Spring Python 1.1: Create powerful and versatile Spring Python applications using pragmatic libraries and useful abstractions

264 Pages·2010·5.88 MB·English

by  Greg Lee Turnquist

Spring Python 1.1
Create powerful and versatile Spring Python applications
using pragmatic libraries and useful abstractions
Greg Lee Turnquist
BIRMINGHAM - MUMBAI
Spring Python 1.1
Copyright © 2010 Packt Publishing
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First published: May 2010
Production Reference: 1180510
Published by Packt Publishing Ltd.
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ISBN 978-1-849510-66-0
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Cover Image by Parag Kadam ([email protected])
Credits
Author Editorial Team Leader
Greg Lee Turnquist Aanchal Kumar
Reviewers Project Team Leader
Bala Sundarasamy Lata Basantani
Russ Miles
Sylvain Hellegouarch Project Coordinator
Joel Goveya
Acquisition Editor
Steven Wilding Proofreader
Lesley Harrison
Development Editor
Mehul Shetty Graphics
Geetanjali Sawant
Technical Editor
Aditya Belpathak Production Coordinator
Shantanu Zagade
Indexer
Hemangini Bari Cover Work
Shantanu Zagade
About the Author
Greg Lee Turnquist has worked in the software industry since 1997. He is an
active participant in the open source community, and has contributed patches to
several projects including MythTV, Spring Security, MediaWiki, and the TestNG
Eclipse plugin. As a test-bitten script junky, he has always sought the right tool
for the job. He is a firm believer in agile practices and automated testing. He has
developed distributed systems, LAMP-based setups, and supported mission critical
systems hosted on various platforms.
After graduating from Auburn University with a Master's in Computer Engineering,
Greg started working with Harris Corporation. He worked on many contracts
utilizing many types of technology. In 2006, he created the Spring Python project,
which became the first official Spring Extension to reach live status. He recently
joined SpringSource as part of their international software development team.
I would like to extend thanks to Russ Miles and Sylvain
Hellegouarch for taking the time to technically review this book
and provide valuable feedback. I also thank my father, Dr. Paul
Turnquist, for providing inspiration to write. And most importantly,
I thank my wife Sara, for the support, encouragement, and patience.
About the Reviewers
Bala Sundarasamy, graduated from the College of Engineering, Guindy. He
has an extensive experience of more than 17 years in designing and building
applications using Java and .Net technologies. He has performed various roles in
technical functions and project delivery with some of the leading software consulting
companies in India.
He has also taught numerous young developers to write good object-oriented code
using Java and C#. He has proven expertise in training fresh engineers to adopt
industry standard best practices and processes in software writing.
Russ Miles is the author of three bestselling books: AspectJ Cookbook, Learning UML
2.0, and Head First Software Development (all by O' Reilly Media). In particular, writing
for the Head First series was an incredible learning experience in how to turn dry,
technical subjects into great learning experiences; he has successfully applied these
skills to the development of several successful courses and workshops.
He is a frequent speaker on many, wide-ranging technical subjects including
the fun of being a self-proclaimed 'polyglot programmer'. A certified Scrum
Master and, alongside the more specific technical coaching, he works with many
companies as they come to terms with the fact that software development is
ultimately about people.
He is the principle consultant and founder of OpenCredo, a high level software
development consultancy based in London. As part of his daily activities, Russ
writes for several publications (when he finds the time!) on topical software
development subjects of the day.
I'd like to thank my beautiful wife, Corinne and my 'little monster',
Mali for their support, laughs and hair tugs (just Mali).
Sylvain Hellegouarch, is a senior software developer at Ubikod, a company
dedicated to innovative mobile solutions. He has a passion for open-source software
and has created many Python projects targeting social communication based on the
AtomPub and XMPP protocols. He wrote the CherryPy Essentials book, which was
