Bottom-Up Architecture – Bridging the Achitecture Code Gap

Hard to change code bases often suffer from two primary problems: a lack of alignment with domain boundaries and failure to effectively express architectural ideas in code. To address that critical issue, developers have turned to Separation of Concerns Architectures, such as Onion-, Clean and Hexagonal Architecture. However, these approaches typically yield mixed results, as they primarily focus on separating technical and business code, without addressing the structural aspects of the domain.

This presentation explores strategies for transferring architectural ideas and design pattern languages into code at various levels of abstraction. We will discuss how different frameworks and libraries in the Java ecosystem can aid in this process, leveraging the presence of meta-information within the code to support critical aspects such as structural verification, testability, and documentation. By employing these approaches and tools, developers can write more maintainable code that is less susceptible to degradation over time.

Version:
- Java Forum Nord (current) – https://static.odrotbohm.de/slides/2024/09/bottom-up-architecture-jfn.pdf
- GOTO Amsterdam 2024 – https://static.odrotbohm.de/slides/2024/06/bottom-up-architecture-goto-ams.pdf

Transcript

1. BOTTOM-UP ARCHITECTURE BRIDGING THE ARCHITECTURE CODE GAP Oliver Drotbohm oliver.drotbohm@broadcom.com odrotbohm
3. Architectural Goal Architectural Concept Supporting Technology Development Practice supports drives selection drives selection enables supports supported by
4. We want to build evolvable systems.
5. Complexity …while the actual challenge is this. Most teams focus on that… 1.0 1.2 1.1 2.0
6. Understandability
8. Chunking Hierarchization Pattern languages
9. "Architecture is a property of a system, not a description of its intended design." — Stefan Tilkov in "Good Enough Architecture"
12. Abstraction Vocabulary Pattern languages Level of detail Encapsulation Domain terms Concepts & Rules Extensional Intensional Enumerated Specified
13. Architecturally- Evident Code? !
14. Deployables / Build modules / Packages Classes, methods, fields Extensional Intensional Naming conventions What else? " Invoicing, Shipment Components / Modules EmailAddress, ZipCode Domain language Concepts ValueObject, Entity, Aggregate Layers, Rings Concepts & Rules
15. Architecture Design DDD Events Strategic Bounded Contexts Context Maps Modules Tactical Repositories Aggregates Entities Value Objects Architecture Event Listeners Events Layers Rings Ports Adapters Commands Queries
16. Architecture Design DDD Strategic Bounded Contexts Context Maps Modules Tactical Repositories Aggregates Entities Value Objects
17. A simple Aggregate arrangement Orders Customers «Aggregate» Order id: OrderId lineItems: List<LineItem> customer: Customer «Entity» LineItem amount: int price: MonetaryAmount «Aggregate» Customer id: CustomerId contains 1 1..* belongs to * 1
18. A simple Aggregate arrangement Orders Customers «Aggregate» Order id: OrderId lineItems: List<LineItem> customer: Customer «Entity» LineItem amount: int price: MonetaryAmount «Aggregate» Customer id: CustomerId contains 1 1..* belongs to * 1 This and that imply that this is wrong! #
19. Tools Frameworks User Code Concepts Rules Code Architecture Technology
20. Responsibility of definition Means of definition
22. MATCH (repo:Java:Type) -[:IMPLEMENTS_GENERIC]-# (superType) -[:OF_RAW_TYPE]-# (:Java:Type { fqn: "o.s.d.r.Repository"}), (superType) -[:HAS_ACTUAL_TYPE_ARGUMENT { index: 0 }]-# () -[:OF_RAW_TYPE]-# (aggregateType) SET aggregateType:Aggregate RETURN repo, aggregateType Establishing an Aggregate… in jQAssistant MATCH (aggregate:Aggregate) -[:DECLARES]-# (f:Field) -[:OF_TYPE]-# (fieldType:Aggregate) WHERE aggregate <& fieldType RETURN aggregate, fieldType Establishes the concept Establishes the rule Reference to tech stack $
23. @AnalyzeClasses(packagesOf = Application.class) public class ArchitectureTest { @ArchTest void verifyAggregates(JavaClasses types) { var aggregates = new AggregatesExtractor(); var aggregateTypes = aggregates.doTransform(types); all(aggregates) .should(notReferToOtherAggregates(aggregateTypes)) .check(types); } } Establishing an Aggregate… in ArchUnit Establishes the concept Establishes the rule
24. Responsibility of definition
25. xMolecules
26. jMolecules
27. Architectural Goal Architectural Concept Supporting Technology Development Practice supports drives selection drives selection enables supports supported by Evolvability DDD Building Blocks jMolecules
28. Explicit concepts
29. @Entity @NoArgsConstructor(force = true) @EqualsAndHashCode(of = "id") @Table(name = "SAMPLE_ORDER") @Getter public class Order { private final @EmbeddedId OrderId id; @OneToMany(cascade = CascadeType.ALL) private List<LineItem> lineItems; private CustomerId customerId; public Order(CustomerId customerId) { this.id = OrderId.of(UUID.randomUUID()); this.customerId = customerId; } @Value @RequiredArgsConstructor(staticName = "of") @NoArgsConstructor(force = true) public static class OrderId implements Serializable { private static final long serialVersionUID = …; private final UUID orderId; } }
