The document discusses various aspects of Contexts and Dependency Injection (CDI) in Java EE, including how to use @Inject for dependency injection, qualifiers to select specific implementations, producers to provide dependencies, and events to communicate between components in a loosely coupled way. It also demonstrates CDI concepts like qualifiers, producers, scopes, and alternatives through examples.

1. CDI : How do I ?
by antonio goncalves
@agoncal

2. 2@agoncal
Antonio Goncalves

3. What is CDI ?

4. 4@agoncal
What is CDI ?
● Dependency injection
● Lose coupling, strong typing
● Context management
● Interceptors and decorators
● Event bus
● Extensions

5. 5@agoncal
History of CDI

6. 6@agoncal
Implementations

7. Demo
-
Creating a Web App

8. 8@agoncal
Demos with JBoss Forge
● Java EE scaffolding tool
● Shell commands
● CRUD application
● Gets you start quickly
● Takes care of integration
● Plugin based

9. 9@agoncal
Demo: Creating a Web App

10. Dependency Injection

11. 11@agoncal
How Do I ?

12. 12@agoncal
Use @Inject !

13. 13@agoncal
@Inject on Attributes
public class BookBean implements Serializable {
@Inject
private NumberGenerator numberGenerator;
@Inject
private ItemService itemService;
// ...
}

14. 14@agoncal
@Inject on Constructor
public class BookBean implements Serializable {
private NumberGenerator numberGenerator;
private ItemService itemService;
@Inject
public BookBean(NumberGenerator numberGenerator,
ItemService srv){
this.numberGenerator = numberGenerator;
this.itemService = srv;
}
// ...
}

15. 15@agoncal
@Inject on Setters
public class BookBean implements Serializable {
private NumberGenerator numberGenerator;
private ItemService itemService;
@Inject
public void setNumberGenerator(NumberGenerator numGen){
this.numberGenerator = numGen;
}
@Inject
public void setItemService(ItemService itemService) {
this.itemService = itemService;
}
// ...
}

16. 16@agoncal
Activate CDI
● In CDI 1.0 beans.xml in archive
● Since CDI 1.1 it's activated by default
●
All classes having a bean definition annotation
● beans.xml to deactivate or activate all
●
Archive vs Bean archive

17. Demo
-
@Inject

18. 18@agoncal
Demo: @Inject One Implementation

19. Qualifiers

20. 20@agoncal
How Do I ?

21. 21@agoncal
How Do I ?

22. 22@agoncal
How Do I ?
@Default

23. 23@agoncal
Use Qualifiers !
@ThirteenDigits

24. 24@agoncal
Use Qualifiers !
@EightDigits

25. 25@agoncal
A Qualifier
@Qualifier
@Retention(RUNTIME)
@Target({ METHOD, FIELD, PARAMETER, TYPE })
@Documented
public @interface ThirteenDigits {
}

26. 26@agoncal
Qualifying an Injection Point
public class BookBean implements Serializable {
@Inject @ThirteenDigits
private NumberGenerator numberGenerator;
@Inject
private ItemService itemService;
// ...
}

27. 27@agoncal
Qualifying an Injection Point
public class BookBean implements Serializable {
@Inject @ThirteenDigits
private NumberGenerator numberGenerator;
@Inject @Default
private ItemService itemService;
// ...
}

28. 28@agoncal
Qualifying a Bean
@ThirteenDigits
public class IsbnGenerator implements NumberGenerator {
@Override
public String generateNumber() {
return "13-" + Math.abs(new Random().nextInt());
}
}

29. Demo
-
Qualifiers

30. 30@agoncal
Demo: @Inject One Implementation

31. Producers

32. 32@agoncal
How Do I ?
public class BookBean implements Serializable {
@Inject
private EntityManager em;
@Inject
private Logger logger;
// ...
}

33. 33@agoncal
How Do I ?
public class BookBean implements Serializable {
@Inject
private EntityManager em;
@Inject
private Logger logger;
// ...
}