published by Packt Publishing in 2007, a hands-on book about CherryPy, a popular
web framework. His interests are currently pushing him to the rich world of the
semantic web, linked data and how people interact with each other.
Table of Contents
Preface 1
Chapter 1: Getting Started with Spring Python 7
Spring Python for Python developers 8
Exploring Spring Python's non-invasive nature 8
Adding in some useful templates 11
Spring Python for Java developers 15
Extending Spring Python 18
Installing Spring Python 19
Setting up an environment for Spring Python 19
Installing from a pre-built binary download 20
Installing from source 22
Spring Python community 23
Summary 24
Chapter 2: The Heart of Spring Python—Inversion of Control 25
Swapping production code with test doubles 26
More about Inversion of Control 29
Adding Inversion of Control to our application 30
Dependency Injection a.k.a. the Hollywood principle 33
Adding Inversion of Control to our test 35
Container versus Context 36
Lazy objects 37
Scoped objects 38
Property driven objects 39
Post processor objects 39
Context aware objects 40
Debate about IoC in dynamic languages 40
Migrating a Spring Java application to Python 42
Summary 49
Table of Contents
Chapter 3: Adding Services to APIs 51
AOP from 10,000 feet 52
Crosscutting versus hierarchical 52
Crosscutting elements 53
Weaving crosscutting behavior 53
Adding caching to Spring Python objects 54
Applying many advisors to a service 65
Performance cost of AOP 68
AOP is a paradigm, not a library 69
Distinct features of Spring Python's AOP module 71
The risks of AOP 72
AOP is part of the Spring triangle 73
Testing our aspects 73
Decoupling the service from the advice 74
Testing our service 76
Confirming that our service is correctly woven into the API 78
Summary 79
Chapter 4: Easily Writing SQL Queries with Spring Python 81
The classic SQL issue 82
Parameterizing the code 84
Replacing multiple lines of query code with one line of Spring Python 86
The Spring triangle—Portable Service Abstractions 86
Using DatabaseTemplate to retrieve objects 87
Mapping queries by convention over configuration 89
Mapping queries into dictionaries 89
DatabaseTemplate and ORMs 90
Solutions provided by DatabaseTemplate 90
How DatabaseTemplate and ORMs can work together 91
Testing our data access layer with mocks 92
How much testing is enough? 94
Summary 95
Chapter 5: Adding Integrity to your Data Access with
Transactions 97
Classic transaction issues 98
Creating a banking application 99
Transactions and their properties 101
Getting transactions right is hard 102
Simplify by using @transactional 102
More about TransactionTemplate 105
[ ii ]
Table of Contents
The Spring Triangle—Portable Service Abstractions 107
Programmatic transactions 108
Configuring with the IoC container 108
Configuring without the IoC container 109
@transactional versus programmatic 110
Making new functions play nice with existing transactions 110
How Spring Python lets us define a transaction's ACID properties 113
Applying transactions to non-transactional code 115
Testing your transactions 117
Summary 118
Chapter 6: Securing your Application with Spring Python 119
Problems with coding security by hand 120
Building web applications ignoring security 122
Looking at our web application from 10,000 feet 130
Handling new security requirements 131
Authentication confirms "who you are" 131
Authorization confirms "what you can do" 132
Time to add security to our application 133
Accessing security data from within the app 141
Testing application security 142
Configuring SQL-based security 143
Configuring LDAP-based security 144
Using multiple security providers is easy 146
Migrating from an old security solution to a new one 147
Supporting multiple user communities 148
Providing redundant security access 148
Coding our own security extension 150
Coding a custom authentication provider 150
Some of the challenges with Spring Python Security 152
Summary 153
Chapter 7: Scaling your Application Across Nodes with
Spring Python's Remoting 155
Introduction to Pyro (Python Remote Objects) 156
Converting a simple application into a distributed one on the
same machine 157
Fetching the service from an IoC container 158
Creating a client to call the service 159
Making our application distributed without changing the client 159
Is our example contrived? 163
Spring Python is non-invasive 163
[ iii ]