Spring Boot : Different ObjectMapper instances for Request and Response

Question

I have following controller in my spring boot application:

@RequestMapping(method = RequestMethod.POST)
public ResponseEntity<ResponseDto<MyClass> process(@RequestBody RequestDto<MyClass> request){
    return null;
}

MyClass has a field, let's say 'myField' and I want different NamingStrategyconfiguration for request and response for this field (this is because I don't want to create a new class just for one field). I have configured ObjectMapper instance as below:

@Bean
public ObjectMapper objectMapper(){
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setPropertyNamingStrategy(namingStrategy);
    return objectMapper;
}

This will be used both for Request and Response (i.e. deserialization and serialization), is there any way in spring boot by which I can instruct the controller to use different ObjectMapper instances?

Answer 1

You can solve it with content negotiation. Firstly, define your custom HttpMessageConverter. In following example I have defined a custom converter that is applied when the request Content-Type header is set to application/test+json:

@Bean
public HttpMessageConverters customConverters() {
    final AbstractJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter(new ObjectMapper());
    converter.setSupportedMediaTypes(Collections.singletonList(MediaType.valueOf("application/test+json")));

    return new HttpMessageConverters(true, Collections.singletonList(converter));
}

For simplicity of this example I've used newly created ObjectMapper - in your case you will have to pass here previously configured object.

Next thing is to tell your action to accept only appliction/test+json requests (keep in mind, that from now on it requires to Content-Type:application/test+json header to present in every request to this endpoint):

@RequestMapping(method = RequestMethod.POST, consumes = "application/test+json")
public ResponseEntity<ResponseDto<MyClass> process(@RequestBody RequestDto<MyClass> request){
    return null;
}

Last thing is to make sure that when you call this endpoint, Content-Type:application/test+json header is set. Of course you can use any other name for desired content type, presented name is just an example.