34. 34@agoncal
How Do I ?
public class BookBean implements Serializable {
@Inject
private EntityManager em;
@Inject
private Logger logger;
// ...
}
Several persistence units
@PersistenceContext(unitName = "myPU1")
@PersistenceContext(unitName = "myPU2")

35. 35@agoncal
How Do I ?
public class BookBean implements Serializable {
@Inject
private EntityManager em;
@Inject
private Logger logger;
// ...
}
Third party framewok

36. 36@agoncal
Use Producers !
public class BookBean implements Serializable {
@Inject
private EntityManager em;
// ...
}
public class ResourceProducer {
@Produces
@PersistenceContext(unitName = "myPU")
private EntityManager entityManager;
}

37. 37@agoncal
Use Producers !
public class BookBean implements Serializable {
@Inject
private Logger logger;
// ...
}
public class ResourceProducer {
@Produces
private Logger produceLogger(InjectionPoint ip) {
return
Logger.getLogger(ip.getMember().getDeclaringClass().getName());
}
}

38. Demo
-
Producers

39. 39@agoncal
Demo: Producers

40. Web tier
&
Service tier

41. 41@agoncal
How Do I ?

42. 42@agoncal
How Do I ?

43. 43@agoncal
Use Expression Language...

44. 44@agoncal
Use Expression Language and Scopes !

45. 45@agoncal
Service Tier
@Transactional
public class BookBean implements Serializable {
@Inject
private EntityManager em;
public void update() {
em.persist(book);
}
}

46. 46@agoncal
Service Tier + Web Tier
@Named
@Transactional
public class BookBean implements Serializable {
@Inject
private EntityManager em;
public void update() {
em.persist(book);
}
}
<h:commandLink value="Create"
action='#{bookBean.update}'/>

47. 47@agoncal
Service Tier + Web Tier
@Named("service")
@Transactional
public class BookBean implements Serializable {
@Inject
private EntityManager em;
public void update() {
em.persist(book);
}
}
<h:commandLink value="Create"
action='#{service.update}'/>

48. 48@agoncal
Several scopes
● @Dependent (default)
● @ApplicationScoped, @SessionScoped,
@RequestScoped
● @ConversationScoped
● Create your own
● @TransactionalScoped
● @ViewScoped
● @ThreadScoped
● @ClusterScoped

49. 49@agoncal
Just choose the right scope
@Named
@RequestScoped
@Transactional
public class BookBean implements Serializable {
public void update() {
}
public void delete() {
}
}

50. 50@agoncal
Just choose the right scope
@Named
@SessionScoped
@Transactional
public class BookBean implements Serializable {
public void update() {
}
public void delete() {
}
}

51. 51@agoncal
Just choose the right scope
@Named
@ConversationScoped
@Transactional
public class BookBean implements Serializable {
@Inject
private Conversation conversation;
public void update() {
conversation.begin();
}
public void delete() {
conversation.end();
}
}

52. Demo
-
@Named & scope

53. 53@agoncal
Demo: @Named & Scope

54. </>

55. Alternatives

56. 56@agoncal
How Do I ?
public class MockGenerator implements NumberGenerator {
public String generateNumber() {
return "mock-" + Math.abs(new Random().nextInt());
}
}

57. 57@agoncal
How Do I ?
@Mock
public class MockGenerator implements NumberGenerator {
public String generateNumber() {
return "mock-" + Math.abs(new Random().nextInt());
}
}
public class BookBean implements Serializable {
@Inject @Mock
private NumberGenerator numberGenerator;
// ...
}

58. 58@agoncal
How Do I ?
@Mock
public class MockGenerator implements NumberGenerator {
public String generateNumber() {
return "mock-" + Math.abs(new Random().nextInt());
}
}
public class BookBean implements Serializable {
@Inject @Mock
private NumberGenerator numberGenerator;
// ...
}

59. 59@agoncal
Use an Alternative !
@Alternative
@EightDigits
public class MockGenerator implements NumberGenerator {
public String generateNumber() {
return "mock-" + Math.abs(new Random().nextInt());
}
}
public class BookBean implements Serializable {
@Inject @EightDigits
private NumberGenerator numberGenerator;
// ...
}

60. 60@agoncal
Activate the Alternative
<beans xmlns="http://xmlns.jcp.org/xml/ns/javaee"
...
version="1.1" bean-discovery-mode="all">
<alternatives>
<class>com.foo.MockGenerator</class>
</alternatives>
</beans>

61. Demo
-
Alternatives

62. 62@agoncal
Demo: Alternatives

63. Events

64. 64@agoncal
How Do I ?

