#Jackson annotations how to#
#Jackson annotations code#

Since the Documentation for jackson is new, you may need to create initial versions of those related topics. It should also mention any large subjects within jackson, and link out to the related topics.

#Jackson annotations how to#

In this post, we learned how to handle, in the same endpoint, variable requests (polymorphism) in Jackson by using custom deserializer and without polluting our domain classes with annotations and external libraries.This section provides an overview of what jackson is, and why a developer might want to use it. public class PlayerDeserializer extends StdDeserializer Deserialization logic based on fields of the Player abstract instances Conclusion To implement a custom deserializer, we need to create an implementation of StdDeserializer which is an abstract type and the base class for common Jackson deserializers. Simply because of some technical constraints in your company/project.įirst thing to do is to create a custom Jackson deserializer and implement the logic of deserialization. You are using DDD and hexagonal architecture where purists say : No framework or libraries inside the domain ) are hidden behind an imported jar dependency and you can't access them for annotating

Sometimes, your domain classes (Player, FootballPlayer. Not every project gives the possibility to add annotations on your domain classes.

Some resources describe how it can be done, you can check here or here if you are curious. Using annotation is probably the most used technique because of it's simplicity and time-saving, but sometimes it's impossible to go with it. The deserialization part will have to determine which concrete class the JSON represents, and instantiate an instance of it. I'll use Spring Boot in this post but if you want to go without it, just grab the latest dependency of Jackson Databind on Maven Central. Simply, Jackson is a Java library to serialize and deserialize objects to/from JSON. What's Jackson ?Īs claimed by it's creators : Jackson has been known as 'the Java JSON library' or 'the best JSON parser for Java'. If we go directly invoking the /players endpoint, we'll face the InvalidDefinitionException as Jackson can't define to which class instance the PLAYER request body should be deserialized. ResponseEntity Player player) POST /players endpoint Problem = '/players', consumes = MediaType.APPLICATION_JSON_VALUE) Something like : you POST /players when PLAYER can be FootballPlayer, TennisPlayer or BasketPlayer. Suppose you have an POST endpoint which supports creation of multiple objects by abstraction. Let's consider the following abstraction : Player abstraction Same idea presented below can be used to serialize objects. This post is about how to deserialize objects by their abstract. Polymorphism is the ability to have different implementations represented by a single interface or abstract class.

#Jackson annotations code#

This post has a working code example available here. ) but maybe each one has something that the other cups don't have. Suppose I asked you to take a cup from the multiple choices in the header photo, certainly you'll ask which one to choose as there is many cups and you need something precise and maybe unique by cup to decide.Īll the choices are cups, they share some common points (color, weight.