• Was ist die Kopplung (coupling) zwischen Klassen?
  • Coupling measures the number of classes with which a specific class interacts by accessing them or being accessed by them through variables or methods.
  • Höhere Kopplung - mehr Abhängigkeiten. Wir wollen die Kopplung reduzieren.
• Sollten Sie die Kopplung (coupling) zwischen Klassen in unterschiedlichen Paketen erhöhen oder reduzieren?
  • Kopplung zwischen Klassen sollte reduziert werden.
• Was die Kohäsion (cohesion) einer Klasse?
  • cohesion refers to the degree to which the elements inside a class belong together.
  • Höhere Kohäsion - Methoden der Klasse verwenden viele Attribute-
• Sollten Sie die Kohäsion (cohesion) einer Klasse erhöhen oder reduzieren?
  • Kohäsion einer Klasse sollte erhöht werden.

• SOLID Prinzipien erklären

  • Single Responsibility Principle: one class should be responsible for one piece of functionality. One method should do one thing.

    • Bad smell: Big classes
    • Solution: Refactoring - divide class in several classes, use interfaces to create clean abstractions.

  • Open Closed Principle: Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification. Modify behaviour by adding new code, not by changing old code.

    • Bad smell: changing existing code for new functionality
    • Solution: Usage of common interfaces and inheritance. Design Patterns like Stategy, Factory Method

  • Liskov Substitution Principle: When redefining a routine in a child class, you may only replace its precondition by a weaker one, and its postcondition by a stronger one. If parent class works with Square, child class can work with Shape, but not with cube. If parent class returns List, child can return LinkedList

    • Bad smell: overriding a functions in child classes with argument specification (float → int)

  • Interface Segregation Principle: interfaces should be as small as possible.

    • Bad smell: class implements an interface, but one function stays empty

    • Solution: divide interface in several interfaces

      

  • Dependency Inversion Principle: ****high level modules should not depend on low level modules. Only interfaces should be used for referencing low-level functions

    • Attribute Fridge violates DIP. We should add an Interface for Frigde (like FoodContainer) and use it instead.

      

    • Attribute UserManager violates DIP. We should add an Interface for UserManager and use it instead.

      

  

Patterns of Enterprise Applications

• Fünf Architekturmuster für Datenquellen: siehe Patterns of Entrerprise Applications
• Nennen Sie die fünf Architekturmuster für Datenquellen:
  • Record Set
  • Table Data Gateway
  • Active Record
  • Row Data Gateway
  • Data Mapper

Software Components

• Vier Einflussfaktoren, die die Leistung (performance) einer Softwarekomponente beeinussen

Microservices

• Sieben internen Bestandteile eines Microservices nach Toby Clemson

  1. Resources
  2. Service Layer
  3. Domain
  4. Gateway
  5. HTTP Client
  6. Data Mapper
  7. Repository

  

• Neun Charakteristiken von Microservice-Architekturen

Domain Driven Design

• Interaktionen zwischen Domänen des strategischen Entwurfs
  • Consumer/Supplier
  • Shared Kernel
  • Conformist
  • Anticorruption Layer