Conflicting setter for property in jackson - json

Question

I have a problem in my webservice controller, due to jackson's serialisation of a third party object.
java.lang.IllegalArgumentException: Conflicting setter definitions for
property "X": ThirdPartyClass#setX(1 params) vs ThirdPartyClass#setX(1
params)
I've read that you can solve it thanks to MixIn annotation.
In my controller i'm giving a list, i'd like to know if there is a way to automatically define somewhere the use of the MixInAnnotation ?
If i had to do return a String instead of objects, i'd do something like that:
ObjectMapper mapper = new ObjectMapper();
mapper.getSerializationConfig().addMixInAnnotations(xxx);
return mapper.writeValueAsString(myObject);
Nevertheless, my controller is giving List:
#RequestMapping(method = RequestMethod.GET)
public #ResponseBody List<MyObject> getMyObjects
and several times returning MyObject in other methods, and so i'd like to declare only one time the use of the MixInAnnotation for jackson serialisation ?
Thank you,
RoD

Answer 1

I suggest that you use the "Spring Way" of doing this by following the steps provided in the Spring Docs.
If you want to replace the default ObjectMapper completely, define a #Bean of that type and mark it as #Primary.
Defining a #Bean of type Jackson2ObjectMapperBuilder will allow you to customize both default ObjectMapper and XmlMapper (used in MappingJackson2HttpMessageConverter and MappingJackson2XmlHttpMessageConverter respectively).
Another way to customize Jackson is to add beans of type com.fasterxml.jackson.databind.Module to your context. They will be registered with every bean of type ObjectMapper, providing a global mechanism for contributing custom modules when you add new features to your application.
Basically this means that if you simply register a Module as a bean with the provided mixin-settings you should be all set and there will be no need to define your own ObjectMapper or to alter the HttpMessageConverters.

Answer 2

So, in order to do this, i customised the Jackson JSON mapper in Spring Web MVC.
Custom mapper:
#Component
public class CustomObjectMapper extends ObjectMapper {
public CustomObjectMapper() {
this.addMixInAnnotations(Target.class, SourceMixIn.class);
}
}
Register the new mapper at start up of spring context:
#Component
public class JacksonInit {
#Autowired
private RequestMappingHandlerAdapter requestMappingHandlerAdapter;
#Autowired
private CustomObjectMapper objectMapper;
#PostConstruct
public void init() {
List<HttpMessageConverter<?>> messageConverters = requestMappingHandlerAdapter.getMessageConverters();
for (HttpMessageConverter<?> messageConverter : messageConverters) {
if (messageConverter instanceof MappingJackson2HttpMessageConverter) {
MappingJackson2HttpMessageConverter m = (MappingJackson2HttpMessageConverter) messageConverter;
m.setObjectMapper(objectMapper);
}
}
}
}
Thanks to that, i didn't modify my WebService Controller.