My personal take on the Data, Context and Interaction best practice.

1. DCI
Data, Context and
Interaction
Fabrizio Giudici, Senior Java Architect
Tidalwave s.a.s - fabrizio.giudici@tidalwave.it
Wednesday, April 20, 2011 1

2. About the speaker
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3. About the speaker
• Senior Software Architect, Mentor, Technical Writer
• Fourteen years of Java experience (JSE, JEE, JME, etc...)
• Sun partner since 1998, Oracle consultant since 2010
• Author of a number of open source projects
• Speaker at JavaOne, Devoxx, Jazoon, JAX and other events
• Member of the NetBeans Dream Team
• Co-leader of JUG Milano
• Java.Net blogger at http://www.java.net/blogs/fabriziogiudici
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4. Agenda
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5. Agenda
• Two real world examples
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6. Agenda
• Two real world examples
• DCI - Basic concepts
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7. Agenda
• Two real world examples
• DCI - Basic concepts
• DCI - How to implement?
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8. Agenda
• Two real world examples
• DCI - Basic concepts
• DCI - How to implement?
• Some simple examples
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9. Agenda
• Two real world examples
• DCI - Basic concepts
• DCI - How to implement?
• Some simple examples
• Abstracting and sweetening
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10. Two real world
examples
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11. Shameless Plug
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12. Shameless Plug
• Exercises of Design - my design book...
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13. Shameless Plug
• Exercises of Design - my design book...
• Just started!
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14. Shameless Plug
• Exercises of Design - my design book...
• Just started!
• http://exercisesofdesign.java.net
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15. The Observation API
• A core component of blueBill Mobile
• An application about recording bird observations
• Designed with a high degree of abstraction
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16. The Observation API
• A core component of blueBill Mobile
• An application about recording bird observations
• Designed with a high degree of abstraction
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17. The Observation API
• A core component of blueBill Mobile
• An application about recording bird observations
• Designed with a high degree of abstraction
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18. DCI 7
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19. The Taxonomy API
• Models the taxonomy of a philogenetic tree
• The standard way of biology for representing living beings species
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20. DCI 9
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21. DCI - Basic Concepts
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22. Data, Context and Interaction
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23. Data, Context and Interaction
• OOD best practice invented by Trygve Reenskaug
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24. Data, Context and Interaction
• OOD best practice invented by Trygve Reenskaug
• The formalizer of MVC
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25. Data, Context and Interaction
• OOD best practice invented by Trygve Reenskaug
• The formalizer of MVC
• Seen as an evolution of MVC
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26. Data, Context and Interaction
• OOD best practice invented by Trygve Reenskaug
• The formalizer of MVC
• Seen as an evolution of MVC
• But it doesn’t replace it
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27. Data, Context and Interaction
• OOD best practice invented by Trygve Reenskaug
• The formalizer of MVC
• Seen as an evolution of MVC
• But it doesn’t replace it
• It rather broadens the analysis scope
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28. Data, Context and Interaction
• OOD best practice invented by Trygve Reenskaug
• The formalizer of MVC
• Seen as an evolution of MVC
• But it doesn’t replace it
• It rather broadens the analysis scope
• http://www.artima.com/articles/dci_vision.html
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29. DCI - aims
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30. DCI - aims
• Improve readability of a OO system
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31. DCI - aims
• Improve readability of a OO system
• Give system behaviour first-class status
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32. DCI - aims
• Improve readability of a OO system
• Give system behaviour first-class status
• Recover readability of system properties on the whole
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33. DCI - aims
• Improve readability of a OO system
• Give system behaviour first-class status
• Recover readability of system properties on the whole
• Separate responsibilities for behaviour and domain
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34. DCI - aims
• Improve readability of a OO system
• Give system behaviour first-class status
• Recover readability of system properties on the whole
• Separate responsibilities for behaviour and domain
• Behaviour: what the system does
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35. DCI - aims
• Improve readability of a OO system
• Give system behaviour first-class status
• Recover readability of system properties on the whole
• Separate responsibilities for behaviour and domain
• Behaviour: what the system does
• Domain: what the system is
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36. DCI - aims
• Improve readability of a OO system
• Give system behaviour first-class status
• Recover readability of system properties on the whole
• Separate responsibilities for behaviour and domain
• Behaviour: what the system does
• Domain: what the system is
• Be close to people’s mental model
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37. DCI - Data
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38. DCI - Data
• What the system is
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39. DCI - Data
• What the system is
• Relatively static with relations
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40. DCI - Data
