JacksonMigration

java.lang.Object
- akka.serialization.jackson.JacksonMigration

```
public abstract class JacksonMigration
extends java.lang.Object
```
Data migration of old formats to current format can be implemented in a concrete subclass and configured to be used by the JacksonSerializer for a changed class.
It is used when deserializing data of older version than the currentVersion(). You implement the transformation of the JSON structure in the transform(int, com.fasterxml.jackson.databind.JsonNode) method. If you have changed the class name you should override transformClassName(int, java.lang.String) and return current class name.

Constructor Summary

Constructors
Constructor Description

JacksonMigration()

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`abstract int`	`currentVersion()`	Define current version, that is, the value used when serializing new data.
`int`	`supportedForwardVersion()`	Define the supported forward version this migration can read (must be greater or equal than `currentVersion`).
`abstract com.fasterxml.jackson.databind.JsonNode`	`transform(int fromVersion, com.fasterxml.jackson.databind.JsonNode json)`	Implement the transformation of the old JSON structure to the new JSON structure.
`java.lang.String`	`transformClassName(int fromVersion, java.lang.String className)`	Override this method if you have changed the class name.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - JacksonMigration
```
public JacksonMigration()
```
- Method Detail
  - currentVersion
```
public abstract int currentVersion()
```
    Define current version, that is, the value used when serializing new data. The first version, when no migration was used, is always 1.
  - supportedForwardVersion
```
public int supportedForwardVersion()
```
    Define the supported forward version this migration can read (must be greater or equal than currentVersion). If this value is different from currentVersion() a JacksonMigration may be required to downcast the received payload to the current schema.
  - transform
```
public abstract com.fasterxml.jackson.databind.JsonNode transform(int fromVersion,
                                                                  com.fasterxml.jackson.databind.JsonNode json)
```
    Implement the transformation of the old JSON structure to the new JSON structure. The JsonNode is mutable so you can add and remove fields, or change values. Note that you have to cast to specific sub-classes such as ObjectNode and ArrayNode to get access to mutators.
    
    Parameters:
    
    fromVersion - the version of the old data
    
    json - the old JSON data
  - transformClassName
```
public java.lang.String transformClassName(int fromVersion,
                                           java.lang.String className)
```
    Override this method if you have changed the class name. Return current class name.