6. Querying | Java Hibernate Cookbook

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Java Hibernate Cookbook

By : Prajapati, Ranapariya

Java Hibernate Cookbook

By: Prajapati, Ranapariya

Overview of this book

This book will provide a useful hands-on guide to Hibernate to accomplish the development of a real-time Hibernate application. We will start with the basics of Hibernate, which include setting up Hibernate – the pre-requisites and multiple ways of configuring Hibernate using Java. We will then dive deep into the fundamentals of Hibernate such as SessionFactory, session, criteria, working with objects and criteria. This will help a developer have a better understanding of how Hibernate works and what needs to be done to run a Hibernate application. Moving on, we will learn how to work with annotations, associations and collections. In the final chapters, we will see explore querying, advanced Hibernate concepts and integration with other frameworks.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Sections

Conventions

Reader feedback

Customer support

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1. Setting Up Hibernate

1. Setting Up Hibernate

Introduction

Getting the required libraries for hibernate

Creating a hibernate persistent class

Providing an XML-based hibernate mapping

Providing an annotation-based hibernate mapping

Providing a hibernate configuration using an XML file

Providing a hibernate configuration using the properties file

Configuring hibernate programmatically

2. Understanding the Fundamentals

2. Understanding the Fundamentals

Introduction

Building a SessionFactory

Creating a generic SessionFactory provider class

Opening a new session

Opening a stateless session

Saving an object to the database

Fetching an object from the database

Removing an object from the database

Updating an object

Creating a criteria

Restricting the results using a criteria

Pagination using a criteria

Sorting the results

Transforming a result

Using basic projection

3. Basic Annotations

3. Basic Annotations

Introduction

Declaring a class as an entity and creating a table in the database – @Entity and @Table

Creating a column in the table – @Column

Creating a primary key and composite primary key column – @Id and @IdClass

Creating an autogenerator column

4. Working with Collections

4. Working with Collections

Introduction

Persisting List

Persisting Set

Persisting Map

Persisting Array

5. Working with Associations

5. Working with Associations

Introduction

One-to-one mapping using foreign key association

One-to-one mapping using a common join table

One-to-one mapping using a common primary key

One-to-many mapping or many-to-one mapping

Many-to-many mapping

6. Querying

6. Querying

Introduction

Working with an alias

Performing aggregate operations

Executing a subquery using a criteria

Executing a native SQL query

Executing a query using HQL

Using formula in hibernate

Working with NamedQuery

7. Advanced Concepts

7. Advanced Concepts

Introduction

Working with a first-level cache

Working with a second-level cache

Working with a query cache

Working with the table per class hierarchy strategy of inheritance

Working with the table per subclass strategy of inheritance

Working with the table per concrete class strategy of inheritance

Working with the versioning of objects

Maintaining the history of an object

Working with an interceptor

Working with batch processing

8. Integration with Other Frameworks

8. Integration with Other Frameworks

Introduction

Integration with Spring

Integration with Struts

Index

Index

Customer Reviews

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Executing a query using HQL

HQL stands for Hibernate Query Language and is a fully object-oriented language. This language is a bit similar to the native query, but in the native SQL query, we use the physical table name and actual physical columns to execute a query, and in HQL, we have to use a class name instead of a table name and a field name instead of a column name.

HQL queries are converted to SQL queries by hibernate; so, we can use any of the styles. However, HQL is preferable from a performance point of view, because hibernate uses SQL directly without any optimization, and the HQL query uses hibernate's query generation strategy and caching mechanism.

How to do it…

There are multiple clauses available to work with HQL.

The FROM clause

We will use the simple FROM clause to query an object to load the complete object.

Here, we will use the FROM Category query, which is equal to SELECT * FROM category in native SQL. Execute the following code:

Code

Query query = session.createQuery("FROM...

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