ParameterizedType gets java generic parameter type

ParameterizedType

• getClass().getGenericSuperclass() 
  returns the Type representing the immediate superclass of the entity (class, interface, primitive type, or void) represented by this Class, then converts it to ParameterizedType.
• getActualTypeArguments() 
  returns an array of Type objects representing the actual type arguments of this type. [0] is the first one in this array. In short, get the actual type of the superclass's generic parameter.

Base Service

public abstract class BaseService<T> implements ServiceInterface<T> {

    private Class<T> clazz;

    /**
     * Entity manager reference
     *
     * @return EntityManager
     */
    protected abstract EntityManager getEntityManager();

    /**
     * DAO interface reference
     *
     * @return DAOInterface<T>
     */
    protected abstract DAOInterface<T> getDAOInterface();

    /**
     * The constructor reflects the real type of the generic object
     */ 
    @SuppressWarnings( "unchecked" )
     public BaseService() {
         // Get the generic parent class of the current new object 
        ParameterizedType pType = (ParameterizedType) this .getClass().getGenericSuperclass();
         // Get the true value of the type parameter , is the number of generic parameters; 
        this .clazz = (Class<T>) pType.getActualTypeArguments()[0 ];
    }

    @Override
    public T find(String id) throws Exception {
        return getEntityManager().find(clazz, id);
    }

    @Override
    public T save(T t) throws Exception {
        T save = getDAOInterface().save(t);
        return save;
    }

    @Override
    public void update(T t) throws Exception {
        getEntityManager().merge(t);

    }

    @Override
    public void del(String id) throws Exception {
        T t = getEntityManager().find(clazz, id);
        if (t != null) {
            getEntityManager().remove(t);
        }
    }

    @Override
    public List<T> findAll() throws Exception {
        return getDAOInterface().findAll();
    }

}