Spring Boot 1.3 WebSocket JSON converter Produces Invalid JSON - grails

Question

After upgrading to Spring Boot 1.3 (via Grails 3.1), the JSON output is rendered incorrectly. I believe it is because of the new auto-configured WebSocket JSON converter.
For example, with previous versions of Spring Boot (via Grails 3.0), using the following code:
#MessageMapping("/chat")
#SendTo("/sub/chat")
protected String chatMessage() {
def builder = new groovy.json.JsonBuilder()
builder {
type("message")
text("foobar")
}
builder.toString()
}
This would produce:
{"type": "message", "text": "foobar"}
With Spring Boot 1.3 (via Grails 3.1), that web socket produces the following:
"{\"type\":\"message\",\"text\":\"foobar\"}"
This is not valid JSON. How can I get rid of this new behavior and have it render the JSON as it was before? Please let me know if you have any suggestions.
I tried overriding the new configureMessageConverters method, but it did not have any effect.

Answer 1

looks like you are right. referenced commit shows questionable autoconfiguration imho.
especially b/c in the past, the converter ordering was intentionally changed to that StringMessageConverter takes precedence before MappingJackson2MessageConverter: https://github.com/spring-projects/spring-framework/commit/670c216d3838807fef46cd28cc82165f9abaeb45
for now, you can either disable that autoconfiguration:
#EnableAutoConfiguration(exclude = [WebSocketMessagingAutoConfiguration])
class Application extends GrailsAutoConfiguration { ... }
or, you add yet another StringMessageConverter to the top of the configured converters (maybe because you do want the boot autoconfiguration behavior because it is using the jackson ObjectMapper bean instead of creating a new one):
#Configuration
#EnableWebSocketMessageBroker
class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {
#Override
boolean configureMessageConverters(List<MessageConverter> messageConverters) {
messageConverters.add 0, new StringMessageConverter()
return true
}
...
}
hope that helps.

Answer 2

I don't know how to do it in Grails but in Java you have to now pass the object instead of an object in the String class. I believe the old behavior was actually incorrect as it was returning a string as an object so there was no way to return a String that had JSON inside it as a String. So create an object with the structure you want and return it and you should be fine. I went through the same issue when upgrading from 1.2.X to 1.3.X. I am not exactly sure what change caused this but I think in the long run it is the correct thing to do.