Service-Oriented Architecture in ServiceNow: Integrating Two Services Using Dependency Injection

[BillMartin]

Introduction: Why Service-Oriented Architecture (SOA) Matters for ServiceNow Developers & Architects

For ServiceNow developers and architects, implementing Service-Oriented Architecture (SOA) is essential for creating modular, scalable, and maintainable applications. By leveraging Dependency Injection (DI) and Object-Oriented Programming (OOP) principles, you can design systems that are loosely coupled, easily testable, and extensible—ensuring efficient collaboration across teams and workflows.

This article demonstrates how ServiceNow developers and architects can:

• ✅ Build IncidentService for managing incidents
• ✅ Build ChangeRequestService for managing change requests
• ✅ Use Service Integration with Dependency Injection for seamless interaction between services

By following OOP principles such as Encapsulation, Inheritance, Polymorphism, and Abstraction, this architecture ensures that components are both modular and maintainable, supporting the needs of both developers and architects as they scale enterprise solutions.

What is Service-Oriented Architecture (SOA)?

Service-Oriented Architecture (SOA) structures applications as collections of independent services, each responsible for a specific business function. This approach benefits both developers and architects by providing:

• ✅ Loose Coupling: Services communicate via well-defined interfaces, reducing dependencies
• ✅ Reusability: Services can be reused across different workflows
• ✅ Scalability: Services can be scaled independently
• ✅ Maintainability: Simplified code that is easier to maintain and extend

In ServiceNow, SOA is implemented using Script Includes to create reusable services, with Dependency Injection ensuring that components remain loosely coupled and testable. This approach aligns with best practices for both developers writing maintainable code and architects designing scalable enterprise solutions.

Core Components of This Use Case

1. Service Layer:

   • IncidentService handles incidents, and ChangeRequestService manages change requests
   • Both services interact using Dependency Injection for modular and maintainable code

2. Repository Layer (Repository Pattern):

   • BaseRepository provides common data access methods
   • IncidentRepository and ChangeRequestRepository extend BaseRepository for specific tables

3. Entity Layer:

   • IncidentEntity and ChangeRequestEntity encapsulate data for consistency and reusability

4. Utility Layer:

   • ResponseObject standardizes responses across services
   • BaseLogger provides reusable logging for both services and repositories

Why Use Dependency Injection in SOA with ServiceNow?

Dependency Injection (DI) allows services to receive dependencies (repositories and loggers) via constructors rather than creating them internally. This promotes:

• ✅ Loose Coupling: Services are independent of specific implementations
• ✅ Testability: Easy to test services using mock dependencies
• ✅ Reusability: Components can be reused across different services
• ✅ Maintainability: Simplifies code and makes it easier to extend

For ServiceNow developers, this means writing cleaner, more modular code. For architects, this means designing systems that are scalable, extensible, and aligned with enterprise architecture best practices.

ServiceNow Key Object-Oriented Principles in This Use Case

🔹 Encapsulation:

• IncidentEntity and ChangeRequestEntity encapsulate data
• ResponseObject standardizes responses

🔹 Inheritance:

• IncidentRepository and ChangeRequestRepository inherit from BaseRepository

🔹 Polymorphism:

• IncidentRepository and ChangeRequestRepository override methods for specific functionality

🔹 Abstraction:

• BaseRepository and BaseLogger hide complex logic, simplifying usage

🔹 Dependency Injection:

• IncidentService and ChangeRequestService receive repositories and loggers via constructor injection

 

Use Case: Incident and Change Request Integration in ServiceNow

In this example, we build a Service-Oriented Incident and Change Request System where:

• IncidentService manages incidents using IncidentRepository
• ChangeRequestService manages change requests using ChangeRequestRepository
• Dependency Injection allows ChangeRequestService to interact with IncidentService to link incidents to change requests

This use case is designed to meet the needs of both ServiceNow developers (who write and maintain the code) and architects (who design scalable enterprise solutions).

Benefits of This Integration

🔥 Modular Design: Each service is responsible for a specific business function
🔥 Loose Coupling: Services are loosely coupled and easily extendable
🔥 Code Reusability: Shared components like repositories and loggers can be reused across services
🔥 Scalability: New services can be added without modifying existing ones
🔥 Maintainability: Simplified code that is easier to understand, maintain, and debug
🔥 Testability: Services can be tested independently using mock dependencies

See It in Action!

Want to see a live demo of this Service-Oriented Architecture in ServiceNow?

📺 Watch my YouTube video, where I walk you through:
🔹 Implementing IncidentService and ChangeRequestService using SOA and Dependency Injection
🔹 Using the Repository Pattern for modular and reusable data access
🔹 Standardizing responses with ResponseObject
🔹 Reusing logging functionality with BaseLogger
🔹 Linking incidents to change requests using Service Integration

🎯 Watch the full tutorial here!  

Best Practices for Service Oriented Architecture in ServiceNow

💡 1. Use Constructor Injection: Always inject dependencies via constructors to promote loose coupling and testability
💡 2. Separate Business Logic from Data Access: Keep business logic in services and data access in repositories
💡 3. Standardize Responses and Logging: Use ResponseObject and BaseLogger for consistent responses and logs
💡 4. Follow the Single Responsibility Principle: Ensure that each service and repository has a single responsibility
💡 5. Use Mock Dependencies for Testing: Inject mock repositories and loggers during unit testing to isolate each component

Conclusion

By combining Service-Oriented Architecture (SOA) with Dependency Injection and Object-Oriented Programming (OOP) principles, ServiceNow developers and architects can build modular, maintainable, and scalable applications. Using IncidentService and ChangeRequestService, along with shared components like ResponseObject and BaseLogger, ensures that services are loosely coupled, reusable, and easy to integrate.

Have questions or want to share your experience? Comment below! And don’t forget to watch the YouTube demo for a live walkthrough! 🚀

Tags:

#ServiceNow #ServiceOrientedArchitecture #DependencyInjection #ObjectOrientedProgramming #RepositoryPattern #IncidentService #ChangeRequestService #SOA #BestPractices #MaintainableCode #Scalability #ServiceNowDevelopers #ServiceNowArchitects #EnterpriseDevelopment #ITSM