The Definitive Guide to Grails 2

Transcription

1 The Definitive Guide to Grails 2 Jeff Scott Brown Graeme Rocher Apress

2 The Definitive Guide to Grails 2 Copyright 2013 by Jeff Scott Brown and Graeme Rocher This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Exempted from this legal reservation are brief excerpts in connection with reviews or scholarly analysis or material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher s location, in its current version, and permission for use must always be obtained from Springer. Permissions for use may be obtained through RightsLink at the Copyright Clearance Center. Violations are liable to prosecution under the respective Copyright Law. ISBN ISBN (ebook) 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. While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. President and Publisher: Paul Manning Lead Editor: Douglas Pundick Technical Reviewer: Graeme Rocher Editorial Board: Steve Anglin, Ewan Buckingham, Gary Cornell, Louise Corrigan, Morgan Ertel, Jonathan Gennick, Jonathan Hassell, Robert Hutchinson, Michelle Lowman, James Markham, Matthew Moodie, Jeff Olson, Jeffrey Pepper, Douglas Pundick, Ben Renow-Clarke, Dominic Shakeshaft, Gwenan Spearing, Matt Wade, Tom Welsh Coordinating Editor: Katie Sullivan Copy Editor: Thomas McCarthy Compositor: Bytheway Publishing Services Indexer: SPi Global Artist: SPi Global Cover Designer: Anna Ishchenko Distributed to the book trade worldwide by Springer Science+Business Media New York, 233 Spring Street, 6th Floor, New York, NY Phone SPRINGER, fax (201) , orders-ny@springer-sbm.com, or visit www. springeronline.com. 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 Any source code or other supplementary materials referenced by the author in this text is available to readers at www. apress.com. For detailed information about how to locate your book s source code, go to

3 To Mom. Thanks for everything. Jeff Scott Brown To Birjinia. Thanks for being you. Maite zaitut. Graeme Rocher

4 Contents at a Glance About the Author...xiii About the Technical Reviewer...xiv Acknowledgments...xv Chapter 1: The Essence of Grails...1 Chapter 2: Getting Started with Grails...15 Chapter 3: Understanding Domain Classes...41 Chapter 4: Understanding Controllers...63 Chapter 5: Understanding Views Chapter 6: Mapping URLs Chapter 7: Internationalization Chapter 8: Ajax Chapter 9: GORM Chapter 10: Services Chapter 11: Integration and Dependency Management Chapter 12: Plug-ins Index iv

5 Contents About the Author...xiii About the Technical Reviewer...xiv Acknowledgments...xv Chapter 1: The Essence of Grails...1 Simplicity and Power...1 Grails, the Platform...2 Living in the Java Ecosystem...3 Installing and Configuring Grails...4 Creating Your First Application...5 Step 1: Creating the Application...5 Step 2: Creating a Controller...6 Step 3: Printing a Message...8 Step 4: Testing the Code...8 Step 5: Running the Tests...9 Step 6: Running the Application...10 Grails Interactive Mode...12 Summary...13 Chapter 2: Getting Started with Grails...15 What Is Scaffolding?...15 Creating a Domain...15 Introducing Dynamic Scaffolding...17 The Create Operation...19 The Read Operation...21 v

6 CONTENTS vi The Update Operation...23 The Delete Operation...24 Static Scaffolding...25 Generating a Controller...25 Generating the Views...29 Being Environmentally Friendly...31 Configuring Data Sources...32 The DataSource.groovy File...32 Configuring a MySQL Database...34 Configuring a JNDI Data Source...37 Supported Databases...37 Deploying the Application...38 Deployment with run-war...38 Deployment with a WAR file...39 Summary...40 Chapter 3: Understanding Domain Classes...41 Persisting Fields to the Database...41 Validating Domain Classes...42 Using Custom Validators...45 Understanding Transient Properties...45 Customizing Your Database Mapping...47 Building Relationships...49 Extending Classes with Inheritance...52 Embedding Objects...56 Testing Domain Classes...58 Summary...61 Chapter 4: Understanding Controllers...63 Defining Controllers...63 Setting the Default Action...64 Logging...65 Logging Exceptions...66 Accessing Request Attributes...66 Using Controller Scopes...67 Understanding Flash Scope...68 Accessing Request Parameters...70

