Java EE 8 Design Patterns and Best Practices

Implementing DAO

In order to reuse a lot of code and promote best practices to implement DAO, we will create an abstract DAO, called AbstractDao, which is the superclass of all DAOs, that has methods with the generic logic that can be used by all DAOs:

import javax.persistence.EntityManager;import javax.persistence.PersistenceContext;import javax.persistence.TypedQuery;import java.lang.reflect.ParameterizedType;import java.util.List;import java.util.Map;import java.util.Optional;public abstract class AbstractDao <T extends Entity>{    //EntityManager that provide JPA functionalities    @PersistenceContext    protected EntityManager em;    //Get the type of Subclass that implements Entity interface    protected Class<T> getType() { ParameterizedType genericType ...