Backend Server Features

• RESTful API Server Sample code based on Spring boot
• Major Exceptions are managed by RestControllerAdvice and ExceptionHandler
• Database such as H2DB is accessed such as insert, select, update and delete (CRUD) via Spring Data JPA
• It controls race condition using LockModeType.PESSIMISTIC_WRITE provided JPA
• API Documentation using Springdoc-openapi
• Code simplification using Lombok
• Container creation and execution using Docker
• Logging using Aspect and @Around
• Add security configuration using Spring Security such as basic authentication
• Add link to response using HATEOAS
• Add Server-Sent Event (SSE) example for real-time notification

1. Frameworks And Tools

• JDK 21
• spring-boot 3.3.5
• spring-boot-web
• spring-boot-data-jpa
• spring-boot-security
• spring-boot-cache
• ehcache / hazelcast
• springdoc-openapi
• h2database
• lombok
• spring-boot-hateoas

2. Api Spec URL

• http://localhost:8080/swagger-ui.html

3. Endpoints

• GET /api/v1/announcements
• GET /api/v1/announcements/page
• GET /api/v1/announcement/id/{id}
• POST /api/v1/announcement
• POST /api/v1/announcement/id/{id}
• PUT /api/v1/announcement/id/{id}
• DELETE /api/v1/announcement/id/{id}
• DELETE /api/v1/announcement/id/{id}/file-id/{fileId}

4. Docker container creation and execution command

docker build -t demo-api:local .  && docker run -p 9090:8080  -e"SPRING_PROFILES_ACTIVE=local"  demo-api:local
docker build -t demo-api:local -f Dockerfile_git . && docker run -p 9090:8080  -e"SPRING_PROFILES_ACTIVE=local"  demo-api:local
docker build -t demo-api:local -f Dockerfile_aot . && docker run -p 9090:8080  -e"SPRING_PROFILES_ACTIVE=local"  demo-api:local
docker build -t demo-api:local -f Dockerfile_cds . && docker run -p 9090:8080  -e"SPRING_PROFILES_ACTIVE=local"  demo-api:local
docker-compose up

5. Definition of key problems and solution strategies

• Race condition problem of database access
  • Apply to restrict access to other sessions during change through lock such as LockModeType.PESSIMISTIC_WRITE (for update) in DB table row
• Lack of memory problem by increasing platform threads
  • In order to reduce memory usage per request, using virutal thread
  • Parallel processing through jdk.virtualThreadScheduler.parallelism setting, default value is number of cpu core
• Security Problem
  • Apply universal security configuration to handle spring security
  • Only authenticated users can access the API through basic authentication or OAuth Token
• Problem of frequently access database for authentication in short time
  • Apply local cache through Ehcache
  • Apply cache data sharing through Hazelcast clustering
• Instance startup time and library loading issues
  • Minimize instance startup time through image creation through Graalvm AOT compilation

6. Test account and method

• account
  • robot / play
  • sam / ground
• method
  • swagger-ui.html

7. Effective cache engines adaption via ehcache or hazelcast

• Ehcache can be compiled to native image by GraalVM in order for local caching and executed properly
• It is hard to compile Hazelcast native image via GraalVM, and Hazelcast might not be supported officially
• SpringBoot cache with Hazelcast 5.2.4 is compiled by GraalVM native image and executed properly, however, another Hazelcast versions such as over 5.2.4 can be compiled but occurred runtime error.
• When application is started, Hazelcast needs to get cluster information and make a clustering. so it has needed to time to complete Clustering and synchronizing cache data.

8. Native image size and startup time

• GraalVM 21.0.2
  • The size of native image is about 66.9MB
  • The startup time of native image is about 1.351s
• GraalVM 23
  • https://medium.com/graalvm/welcome-graalvm-for-jdk-23-203928491b2b
  • oracle/graal#7626
  • The size of native image is about 66.9MB
  • The startup time of native image is about 1.351s