Spring Persistence with Hibernate

Transcription

1 Spring Persistence with Hibernate PAUL TEPPER FISHER BRIAN D. MURPHY

2 Spring Persistence with Hibernate Copyright 2010 by Paul Tepper Fisher and Brian D. Murphy All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior written permission of the copyright owner and the publisher. ISBN-13 (pbk): ISBN-13 (electronic): Printed and bound in the United States of America Trademarked names, logos, and images may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, logo, or image we use the names, logos, and images only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. President and Publisher: Paul Manning Lead Editors: Steve Anglin, Tom Welsh Technical Reviewer: Sia Cyrus Editorial Board: Steve Anglin, Mark Beckner, Ewan Buckingham, Gary Cornell, Jonathan Gennick, Jonathan Hassell, Michelle Lowman, Matthew Moodie, Duncan Parkes, Jeffrey Pepper, Frank Pohlmann, Douglas Pundick, Ben Renow-Clarke, Dominic Shakeshaft, Matt Wade, Tom Welsh Coordinating Editor: Mary Tobin Copy Editor: Marilyn Smith Compositor: Kimberly Burton Indexer: Julie Grady Artist: April Milne Cover Designer: Anna Ishchenko Distributed to the book trade worldwide by Springer Science+Business Media, LLC., 233 Spring Street, 6th Floor, New York, NY Phone SPRINGER, fax (201) , orders-ny@springersbm.com, or visit For information on translations, please rights@apress.com, or visit Apress and friends of ED books may be purchased in bulk for academic, corporate, or promotional use. ebook versions and licenses are also available for most titles. For more information, reference our Special Bulk Sales ebook Licensing web page at The information in this book is distributed on an as is basis, without warranty. Although every precaution has been taken in the preparation of this work, neither the author(s) nor Apress shall have any liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the information contained in this work. The source code for this book is available to readers at You will need to answer questions pertaining to this book in order to successfully download the code. ii

3 To Melanie, for making it all worthwhile Paul I would like to dedicate this, my first print book, to my mom. I miss you always Brian

4 Contents at a Glance About the Authors...xii About the Technical Reviewer...xiii Acknowledgments... xiv Preface... xvi Chapter 1: Architecting Your Application with Spring, Hibernate, and Patterns...1 Chapter 2: Spring Basics...17 Chapter 3: Basic Application Setup...33 Chapter 4: Persistence with Hibernate...49 Chapter 5: Domain Model Fundamentals...69 Chapter 6: DAOs and Querying...85 Chapter 7: Transaction Management Chapter 8: Effective Testing Chapter 9: Best Practices and Advanced Techniques Chapter 10: Integration Frameworks Chapter 11: GORM and Grails Chapter 12: Spring Roo Index iv

5 Contents About the Authors...xii About the Technical Reviewer...xiii Acknowledgments... xiv Preface... xv Chapter 1: Architecting Your Application with Spring, Hibernate, and Patterns...1 The Benefit of a Consistent Approach...1 The Significance of Dependency Injection... 2 A Synergistic Partnership...2 The Story of Spring s and Hibernate s Success... 3 A Better Approach for Integration... 3 Best Practices for Architecting an Application... 4 Other Persistence Design Patterns...12 The Template Pattern The Active-Record Pattern Summary...15 Chapter 2: Spring Basics...17 Exploring Spring s Architecture...18 The Application Context Beans, Beans, the Magical Fruit The Spring Life Cycle Understanding Bean Scopes Dependency Injection and Inversion of Control...24 Setter-Based Dependency Injection v

6 CONTENTS Constructor-Based Dependency Injection Instance Collaboration Coding to Interfaces Dependency Injection via Autowiring... Dependency Injection Set It and Forget It! Injecting Code Using AOP and Interceptors...31 Summary...32 Chapter 3: Basic Application Setup...33 Application Management with Maven...33 Managed Dependencies Standard Directory Structure POM Deconstruction Spring Configuration...37 Namespace Support Externalizing Property Configurations Component Scanning Import Statements Database Integration...40 JDBC Support Integration with JNDI Web Application Configuration...43 Servlet Definition Spring MVC Summary...47 Chapter 4: Persistence with Hibernate...49 The Evolution of Database Persistence in Java...49 EJB, JDO, and JPA vi vi

7 CONTENTS How Hibernate Fits In JPA Interface Hierarchy...52 The Art Gallery Domain Model and DAO Structure...54 POJO Simplified DAO Pattern with Generics The Life Cycle of a JPA Entity JPA Configuration...64 Bare-Bones JPA Setup Spring Integration Summary...68 Chapter 5: Domain Model Fundamentals...69 Understanding Associations...69 Building the Domain Model...71 Convention over Configuration Managing Entity Identifiers Using Cascading Options to Establish Data Relationships Adding Second-Level Caching Using Polymorphism with Hibernate Summary...84 Chapter 6: DAOs and Querying...85 A Basic Hibernate DAO Implementation...85 Building a DAO Using Spring s Hibernate Support Classes Enabling Query Caching with the HibernateTemplate Going Template-less Querying in Hibernate...92 Loading an Entity Querying for a Particular Type vii vii

