@Iiyama, Masatoshi Thank you for reaching out to Microsoft Q&A. Both Azure App service & Azure springs apps are PAAS offering solutions which can run spring boot applications. Based on your business requirement you need to choose which service suits for you.
- App Service is a fully managed hosting for web applications including websites and web APIs. These web applications may be deployed using code or containers. It is optimized for web applications and can be integrated with other services like Azure Container Apps or Azure Functions.
- Azure Spring Apps is considered for microservice architectures to run spring boot, spring cloud or any spring applications. This service manages the infrastructure of Spring applications so developers can focus on their code. Azure Spring Apps provides lifecycle management using comprehensive monitoring and diagnostics, configuration management, service discovery, CI/CD integration, blue-green deployments, and more.
Refer to these documentations to know more about the features supported by Azure App service and Azure Spring apps.
For additional information go through this documentation About comparing different container options and able different compute service in Azure.
Feel Free to reach back to me if you have any further questions on this.