Enterprise OSGi in Action: With examples using Apache Aries

400 Pages·2013·23.6 MB·English

by  Holly Cummins

Holly Cummins
Timothy Ward
M A N N I N G
Enterprise OSGi in Action

Enterprise OSGi
in Action
W A A
ITH EXAMPLES USING PACHE RIES
HOLLY CUMMINS
TIMOTHY WARD
MANNING
SHELTER ISLAND
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1 2 3 4 5 6 7 8 9 10 – MAL – 18 17 16 15 14 13
brief contents
P 1 P H W . .............................1
ART ROGRAMMING BEYOND ELLO ORLD
1 ■ OSGi and the enterprise—why now? 3
2 ■ Developing a simple OSGi-based web application 26
3 ■ Persistence pays off 55
4 ■ Packaging your enterprise OSGi applications 86
P 2 B OSG ...........111
ART UILDING BETTER ENTERPRISE I APPLICATIONS
5 ■ Best practices for enterprise applications 113
6 ■ Building dynamic applications with OSGi services 132
7 ■ Provisioning and resolution 164
8 ■ Tools for building and testing 190
9 ■ IDE development tools 222
P 3 I OSG ....239
ART NTEGRATING ENTERPRISE I WITH EVERYTHING ELSE
10 ■ Hooking up remote systems with distributed OSGi 241
11 ■ Migration and integration 270
12 ■ Coping with the non-OSGi world 291
13 ■ Choosing a stack 318
v

contents
preface xiii
acknowledgments xv
about this book xvii
about the authors xx
about the cover illustration xxi
P 1 P H W . .................1
ART ROGRAMMING BEYOND ELLO ORLD
1 OSGi and the enterprise—why now? 3
1.1 Java’s missing modularity 4
Thinking about modularity 5 ■ Enterprise Java and modularity—
even worse! 7
1.2 OSGi to the rescue 9
Modularity, versioning, and compatibility 9 ■ Dynamism and
lifecycle management 14 ■ Why isn’t everyone using OSGi? 19
Why OSGi and Java EE don’t work together 21
1.3 Programming with enterprise OSGi 23
Enterprise OSGi and OSGi in the enterprise 23 ■ Dependency
injection 24 ■ Java EE integration 24
1.4 Summary 25
vii
viii CONTENTS
2 Developing a simple OSGi-based web application 26
2.1 The development sandbox 27
Introducing Apache Aries 27 ■ My first enterprise OSGi runtime 28
2.2 Writing an OSGi web application 31
Building a simple OSGi web application bundle 31 ■ Deploying and
testing 34 ■ A familiar feeling—and important differences 35
Spicing things up with fragments 38
2.3 Decoupling with dependency injection 41
Inversion of control 42 ■ Introducing the Blueprint service 43
Coupling two components with Blueprint 43
2.4 Bridging JNDI and OSGi 50
2.5 Summary 54
3 Persistence pays off 55
3.1 Java and persistence 56
Making persistence easy 56 ■ The problems with traditional
persistence in OSGi 57
3.2 Building a persistent application 59
Setting up a datasource 59 ■ Creating a persistence bundle 65
Making use of the data 72
3.3 Transactions—the secret ingredient 75
What is a transaction? 75 ■ Handling multipart transactions 76
3.4 Summary 85
4 Packaging your enterprise OSGi applications 86
4.1 The need for more than modules 87
Java EE applications 88 ■ Enterprise OSGi applications 90
4.2 Enterprise OSGi subsystems 90
ESA structure 91 ■ Subsystem metadata 92 ■ Provisioning and
resolution 94
4.3 The Enterprise Bundle Archive (EBA) 99
Sharing and isolation 99
4.4 Alternative approaches 100
Spring plan and PAR files 101 ■ Apache Karaf features 102
4.5 Developing an enterprise OSGi application 103
Building your metadata 104
4.6 Summary 109
CONTENTS ix
P 2 B OSG 111
ART UILDING BETTER ENTERPRISE I APPLICATIONS
5 Best practices for enterprise applications 113
5.1 The benefits of sharing—and how to achieve them in your
bundles 114
Versioning bundles and packages 115 ■ Scoping your
bundles 116 ■ Why isolation is important to sharing 123
5.2 Structuring for flexibility 124
Separate interfaces from implementation 124 ■ If you can’t
separate out your API 124 ■ Avoid static factory classes 125
Building a better listener with the whiteboard pattern 126
5.3 A better enterprise application architecture 127
Use small WABs 128 ■ Make a persistence bundle 128
The rewards of well-written bundles 131
5.4 Summary 131
6 Building dynamic applications with OSGi services 132
6.1 OSGi dynamism 133
6.2 Using OSGi services 134
Registering and looking up services the old-fashioned way 135
Blueprint 138 ■ Declarative Services 138 ■ iPojo 141
Google Guice and Peaberry 141
6.3 Getting the most out of Blueprint 142
Using Blueprint for things other than services 142 ■ Values 143
Understanding bean scopes 144 ■ Constructing beans 146
Lifecycle callbacks 147 ■ Service ranking 149 ■ Registering
services under multiple interfaces 149
6.4 Blueprint and service dynamism 150
The remarkable appearing and disappearing services 150
Multiplicity and optionality 156 ■ Monitoring the lifecycle 160
6.5 Summary 163
7 Provisioning and resolution 164
7.1 Describing OSGi bundles 165
Describing bundles as resources 165 ■ Requirements and capabilities 167
Directives affecting the resolver 168 ■ Repositories 172
7.2 Provisioning bundles 174
Package-based provisioning 174 ■ Service-based provisioning 179