JSON Support

JavaScript Object Notation (JSON) support in Apex enables the serialization of Apex objects into JSON format and the deserialization of serialized JSON content. Apex provides a set of classes that expose methods for JSON serialization and deserialization. The following table describes the classes available.

Class	Description
System.JSON	Contains methods for serializing Apex objects into JSON format and deserializing JSON content that was serialized using the serialize method in this class.
System.JSONGenerator	Contains methods used to serialize Apex objects into JSON content using the standard JSON encoding.
System.JSONParser	Represents a parser for JSON-encoded content.

The following are some limitations of JSON support:

• Only custom objects, which are sObject types, of managed packages can be serialized from code that is external to the managed package. Objects that are instances of Apex classes defined in the managed package can't be serialized.
• Deserialized Map objects whose keys are not strings won't match their corresponding Map objects before serialization. Key values are converted into strings during serialization and will, when deserialized, change their type. For example, a Map<Object, sObject> will become a Map<String, sObject>.
• When an object is declared as the parent type but is set to an instance of the subtype, some data may be lost. The object gets serialized and deserialized as the parent type and any fields that are specific to the subtype are lost.
• An object that has a reference to itself won’t get serialized and causes a JSONException to be thrown.
• Reference graphs that reference the same object twice are deserialized and cause multiple copies of the referenced object to be generated.
• The System.JSONParser data type isn’t serializable. If you have a serializable class, such as a Visualforce controller, that has a member variable of type System.JSONParser and you attempt to create this object, you’ll receive an exception. To use JSONParser in a serializable class, use a local variable instead in your method.