65. 65@agoncal
How Do I ?
Still too coupled

66. 66@agoncal
Use Events !





67. 67@agoncal
Fire and Observe
public class BookBean implements Serializable {
@Inject
private Event<Book> boughtEvent;
public void update() {
boughtEvent.fire(book);
}
}
public class InventoryService {
private void observeBooks (@Observes Book book) {
logger.info("Book recevied " + book.getTitle());
}
}

68. 68@agoncal
Fire and Observe with Qualifier
public class BookBean implements Serializable {
@Inject @Paper
private Event<Book> boughtEvent;
public void update() {
boughtEvent.fire(book);
}
}
public class InventoryService {
private void observeBooks (@Observes @Paper Book book) {
logger.info("Book recevied " + book.getTitle());
}
}

69. Demo
-
Events

70. 70@agoncal
Demo: Events

71. CDI : So Much More

72. 72@agoncal
CDI : So Much More

73. 73@agoncal
CDI Extension ecosystem

74. 74@agoncal
CDI Course on PluralSight
http://www.pluralsight.com/courses/context-dependency-injection-1-1

75. Thanks
www.antoniogoncalves.org
antonio.goncalves@gmail.com
@agoncal
@devoxxfr
@lescastcodeurs

76. Q & A

77. 77@agoncal
Creative Commons
● Attribution — You must attribute the work in
the manner specified by the author or licensor
(but not in any way that suggests that they
endorse you or your use of the work).
● Noncommercial — You may not use this work for
commercial purposes.
● Share Alike — If you alter, transform, or build
upon this work, you may distribute the resulting
work only under the same or similar license to
this one.

78. CDI : How do I ?
by antonio goncalves
@agoncal

79. 2@agoncal
Antonio Goncalves

80. What is CDI ?

81. 4@agoncal
What is CDI ?
●
Dependency injection
● Lose coupling, strong typing
●
Context management
●
Interceptors and decorators
● Event bus
●
Extensions

82. 5@agoncal
History of CDI

83. 6@agoncal
Implementations

84. Demo
-
Creating a Web App

85. 8@agoncal
Demos with JBoss Forge
●
Java EE scaffolding tool
● Shell commands
●
CRUD application
●
Gets you start quickly
● Takes care of integration
●
Plugin based

86. 9@agoncal
Demo: Creating a Web App

87. Dependency Injection

88. 11@agoncal
How Do I ?

89. 12@agoncal
Use @Inject !

90. 13@agoncal
@Inject on Attributes
public class BookBean implements Serializable {
@Inject
private NumberGenerator numberGenerator;
@Inject
private ItemService itemService;
// ...
}

91. 14@agoncal
@Inject on Constructor
public class BookBean implements Serializable {
private NumberGenerator numberGenerator;
private ItemService itemService;
@Inject
public BookBean(NumberGenerator numberGenerator,
ItemService srv){
this.numberGenerator = numberGenerator;
this.itemService = srv;
}
// ...
}

92. 15@agoncal
@Inject on Setters
public class BookBean implements Serializable {
private NumberGenerator numberGenerator;
private ItemService itemService;
@Inject
public void setNumberGenerator(NumberGenerator numGen){
this.numberGenerator = numGen;
}
@Inject
public void setItemService(ItemService itemService) {
this.itemService = itemService;
}
// ...
}

93. 16@agoncal
Activate CDI
● In CDI 1.0 beans.xml in archive
● Since CDI 1.1 it's activated by default
●
All classes having a bean definition annotation
● beans.xml to deactivate or activate all
●
Archive vs Bean archive

94. Demo
-
@Inject

95. 18@agoncal
Demo: @Inject One Implementation

96. Qualifiers

97. 20@agoncal
How Do I ?

