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This chapter discusses the states an object goes through during its life cycle. The session is responsible for managing object state in Hibernate, and the EntityManager does the same in Java Persistence. Hibernate provides a persistence mechanism that is transparent to the entities and the application; the application has to know the state of an object.

is the processing of groups of elements. From an application standpoint, batch processing means reading data from a persistent store, doing something with the data, and then possibly storing the processed data in the persistent store as a single conceptual operation. Batch processing, which allows for the automation and sharing of computer resources, is usually run when computer resources are less busy.

In general, entities are related or associated to each other. For example, a Customer entity is associated with an Address entity. A Customer entity can have one or more than one Address entity (for example, Billing and Shipping). These relationships or associations are represented differently in a relational model and the domain/object model.

A primary key in a database table is used to uniquely identify a record in that table. The primary key value can't be null and is unique within a table. The primary key is also used to establish a relationship between two tables; it is defined as a foreign key in the associated table. Because the primary key is used to identify a particular record, it can also be called the database identifier, which is exposed to the application by Hibernate through an identifier property of the persistent entity. This chapter discusses the various ways to generate an identifier (primary key) for a database record. You learn about metadata configurations and their effect on the persistence mechanism.

Let’s say that a buyer logs in to the bookshop application and purchases a book. The following actions should take place in the event of a purchase

Caching is one of the important features implemented by an application for better performance. From an ORM perspective, data retrieved from a database is cached in memory or to disk, so there is no need to make a call to the database for every request. A cache is a local copy of the information from the database that can be used to avoid a database call whenever the following situations occur

Inheritance, polymorphic associations, and polymorphic queries are supported by entities. The JPA specification says that both concrete and abstract classes can be entities and can be mapped with the Entity annotation. Non-entity classes and entity classes can extend each other. Hibernate provides the MappedSuperclass annotation (@MappedSuperclass) to enable inheritance mapping and to let you map abstract or concrete entity subclasses. The mapped superclass doesn't necessarily have its own separate table.

Integrating Hibernate into a Java application is easy. The designers of Hibernate avoided some of the more common pitfalls and problems with the existing Java persistence solutions, and created a clean but powerful architecture. In practice, this means that you do not have to run Hibernate inside any particular Java EE container or framework. As of Hibernate 5.2, Java 8 or later is required, thanks to the integration of the date and time API and other such useful features.

In this chapter, we discuss the life cycle of persistent objects in Hibernate. These persistent objects can be POJOs without any special marker interfaces or inheritance related to Hibernate. Part of Hibernate’s popularity comes from its ability to work with a normal object model.

Most significant development projects involve a relational database. The mainstay of most commercial applications is the large-scale storage of ordered information, such as catalogs, customer lists, contract details, published text, and architectural designs.

In this appendix, we discuss some of the features that, strictly speaking, lie outside the scope of this book, but that you should be aware of if you go on to use Hibernate in more depth.

Hibernate doesn’t limit you to using purely relational databases; Hibernate OGM stands as a project that can carry an object model into the realm of the NoSQL datastore, allowing developers to use a familiar mechanism to access multiple types of storage.