Json.kt

/**
 * Not thread safe due to asJson() indentation switching, but good enough for testing
 */
@NotThreadSafe
@SuppressFBWarnings(value = ["ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD"],
        justification = "Findbugs doesn't understand Kotlin init")
object Json {
    val objectMapper: ObjectMapper = ObjectMapper()

    init {
        objectMapper.registerModule(KotlinModule())
        objectMapper.registerModule(JavaTimeModule())

        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
        objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false)
        objectMapper.configure(SerializationFeature.WRITE_ENUMS_USING_TO_STRING, false)
        objectMapper.configure(SerializationFeature.INDENT_OUTPUT, true)
        objectMapper.setConfig(objectMapper.serializationConfig.withView(Views.Public::class.java))
    }

    /**
     * Converts the given object into a canonical JSON string.
     *
     * @param thing    an object
     * @return {@code thing} as a JSON string
     * @throws IllegalArgumentException if there is an error encoding `object`
     */
    fun asJson(thing: Any, indent: Boolean = true): String {
        if (indent) {
            return objectMapper.writeValueAsString(thing)
        } else {
            Json.objectMapper.configure(SerializationFeature.INDENT_OUTPUT, false)
            val json = objectMapper.writeValueAsString(thing)
            Json.objectMapper.configure(SerializationFeature.INDENT_OUTPUT, true)
            return json
        }
    }

    /**
     * Converts the given JSON string into an object of the given type.
     *
     * @param json     a JSON string
     * @param klass    the class of the type that `json` should be converted to
     * @param <T>      the type that {@code json} should be converted to
     * @return {@code json} as an instance of `T`
     * @throws IOException if there is an error reading `json` as an instance of `T`
     */
    fun <T> fromJson(json: String, klass: Class<T>): T {
        return objectMapper.readValue(json, klass)
    }

    /**
     * Converts the given JSON string into an object of the given type.
     *
     * @param json         a JSON string
     * @param reference    a reference of the type that `json` should be converted to
     * @param <T>          the type that {@code json} should be converted to
     * @return {@code json} as an instance of {@code T}
     * @throws IOException if there is an error reading `json` as an instance of `T`
     */
    fun <T> fromJson(json: String, reference: TypeReference<T>): T {
        return objectMapper.readValue<T>(json, reference)
    }
}