Json-logic-scala provides classes that perform operations that serialize, marshall, deserialize, and unmarshall data.

You can modify these classes for your own workflow.

Table of Contents

• About these terms
• Note on custom implementations
• The marshaller and serializer
  • Build a custom Marshaller
  • Build a custom serializer
• The unmarshaller and deserializer
  • What is an Unmarshaller ?
  • What is a Deserializer ?

About these terms

While the terms marshall, serialize, unmarshall, and deserialize are closely related, they each have different functions. Consider the following objects in Json-logic-scala:

• Marshaller transforms a Scala data structure into a JSON value

• Serializer transforms a Scala data structure into a JSON representation

The Unmarshaller and Deserializer objects perform the reverse processes:

• Unmarshaller transforms a JSON value to a Scala data structure

• Deserializer parses JSON in JsonLogic-Typed format into the Scala data structure JsonLogicCore, which corresponds to a leaf node in the abstract syntax tree.

  • To parse values in leaf nodes, Deserializer relies on several Unmarshaller objects

Note on custom implementations

🛈 Json Logic Scala relies on the Play-Json library.

To implement custom marshall and unmarshall operations, you may need to read the Play-Json documentation (or at least understand the classes/traits described in these sections: JsValue, and JsObject).

The marshaller and serializer

Json Logic Scala comes a built-in Serializer that handles a number of pre-defined Types.

You may want to serialize more Types than those predefined by the library. For example, you may want to serialize a custom class you have implemented.

Build a custom Marshaller

A marshaller is an object that converts a value from Json-Logic-Typed (leaf node in syntax tree) into a Scala data type.

A marshaller is defined by the trait Marshaller and must implement the method:

def marshal(value: Any): JsValue

Each Type is associated with its own Marshaller.

Example: If you define a custom class A, you may define its Marshaller:

class A(val param1: String, val param2: Int)

object UnmarshallerA {
  def marshal(value: Any): JsValue = {
    value match {
      case a: A => JsObject(Map("param1" -> JsString(a.param1), "param2" -> JsNumber(a.param2)))
      case _ => throw ...
    }
  }
}

Build a custom serializer

A Serializer converts a Scala data structure JsonLogicScala into a json in Json-Logic-Typed format.

A Serializer parses a json following the Json-Logic-Typed format and to every found Type relies on its associated Marshaller.

The association between Type and Marshaller is provided in the SerializerConf object.

The unmarshaller and deserializer

Json Logic Scala comes a built-in Deserializer that handles a number of pre-defined Types.

You may want to parse more Types than those predefined by the library. For example, you may want to parse a custom class that you have implemented.

What is an Unmarshaller ?

An unmarshaller is an object that converts a value from Json-Logic-Typed JSON (i.e. a leaf node in syntax tree) to a Scala data structure JsonLogicCore.

An unmarshaller is defined by the trait Unmarshaller and must implement the method

def unmarshal(jsValue: JsValue): Any

Each Type is associated with its own Unmarshaller.

class A(val param1: String, val param2: Int)

object UnmarshallerA {
  def unmarshal(jsValue: JsValue): Any = {
    val param1 = (jsValue \ "param1").as[String]
    val param2 = (jsValue \ "param2").as[String]
    new A(param1, param2)
  }
}

What is a Deserializer ?

A Deserializer parses JSON in Json-Logic-Typed format into a Scala data structure JsonLogicScala.

A Deserializer follows the Json-Logic-Typed format to parse JSON. For every found Type, the operation relies on its associated Unmarshaller.

The association between Type and Unmarshaller is provided in the DeserializerConf object.