8 CONTENTS Using Named Parameters Querying Using Core Hibernate Using Named Queries Working with Polymorphic Queries Persisting Data with Hibernate...97 Saving and Updating Data Handling Binary Data Understanding the Benefits of the Criteria API Using the JPA 2.0 Criteria API Summary Chapter 7: Transaction Management The Joy of ACID Understanding Isolation Levels Serializable Repeatable Read Read Committed Read Uncommitted Controlling ACID Reflux Platform Transaction Management Declarative Transaction Management Programmatic Transaction Management Transactional Examples Creating a Batch Application Using Two Datasources Summary Chapter 8: Effective Testing Unit, Integration, and Functional Testing Using JUnit for Effective Testing viii viii

9 CONTENTS Unit Testing with Mocks Spring Dependency Injection and Testing Testing with a Database Summary Chapter 9: Best Practices and Advanced Techniques Lazy Loading Issues The N+1 Selects Problem Lazy Initialization Exceptions Caching Integrating a Caching Implementation Caching Your Queries Caching in a Clustered Configuration Summary Chapter 10: Integration Frameworks RESTful Web Services with Spring Nouns, Verbs, and Content-Types Serializing the Object Graph Using the Dreaded DTO Pattern Leveraging Spring 3 s REST Support Marshaling Data with Spring OXM Handling Concurrency Free-Text Search Introducing Lucene Introducing Hibernate Search Putting Lucene and Hibernate in Sync Building a Domain-Specific Search Summary ix ix

10 CONTENTS Chapter 11: GORM and Grails A Crash Course in Groovy Letting Your Types Loose GStrings Strings on Steroids Default Constructors in Groovy Closures in Groovy Getting Grails Running Installing Grails Creating a Grails Application Configuring Your Application Configuring Your Datasource Mapping URLs Defining the Grails Domain Model Adding Constraints and Validation Defining Associations and Properties Customizing Domain Class Hibernate Mappings Using Active Record As an Alternative to DAOs Looking Under the Hood of GORM Working with Dynamic Finder Methods Creating Advanced Query Methods Using the Criteria API Handling Associations in Grails Scaffolding and Building Your Grails Application Defining a Transactional Service Layer in Grails Summary x x

11 CONTENTS Chapter 12: Spring Roo What Roo Is (and What It Is Not) Creating a Domain Model with Roo Getting Started with Roo Creating a New Project Adding Entities Adding Fields Exploring the Automatically Generated Testing Infrastructure Mapping Associations Modeling Inheritance Adding Spring MVC Adding Service Layers and DAOs Now You See Me, Now You Don t Removing Roo Summary Index xi xi

12 About the Authors Paul Tepper Fisher first began working in technology at Johns Hopkins University, where he spent several years developing a distance-learning application for neuroscience, while completing graduate school there. He has founded two technology start-ups: SmartPants Media, Inc., a software development company specializing in interactive multimedia technology; and dialmercury.com, which develops telephony applications using VOIP and Java. Paul was also Manager of Technology at Wired.com, where he led the software development team for the online publications of Wired.com, webmonkey.com, and howto.wired.com, using Spring, Grails, and Java technology. Currently, Paul is Director of Engineering for a new Music Service at Lime Wire, where he manages several development teams using agile methodologies. Comprised of client-side and distributed server-side components, the Music Service is designed for horizontal scalability with a goal of supporting millions of end-users and terabytes of data. You can read Paul s blog at: Brian D. Murphy is the Chief Architect and Director of Engineering at Condé Nast. He was an early adopter of Spring and Hibernate and uses both technologies to power all of Condé s brands online, including wired.com, newyorker.com, epicurious.com, and vanityfair.com, drawing tens of millions of unique visitors each month. Brian deals with the challenges of building scalable, distributed systems every single day. He has a B.S. in Computer Science from Rutgers University. You can follow Brian on Twitter at or read his blog at xii

13 About the Technical Reviewer Sia Cyrus s experience in computing spans many decades and areas of software development. During the 1980s, he specialized in database development in Europe. In the 1990s, he moved to the US where he focused on client-server applications. Since 2000, he has architected a number of middle-tier business processes incorporating Spring and Hibernate. Most recently, he has been specializing in Web 2.0, Ajax, GWT, and Android. Sia is an independent software consultant who is an expert in Java and development of Java enterprise-class applications. He has been responsible for innovative and generic software, holding a US Patent in database-driven user interfaces. Sia created a very successful configuration-based framework for the telecommunications industry, which he later converted to Spring Framework. His passion could be entitled Enterprise Architecture in Open Source. When not experimenting with new technologies, he enjoys playing ice hockey especially with his two boys, Jason and Brandon. He can be reached at sia.cyrus@comcast.net. xiii