7 CONTENTS Request Parameter Type Conversions...70 Rendering Text...72 Redirecting a Request...73 Creating a Model...74 Rendering a View...74 Finding the Default View...75 Selecting a Custom View...75 Rendering Templates...75 Performing Data Binding...76 Validating Incoming Data...77 The Errors API and Controllers...77 Data Binding to Multiple Domain Objects...78 Data Binding with the binddata Method...79 Data Binding and Associations...79 The Bindable Constraint...80 Working with Command Objects...81 Defining Command Objects...81 Using Command Objects...82 Imposing HTTP Method Restrictions...83 Implementing an Imperative Solution...83 Taking Advantage of a Declarative Syntax...84 Controller IO...84 Handling File Uploads...85 Reading the Request InputStream...87 Writing a Binary Response...87 Using Simple Interceptors...88 Before Advice...88 After Advice...89 Testing Controllers...89 Controllers in Action...92 Creating the gtunes Home Page...92 Adding the User Domain Class...93 Adding a Login Form...94 Implementing Registration...96 Testing the Registration Code...99 Allowing Users to Log In vii

8 CONTENTS Testing the Login Process Summary Chapter 5: Understanding Views The Basics Understanding the Model Page Directives Groovy Scriptlets GSP As GStrings Built-in Grails Tags Setting Variables with Tags Logical Tags Iterative Tags Filtering and Iteration Grails Dynamic Tags Linking Tags The createlink and resource Tags Creating Forms and Fields Validation and Error Handling Paginating Views Rendering GSP Templates Creating Custom Tags Creating a Tag Library Custom Tag Basics Testing a Custom Tag Summary Chapter 6: Mapping URLs Understanding the Default URL Mapping Including Static Text in a URL Mapping Removing the Controller and Action Names from the URL Embedding Parameters in a Mapping Specifying Additional Parameters Mapping to a View Applying Constraints to URL Mappings Including Wildcards in a Mapping Mapping to HTTP Request Methods viii

9 CONTENTS Mapping HTTP Response Codes Taking Advantage of Reverse URL Mapping Named URL Mappings Defining Multiple URL Mappings Classes Testing URL Mappings Summary Chapter 7: Internationalization Localizing Messages Defining User Messages Retrieving Message Values Using URL Mappings for Internationalization Using Parameterized Messages Using java.text.messageformat Using the message Tag for Parameterized Messages Using Parameterized Messages for Validation Using messagesource Summary Chapter 8: Ajax Writing Ajax Code Ajax in Action Changing Your Ajax Provider Asynchronous Form Submission Fun with Ajax Remote Linking Adding Effects and Animation Ajax-Enabled Form Fields A Note on Ajax and Performance Summary Chapter 9: GORM Persistence Basics Reading Objects Listing, Sorting, and Counting Saving, Updating, and Deleting Associations Relationship Management Methods ix

10 CONTENTS Transitive Persistence Querying Dynamic Finders Criteria Queries Detached Criteria Queries Where Queries Query by Example HQL and SQL Pagination Configuring GORM SQL Logging Specifying a Custom Dialect Other Hibernate Properties The Semantics of GORM The Hibernate Session Session Management and Flushing Obtaining the Session Automatic Session Flushing Transactions in GORM Detached Objects The Persistence Life Cycle Reattaching Detached Objects Merging Changes Performance Tuning GORM Eager vs. Lazy Associations Batch Fetching Caching Inheritance Strategies Locking Strategies Events Auto Time Stamping Summary Chapter 10: Services Understanding Service Basics Services and Dependency Injection Services in Action x