• What the system is
• Relatively static with relations
• Domain structure implemented with “conventional” classes
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41. DCI - Data
• What the system is
• Relatively static with relations
• Domain structure implemented with “conventional” classes
• Typically it includes persistence
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42. DCI - Data
• What the system is
• Relatively static with relations
• Domain structure implemented with “conventional” classes
• Typically it includes persistence
• Comes from the mental model of system stakeholders
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43. DCI - Data
• What the system is
• Relatively static with relations
• Domain structure implemented with “conventional” classes
• Typically it includes persistence
• Comes from the mental model of system stakeholders
• Close to the “model” in MVC
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44. DCI - Data
• What the system is
• Relatively static with relations
• Domain structure implemented with “conventional” classes
• Typically it includes persistence
• Comes from the mental model of system stakeholders
• Close to the “model” in MVC
• Example: BankAccount with increase(), decrease(); no deposit()
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45. DCI - Context (and Roles)
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46. DCI - Context (and Roles)
• Associated to a use case, user story, scenario, or algorithm
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47. DCI - Context (and Roles)
• Associated to a use case, user story, scenario, or algorithm
• Identifies objects participating in a scenario
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48. DCI - Context (and Roles)
• Associated to a use case, user story, scenario, or algorithm
• Identifies objects participating in a scenario
• Assign to each object one or more stateless roles
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49. DCI - Context (and Roles)
• Associated to a use case, user story, scenario, or algorithm
• Identifies objects participating in a scenario
• Assign to each object one or more stateless roles
• Objects can have multiple roles at the same time
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50. DCI - Context (and Roles)
• Associated to a use case, user story, scenario, or algorithm
• Identifies objects participating in a scenario
• Assign to each object one or more stateless roles
• Objects can have multiple roles at the same time
• Decompose the use case (etc...) into roles, not objects
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51. DCI - Context (and Roles)
• Associated to a use case, user story, scenario, or algorithm
• Identifies objects participating in a scenario
• Assign to each object one or more stateless roles
• Objects can have multiple roles at the same time
• Decompose the use case (etc...) into roles, not objects
• Contrast this with polymorphism and classic OO decomposition
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52. DCI - Context (and Roles)
• Associated to a use case, user story, scenario, or algorithm
• Identifies objects participating in a scenario
• Assign to each object one or more stateless roles
• Objects can have multiple roles at the same time
• Decompose the use case (etc...) into roles, not objects
• Contrast this with polymorphism and classic OO decomposition
• Example: MoneyTransfer with SrcAccount and DestAccount
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53. Quick terminology note
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54. Quick terminology note
• Methodless role: abstract role
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55. Quick terminology note
• Methodless role: abstract role
• Interface, abstract class
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56. Quick terminology note
• Methodless role: abstract role
• Interface, abstract class
• Methodful role: concrete role
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57. Quick terminology note
• Methodless role: abstract role
• Interface, abstract class
• Methodful role: concrete role
• Regular class
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58. DCI - Interaction
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59. DCI - Interaction
• What the system does
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60. DCI - Interaction
• What the system does
• Occurs among roles, which act as adapters to objects
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61. DCI - Interaction
• What the system does
• Occurs among roles, which act as adapters to objects
• Roles are bound in different ways for each context
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62. DCI - Interaction
• What the system does
• Occurs among roles, which act as adapters to objects
• Roles are bound in different ways for each context
• Roles should be generic
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63. DCI - Interaction
• What the system does
• Occurs among roles, which act as adapters to objects
• Roles are bound in different ways for each context
• Roles should be generic
• Roles life cycle is likely to be bound to a given interaction
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64. DCI - Interaction
• What the system does
• Occurs among roles, which act as adapters to objects
• Roles are bound in different ways for each context
• Roles should be generic
• Roles life cycle is likely to be bound to a given interaction
• Interaction should be explicit given role nature, rather than
emergent as in (agile) OOD
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65. DCI - Execution Model
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66. DCI - Execution Model
• The Context finds object participants
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67. DCI - Execution Model
• The Context finds object participants
• Then, it assigns (injects?) roles to them
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68. DCI - Execution Model
• The Context finds object participants
• Then, it assigns (injects?) roles to them
• Roles find each other by type (methodless)
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69. DCI - Execution Model
• The Context finds object participants
• Then, it assigns (injects?) roles to them
• Roles find each other by type (methodless)
• What about static languages and designs?
