Requirements for mapping

Requirements for the POJO to JSON mapping:

Define the POJO class as a public or package scope. You can also specify the final modifier.
You can include any constructors.
If you map multiple fields or properties to the same JSON element, the JsonMappingException exception is thrown. For details on exception handling, see 18.3.3 Exception handling.
If a field name is same as that of a Bean property name, the Bean property name is preferred.

(2) Field

Define the field with a public scope. Otherwise, mapping will not proceed.
Do not specify a static or transient modifier in the field. Otherwise, mapping will not proceed.
You can also specify the final modifier.

(3) Bean property

Define the getter method of Bean property as public scope. Otherwise, mapping will not proceed.
If you define multiple getter methods with the same name in upper and lower cases for the same property, the JsonMappingException exception is thrown. For details on exception handling, see 18.3.3 Exception handling.
Do not specify static in Bean property. Otherwise, mapping will not proceed.
You can also specify the final modifier.
The Bean property does not need to be writable. For details on the Bean property, see the JavaBeans specifications.