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)

Filters


In the previous chapter, we showed you how to apply filters using annotation. Another way is to apply filters to a collection that is already in the persistence context. This is quite useful to fetch only a subset of a collection.

For example, if you have a list of teachers and their students in the database and you are simply interested in fetching the records for all the female students, you can use filters, which can be very efficient in some cases.

To demonstrate how to use filters, let's assume that we have the following entities:

@Entity
public class Teacher {
  @Id
  @GeneratedValue
  private long id;
  private String name;
  
  @OneToMany(cascade=CascadeType.ALL)
  Set<Student> students = new HashSet<Student>();
  // getters and setters
}

@Entity
public class Student {
  @Id
  @GeneratedValue
  private long id;
  private String name;
  private String gender;
  // getters and setters
}

You can get the teacher record using a simple fetch:

Teacher teach = (Teacher) session...