This presentation shows you how to do dependency injection with CDI (Context & Dependency Injection)

1. To inject or not to inject : CDI is the question by a ntonio g oncalves

2. Welcome to a type-safe injection journey

4. Author (Java EE 5 and Java EE 6)

5. JCP expert member (Java EE 6, Java EE 7)

6. Co-leader of the Paris JUG

7. Les Cast Codeurs podcast

8. Java Champion

10. Dependency Injection

11. @Inject & CDI

12. And that's it

15. lifecycle

17. ...not the component itself

18. It brings loose coupling

19. Own deps Own config Own lifecycle Dependencies injected Config injected Lifecycle Managed from outside

20. Own deps Own config Own lifecycle Dependencies injected Config injected Lifecycle Managed from outside

21. Own deps Own config Own lifecycle Dependencies injected Config injected Lifecycle Managed from outside

22. Example of dependency

23. The good old new public class ItemService { private IsbnGenerator isbnGenerator ; public ItemService() { this. isbnGenerator = new IsbnGenerator() ; } public Book createBook(Book book) { ... book.setIsbn( isbnGenerator .generateNumber()); } }

26. Creating an instance, opening, closing

29. How to choose implementation?

30. Constructor (or setter) injection public class ItemService { private NumberGenerator numberGenerator ; public ItemService(NumberGenerator numberGenerator ) { this.numberGenerator = numberGenerator ; } public Book createBook(Book book) { ... book.setIsbn( numberGenerator .generateNumber()); } }

31. With the good old new again // With constructor injection ItemService itemService = new ItemService( new IsbnGenerator() ); ItemService itemService = new ItemService( new IssnGenerator() ); // With setter injection ItemService itemService = new ItemService(); itemService.setNumberGenerator( new IsbnGenerator() ); itemService.setNumberGenerator( new IssnGenerator() );

33. Factory design pattern (GoF)

35. java.util.Arrays#asList()

36. java.sql.DriverManager#getConnection()

37. java.lang.Class#newInstance()

38. java.lang.Integer#valueOf()

39. With a Factory public class ItemServiceFactory { public ItemService newIsbnGenerator() { return new ItemService( new IsbnGenerator() ); } public ItemService newIssnGenerator() { return new ItemService( new IssnGenerator() ); } } // Client ItemService itemService = new ItemServiceFactory(). newIsbnGenerator ();

41. Used to find services

42. May reside in the same application, machine or network

43. JNDI is a perfect service locator ItemService itemService = new ServiceLocator() .get(” IsbnGeneratorService ”);

44. All that is constructing by hand // new() public ItemService() { this. isbnGenerator = new IsbnGenerator() ; } // Factory ItemService itemService = new ItemServiceFactory(). newIsbnGenerator (); // Service locator ItemService itemService = new ServiceLocator() .get(” IsbnGeneratorService ”);

46. Creating, assembling and wiring done by an external framework with Provides

48. Spring framework

49. Pico container

50. Nano container

51. Apache Hivemind

52. Seam

53. Google Guice

54. Contexts and Dependency Injection (CDI)

55. A bit of history May 1998 Project JPE Dec 1999 J2EE 1.2 Servlet/JSP EJB JMS RMI/IIOP Sept 2001 J2EE 1.3 CMP JCA Nov 2003 J2EE 1.4 WS Management Deployment May 2006 Java EE 5 Annotations EJB 3 JPA 1.0 WS-* JSF Q4 2009 Java EE 6 EJB 3.1 JPA 2.0 Servlet 3.0 JSF 2.0 JAX-RS 1.1 CDI 1.0 @Inject Bean Validat° Web Profile Managed Bean Resource injection Dependency injection

59. … and even outside Java EE

60. EE 5 resource injection @EJB @EJB @EJB @Resource @PersistenceContext

61. EE 6 dependency injection @Inject @Inject @Inject @Inject @Inject @Inject @Inject @Resource @PersistenceContext @Inject

63. JSR 330

64. javax.inject

65. @Inject

66. @Named

67. @Singleton

68. @Qualifier

70. JSR 299

71. javax.enterprise.context

72. Alternatives

73. Producers

74. Scopes & context

75. Stereotypes

76. Decorators, Events

77. Extensions

78. Injection with @Inject

79. @Inject @WebServlet(urlPatterns = "/itemServlet") public class ItemServlet extends HttpServlet { @Inject private IsbnGenerator numberGenerator; ... book.setIsbn( isbnGenerator.generateNumber() ); } public class IsbnGenerator { public String generateNumber () { return "13-84356-" + nextNumber()); } } Injection point POJO Servlet

81. CDI

83. WEB-INF

84. @Inject @WebServlet(urlPatterns = "/itemServlet") public class ItemServlet extends HttpServlet { @Inject private IsbnGenerator numberGenerator; ... book.setIsbn(isbnGenerator.generateNumber()); } public class IsbnGenerator { public String generateNumber () { return "13-84356-" + nextNumber()); } }

