No.Your entity class can remain the same. However, you may have to change the primary key generation strategy. You may also have to change values of some attributes of the @Column annotation.
Your tables may slightly change due to the fact that different databases have their own ways of storing data. You can regenerate the tables by editing your persistence.xml
<properties>
<property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/>
</properties>