Spring rest api filter fields in the response

Question

I am using spring rest api 4.x. We have a requirement to filter the fields in the response based on the request parameters.

My User object:

private class UserResource {
   private String userLastName;
   private String userFirstName;
   private String email;
   private String streetAddress;
}

E.g. URL:  curl -i http://hostname:port/api/v1/users?fields=firstName,lastName. 

In this case I need to return only the fields which are in the request param "fields". JSON output should contain only firstName, lastName.

There are several ways filter the fields in Jackson based on the object. In my case I need to filter dynamically by passing the list of fields to Jackson serializer.

Please share some ideas.

Answer 1

It appears this is supported in Spring 4.2 as per https://jira.spring.io/browse/SPR-12586 via Jackson JsonFilter (though the jira is returning an error at the moment).

Answer 2

Use a ResponseBodyAdvice in order to change the response before it got written to the HTTP response. In beforeBodyWrite(...) method you have access to the current ServerHttpRequest which you can read the fields value. Your body advice would look like following:

@ControllerAdvice
public class MyResponseBodyAdvisor implements ResponseBodyAdvice<UserResource> {
    @Override
    public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
        return returnType.getParameterType().equals(UserResource.class);
    }

    @Override
    public UserResource beforeBodyWrite(UserResource body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {
        String fields = ((ServletServerHttpRequest) request).getServletRequest().getParameter("fields");
        // body.set...(null) for each field not in fields

        return body;
    }
}

Answer 3

Thanks Ali. It is a great help. Let me implement it today. I will post the result

@JsonFilter("blah.my.UserEntity")
public class UserEntity implements Serializable {
//fields goes here
}

@RequestMapping(value = "/users", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
public MappingJacksonValue getUsers(@RequestParam MultiValueMap<String, String> params) {
//Build pageable here
Page<UserEntity> users = userService.findAll(pageable);

    MappingJacksonValue mappingJacksonValue = new MappingJacksonValue(users);
    FilterProvider filters = new SimpleFilterProvider()
                .addFilter("blah.my.UserEntity", SimpleBeanPropertyFilter
                        .filterOutAllExcept("userFirstName"));
    mappingJacksonValue.setFilters(filters);
    return mappingJacksonValue;
}