Summary of "Hexagonal Architecture & Legacy Code" by Jim Humelsine (@jhumelsine)

00:00:00 - 00:55:00

Jim Humelsine discusses how hexagonal architecture can be used to improve the efficiency of code by separating functionality into different layers. This design can be implemented in software by using a special framework and keeping data information out in a database. A repo adapter is used to allow communication between the layers. However, problems with the adapter led to the need to take a break and refactor the design. After making these adjustments, the microservice was able to run smoothly again.

• 00:00:00 Jim Humelsine discusses hexagonal architecture, which is a pattern that originated in 2005 and is focused on cocooning an system. He also discusses the origins of the hexagon shape and how it was chosen.
• 00:05:00 The three principles of design patterns are polymorphism, delegation, and strategy. The command pattern is a polymorphic pattern that turns behavior into an object, and the adapter pattern is a polymorphic pattern that joins a language with an interface. The strategy pattern says there are more than one way to implement an interface, and the dependency injection pattern says that all of the concrete classes in a design should talk to interfaces.
• 00:10:00 The video discusses the design principle of hexagons, which are boundaries between conventions. It explains that hexagons can be used to denote boundaries between different concepts in a design, such as between different modules, between different tiers of a system, and between different countries.
• 00:15:00 Hexagonal Architecture & Legacy Code is a video that demonstrates how hexagonal architecture can be used to encapsulate legacy code and reduce the risk of future changes. Hexagonal architecture divides the product into two concentric hexagons - the driver side, which is where requests come from and the driven side, which is where resources are needed to complete tasks. The driver side is implemented by a service that delegates to an authorization service and a repository interface, while the driven side is implemented by a select query that gets orders from a data store. External boundaries are defined by the business logic and the authorizer, which both communicate with an authorization service.
• 00:20:00 The Hexagonal Architecture & Legacy Code video by Jim Humelsine discusses the benefits of using a hexagonal architecture for legacy code. The hexagonal architecture separates business logic from the framework and adapter layers, which allows for easier portability and adaptability. The video also discusses how interfaces work as boundary constraints for code and how classes can change without major impact.
• 00:25:00 The video discusses the benefits of hexagonal architecture, which is a design pattern where different teams work independently and don't have to bump into each other. The presenter explains how this architecture is used in a real world example of a legacy codebase that is over 20 years old. The presenter also discusses the benefits of using adapters, which allow different teams to call the same service without needing to go through a middleman.
• 00:30:00 Hexagonal architecture is a design pattern that is used to improve the efficiency of code by separating functionality into different layers. This design can be implemented in software by using a special framework and keeping data information out in a database. A repo adapter is used to allow communication between the layers. However, problems with the adapter led to the need to take a break and refactor the design. After making these adjustments, the microservice was able to run smoothly again.
• 00:35:00 This video discusses how hexagonal architecture can help simplify testing of a business logic. The presenter shows how to set up a test environment that simulates the contract a business object implements, without needing to stand up the business object itself.
• 00:40:00 This video discusses the different types of testing that can be done with hexagonal architecture. It recommends that the consumer contract driven testing be avoided in order to avoid vendor lock-in.
• 00:45:00 The speaker discusses the importance of hexagonal architecture in software development, emphasizing the importance of keeping internationalization and form factor independence inside the code, as well as scope and composability. He also mentions the importance of preventing vendor locking, which can be difficult in a code base with many external dependencies.
• 00:50:00 Jim Humelsine discusses how the Hexagonal Architecture separates the code that performs an action from the code that informs the user of that action, which reduces the chances of having side effects. He also talks about how adapters should be humble, as they should only do what is necessary to perform the task at hand.
• 00:55:00 Jim Humelsine explains how hexagonal architecture can help reduce the amount of testing required for legacy code. This approach separates code into easy and hard to test parts, and relies on regular, exhaustive testing to catch any issues.