AgileDev
- Last Published: 2016-12-13
- |
- Version: 0.1.15-SNAPSHOT
- Guidelines
- Developers Setup
- Site Documentation
- Documentation
- Branching Models
- Javadoc guidelines
- Software Design Principles
-
Patterns
- API gateway
- Automated testing
- Builder
- Bulkheads
- Caching
- Circuit Breaker
- Client Side Discovery
- Command Query Responsibility Separation
- Deployment microservices
- Domain Driven Design
- Enterprise Integration Pattern
- Exception Handling
- Event Sourcing
- Microservice Architecture
- Monitoring
- Monolithic Architecture
- Scale Cube
- Self registration
- Server Side Discovery
- Service Connector
- Service Registry
- Service Statelessness
- Single Responsibility Principle
- System of Record
- Timeouts
- Try-Cancel/Confirm
- UUID
- 3rd party registration
- Glossary
- Abbreviations
- Modules
- Build Configuration
- AsciiDoctor output Doclet
- AsciiDoctor Site Diagram Activator
- Maven Site Indexer
- AgileDev common
- AgileDev parent POM
- JUnit BDD
- Design By Contracts for Java
- Cucumber Reporting
- Cucumber Reporting example
- Embedded MySQL Server
- Maven plugin Embedded MySQL Server
- CQRS for Spring
- Event Sourcing for Spring
- Try Cancel/Commit transactions for Spring
- Narayana Tomcat listener
- Tutorial ArchiMate
- Tutorial regarding CQRS and Event sourcing
- Tutorial Design by Contract
- Tutorial Domain Driven Design
- Tutorial Rest
- Project Documentation
- Project Information
Aggregates.
It is difficult to guarantee the consistency of changes to objects in a model with complex associations. Invariants need to be maintained that apply to closely related groups of objects, not just discrete objects. Yet cautious locking schemes cause multiple users to interfere pointlessly with each other and make a system unusable.
Therefore, cluster the Entities and Value Objects into Aggregates and define boundaries around each. Choose one Entity to be the root of each Aggregate, and control all access to the object inside the boundary through the root. Allow external objects to hold references to the root only. Transient references to internal members can be passed out for use within a single operation only. Because the root controls access, it cannot be blindsided by changes to the internals. This arrangement makes it practical to enforce all invariants for objects in the Aggregate and for the Aggregate as a whole in any state change.