Encoding the request body - json

Question

I am using a simple form where a user can input some JSON.
I add that input to the body of the request.
When I retrieve the value from the body, it is not formatted/encoded as JSON.
Instead I get something like json=%7B%22vrt%22%3A%7B ...
How/where do I specify that the value in the body must be JSON in such way that my controller can parse it using GSON?
Thanks in advance.
Regards
The controller
#PostMapping(value = "/api/sendMessage")
public ModelAndView sendIoTMessage(#RequestBody String json) {
VehicleMessage vehicleMessage = new Gson().fromJson(json, VehicleMessage.class);
MessageProcessor.postVehicleMessage(vehicleMessage);
ModelAndView mav = new ModelAndView();
mav.setViewName("iot");
return mav;
}
The form
<form id="sendMessage" th:action="#{/api/sendMessage}" method="post">
<div class="form-group">
<input class="form-control" th:value="*{json}" id="json" name="json">
</div>
<button type="submit" class="btn btn-primary">Submit</button>
</form>

Answer 1

By default, Spring uses Jackson convertor for APPLICATION JSON, if you want to use GSON convertors, then you need to add GSONConvertor.
I personly perfer Option 1
Different ways to add GSONConvertor:
Using JavaConfig
#Configuration #EnableWebMvc
public class Application extends WebMvcConfigurerAdapter {
#Override
public void configureMessageConverters(List<HttpMessageConverter < ? >> converters) {
GsonHttpMessageConverter gsonHttpMessageConverter = new GsonHttpMessageConverter();
converters.add(gsonHttpMessageConverter);
}
}
Using customize converters
#Configuration
public class CustomConfiguration {
#Bean
public HttpMessageConverters customConverters() {
Collection<HttpMessageConverter<?>> messageConverters = new ArrayList<>();
GsonHttpMessageConverter gsonHttpMessageConverter = new GsonHttpMessageConverter();
messageConverters.add(gsonHttpMessageConverter);
return new HttpMessageConverters(true, messageConverters);
}
}
Using Auto-configuration ..follow this link

Answer 2

Why not let Spring (de)serialize JSON for you? This functionality should work out of the box without any custom configuration.
#PostMapping(value = "/api/sendMessage", consumes="application/json")
public ModelAndView sendIoTMessage(#RequestBody VehicleMessage vehicleMessage) {
MessageProcessor.postVehicleMessage(vehicleMessage);
ModelAndView mav = new ModelAndView();
mav.setViewName("iot");
return mav;
}