Book Image

Mastering Hibernate

By : Ramin Rad, Koushik Srinivas Kothagal
Book Image

Mastering Hibernate

By: Ramin Rad, Koushik Srinivas Kothagal

Overview of this book

Hibernate has been so successful since its inception that it even influenced the Java Enterprise Edition specification in that the Java Persistence API was dramatically changed to do it the Hibernate way. Hibernate is the tool that solves the complex problem of Object Relational Mapping. It can be used in both Java Enterprise applications as well as .Net applications. Additionally, it can be used for both SQL and NoSQL data stores. Some developers learn the basics of Hibernate and hit the ground quickly. But when demands go beyond the basics, they take a reactive approach instead of learning the fundamentals and core concepts. However, the secret to success for any good developer is knowing and understanding the tools at your disposal. It’s time to learn about your tool to use it better This book first explores the internals of Hibernate by discussing what occurs inside a Hibernate session and how Entities are managed. Then, we cover core topics such as mapping, querying, caching, and we demonstrate how to use a wide range of very useful annotations. Additionally, you will learn how to create event listeners or interceptors utilizing the improved architecture in the latest version of Hibernate.
Table of Contents (16 chapters)

SQL/DDL modifier


In this section, we will discuss annotations that modify the SQL or the DDL used by Hibernate to perform a query or generate schema objects. The DDL modifying annotations are important if you use Hibernate to generate your tables.

@Check

Using the @Check Hibernate annotation, you can add the CHECK constraints to your table. The constraint defined in the @Check annotation uses the syntax that is supported by the database of your choice.

The following listing adds a constraint to the price column:

@Entity
@Check(constraints = "price >= 0")
public class Item {
  @Id
  @GeneratedValue
  private long id;
  private String description;
  private double price;
  // setters and getters
}

The DDL generated using PostgreSQL, is shown here:

    create table Item (
        id int8 not null,
        description varchar(255),
        price float8 not null,
        primary key (id),
        check (price >= 0)
    )

@ColumnDefault

Another DDL modifier is the Hibernate annotation @ColumnDefault...