11 CONTENTS Defining a Service Configuring Service Bean Properties Caching Service Methods Using a Service Managing Transactions Scoping Services Testing Services Exposing Services Summary Chapter 11: Integration and Dependency Management Grails and Configuration Configuration Basics Environment-Specific Configuration Configuring Logging Stack Trace Filtering Externalized Configuration Declaring Dependencies Inheriting Dependencies Declaring Repositories Understanding the Grails Build System Creating Gant Scripts Command-Line Variables Parsing Command-Line Arguments Documenting Your Scripts Reusing More of Grails Bootstrapping Grails from the Command Line Gant in Action Continuous Integration with Hudson Adding Support to Your Favorite IDE Using The Groovy/Grails Tool Suite (GGTS) Using Spring Tool Suite (STS) and Eclipse IntelliJ IDEA NetBeans Text Editors Integration with Servers Deployment xi

12 Deploying with Grails Deploying to a Container Application Versioning and Metadata Customizing the WAR Summary Chapter 12: Plug-ins Plug-in Basics Plug-in Discovery Supplying Application Artefacts Plug-in Hooks Providing Spring Beans Dynamic Spring Beans Using Conventions Plug-in Events and Application Reloading Modifying the Generated WAR Descriptor Packaging and Distributing a Grails Plug-in Local Plug-in Repositories Plug-ins in Action Adding Behavior With Plug-ins Specifying Plug-in Locations on the File System Plug-ins for Application Modularity Using the Resources Plug-in Using the Database Migration Plug-in Summary Index xii

13 About the Author Jeff Scott Brown is an engineer at SpringSource, where he works as a member of the Groovy and Grails development team. Jeff, a technologist for nearly 20 years, has been a member of the Grails team since the framework s very early days. Earlier he was part of G2One, the Groovy/Grails company that eventually became part of SpringSource. xiii

14 About the Technical Reviewer Graeme Rocher, a software engineer, a consultant, and an expert in dynamic language, serves as head of Grails Development at SpringSource (www. springsource.com). Graeme is the project lead of the open source Grails web application framework ( and a coauthor of The Definitive Guide to Grails (Apress). With Jeff Scott Brown, he is also an author of the present book. xiv

15 Acknowledgments First of all, I am grateful to my lovely wife, Betsy, and our boys, Jake and Zack, for all of their support. Without them, none of what I get to do would be possible. Thank you! To Graeme I have to say a giant thank-you as well. He and I have worked together on the Grails technology for quite a few years, and that experience has been invaluable. I hope we continue enjoying accomplishments together for a very long time. Thanks, too, to the whole Groovy and Grails team at SpringSource. I have never worked with a smarter group of people or a group that made work seem so much like pleasure. Thanks as well to the whole Apress team for their support in completing this project. I appreciate their patience and their willingness to help me get this thing done. In particular, thanks to Katie Sullivan, Douglas Pundick, and Steve Anglin for seeing this project through to the end. Last but not least, I have to extend a big thank-you to Damien Vitrac for contributing some fantastic CSS work to the sample application for this book. The thing looks so much nicer because of his contributions. Well done! Jeff Scott Brown Writing a book is no small task. It requires hours of dedication every day valuable time stripped away from loved ones. For this alone I thank my wife, Birjinia, whose patience and support drive me to achieve more. Also, thanks to my kids, Alex and Lexeia, who showed remarkable restraint when tempted to wrestle me away from the computer. You guys rock. To the Grails team at SpringSource, you are a really special group. It continues to be a privilege to work with you all. I count myself extremely lucky to work in the Open Source sector, where cutting-edge innovation and technology leadership are daily occurrences. There is a very special kind of enjoyment that comes from working with such a talented team of innovators. Thanks to the team at Apress for getting the book done. It is not easy managing all the moving pieces that go into the making of a great technical book. Kudos. Graeme Rocher xv