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1.4.0.M3: SseEmitter, Jetty, CORS: Wrong charset in Content-Type header

See original GitHub issue

There is a problem in 1.4.0.M3 and 1.4.0.BUILD-SNAPSHOT, Jetty, EventSource (SseEmitter) and CORS. With this setup spring boot sends a wrong Content-Type response header back to the client. Content-Type: text/event-stream; charset=ISO-8859-1

Chrome 51 complains with this error message EventSource's response has a charset ("iso-8859-1") that is not UTF-8. Aborting the connection.

When the request is not sent with CORS the server sends this header Content-Type: text/event-stream which is okay for Chrome. Event streams must always be encoded using UTF-8

Here is a github repository that demonstrates the problem: https://github.com/ralscha/sse-encoding

Requests to http://localhost:8080 work fine but when you do a CORS request (for example by opening index.html directly from filesystem) Chrome will complain with the above-mentioned error message.

This problem does not occur with Spring Boot 1.4.0.M2 and it does not occur with Tomcat and Undertow with 1.4.0.M3 and 1.4.0.BUILD-SNAPSHOT