98. 21@agoncal
How Do I ?

99. 22@agoncal
How Do I ?
@Default

100. 23@agoncal
Use Qualifiers !
@ThirteenDigits

101. 24@agoncal
Use Qualifiers !
@EightDigits

102. 25@agoncal
A Qualifier
@Qualifier
@Retention(RUNTIME)
@Target({ METHOD, FIELD, PARAMETER, TYPE })
@Documented
public @interface ThirteenDigits {
}

103. 26@agoncal
Qualifying an Injection Point
public class BookBean implements Serializable {
@Inject @ThirteenDigits
private NumberGenerator numberGenerator;
@Inject
private ItemService itemService;
// ...
}

104. 27@agoncal
Qualifying an Injection Point
public class BookBean implements Serializable {
@Inject @ThirteenDigits
private NumberGenerator numberGenerator;
@Inject @Default
private ItemService itemService;
// ...
}

105. 28@agoncal
Qualifying a Bean
@ThirteenDigits
public class IsbnGenerator implements NumberGenerator {
@Override
public String generateNumber() {
return "13-" + Math.abs(new Random().nextInt());
}
}

106. Demo
-
Qualifiers

107. 30@agoncal
Demo: @Inject One Implementation

108. Producers

109. 32@agoncal
How Do I ?
public class BookBean implements Serializable {
@Inject
private EntityManager em;
@Inject
private Logger logger;
// ...
}

110. 33@agoncal
How Do I ?
public class BookBean implements Serializable {
@Inject
private EntityManager em;
@Inject
private Logger logger;
// ...
}

111. 34@agoncal
How Do I ?
public class BookBean implements Serializable {
@Inject
private EntityManager em;
@Inject
private Logger logger;
// ...
}
Several persistence units
@PersistenceContext(unitName = "myPU1")
@PersistenceContext(unitName = "myPU2")

112. 35@agoncal
How Do I ?
public class BookBean implements Serializable {
@Inject
private EntityManager em;
@Inject
private Logger logger;
// ...
}
Third party framewok

113. 36@agoncal
Use Producers !
public class BookBean implements Serializable {
@Inject
private EntityManager em;
// ...
}
public class ResourceProducer {
@Produces
@PersistenceContext(unitName = "myPU")
private EntityManager entityManager;
}

114. 37@agoncal
Use Producers !
public class BookBean implements Serializable {
@Inject
private Logger logger;
// ...
}
public class ResourceProducer {
@Produces
private Logger produceLogger(InjectionPoint ip) {
return
Logger.getLogger(ip.getMember().getDeclaringClass().getName());
}
}

115. Demo
-
Producers

116. 39@agoncal
Demo: Producers

117. Web tier
&
Service tier

118. 41@agoncal
How Do I ?

119. 42@agoncal
How Do I ?

120. 43@agoncal
Use Expression Language...

121. 44@agoncal
Use Expression Language and Scopes !

122. 45@agoncal
Service Tier
@Transactional
public class BookBean implements Serializable {
@Inject
private EntityManager em;
public void update() {
em.persist(book);
}
}

123. 46@agoncal
Service Tier + Web Tier
@Named
@Transactional
public class BookBean implements Serializable {
@Inject
private EntityManager em;
public void update() {
em.persist(book);
}
}
<h:commandLink value="Create"
action='#{bookBean.update}'/>

124. 47@agoncal
Service Tier + Web Tier
@Named("service")
@Transactional
public class BookBean implements Serializable {
@Inject
private EntityManager em;
public void update() {
em.persist(book);
}
}
<h:commandLink value="Create"
action='#{service.update}'/>

125. 48@agoncal
Several scopes
● @Dependent (default)
● @ApplicationScoped, @SessionScoped,
@RequestScoped
● @ConversationScoped
● Create your own
● @TransactionalScoped
● @ViewScoped
● @ThreadScoped
● @ClusterScoped