14 Acknowledgments Writing a book always ends up being more difficult than you initially imagined. Although the absurdly late nights and lost weekends prove difficult to the authors, it is often the people around them that end up suffering the most. To that end, I d like to thank Melanie Colton for her endless patience and perseverance. She deserves more than a medal for putting up with the many 4am nights and my noisy typing. This book would not have been possible without her support, understanding, and muse. I would also like to acknowledge my colleagues at Lime Company, for their continued trust and support. It is a rare experience to work with such a talented and committed group of people, and I am grateful for the opportunity to be a part of such an important adventure. I d also like to thank Solomon Duskis for starting this journey, and for his unwavering enthusiasm for technology especially Java and Spring. I would be remiss if I didn t offer my appreciation and gratitude to my parents, who have inspired me through their relentless trust, support, and faith in everything I set out to do. Finally, my sincere appreciation goes to Brian Murphy for joining the project and keeping things rolling along. If it hadn t been for Brian s tenacity and motivation, this book would never have seen the light of day. It s been an honor and privilege working with you again. Paul Tepper Fisher We d like to thank Apress for the opportunity to write this book. Special thanks to Steve Anglin for believing in us and letting us stretch the schedule to cover advanced topics in depth. We owe Mary Tobin a special debt of gratitude for shepherding us through this process and ultimately dragging us across the finish line. Thanks to Tom Welsh, Marilyn Smith, and Sia Cyrus, who provided invaluable feedback, suggestions and encouragement along the way. This is a much better book as a result of their wisdom and patience. Any issues or errors in this text are ours alone. I would like to thank my wife, Dania, without whom this book wouldn t be possible. She graciously took on the role of super mom while I devoted nights and weekends to writing for far longer than bargained for. I d like to thank my son Liam for being the most terrific little kid. You provide me with more joy and a new appreciation for the world than you ll ever know. I d also like to acknowledge our second son, who is due shortly after this book will be published. I can t wait to meet you! Lastly, I d like to thank Paul Fisher for sharing this experience with me. This book was Paul s brainchild and I m glad he invited me along for the ride. Writing this book has been both rewarding and challenging. I learned a ton and it s been great to work with you again. Brian D. Murphy xiv

15 Preface Since its inception, the Spring Framework has gradually changed the rules of application development in the Java community. This book is the ideal guide and teaching companion for developers interested in learning about the Spring Framework and how it can be leveraged to build persistence-driven applications using Hibernate, one of the most popular Java persistence frameworks today. Spring Persistence with Hibernate gets you rolling with fundamental Spring concepts, as well as proven design patterns for integrating persistence into your applications. Many of the lessons illustrated in this book were culled from years of practical experience building scalable, high-volume web applications using Spring and Hibernate. One of the details that stands out in our joint experience is the importance and benefit of learning through hands-on experience. To this end, we will build a real-world application that utilizes Spring 3, Hibernate 3.5, JPA 2.0, Hibernate-Search, Grails, Spring Roo, and Dozer. We firmly believe that learning about Spring and Hibernate implies far more than simply understanding the respective APIs of each framework. To be able to effectively develop with these two amazing technologies, it is necessary to understand the design patterns and best practices for getting the best from these frameworks, and building on them in a consistent, proven manner. We hope this book will teach you more than just how to use Spring and Hibernate together. Our goal is to channel the development experience, lessons, and best practices we ve seen work successfully in our experience, so that you can apply these skills and tools in your own applications. Throughout these pages, we will introduce core Hibernate fundamentals, demonstrating how the framework can be best utilized within a Spring context. We will start with foundational concepts, such as strategies for developing an effective domain model and DAO layer, and then move into querying techniques using HQL, JPQL, and the Criteria API. After fundamental concepts are introduced, we will move on to more advanced topics, such as fetching and caching strategies. We will also illustrate several approaches for architecting a transactional service facade. Both programmatic and declarative transactions will be examined, showcasing the benefits of using Spring for expressing transactional semantics. Spring Persistence with Hibernate will also introduce JPA, covering its history and the ways in which Hibernate influenced its development. We will discuss the benefits of following the JPA standard, as well as when it makes sense to utilize Hibernate-specific features. The book will also introduce Grails and GORM, illustrating the differences between the DAO and Active Record patterns. We will port our sample application (which will be developed in the course of the book) into both Grails and Spring Roo, highlighting the benefits and differences of using a rapid-development, convention-over-configuration platform. In these sections, we will explore topics related to concurrency/optimistic locking, Hibernate Session state, caching approaches, and transaction management. The last part of the book will introduce several advanced techniques, important for working with enterprise Spring/Hibernate applications. We will illustrate some of the pitfalls with integrating legacy databases, as well as best practices for developing REST web services, handling Hibernate proxies and lazy collections, as well as building search functionality using Hibernate-Search. Here are some of the main topics we will discuss in this book: xv

16 PREFACE CONTENTS Basic Spring Framework features such as IoC and AOP Core concepts for architecting a well-layered persistence tier JPA concepts and steps for integrating JPA Foundational and advanced concepts for working with Hibernate Hibernate querying techniques DAO and Service Facade layer development Grails, along with the introduction of Active-Record Pattern Introduction of Spring Roo Building a REST web service Translating between a domain model and a DTO using Dozer Leveraging other frameworks and technologies, such as Hibernate-Search Advanced Caching and Integration strategies xvi xvi