Today, server app developers declare their components using a mixture of technologies that includes atlassian-plugin.xml, Spring XML files, and Spring Scanner. This fragmented approach comes with its own learning curve and an array of pitfalls. In this talk, Andrew Swan from Atlassian's Server Java Platform team will describe how server app developers can declare their Spring components in pure Java code. This approach is cleaner, more powerful, more flexible, easier to reason about, and more industry-standard. Attendees will also learn about a new Atlassian library that facilitates this approach by providing easy importing and exporting of OSGi services. Attendees will come away being immediately able to start using Java-based configuration in their server apps. Links to documentation and working sample code will be provided.

1. ANDREW SWAN | SENIOR DEVELOPER | ATLASSIAN | @ANDREWSWAN_AU
Declaring
Server App Components
in Pure Java

2. Back-end
developers of
Server apps (P2
plugins)
INTENDED AUDIENCE

3. About me

4. About me
6 Year Atlassian

5. About me
6 Year Atlassian 1st Atlas Camp!

6. About me
6 Year Atlassian Sydney, Australia1st Atlas Camp!

7. About me
6 Year Atlassian Sydney, Australia Server Java
Platform team
1st Atlas Camp!

8. Agenda
What are components?
Current technologies
Spring Java config
Using Java config in Server apps
Resources

9. What are components?

10. What are components?
All Server products support
apps
P2 plugins

11. What are components?
All Server products support
apps
P2 plugins
Apps are made up of
components
Spring beans

12. What are components?
Some components are
internal to the app
Optionally exported to OSGi
All Server products support
apps
P2 plugins
Apps are made up of
components
Spring beans

13. What are components?
Some components are
internal to the app
Optionally exported to OSGi
Some components are
external to the app
Imported via OSGi from product or
other apps
All Server products support
apps
P2 plugins
Apps are made up of
components
Spring beans

14. Product

15. Product
OSGi container

16. Product
OSGi container
OSGi Service Registry

17. Product
OSGi container
OSGi Service Registry
System bundle (0)
(core product)

18. Product
OSGi container
OSGi Service Registry
App 1 App 2..nSystem bundle (0)
(core product)

19. Product
OSGi container
OSGi Service Registry
App 1 App 2..n
Spring Spring
System bundle (0)
(core product)

20. Product
OSGi container
OSGi Service Registry
App 1 App 2..n
Spring Spring
System bundle (0)
(core product)
A

21. Product
OSGi container
OSGi Service Registry
App 1 App 2..n
Spring Spring
System bundle (0)
(core product)
A
B

22. Product
OSGi container
OSGi Service Registry
App 1 App 2..n
Spring Spring
System bundle (0)
(core product)
A
B` B

23. Product
OSGi container
OSGi Service Registry
App 1 App 2..n
Spring Spring
System bundle (0)
(core product)
A
C
B` B

24. Agenda
What are components?
Current technologies
Spring Java config
Using Java config in Server apps
Resources

25. Current technology 1
Plugin XML
(c. 2004)

26. Plugin XML
How
Cons

27. Plugin XML
How
Cons
Internal components
<component key=“…” class=“…”>

28. Plugin XML
How
Cons
Internal components
<component key=“…” class=“…”>
Exported components
<component key=“…” class=“…” public=“true”>

29. Plugin XML
How
Cons
Internal components
<component key=“…” class=“…”>
Exported components
<component key=“…” class=“…” public=“true”>
Imported components
<component-import key=“…”>
<interface class=“…”/>

30. Plugin XML
How
Cons
Internal components
<component key=“…” class=“…”>
Exported components
<component key=“…” class=“…” public=“true”>
Imported components
<component-import key=“…”>
<interface class=“…”/>
Module types (custom plugin points)
<module-type key=“…” class=“…”>

31. Plugin XML
How
Cons

32. Plugin XML
How
Cons
Runtime cost
Plugin system transforms your JAR to a Spring-powered
OSGi bundle

33. Plugin XML
How
Cons
Runtime cost
Plugin system transforms your JAR to a Spring-powered
OSGi bundle
Inflexible
Limited to a few XML elements & attributes; no support
for conditions; no control over autowiring

34. Plugin XML
How
Cons
Runtime cost
Plugin system transforms your JAR to a Spring-powered
OSGi bundle
Inflexible
Limited to a few XML elements & attributes; no support
for conditions; no control over autowiring
Unreliable
e.g. problems with Java 9 module-info.class files

35. Plugin XML
How
Cons
Runtime cost
Plugin system transforms your JAR to a Spring-powered
OSGi bundle
Inflexible
Limited to a few XML elements & attributes; no support
for conditions; no control over autowiring
Unreliable
e.g. problems with Java 9 module-info.class files
Poor tooling
No XML schema

