kafka.utils.json.JsonValue.scala Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package kafka.utils.json
import com.fasterxml.jackson.databind.{JsonMappingException, JsonNode}
import com.fasterxml.jackson.databind.node.{ArrayNode, ObjectNode}
/**
* A simple wrapper over Jackson's JsonNode that enables type safe parsing via the `DecodeJson` type
* class.
*
* Typical usage would be something like:
*
* {{{
* val jsonNode: JsonNode = ???
* val jsonObject = JsonValue(jsonNode).asJsonObject
* val intValue = jsonObject("int_field").to[Int]
* val optionLongValue = jsonObject("option_long_field").to[Option[Long]]
* val mapStringIntField = jsonObject("map_string_int_field").to[Map[String, Int]]
* val seqStringField = jsonObject("seq_string_field").to[Seq[String]
* }}}
*
* The `to` method throws an exception if the value cannot be converted to the requested type. An alternative is the
* `toEither` method that returns an `Either` instead.
*/
trait JsonValue {
protected def node: JsonNode
/**
* Decode this JSON value into an instance of `T`.
*
* @throws JsonMappingException if this value cannot be decoded into `T`.
*/
def to[T](implicit decodeJson: DecodeJson[T]): T = decodeJson.decode(node)
/**
* Decode this JSON value into an instance of `Right[T]`, if possible. Otherwise, return an error message
* wrapped by an instance of `Left`.
*/
def toEither[T](implicit decodeJson: DecodeJson[T]): Either[String, T] = decodeJson.decodeEither(node)
/**
* If this is a JSON object, return an instance of JsonObject. Otherwise, throw a JsonMappingException.
*/
def asJsonObject: JsonObject =
asJsonObjectOption.getOrElse(throw new JsonMappingException(null, s"Expected JSON object, received $node"))
/**
* If this is a JSON object, return a JsonObject wrapped by a `Some`. Otherwise, return None.
*/
def asJsonObjectOption: Option[JsonObject] = this match {
case j: JsonObject => Some(j)
case _ => node match {
case n: ObjectNode => Some(new JsonObject(n))
case _ => None
}
}
/**
* If this is a JSON array, return an instance of JsonArray. Otherwise, throw a JsonMappingException.
*/
def asJsonArray: JsonArray =
asJsonArrayOption.getOrElse(throw new JsonMappingException(null, s"Expected JSON array, received $node"))
/**
* If this is a JSON array, return a JsonArray wrapped by a `Some`. Otherwise, return None.
*/
def asJsonArrayOption: Option[JsonArray] = this match {
case j: JsonArray => Some(j)
case _ => node match {
case n: ArrayNode => Some(new JsonArray(n))
case _ => None
}
}
override def hashCode: Int = node.hashCode
override def equals(a: Any): Boolean = a match {
case a: JsonValue => node == a.node
case _ => false
}
override def toString: String = node.toString
}
object JsonValue {
/**
* Create an instance of `JsonValue` from Jackson's `JsonNode`.
*/
def apply(node: JsonNode): JsonValue = node match {
case n: ObjectNode => new JsonObject(n)
case n: ArrayNode => new JsonArray(n)
case _ => new BasicJsonValue(node)
}
private class BasicJsonValue private[json] (protected val node: JsonNode) extends JsonValue
}