The Entity Manager API is probably the most important and interesting part of the Java Persistence API. In this section you’ll learn about the Entity Manager interface and its methods.

We’ll explore the entity lifecycle, and you’ll also learn about persistence contexts and their types.

In the first case the entity is saved, in the latter case it is updated.

When switching from Hibernate to JPA a lot of peopleare dismayed to findthat method missing.

Figure 9.1 The Entity Manager acts as a bridge between the OO and relational worlds.Those of you that have worked with plain Hibernate will probably have grown quite accustomed to using the Or Update method to save entities.The save Or Update method figures out whether the object is new or has already been saved before. Code: Transaction().begin(); Parent DBO parent = new Parent DBO(); ...The Java Persistence API (JPA) is used for mapping domain object classes to database tables.