RestApiRuleImpl.kt

data class Search(
        var bounds: Bounds?,
        var orders: List<Order>?,
        var filters: List<Map<String, List<Map<Operator, String>>>>?
)

data class Bounds(
        var limit: Long = 0,
        var offset: Long = Long.MAX_VALUE
)

data class Order(
        var property: String? = null,
        var direction: Direction? = null,
        var nulls: Nulls? = null
)

enum class Direction {
    ASC, DESC
}

enum class Nulls {
    FIRST, LAST
}

enum class Operator {
    EQ, NE, IN, SW, EW, IC, EC, LT, LE, GT, GE
}

@Component
class RequestParamJsonHandlerMethodArgumentResolver: HandlerMethodArgumentResolver {

    @Autowired
    private lateinit var objectMapper: ObjectMapper

    override fun supportsParameter(parameter: MethodParameter): Boolean {
        return parameter.hasParameterAnnotation(RequestParamJson::class.java)
    }

    override fun resolveArgument(parameter: MethodParameter, container: ModelAndViewContainer?, request: NativeWebRequest, factory: WebDataBinderFactory?): Any? {
        val requestParamJson = parameter.getParameterAnnotation(RequestParamJson::class.java)
        val name = requestParamJson?.name ?: throw IllegalStateException("Assertion Error")
        val required = requestParamJson?.required ?: false
        var paramValue = name?.let {
            val value = if (required) {
                request.getParameter(it)
                        ?: throw MissingServletRequestParameterException(name, parameter.nestedParameterType.simpleName)
            } else {
                request.getParameter(it) ?: "{}"
            }
            value.trim()
        }
        paramValue = if (paramValue.length > 0 ) {
            paramValue
        } else {
            "{}"
        }
        return objectMapper.readValue(paramValue, parameter.parameterType)
    }
}

@Target(AnnotationTarget.VALUE_PARAMETER)
@Retention(AnnotationRetention.RUNTIME)
@MustBeDocumented
annotation class RequestParamJson(val name: String, val required: Boolean)