36. Current technology 2
Spring Scanner
(c. 2013)

37. Spring
Scanner
How (1)
How (2)
Pros
Cons

38. Spring
Scanner
How (1)
How (2)
Pros
Cons
Internal components
@Component, @Named

39. Spring
Scanner
How (1)
How (2)
Pros
Cons
Internal components
@Component, @Named
Exported components
@ExportAsService

40. Spring
Scanner
How (1)
How (2)
Pros
Cons
Internal components
@Component, @Named
Exported components
@ExportAsService
Imported components
@ComponentImport

41. Spring
Scanner
How (1)
How (2)
Pros
Cons
Internal components
@Component, @Named
Exported components
@ExportAsService
Imported components
@ComponentImport
Module types (custom plugin points)
@ModuleType

42. Spring
Scanner
How (1)
How (2)
Pros
Cons

43. Spring
Scanner
How (1)
How (2)
Pros
Cons
1. Scan for annotations
@Component, @ComponentImport, etc.

44. Spring
Scanner
How (1)
How (2)
Pros
Cons
1. Scan for annotations
@Component, @ComponentImport, etc.
2. Generate “index” files
In META-INF/plugin-components

45. Spring
Scanner
How (1)
How (2)
Pros
Cons
1. Scan for annotations
@Component, @ComponentImport, etc.
2. Generate “index” files
In META-INF/plugin-components
3. Bundle index files into JAR
Using maven-resources-plugin

46. Spring
Scanner
How (1)
How (2)
Pros
Cons
1. Scan for annotations
@Component, @ComponentImport, etc.
2. Generate “index” files
In META-INF/plugin-components
3. Bundle index files into JAR
Using maven-resources-plugin
4. (runtime) Generate bean definitions
The scan-indexes element in Spring XML activates a
BeanFactoryPostProcessor

47. Spring
Scanner
How (1)
How (2)
Pros
Cons

48. Spring
Scanner
How (1)
How (2)
Pros
Cons
No transformation
Maven build generates a valid OSGi bundle

49. Spring
Scanner
How (1)
How (2)
Pros
Cons
No transformation
Maven build generates a valid OSGi bundle
Less XML
Plugin XML no longer defines components

50. Spring
Scanner
How (1)
How (2)
Pros
Cons

51. Spring
Scanner
How (1)
How (2)
Pros
Cons
Long toolchain
Several places where things can go wrong

52. Spring
Scanner
How (1)
How (2)
Pros
Cons
Long toolchain
Several places where things can go wrong
No good place for @ComponentImport
Separate wiring class, or per parameter?

53. Spring
Scanner
How (1)
How (2)
Pros
Cons
Long toolchain
Several places where things can go wrong
No good place for @ComponentImport
Separate wiring class, or per parameter?
Clashes between imported services
e.g. Jira’s vs SAL’s ApplicationProperties

54. Spring
Scanner
How (1)
How (2)
Pros
Cons
Long toolchain
Several places where things can go wrong
No good place for @ComponentImport
Separate wiring class, or per parameter?
Clashes between imported services
e.g. Jira’s vs SAL’s ApplicationProperties
DI concerns leak into production code
All components require annotations

55. Spring
Scanner
How (1)
How (2)
Pros
Cons
Long toolchain
Several places where things can go wrong
No good place for @ComponentImport
Separate wiring class, or per parameter?
Clashes between imported services
e.g. Jira’s vs SAL’s ApplicationProperties
DI concerns leak into production code
All components require annotations
Atlassian-specific
New hires require special training

56. Current technology 3
Spring XML
(c. 2002)

57. Spring
XML
How
Pros
Cons

58. Spring
XML
How
Pros
Add <bean> elements
Any XML file in META-INF/spring
Cons

59. Spring
XML
How
Pros
Add <bean> elements
Any XML file in META-INF/spring
Cons
Use osgi namespace
Import and export services

60. Spring
XML
How
Pros
Cons

61. Spring
XML
How
Pros
Cohesive
All DI concerns in one place
Cons

62. Spring
XML
How
Pros
Cohesive
All DI concerns in one place
Cons
Tool support
Most IDEs understand Spring XML

63. Spring
XML
How
Pros
Cons

64. Spring
XML
How
Pros
Inflexible
Limited to what the schemas allow
Cons

65. Spring
XML
How
Pros
Inflexible
Limited to what the schemas allow
Limited reuse
Importing is the only way to compose XML files
Cons

66. Spring
XML
How
Pros
Inflexible
Limited to what the schemas allow
Limited reuse
Importing is the only way to compose XML files
Cons
Slow dev loop
Errors only apparent at runtime

67. Agenda
What are components?
Current technologies
Spring Java config
Using Java config in Server apps
Resources

68. Spring Java config
(c. 2009)

69. Spring
Java config
How
Pros
Cons

70. Spring
Java config
How
Pros
Define @Configuration classes
Anywhere in your project.
Cons

71. Spring
Java config
How
Pros
Define @Configuration classes
Anywhere in your project.
Cons
Define @Bean methods
In your @Configuration classes.

