Domain-Driven Transformation

Transcript

1. Starring
   Directed By
   Special
   Appearance
   Presented by
   Photo: Hackercatxxy/Wikipedia
   

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3. THE NAME OF THIS SPEAKER IS HENNING SCHWENTNER
   LIVE 45 MIN TALK
   

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4. !"#
   Kolleg:in gesucht
   (Deutschlandweit)
   

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5. View Slide

6. @hschwentner
   

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7. @hschwentner
   Alphorn
   Auto Leasing Inc.
   

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8. @hschwentner
   

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9. @hschwentner
   

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10. Monolease A
    

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11. salesperson
    [person]
    Monolease
    [software system]
    Central car leasing tool
    customer
    [external person]
    risk manager
    [person]
    closes leasing
    contracts with
    creates and
    calculates contracts in
    assesses risk of
    contracts in
    Alphorn Auto Leasing Inc.
    [enterprise]
    Context
    

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12. @hschwentner
    Alphorn’s boss:
    “Modernize it!”
    

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13. @hschwentner
    Diagnosis:
    From Which Diseases Does
    Our Patient suffer?
    

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14. @hschwentner
    Different diseases require
    different treatment
    

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15. @hschwentner
    big ball
    of mud
    anemic
    domain model
    bad
    team
    organization
    Typical Diseases of
    Legacy Systems
    

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16. @hschwentner
    big ball
    of mud
    anemic
    domain model
    bad
    team
    organization
    Cures
    strategic
    transformation
    tactical
    transformation socio-technical
    transformation
    

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17. @hschwentner
    Domain-Driven
    Refactorings
    • Strategic
    • Socio-Technical
    • Tactical (Against Model Anemia)
    • Tactical (Against Big Ball of Mud)
    Catalog:
    https://hschwentner.io/domain-driven-refactorings
    

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18. @hschwentner
    Strategic
    

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19. @hschwentner
    Strategic Transformation
    1. Step: Domain re-discovery
    2. Step: Modeling the to-be
    3. Step: Aligning as-is with to-be
    4. Step: Do the move
    RISK
    MANAGE-
    MENT
    SALES
    

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20. @hschwentner
    Controlling Complexity
    as Key to
    Modernization
    

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21. “The most
    fundamental problem
    in software
    development is
    complexity. ”
    Bjarne Stroustrup
    

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22. Controlling
    complexity is
    the essence of
    computer
    programming
    Brian
    Kernighan
    

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23. “There is only one
    basic way of dealing
    with complexity:
    divide and conquer.”
    Bjarne Stroustrup
    

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26. @hschwentner
    Too big
    to be understood
    as a whole
    

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27. Photo: Henning Schwentner
    

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28. View Slide

29. @hschwentner
    How to Modernize
    IT Infratructure?
    

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30. @hschwentner
    Replace or
    Transform
    

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31. old old old old
    new
    new new new
    “just flip
    the lever”
    1 2 3 4 5
    a.k.a.
    big bang
    replacement
    

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32. old old old
    new
    new new new
    2 3 4 5
    old
    1
    

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33. Strangler
    Fig
    Application
    Photo: Henning Schwentner
    

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34. Strangler Fig Application
    

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35. Lesson:
    is better than
    Strangler Fig
    Application
    Big Bang
    Replacement
    

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36. =>
    bounded
    contexts
    monolith
    buy
    to
    carve out
    build
    new
    

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37. @hschwentner
    Step 1:
    Domain Re-Discovery
    

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38. @hschwentner
    To split the monolith
    we first have to
    put it aside
    

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39. @hschwentner
    Mindset Switch
    

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40. thinking
    about
    business
    =>
    thinking
    about
    technology
    to
    

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41. Collaborative Modeling
    

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42. Collaborative Modeling
    

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43. customer
    tells wish for
    1
    salesperson
    signs
    to
    gives
    for
    contract
    3
    risk manager
    contract
    passes on
    to
    4
    contract
    votes
    checks
    calculates
    5
    6
    7
    calculates
    to
    8
    2
    car
    credit
    rating
    installment
    car
    resale
    value
    contract
    

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44. https://hschwentner.io
    Read on in:
    

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45. @hschwentner
    Step 2:
    Determining the
    To-Be Architecture
    

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46. @hschwentner
    Drawing Boundaries
    

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47. @hschwentner
    Scope:
    coarse-grained
    to-be (optimized)
    pure
    

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48. Which activities
    belong together
    (from an actor’s
    perspective)?
    

