HttpClient, REST API Integration, Interceptors, and Error Handling
Connect Angular applications to backend services safely and predictably using HttpClient and layered API patterns.
Inside this chapter
- Why HTTP Integration Is Central
- Basic GET Request Example
- POST, PUT, DELETE, and API Layer Design
- Interceptors
- Error Handling Example
Series navigation
Study the chapters in order for the clearest path from Angular fundamentals to advanced architecture, testing, performance, and deployment. Use the navigation at the bottom to move smoothly across the full tutorial series.
Why HTTP Integration Is Central
Most Angular applications are not isolated frontend demos. They depend on backend APIs for authentication, data retrieval, updates, search, uploads, and analytics. Clean HTTP design is therefore a core skill, not an optional topic.
Basic GET Request Example
getCourses(): Observable<Course[]> {
return this.http.get<Course[]>('/api/courses');
}HttpClient returns Observables, which fit naturally with Angular and RxJS. Services usually own API communication and expose typed streams or methods to components.
POST, PUT, DELETE, and API Layer Design
Production applications typically wrap raw HTTP calls inside feature services. This centralizes endpoint paths, request models, response transformation, error handling, and authentication concerns instead of scattering them across components.
Interceptors
Interceptors can add auth tokens, log requests, normalize errors, measure timings, or refresh sessions. They are one of the most important Angular extension points for enterprise applications.
Error Handling Example
If a course creation request fails because of validation or server issues, the UI should not only show an error. It should preserve entered data, communicate clearly, and support retry or correction. Good HTTP handling is part of user experience design.