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70. DCI - Execution Model
• The Context finds object participants
• Then, it assigns (injects?) roles to them
• Roles find each other by type (methodless)
• What about static languages and designs?
• Then, it invokes a method on the first role
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71. DCI - Execution Model
• The Context finds object participants
• Then, it assigns (injects?) roles to them
• Roles find each other by type (methodless)
• What about static languages and designs?
• Then, it invokes a method on the first role
• Interaction goes on among other roles
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72. DCI - How to
implement?
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73. Some design issues
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74. Some design issues
• Static vs dynamic
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75. Some design issues
• Static vs dynamic
• Traits, Mix-ins
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76. Some design issues
• Static vs dynamic
• Traits, Mix-ins
• AOP, annotations (e.g. Qi4J)
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77. Some design issues
• Static vs dynamic
• Traits, Mix-ins
• AOP, annotations (e.g. Qi4J)
• Problems: schizophrenia
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78. Some design issues
• Static vs dynamic
• Traits, Mix-ins
• AOP, annotations (e.g. Qi4J)
• Problems: schizophrenia
• Which is the identity of an object that becomes a cluster of roles
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79. Some design issues
• Static vs dynamic
• Traits, Mix-ins
• AOP, annotations (e.g. Qi4J)
• Problems: schizophrenia
• Which is the identity of an object that becomes a cluster of roles
• Partly solved by the clear separation object (stateful) / role
(stateless)
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80. Some design issues
• Static vs dynamic
• Traits, Mix-ins
• AOP, annotations (e.g. Qi4J)
• Problems: schizophrenia
• Which is the identity of an object that becomes a cluster of roles
• Partly solved by the clear separation object (stateful) / role
(stateless)
• What about equals() / hashcode()?
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81. Some design issues
• Static vs dynamic
• Traits, Mix-ins
• AOP, annotations (e.g. Qi4J)
• Problems: schizophrenia
• Which is the identity of an object that becomes a cluster of roles
• Partly solved by the clear separation object (stateful) / role
(stateless)
• What about equals() / hashcode()?
• Problem: anemic objects
DCI 19
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82. Some design issues
• Static vs dynamic
• Traits, Mix-ins
• AOP, annotations (e.g. Qi4J)
• Problems: schizophrenia
• Which is the identity of an object that becomes a cluster of roles
• Partly solved by the clear separation object (stateful) / role
(stateless)
• What about equals() / hashcode()?
• Problem: anemic objects
• Really a problem in this perspective?
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83. Designing with DCI
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84. Designing with DCI
• First, acknowledge that DCI is a best practice
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85. Designing with DCI
• First, acknowledge that DCI is a best practice
• Some languages can fit better than others
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86. Designing with DCI
• First, acknowledge that DCI is a best practice
• Some languages can fit better than others
• Frameworks might help... but they force a new nature
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87. Designing with DCI
• First, acknowledge that DCI is a best practice
• Some languages can fit better than others
• Frameworks might help... but they force a new nature
• My point: DCI must be addressed in design
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88. Some UI-oriented
examples
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89. NodesExample 1
• Static role implementation
• Introduce some generic, (G)UI oriented roles
• NetBeans Platform’s Lookup based implementation
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90. NodesExample 2
• Dynamically replacing roles with decorators
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91. NodesExample 4
• Adding contextual Actions and ToolTips
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92. NodesExample 5
• Removing UI dependencied
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93. NodesExample 6
• Injecting roles from the Context
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94. NodesExample 7
• Injecting Roles in function of the Context
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95. Abstracting and
sweetening
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96. Abstracting and sweetening
• Would be nice to be technology independent
• Would be nice to have some syntactic sugar
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97. as()
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98. as()
• From Role role = object.getLookup().lookup(Role.class) ...
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99. as()
• From Role role = object.getLookup().lookup(Role.class) ...
• ... to Role role = object.as(Role);
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100. as()
• From Role role = object.getLookup().lookup(Role.class) ...
• ... to Role role = object.as(Role);
• As a wrapper around Lookup
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101. as()
• From Role role = object.getLookup().lookup(Role.class) ...
• ... to Role role = object.as(Role);
• As a wrapper around Lookup
• With annotations and Lombok
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102. as()
• From Role role = object.getLookup().lookup(Role.class) ...
• ... to Role role = object.as(Role);
• As a wrapper around Lookup
• @AsCapable
With annotations and Lombok
public class MyObject
{
@Role
private Role1 r1 = new Role1();
@Role // lazy
private Provider<Role> r2 = ...;
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103. Q &A
• Question Time
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