STaX exception raised when reading resource with Unicode character

[nieciecki]

Description

If server supports both xml and json formats, it is possible to add resource with an unicode with json, but if someone reads or search this resource with XML format, STaX exception is raised. Server will return 200 OK without any content.

This error occurs in my system that uses HAPI FHIR Server as well as on the hapi fhir test server.
I used https://hapi.fhir.org/baseR4 to reproduce the error.

Steps to reproduce the behavior:

1. Create a resource with an unicode character

{ "resourceType": "NamingSystem", ... "uniqueId": [ { ... "comment": "\u0001" } ] }

2. Read or search for this resource with Accept: application/fhir+xml

Expected behavior

Probably character should be escaped or removed.