JSON reponse with Spring Controllers in Jetty vs Tomcat - json

Question

I am building a simple Spring MVC webapp and was developing on jetty. My controller binding used this:
#RequestMapping(value = RESTRoutes.CREATE_DOC, method = RequestMethod.POST)
public #ResponseBody String getDoc
And returning a String from a JSONObject correctly resolves to JSON in my ajax response.
But using those same controllers, i deployed my gradle war to tomcat and my json came back wrapped as true strings.
So i changed my headers to use Map and that seems to fix things in both jetty and tomcat:
#RequestMapping(value = RESTRoutes.CREATE_DOC, method = RequestMethod.POST)
public #ResponseBody Map<String, String> getDoc
I convert from the string to a map with this:
HashMap<String, String> jsonResponse = new HashMap<String, String>();
if(claimFolder.has("error")){
response.setStatus(500);
}else{
jsonResponse = new ObjectMapper().readValue(claimFolder.toString(), HashMap.class);
}
return jsonResponse;
My question is why this is nessesary?
Here's my jackson converter configuration:
<bean id="formConverter" class="org.springframework.http.converter.FormHttpMessageConverter" />
<!-- add byte[] converter -->
<bean id="byteArrayConverter" class="org.springframework.http.converter.ByteArrayHttpMessageConverter">
<property name="supportedMediaTypes" value="application/octet-stream" />
</bean>
<!-- add in our JSON message converter -->
<bean id="jsonConverter" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
<property name="supportedMediaTypes" value="application/json;charset=UTF-8" />
</bean>
<!-- add in our plain string message converter -->
<bean id="stringHttpMessageConverter" class="org.springframework.http.converter.StringHttpMessageConverter">
<property name="supportedMediaTypes" value="text/plain;charset=UTF-8" />
</bean>
<!-- Expose the authenticated handler to all beans that have been declared via annotation -->
<bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">
</bean>
TL;DR: Why does jetty and tomcat return stringified JSON differently?

Answer 1

Well, it's absolutely normal for Spring content negotiation to translate a String object as a simple string without marshalling it to a JSON object. In order to serialize a java String object in JSON object you need to wrap it previously in some java class. For example:
QuestionStatus {
private String status;
public QuestionStatus(String status) {
this.status = status;
}
public getStatus() {
return status;
}
}
Hence you have to return in your Controller method not a String but QuestionStatus.