85. @Default @Inject @WebServlet(urlPatterns = "/itemServlet") public class ItemServlet extends HttpServlet { @Inject @Default private IsbnGenerator numberGenerator; ... book.setIsbn(isbnGenerator.generateNumber()); } @Default public class IsbnGenerator { public String generateNumber () { return "13-84356-" + nextNumber()); } } Every bean has a @Default qualifier Every injection point has a @Default qualifier

86. Use your own qualifier @WebServlet(urlPatterns = "/itemServlet") public class ItemServlet extends HttpServlet { @Inject @MyOwnQualifier private IsbnGenerator numberGenerator; ... book.setIsbn(isbnGenerator.generateNumber()); } @MyOwnQualifier public class IsbnGenerator { public String generateNumber () { return "13-84356-" + nextNumber()); } }

87. @MyOwnQualifier @Qualifier @Retention(RUNTIME) @Target({FIELD, TYPE, METHOD, PARAMETER}) public @interface MyOwnQualifier { }

88. Ambiguous injection

89. Non ambiguous injection

90. Defining the qualifiers @Qualifier @Retention(RUNTIME) @Target({FIELD, TYPE, METHOD, PARAMETER}) public @interface EightDigits { } @Qualifier @Retention(RUNTIME) @Target({FIELD, TYPE, METHOD, PARAMETER}) public @interface ThirteenDigits { }

91. Defining the beans @EightDigits public class IssnGenerator implements NumberGenerator { public String generateNumber() { return "8-" + nextNumber(); } } @ThirteenDigits public class IsbnGenerator implements NumberGenerator { public String generateNumber() { return "13-84356-" + nextNumber(); } }

92. Injection points @Path ("/items") @ManagedBean public class ItemRestService { @Inject @EightDigits private NumberGenerator numberGenerator; ... } @WebServlet (urlPatterns = "/itemServlet") public class ItemServlet extends HttpServlet { @Inject @ThirteenDigits private NumberGenerator numberGenerator; ... } Strong typing No strings Loose coupling No reference to the implementation

94. 13, 8 digits but also 3, 7, 16, 19, 22, 26...

95. Use qualifiers with enumerations

96. Defining the qualifier & enum @Qualifier @Retention(RUNTIME) @Target({FIELD, TYPE, METHOD, PARAMETER}) public @interface NumberOfDigits { Digits value(); } public enum Digits { TWO, EIGHT, TEN, THIRTEEN }

97. Defining the beans @NumberOfDigits(Digits.EIGHT) public class IssnGenerator implements NumberGenerator { public String generateNumber() { return "8-" + nextNumber(); } } @NumberOfDigits(Digits.THIRTEEN) public class IsbnGenerator implements NumberGenerator { public String generateNumber() { return "13-84356-" + nextNumber(); } }

98. Injection points @Path("/items") @ManagedBean public class ItemRestService { @Inject @NumberOfDigits(Digits.EIGHT) private NumberGenerator numberGenerator; ... } @WebServlet(urlPatterns = "/itemServlet") public class ItemServlet extends HttpServlet { @Inject @NumberOfDigits(Digits.THIRTEEN) private NumberGenerator numberGenerator; ... }

100. Constructor

101. Setter

102. Field injection @WebServlet(urlPatterns = "/itemServlet") public class ItemServlet extends HttpServlet { @Inject @ThirteenDigits private NumberGenerator numberGenerator; @Inject private ItemEJB itemEJB; ... }

103. Constructor injection @WebServlet(urlPatterns = "/itemServlet") public class ItemServlet extends HttpServlet { private NumberGenerator numberGenerator; private ItemEJB itemEJB; @Inject public ItemServlet( @ThirteenDigits NumberGenerator numberGenerator, ItemEJB itemEJB) { this.numberGenerator = numberGenerator; this.itemEJB = itemEJB; } ... }

104. Setter injection @WebServlet(urlPatterns = "/itemServlet") public class ItemServlet extends HttpServlet { private NumberGenerator numberGenerator; private ItemEJB itemEJB; @Inject public void setNumberGenerator( @ThirteenDigits NumberGenerator numberGenerator) { this.numberGenerator = numberGenerator; } @Inject public void setItemEJB(ItemEJB itemEJB) { this.itemEJB = itemEJB; } }

108. Have you seen any XML so far ?

110. Vary at deployment time

111. By default, alternative beans are disabled

112. Enable them with beans.xml file

113. Alternative to @ThirteenDigits @Alternative @ThirteenDigits public class MockGenerator implements NumberGenerator { public String generateNumber() { return "MOCK-" + nextNumber(); } }

