Package com.oracle.coherence.io.json.genson.reflect

Class EvolvableHandler

java.lang.Object

com.oracle.coherence.io.json.genson.reflect.EvolvableHandler

All Implemented Interfaces:

UnknownPropertyHandler

public class EvolvableHandler
extends Object
implements UnknownPropertyHandler

An implementation of an UnknownPropertyHandler that supports evolution of data classes via Evolvable interface.

If the target object we are deserializing into is Evolvable, this handler will add any unknown properties encountered during deserialization into Evolvable.unknownProperties() map, and will write them out along with all known properties during subsequent serialization.

This prevents data loss when serializing and deserializing the same JSON payload using different versions of Java data classes.

Author:

Aleks Seovic 2018.05.20

Constructor Summary

Constructors

Constructor	Description
EvolvableHandler()

Method Summary

Modifier and Type	Method	Description
<T> Consumer<T>	readUnknownProperty(String propName, ObjectReader reader, Context ctx)	Called whenever a property is encountered in a JSON document that doesn't have a corresponding PropertyMutator.
<T> void	writeUnknownProperties(T bean, ObjectWriter writer, Context ctx)	Write unknown properties encountered during deserialization.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EvolvableHandler

public EvolvableHandler()

Method Detail

readUnknownProperty

public <T> Consumer<T> readUnknownProperty(String propName,
                                           ObjectReader reader,
                                           Context ctx)

Description copied from interface: UnknownPropertyHandler

Called whenever a property is encountered in a JSON document that doesn't have a corresponding PropertyMutator.

Typically, the implementation of this interface concerned with schema evolution will handle this event by storing property value somewhere so it can be written later by the UnknownPropertyHandler.writeUnknownProperties(T, com.oracle.coherence.io.json.genson.stream.ObjectWriter, com.oracle.coherence.io.json.genson.Context) method.

Specified by:

readUnknownProperty in interface UnknownPropertyHandler

Parameters:

propName - the name of the unknown property

reader - the ObjectReader to read property value from

ctx - deserialization context

Returns:

the Consumer that will be called with the target bean, once the target bean is known

writeUnknownProperties

public <T> void writeUnknownProperties(T bean,
                                       ObjectWriter writer,
                                       Context ctx)

Description copied from interface: UnknownPropertyHandler

Write unknown properties encountered during deserialization.

This method can be optionally implemented by UnknownPropertyHandlers that want to write unknown properties during serialization. The default implementation is a no-op.

Specified by:

writeUnknownProperties in interface UnknownPropertyHandler

Parameters:

bean - the object we are serializing into JSON

writer - the ObjectReader to read property value from

ctx - serialization context