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49. customer
    tells wish for
    1
    salesperson
    signs
    to
    gives
    for
    contract
    3
    risk manager
    contract
    passes on
    to
    4
    contract
    votes
    checks
    calculates
    5
    6
    7
    calculates
    to
    8
    2
    car
    credit
    rating
    installment
    car
    resale
    value
    contract
    sales
    risk assessment
    

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50. Sales
    Risk
    assessment
    

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51. @hschwentner
    Step 3:
    Aligning As-Is with To-Be
    

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52. salesperson
    [person]
    Monolease
    [software system]
    Central car leasing tool
    customer
    [external person]
    risk manager
    [person]
    closes leasing
    contracts with
    creates and
    calculates contracts in
    assesses risk of
    contracts in
    Alphorn Auto Leasing Inc.
    [enterprise]
    Context
    again
    

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53. salesperson
    [person]
    backend
    [container: EJB 2]
    risk manager
    [person]
    creates and
    calculates contracts in
    assesses risk of
    contracts in
    Monolease
    [software system]
    frontend
    [container: servlets, JSPs]
    database
    [container: IBM DB2]
    Containers
    

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54. Calculator
    [component]
    frontend
    [container]
    LeasingServlet
    [component: servlet]
    CONTRACTS
    [database table]
    PartnerServlet
    [component: servlet]
    ContractService
    [component]
    PartnerService
    [component]
    backend
    [container]
    database
    [container]
    Contract
    [component]
    Partner
    [component]
    PARTNERS
    [database table]
    Components
    

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55. big ball
    of mud
    =>
    no vertical
    structuring
    

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56. Calculator
    [component]
    frontend
    [container]
    LeasingServlet
    [component: servlet]
    CONTRACTS
    [database table]
    PartnerServlet
    [component: servlet]
    ContractService
    [component]
    PartnerService
    [component]
    backend
    [container]
    database
    [container]
    Contract
    [component]
    Partner
    [component]
    PARTNERS
    [database table]
    Components
    

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57. Calculator
    [component]
    ContractService
    [component]
    PartnerService
    [component]
    backend
    [container]
    Contract
    [component]
    Partner
    [component]
    Component Backend
    

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58. Calculator
    [component]
    ContractService
    [component]
    PartnerService
    [component]
    Contract
    [component]
    Partner
    [component]
    Component Bounded
    Contexts
    Sales
    Risk Assessment
    

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59. Calculator
    [component]
    ContractService
    [component]
    PartnerService
    [component]
    Contract
    [component] Partner
    [component]
    Sales
    Risk Assessment
    Contract
    [component]
    Partner
    [component]
    Duplication?
    

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60. ContractService
    [component]
    Contract
    [component]
    Component Backend
    Sales
    Risk
    assessment
    

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61. ContractService
    signContract()
    voteContract()
    Code
    Contract
    getContractNumber()
    setSignatureDate()
    setCreditRa7ng()
    setVo7ngResult()
    Sales Risk Assessment
    

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62. ContractService
    signContract()
    voteContract()
    Code
    Contract
    getContractNumber()
    setSignatureDate()
    setCreditRating()
    setVotingResult()
    Sales Risk Assessment
    ContractService
    signContract()
    voteContract()
    Contract
    getContractNumber()
    setSignatureDate()
    setCreditRating()
    setVotingResult()
    

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63. ContractService
    signContract()
    Code
    Contract
    getContractNumber()
    setSignatureDate()
    Sales Risk Assessment
    ContractService
    voteContract()
    Contract
    getContractNumber()
    setCreditRa7ng()
    setVo7ngResult()
    

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64. ContractService
    signContract()
    Code
    Contract
    getContractNumber()
    setSignatureDate()
    Sales Risk Assessment
    ContractService
    voteContract()
    Contract
    getContractNumber()
    setCreditRating()
    setVotingResult()
    

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65. @hschwentner
    1.2 Extract
    Specialized
    “Contract
    Service”
    1.1 Extract
    Specialized
    “Contract”
    1 Extract
    Context
    “Sales”
    Transformation Backlog
    2 Extract
    Context
    “Risk
    assessment”
    2.1 Extract
    Specialized
    “Contract
    Service”
    2.1 Extract
    Specialized
    “Contract”
    

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66. @hschwentner
    Insertion:
    Domain-Driven
    Refactorings
    

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67. @hschwentner
    Domain-Driven
    Refactorings
    • Strategic
    • Socio-Technical
    • Tactical (Against Model Anemia)
    • Tactical (Against Big Ball of Mud)
    

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68. @hschwentner
    Strategic DDRs
    • Extract Bounded Context
    • Implement Bounded Context from Scratch
    

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69. @hschwentner
    Tactical DDRs
    (to Support Strategic)
    • Extract Specialized Entity
    • Extract Specialized Anemic Entity
    • Extract Specialized Service
    • Extract Specialized Data Model
    

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70. @hschwentner
    Extract Bounded Context
    Mechanics
    • Analyze the domain to find out which bounded contexts should be there.
    • Identify a carve-out candidate context
    • Create an empty package/namespace/module for the to-be carved out context besides the big ball of
    mud.
    • Apply the Tactical (to Support Strategic) refactorings that are right for your situation.
    