126. 49@agoncal
Just choose the right scope
@Named
@RequestScoped
@Transactional
public class BookBean implements Serializable {
public void update() {
}
public void delete() {
}
}

127. 50@agoncal
Just choose the right scope
@Named
@SessionScoped
@Transactional
public class BookBean implements Serializable {
public void update() {
}
public void delete() {
}
}

128. 51@agoncal
Just choose the right scope
@Named
@ConversationScoped
@Transactional
public class BookBean implements Serializable {
@Inject
private Conversation conversation;
public void update() {
conversation.begin();
}
public void delete() {
conversation.end();
}
}

129. Demo
-
@Named & scope

130. 53@agoncal
Demo: @Named & Scope

131. </>

132. Alternatives

133. 56@agoncal
How Do I ?
public class MockGenerator implements NumberGenerator {
public String generateNumber() {
return "mock-" + Math.abs(new Random().nextInt());
}
}

134. 57@agoncal
How Do I ?
@Mock
public class MockGenerator implements NumberGenerator {
public String generateNumber() {
return "mock-" + Math.abs(new Random().nextInt());
}
}
public class BookBean implements Serializable {
@Inject @Mock
private NumberGenerator numberGenerator;
// ...
}

135. 58@agoncal
How Do I ?
@Mock
public class MockGenerator implements NumberGenerator {
public String generateNumber() {
return "mock-" + Math.abs(new Random().nextInt());
}
}
public class BookBean implements Serializable {
@Inject @Mock
private NumberGenerator numberGenerator;
// ...
}

136. 59@agoncal
Use an Alternative !
@Alternative
@EightDigits
public class MockGenerator implements NumberGenerator {
public String generateNumber() {
return "mock-" + Math.abs(new Random().nextInt());
}
}
public class BookBean implements Serializable {
@Inject @EightDigits
private NumberGenerator numberGenerator;
// ...
}

137. 60@agoncal
Activate the Alternative
<beans xmlns="http://xmlns.jcp.org/xml/ns/javaee"
...
version="1.1" bean-discovery-mode="all">
<alternatives>
<class>com.foo.MockGenerator</class>
</alternatives>
</beans>

138. Demo
-
Alternatives

139. 62@agoncal
Demo: Alternatives

140. Events

141. 64@agoncal
How Do I ?

142. 65@agoncal
How Do I ?
Still too coupled

143. 66@agoncal
Use Events !





144. 67@agoncal
Fire and Observe
public class BookBean implements Serializable {
@Inject
private Event<Book> boughtEvent;
public void update() {
boughtEvent.fire(book);
}
}
public class InventoryService {
private void observeBooks (@Observes Book book) {
logger.info("Book recevied " + book.getTitle());
}
}

145. 68@agoncal
Fire and Observe with Qualifier
public class BookBean implements Serializable {
@Inject @Paper
private Event<Book> boughtEvent;
public void update() {
boughtEvent.fire(book);
}
}
public class InventoryService {
private void observeBooks (@Observes @Paper Book book) {
logger.info("Book recevied " + book.getTitle());
}
}

146. Demo
-
Events

147. 70@agoncal
Demo: Events

148. CDI : So Much More

149. 72@agoncal
CDI : So Much More

150. 73@agoncal
CDI Extension ecosystem

151. 74@agoncal
CDI Course on PluralSight
http://www.pluralsight.com/courses/context-dependency-injection-1-1

152. Thanks
www.antoniogoncalves.org
antonio.goncalves@gmail.com
@agoncal
@devoxxfr
@lescastcodeurs

153. Q & A

154. 77@agoncal
Creative Commons
● Attribution — You must attribute the work in
the manner specified by the author or licensor
(but not in any way that suggests that they
endorse you or your use of the work).
●
Noncommercial — You may not use this work for
commercial purposes.
● Share Alike — If you alter, transform, or build
upon this work, you may distribute the resulting
work only under the same or similar license to
this one.