30. @Entity @NoArgsConstructor(force = true) @EqualsAndHashCode(of = "id") @Table(name = "SAMPLE_ORDER") @Getter public class Order implements o.j.d.t.AggregateRoot<Order, OrderId> { private final @EmbeddedId OrderId id; @OneToMany(cascade = CascadeType.ALL) private List<LineItem> lineItems; private CustomerId customerId; public Order(CustomerId customerId) { this.id = OrderId.of(UUID.randomUUID()); this.customerId = customerId; } @Value @RequiredArgsConstructor(staticName = "of") @NoArgsConstructor(force = true) public static class OrderId implements o.j.d.t.Identifier { private static final long serialVersionUID = …; private final UUID orderId; } }
31. Verification
32. Invalid aggregate root reference! Use identifier or Association instead! ☝
33. Eliminate boilerplate
34. @Entity @NoArgsConstructor(force = true) @EqualsAndHashCode(of = "id") @Table(name = "SAMPLE_ORDER") @Getter public class Order { private final @EmbeddedId OrderId id; @OneToMany(cascade = CascadeType.ALL) private List<LineItem> lineItems; private CustomerId customerId; public Order(CustomerId customerId) { this.id = OrderId.of(UUID.randomUUID()); this.customerId = customerId; } @Value @RequiredArgsConstructor(staticName = "of") @NoArgsConstructor(force = true) public static class OrderId implements Serializable { private static final long serialVersionUID = …; private final UUID orderId; } } JPA-induced boilerplate Model characteristics expressed implicitly or through technical means
35. @Entity @NoArgsConstructor(force = true) @EqualsAndHashCode(of = "id") @Table(name = "SAMPLE_ORDER") @Getter public class Order implements AggregateRoot<Order, OrderId> { private final @EmbeddedId OrderId id; @OneToMany(cascade = CascadeType.ALL) private List<LineItem> lineItems; private Association<Customer, CustomerId> customer; public Order(CustomerId customerId) { this.id = OrderId.of(UUID.randomUUID()); this.customer = Association.forId(customerId); } @Value @RequiredArgsConstructor(staticName = "of") @NoArgsConstructor(force = true) public static class OrderId implements Identifier { private static final long serialVersionUID = …; private final UUID orderId; } }
36. @Entity @NoArgsConstructor(force = true) @EqualsAndHashCode(of = "id") @Table(name = "SAMPLE_ORDER") @Getter public class Order implements AggregateRoot<Order, OrderId> { private final @EmbeddedId OrderId id; @OneToMany(cascade = CascadeType.ALL) private List<LineItem> lineItems; private Association<Customer, CustomerId> customer; public Order(CustomerId customerId) { this.id = OrderId.of(UUID.randomUUID()); this.customer = Association.forId(customerId); } @Value @RequiredArgsConstructor(staticName = "of") @NoArgsConstructor(force = true) public static class OrderId implements Identifier { private static final long serialVersionUID = …; private final UUID orderId; } }
37. [INFO] □─ example.order.Order [INFO] ├─ JPA - Adding @j.p.Entity. [INFO] ├─ JPA - Adding default constructor. [INFO] ├─ JPA - Adding nullability verification using new callback methods. [INFO] ├─ JPA - Defaulting id mapping to @j.p.EmbeddedId(). [INFO] ├─ JPA - Defaulting lineItems mapping to @j.p.JoinColumn(…). [INFO] ├─ JPA - Defaulting lineItems mapping to @j.p.OneToMany(…). [INFO] ├─ Spring Data JPA - Implementing o.s.d.d.Persistable<e.o.Order$OrderIdentifier>. [INFO] └─ Spring JPA - customer - Adding @j.p.Convert(converter=…). Meanwhile in your IDE…
38. @Entity @NoArgsConstructor(force = true) @EqualsAndHashcode(of = "id") @Table(name = "SAMPLE_ORDER") @Getter public class Order { private final @EmbeddedId OrderId id; @OneToMany(cascade = CascadeType.ALL) private List<LineItem> lineItems; private CustomerId customerId; public Order(Customer customer) { this.id = OrderId.of(UUID.randomUUID()); this.customerId = customer.getId(); } @Value @RequiredArgsConstructor(staticName = "of") @NoArgsConstructor(force = true) public static class OrderId implements Serializable { private static final long serialVersionUID = …; private final UUID orderId; } } @Table(name = "SAMPLE_ORDER") @Getter public class Order implements AggregateRoot<Order, OrderId> { private final OrderId id; private List<LineItem> lineItems; private Association<Customer, CustomerId> customer; public Order(CustomerId customerId) { this.id = OrderId.of(UUID.randomUUID()); this.customer = Association.forId(customerId); } record OrderId(UUID orderId) implements Identifier {} }
39. Decomposition
40. Infrastructure Application Domain
41. Application Domain Infrastructure
42. Application Domain Infrastructure
43. Infrastructure Infrastructure Domain Domain Domain Application Application Application Infrastructure
44. Infrastructure Infrastructure Domain Domain Domain Application Application Application Infrastructure
45. Module Module Module
46. Architectural Goal Architectural Concept Supporting Technology Development Practice supports drives selection drives selection enables supports supported by Evolvability Modules Spring Modulith
47. Spring Modulith