72. Spring
Java config
How
Pros
Define @Configuration classes
Anywhere in your project.
Cons
Define @Bean methods
In your @Configuration classes.
Compose @Configuration classes
Use normal patterns or @Import.

73. Spring
Java config
How
Pros
Define @Configuration classes
Anywhere in your project.
Cons
Define @Bean methods
In your @Configuration classes.
Compose @Configuration classes
Use normal patterns or @Import.
Apply @Conditional annotations
To turn beans on/off.

74. Spring Java config - examples (1)

75. @Configuration
public class MySpringBeans {
@Bean
public FooService fooService() {
return new FooServiceImpl();
}
}
Spring Java config - examples (1)

76. @Bean
@Conditional(MyCondition.class)
public FooService fooService() {
return new FooServiceImpl();
}
Spring Java config - examples (2)

77. @Bean
@Conditional(MyCondition.class)
public FooService fooService() {
return new FooServiceImpl();
}
Spring Java config - examples (2)
public class MyCondition implements Condition {
public boolean matches(ConditionContext context,
AnnotatedTypeMetadata annotatedType) {
return true;
}
}

78. Spring Java config - examples (3)
@Bean
public FooService fooService1() {
return new FooServiceImpl(bazService()); // method style
}

79. @Bean
public FooService fooService2(BazService bazService) {
return new FooServiceImpl(bazService); // param style
}
Spring Java config - examples (3)
@Bean
public FooService fooService1() {
return new FooServiceImpl(bazService()); // method style
}

80. Spring
Java config
How
Pros
Cons

81. Spring
Java config
How
Pros
It’s Java
Powerful, familiar, great tooling
Cons

82. Spring
Java config
How
Pros
It’s Java
Powerful, familiar, great tooling
Cons
Conditions
Great for cross-product or cross-version apps

83. Spring
Java config
How
Pros
It’s Java
Powerful, familiar, great tooling
Cons
Conditions
Great for cross-product or cross-version apps
Simple
Short toolchain

84. Spring
Java config
How
Pros
It’s Java
Powerful, familiar, great tooling
Cons
Conditions
Great for cross-product or cross-version apps
Simple
Short toolchain
Clean
No DI concerns in production code

85. Spring
Java config
How
Pros
Cons

86. Spring
Java config
How
Pros
More dependencies
… to manage
Cons

87. Spring
Java config
How
Pros
More dependencies
… to manage
Cons
It’s code
… so keep it under control

88. Spring
Java config
How
Pros
More dependencies
… to manage
Cons
It’s code
… so keep it under control
OSGi services require boilerplate
… but sit tight for an Atlas Camp exclusive!

89. Agenda
What are components?
Current technologies
Spring Java config
Using Java config in Server apps
Resources

90. Java config in
Server apps
Products
Dependencies
Spring Java config requires Spring 3.x →
Plugins 4.x → Platform 3.x:
◦ Bamboo >= 6.2
◦ Bitbucket >= 5.3
◦ Confluence >= 6.4
◦ Crowd >= 3.0
◦ Fecru >= 4.5
◦ Jira >= 7.5
Packages
Tips
Examples

91. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
Registering a config class

92. <context:annotation-config />
<bean class=“com.example.javaconfig.MyConfig” />
Registering a config class

93. <context:annotation-config />
<bean class=“com.example.javaconfig.MyConfig” />
Registering a config class
<context:component-scan base-package="com.example.javaconfig" />
or

94. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
Importing an OSGi service
Registering a config class

95. @Bean
public ApplicationProperties applicationProperties() {
return importOsgiService(ApplicationProperties.class);
}
Importing an OSGi service

96. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
Importing an OSGi service
Exporting a service to OSGi
Registering a config class

97. @Bean
public FooService fooService() {
return new FooServiceImpl();
}
Exporting a service to OSGi

98. @Bean
public FactoryBean<ServiceRegistration> exportFooService() {
Map<String, Object> serviceProps = …; // you decide
return exportOsgiService(
fooService(), serviceProps, FooService.class);
}
@Bean
public FooService fooService() {
return new FooServiceImpl();
}
Exporting a service to OSGi

99. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
Importing an OSGi service
Exporting a service to OSGi
Defining a module type
Registering a config class

100. @Bean
public ListableModuleDescriptorFactory
myModuleDescriptorFactory() {
return new MyModuleDescriptorFactory();
}
Defining a module type

101. @Bean
public ListableModuleDescriptorFactory
myModuleDescriptorFactory() {
return new MyModuleDescriptorFactory();
}
@Bean
public FactoryBean<ServiceRegistration> myModuleType() {
return exportAsModuleType(myModuleDescriptorFactory());
}
Defining a module type

102. Where do all
these helper
methods
come from?

103. Atlas Camp
2019
Exclusive!

104. <dependency>
<groupId>com.atlassian.plugins</…>
<artifactId>atlassian-plugins-osgi-javaconfig</…>
<version>0.1.1</…>
</dependency>
NEW JAVA CONFIG LIBRARY!

105. New Java
config library!
Helper methods
Conditions
Config classes
More

106. New Java
config library!
Helper methods
Conditions
Config classes
More
Import an OSGi service (or factory)

107. New Java
config library!
Helper methods
Conditions
Config classes
More
Import an OSGi service (or factory)
Export an OSGi service

108. New Java
config library!
Helper methods
Conditions
Config classes
More
Import an OSGi service (or factory)
Export an OSGi service
Define a module type

109. New Java
config library!
Helper methods
Conditions
Config classes
More

110. New Java
config library!
Helper methods
Conditions
Config classes
More
Host product
All the Server products, e.g. JiraOnly.class

111. New Java
config library!
Helper methods
Conditions
Config classes
More
Host product
All the Server products, e.g. JiraOnly.class
Any system property
Checks the system property of your choice

112. New Java
config library!
Helper methods
Conditions
Config classes
More
Host product
All the Server products, e.g. JiraOnly.class
Dev mode
Checks the atlassian.dev.mode system property
Any system property
Checks the system property of your choice

113. New Java
config library!
Helper methods
Conditions
Config classes
More
Prebuilt config classes with beans for:
◦ ModuleFactory
◦ PluginAccessor

114. New Java
config library!
Helper methods
Conditions
Config classes
More

115. New Java
config library!
Helper methods
Conditions
Config classes
More
Easier plugin points
Superclass for your ListableModuleDescriptorFactory

116. New Java
config library!
Helper methods
Conditions
Config classes
More
Easier plugin points
Superclass for your ListableModuleDescriptorFactory
Automatic package imports
… of packages required for Java Config

117. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
Spring:
◦ org.springframework:
◦ spring-beans
◦ spring-context
OSGi:
◦ org.apache.felix:
◦ org.apache.felix.framework
◦ com.atlassian.plugins:
◦ atlassian-plugins-osgi-javaconfig
NEW LIBRARY!
(OPTIONAL)

118. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
◦ org.springframework.cglib.core
◦ org.springframework.cglib.proxy
◦ org.springframework.cglib.reflect
◦
Import these packages from OSGi:
Tip: if you use our new library, BND will generate these for you.

119. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples

120. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
Keep it simple
No long classes/methods

121. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
Keep it simple
No long classes/methods
Be consistent
Choose params or method calls, and stick to it

122. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
Keep it simple
No long classes/methods
Be consistent
Choose params or method calls, and stick to it
Be aware
Spring turns your classes into bean definitions

123. Java config in
Server apps
Products
Dependencies
Packages
Tips
Examples
Keep it simple
No long classes/methods
Be consistent
Choose params or method calls, and stick to it
Be aware
Spring turns your classes into bean definitions
Be testable
Create seams in your config classes

124. Spring Java config - summary

125. Powerful
Java + conditions
Spring Java config - summary

126. Powerful
Java + conditions
Reliable
Short tool chain
Spring Java config - summary

127. Powerful
Java + conditions
Reliable
Short tool chain
Familiar
It’s Java!
Spring Java config - summary

128. Powerful
Java + conditions
Reliable
Short tool chain
Familiar
It’s Java!
Clean
All DI in one place
Spring Java config - summary

129. Agenda
What are components?
Current technologies
Spring Java config
Using Java config in Server apps
Resources

130. Sample P2 app (Bitbucket):
https://tinyurl.com/sjc-demo
Atlassian documentation (atlassian.com):
https://tinyurl.com/sjc-doco
Spring documentation (spring.io):
https://tinyurl.com/jc-docs
Spring Java config tutorial (YouTube):
https://tinyurl.com/jc-tutorial
Resources