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71. @hschwentner
    Extract Specialized
    Anemic Entity
    Mechanics
    • Create empty new class in carved-out context
    • Add instance field of type new class to the old class
    • Copy to-be-moved fields from old to new class => Move Field
    • Copy first to-be-moved method to new class => Move Method
    • Replace method body in old class with a forward to method in new class
    • Step by step replace calls to the method in the old class with calls to the method in the new class
    • Delete the implementation in the old class
    • Delete now unused fields in old class
    • Repeat with other to-be-moved methods
    • Remove instance field of type new class in the old class
    

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72. Read on at:
    https://hschwentner.io/domain-driven-refactorings
    

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73. @hschwentner
    Step 4:
    Do the Move
    

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74. @hschwentner
    Transformation Backlog
    Planning Transformation
    Tactical
    Refactoring 1.2
    Strategic
    Refactoring 1
    User Story A
    Product Backlog
    User Story E
    User Story B
    User Story C
    User Story D
    Tactical
    Refactoring 1.3
    Tactical
    Refactoring 1.4
    Tactical
    Refactoring 2.1
    Strategic
    Refactoring 2
    Sprint Backlog
    

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75. @hschwentner
    Transformation Backlog
    Planning Transformation
    Tactical
    Refactoring 1.2
    Strategic
    Refactoring 1
    User Story A
    Product Backlog
    User Story E
    User Story B
    User Story C
    User Story D
    Tactical
    Refactoring 1.3
    Tactical
    Refactoring 1.4
    Tactical
    Refactoring 2.1
    Strategic
    Refactoring 2
    Sprint Backlog
    

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76. @hschwentner
    Transformation Backlog
    Planning Transformation
    Strategic
    Refactoring 1
    Product Backlog
    User Story E
    User Story C
    User Story D
    Tactical
    Refactoring 1.4
    Tactical
    Refactoring 2.1
    Strategic
    Refactoring 2
    Sprint Backlog
    

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77. @hschwentner
    Transformation Backlog
    Planning Transformation
    Strategic
    Refactoring 1
    Product Backlog
    User Story E
    User Story C
    User Story D
    Tactical
    Refactoring 1.4
    Tactical
    Refactoring 2.1
    Strategic
    Refactoring 2
    Sprint Backlog
    User Story F
    User Story G
    

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78. @hschwentner
    Transformation Backlog
    Planning Transformation
    Product Backlog
    User Story E
    Tactical
    Refactoring 2.1
    Strategic
    Refactoring 2
    Sprint Backlog
    User Story F
    User Story G
    

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79. @hschwentner
    Transformation Backlog
    Planning Transformation
    Product Backlog
    User Story E
    Tactical
    Refactoring 2.1
    Strategic
    Refactoring 2
    Sprint Backlog
    User Story G
    User Story H User Story F
    User Story I
    

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80. ContractService
    signContract()
    voteContract()
    Code
    Contract
    getContractNumber()
    setSignatureDate()
    setCreditRating()
    setVotingResult()
    Risk Assessment
    ContractService
    Contract
    Monolease
    voteContract()
    getContractNumber()
    setCreditRating()
    setVotingResult()
    

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81. ContractService
    signContract()
    Code
    Contract
    getContractNumber()
    setSignatureDate()
    Risk Assessment
    ContractService
    Contract
    Monolease
    voteContract()
    getContractNumber()
    setCreditRating()
    setVotingResult()
    

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82. @hschwentner
    Tactical
    

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83. Code
    Risk Assessment
    ContractService
    voteContract()
    Contract
    getContractNumber()
    setCreditRating()
    setVotingResult()
    anemic
    

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84. View Slide

85. @hschwentner
    Outlook
    

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86. @hschwentner
    What Else?
    Socio-technical transformation
    Technical transformation
    Tactical transformation
    Anti-Anemia refactorings
    

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87. @hschwentner
    Domain Categories
    Pipeline Domain Blackboard Domain Dialog Domain
    • Logistics
    • Insurances and banks
    • administration
    • healthcare
    • event management
    • control center
    • Software development
    • Communication software
    • Negotiations in various
    domains
    or Domain Patterns?
    

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88. @hschwentner
    Conclusion
    

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89. View Slide

90. https://hschwentner.io
    Read on in:
    https://hschwentner.io/domain-driven-refactorings
    

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91. Lesson:
    is possible
    Monolith transformation
    (and hard)
    =>
    

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92. @hschwentner
    Mistake: Going on the journey alone
    Better:
    

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93. Photo: Henning Schwentner
    

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94. !
    ❤
    

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95. @hschwentner
    

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96. Bibliography
    Foote, Brian and Joseph Yoder. “Big Ball of Mud.” PLoP ’97, Monticello, IL,
    September 1997.
    Fowler, Martin. “Strangler Fig Application.” Bliki, June 29, 2004.
    Hofer, Stefan and Henning Schwentner. Domain Storytelling: a Collaborative,
    Visual, and Agile Way to Develop Domain-Driven Software. Boston: Addison-
    Wesley, 2022.
    Lilienthal, Carola and Henning Schwentner. Domain-Driven Transformation.
    Heidelberg: dpunkt, 2023.
    Kernighan, Brian W. Software Tools in Pascal. Addison-Wesley, 1981.
    

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98. Henning Schwentner
    ⌂ https://hschwentner.io
    @hschwentner
    hs@wps.de
    

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99. (Software) Seam:
    A place where you can alter
    behavior in your program without
    editing in that place
    Every Seam has an
    enabling point, a place
    where you can make the
    decision to use one
    behavior or the other
    

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100. View Slide

101. Typical Seam:
     An interface that can have
     different implementations
     

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