Jackson is a very popular and efficient java based library to serialize or map Java objects to JSON and vice versa.

Jackson

One of the JSON parser libraries for Java
It makes possible the conversion between Java objects and JSON

In summary using Jackson: 

· JSON can be converted to Java objects 
· Java objects can be converted to JSON

Jackson API provides various classes and interfaces for handling JSON in Java.

The following three jars are prepared in Jackson.

Jackson Core

Package containing Jackson Core streaming, parser, the generator function

Jackson Annotations

Package with Jackson Annotations annotation

Jackson databind 

This Package provides data binding and tree model

Characters in Jackson

1. JSON string

{"USA":1534,"UK":1537,"INDIA":1543}

2 Java object

public class Couuntry {   public int usa;   public int uk;   public int india;}

Why use Jackson?

For example, if you try to convert a JSON string to a Java object without considering Jackson (not in use), you need to work by decomposing Java strings using substring etc. and storing them in each field . 
It is very convenient for Jackson to do conversion work easily because it is hard work such as character string editing.