114. Alternative to both @Alternative @ThirteenDigits @EightDigits public class MockGenerator implements NumberGenerator { public String generateNumber() { return "MOCK-" + nextNumber(); } } @Inject @ThirteenDigits private NumberGenerator numberGenerator;

115. beans.xml <?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?> <beans xmlns=&quot;http://java.sun.com/xml/ns/javaee&quot; xmlns:xsi=&quot;http://www.w3.org/2001/XMLSchema-instance&quot; xsi:schemaLocation=&quot; http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/beans_1_0.xsd&quot;> <alternatives> <class>org.agoncal.cdi.MockGenerator</class> </alternatives> </beans>

116. Does this look too verbose ? @Alternative @ThirteenDigits @EightDigits public class MockGenerator implements NumberGenerator { public String generateNumber() { return &quot;MOCK-&quot; + nextNumber(); } }

117. Use stereotypes @MyMock public class MockGenerator implements NumberGenerator { public String generateNumber() { return &quot;MOCK-&quot; + nextNumber(); } } @Stereotype @Retention(RUNTIME) @Target(TYPE) @Alternative @ThirteenDigits @EightDigits public @interface MyMock {}

121. So, we only inject beans ?

123. expose any JDK class as a bean

124. Produce an injectable String public class PrefixGenerator { @Produces @ThirteenDigits public String getIsbnPrefix() { return &quot;13-84356&quot;; } @Produces @EightDigits public String getIssnPrefix() { return &quot;8&quot;; } }

125. Inject the produced String @ThirteenDigits public class IsbnGenerator implements NumberGenerator { @Inject @ThirteenDigits private String prefix ; public String generateNumber() { return prefix + &quot;-&quot; + nextNumber(); } } Bean String

127. a Principal for the current caller identity

128. default Bean Validation ValidationFactory

130. Produce an EntityManager public class DatabaseProducer { @Produces @PersistenceContext(unitName = &quot;cdiPU&quot;) @BookStoreDatabase private EntityManager em; } @Stateless public class ItemEJB { @Inject @BookStoreDatabase private EntityManager em; ... }

131. Produce a FacesContext public class FacesContextProducer { @Produces @RequestScoped FacesContext getFacesContext() { return FacesContext.getCurrentInstance(); } }

132. Produce JMS endpoints public class OrderResources { @Resource (name = &quot;jms/ConnectionFactory&quot;) private ConnectionFactory connectionFactory; @Resource (name = &quot;jms/OrderQueue&quot;) private Queue orderQueue; @Produces @OrderConnection public Connection createOrderConnection() { return connectionFactory.createConnection(); } @Produces @OrderSession public Session createOrderSession( @OrderConnection Connection conn){ return conn.createSession(true, Session.AUTO_ACKNOWLEDGE); } ... }

133. Consume JMS endpoints @Inject @OrderSession QueueSession orderSession; public void sendMessage() { MapMessage msg = orderSession .createMapMessage(); msg.setLong(&quot;orderId&quot;, order.getId()); ... producer.send(msg); }

134. Can I use all that from a JSF page ?

136. Gives it a name (a String)

137. Most commonly from a JSF view

138. Non type safe dependency injection

139. Any bean can be named

140. Do we still need JSF managed beans ?

141. Default name @Named public class IsbnGenerator { public String generateNumber() { return &quot;13-84356-&quot; + nextNumber(); } } <h:outputLabel value=&quot; #{isbnGenerator.generateNumber} &quot;/>

142. A different name @Named(&quot; generator &quot;) public class IsbnGenerator { public String generateNumber() { return &quot;13-84356-&quot; + nextNumber(); } } <h:outputLabel value=&quot;#{ generator .generateNumber}&quot;/>

143. Mix a producer and a default name public class IsbnGenerator { @Produces @Named public String generateNumber() { return &quot;13-84356-&quot; + nextNumber(); } } <h:outputLabel value=&quot;#{ generateNumber }&quot;/>

144. Mix a producer and a name public class IsbnGenerator { @Produces @Named(&quot; isbnNumber &quot;) public String generateNumber() { return &quot;13-84356-&quot; + nextNumber(); } } <h:outputLabel value=&quot;#{ isbnNumber }&quot;/>

145. How can I have all these goodies ?

147. Bootstrap CDI in several environments

149. Tomcat 6.x / 7.x

151. Spring 3.x

153. Only DI is supported (JSR 330)

154. Not CDI (JSR 299)

155. You can replace @Autowired with @Inject

157. Open WebBeans (Apache)

158. CanDI (Caucho)

160. Decorators

161. Events

164. It's type-safe

165. It's extensible

168. Static injection

169. Better support for CDI in certain EE components

170. Application lifecycle events

171. ...

173. Second edition

175. Most specs

176. Hands on labs

177. Contact me

178. Thanks www.antoniogoncalves.org [email_address] @agoncal @lescastcodeurs

180. Noncommercial — You may not use this work for commercial purposes.

181. 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.