bef1b17b1fe0ce774cdf/java/org/apache/coyote/Response.java#L207-L215

I think this is because we made a pure response from TomcatService provided by Armeria.

https://github.com/line/armeria/blob/922d60304651f2e65fcf63a6f9090528fb937da7/tomcat9/src/main/java/com/linecorp/armeria/server/tomcat/TomcatService.java#L366

When we create a pure response, ActionHook is empty.

https://github.com/apache/tomcat/blob/9747a3a6334369deb9b5bef1b17b1fe0ce774cdf/java/org/apache/coyote/Response.java#L108

And ActionHook is set only when it is made through Processor.

https://github.com/apache/tomcat/blob/9747a3a6334369deb9b5bef1b17b1fe0ce774cdf/java/org/apache/coyote/AbstractProcessor.java#L83-L92

We should be able to call the intended ErrorController by executing throwable(...) in the code mentioned above. I know the cause, but I’m not sure exactly how to fix it. 🤣

[heowc]

Who registers the exception handler using Armeria? TomcatService or a user?

user? 🤔

What is ‘white label’?

It is one of the features provided by spring boot.