Spring filter bypassed when a REST endpoint returns a Json stream-CodePudding

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Server logs in normal mode to prove that it's called multiple times :

Debug Mode steps to prove that it got called two times:

The request came to the filter first.

The request came to the controller :

The response comes back from controller and the filter check if the isAsyncStarted() is true. In this case, it returns true which means async context started.

It comes to the same line again -> filterChain.doFilter(request, responseToUse);

Server Log at this point in debug mode :

The response comes back from controller and the filter check if the isAsyncStarted() is true. In this case, it returns false and the async context is skipped.

Server log at the end :

Postman response :

Update : As per Spring's ResponseBodyEmitter Docs, it states that :

Write the given object to the response.

If any exception occurs a dispatch is made back to the app server where Spring MVC will pass the exception through its exception handling mechanism.

Note: if the send fails with an IOException, you do not need to call completeWithError(Throwable) in order to clean up. Instead the Servlet container creates a notification that results in a dispatch where Spring MVC invokes exception resolvers and completes processing.

In simple words :

send() method only writes to the response. It doesn't mean that it will make dispatch to filter/interceptor on send() method call. The send method only combines all the individual send data and append it to the response.