48. package com.acme.modulith @SpringBootApplication class MyApplication { … } Standard Spring Boot Application
49. Package Conventions ….modulith ….modulith.moduleA ….modulith.moduleA.internal ….modulith.moduleB ….modulith.moduleB.internal Access to components residing in internal packages forbidden and checked during tests. API packages
50. package com.acme.modulith @SpringBootApplication class MyApplication { … } var modules = ApplicationModules.of(MyApplication.class); modules.verify(…); Standard Spring Boot Application Verifies rules for MyApplication
51. Web Business logic Data access Module A Module B Module C
52. Web Business logic Data access Module A Module B Module C
53. A B C D E Unit of… - Understanding - Consistency - Testing - Documentation - Observation
54. Testing
55. Web Business logic Data access Module A Module B Module C
56. Web Business logic Data access Module A Module B Module C @Data…Test @WebMvcTest
57. Web Business logic Data access Module A Module B Module C @Data…Test @WebMvcTest
58. Web Business logic Data access Module A Module B Module C @Data…Test @WebMvcTest @ApplicationModuleTest
59. Scope of Individual Tests
60. A B C D E Unit of… - Understanding - Consistency - Testing - Documentation - Observation
61. A B C D E Unit of… - Understanding - Consistency - Testing - Documentation - Observation
62. A B C D E Unit of… - Understanding - Consistency - Testing - Documentation - Observation
63. Scope of Test Execution
64. A B C D E Change detected here. We only need to test A!
65. A B C D E Change detected in C. We need to test C and A!
67. Documentation
68. A B C D E Unit of… - Understanding - Consistency - Testing - Documentation - Observation
69. My Component Provided Interface Exposed Service API Spring Beans available for DI Exposed Aggregates Primary elements of the domain and constraints Published Events Events the component emits Required Interface Consumed Service API External dependencies of Spring beans Configuration Spring Boot configuration properties Consumed Events Events that the component reacts to
70. Salespoint «Component: Module» Salespoint :: Accountancy «Component: Module» Salespoint :: Catalog «Component: Module» Salespoint :: Inventory «Component: Module» Salespoint :: Order «Component: Module» Salespoint :: Payment «Component: Module» Salespoint :: Quantity «Component: Module» Salespoint :: Storage «Component: Module» Salespoint :: Time «Component: Module» Salespoint :: User Account listens t o depends on uses depends on depends on depends on listens t o depends on depends on depends on depends on uses depends on depends on
71. Salespoint «Component: Module» Salespoint :: Accountancy «Component: Module» Salespoint :: Catalog «Component: Module» Salespoint :: Inventory «Component: Module» Salespoint :: Order «Component: Module» Salespoint :: Payment «Component: Module» Salespoint :: Quantity «Component: Module» Salespoint :: Storage «Component: Module» Salespoint :: Time «Component: Module» Salespoint :: User Account listens t o depends on uses depends on depends on depends on listens t o depends on depends on depends on depends on uses depends on depends on Salespoint :: Inventory «Component: Module» Salespoint :: Catalog «Component: Module» Salespoint :: Inventory «Component: Module» Salespoint :: Order «Component: Module» Salespoint :: Quantity depends on depends on listens t o depends on depends on depends on
72. Salespoint «Component: Module» Salespoint :: Accountancy «Component: Module» Salespoint :: Catalog «Component: Module» Salespoint :: Inventory «Component: Module» Salespoint :: Order «Component: Module» Salespoint :: Payment «Component: Module» Salespoint :: Quantity «Component: Module» Salespoint :: Storage «Component: Module» Salespoint :: Time «Component: Module» Salespoint :: User Account listens t o depends on uses depends on depends on depends on listens t o depends on depends on depends on depends on uses depends on depends on Salespoint :: Inventory «Component: Module» Salespoint :: Catalog «Component: Module» Salespoint :: Inventory «Component: Module» Salespoint :: Order «Component: Module» Salespoint :: Quantity depends on depends on listens t o depends on depends on depends on
73. Summary
74. Summary Find means to represent architectural and design concepts in your codebase. Align software engineering practices with architectural abstractions. Favor architecturally aware technologies over allegedly agnostic ones. Understand how technology choices affect the overall architecture of the system.
75. Thank you! Questions? Oliver Drotbohm oliver.drotbohm@broadcom.com odrotbohm
76. Links xMolecules https://xmolecules.org jMolecules https://jmolecules.org jMolecules Examples https://github.com/xmolecules/jmolecules-examples Gitter – Join the community! https://gitter.im/xmolecules/xmolecules
77. Resources Software Architecture for Developers Simon Brown – Books Just Enough Software Architecture George Fairbanks – Book Architecture, Design, Implementation Ammon H. Eden, Rick Kazman – Paper Sustainable Software Architecture Carola Lilienthal – Book The Programmer's Brain Felienne Hermans – Book