Kotlin and Spring boot a pleasant experience and some rough edges

In the last months, we have been working on Karumi with Spring boot building web services with Kotlin. The experience has been quite pleasant. I will explain how we have used Kotlin to write quality backend code, how to write tests and how to get the most out of both technologies.

Besides, we will explain some problems we have had in the development of the applications and how we have solved them.

Transcript

1. Kotlin and Spring boot a pleasant experience and some rough edges Jorge Juan Barroso Carmona Developer and GDE jorge@karumi.com @flipper83 https://greach.contestia.es
2. Sergio Gutierrez Pedro Gomez Davide Mendolia Fran Toro Antonio Lopez
3. Testing for android & iOS. Trainings Architecture, Patterns and principles for Android & iOS. Mastering Git. Advanced mobile development. Testing for android & iOS. Architecture, Patterns and principles for Android & iOS. Companies For Everybody
5. Adam Tornhill “Computer languages differ not so much in what they make possible, but in what they make easy.” Larry Wall
6. Our Needs
7. Fast Iterations
8. Easy for writing Test
9. Big Community
10. Support Static type language
11. Our approach
12. Rest API
13. We don’t need to be full async
14. Clean Architecture
15. Kotlin as main Languge
16. functional data flow Arrow
17. JWT authorization
18. Adam Tornhill RestControllers Use Case Rich Model Repository apiModels DataSources EntityModels
19. A Request Example
20. Adam Tornhill ProjectController GetProject Projects Project Repository ProjectsApi Project DataSources Project Entity GetProject
21. @RestController class ProjectController( private val obtainProjects: ObtainProjects ) { @GetMapping("/projects") fun getProjectsEndpoint( authentication: Authentication ) = obtainProjects( authentication.getCurrentUser() ).fold( ifRight{ ResponseEntity.ok(it.mapToApi()) }, ifLeft = { it.toErrorApi() } ) }
22. @RestController class ProjectController( private val obtainProjects: ObtainProjects ) { @GetMapping("/projects") fun getProjectsEndpoint( authentication: Authentication ) = obtainProjects( authentication.getCurrentUser() ).fold( ifRight{ ResponseEntity.ok(it.mapToApi()) }, ifLeft = { it.toErrorApi() } ) }
23. @RestController class ProjectController( private val obtainProjects: ObtainProjects ) { @GetMapping("/projects") fun getProjectsEndpoint( authentication: Authentication ) = obtainProjects( authentication.getCurrentUser() ).fold( ifRight{ ResponseEntity.ok(it.mapToApi()) }, ifLeft = { it.toErrorApi() } ) }
24. @Component class ObtainProjects( val projectRepository: ProjectRepository ) { operator fun invoke( currentUser: User ): Either<ProjectError, Projects> = projectRepository.getAll(currentUser) }
25. @Component //@Service class ObtainProjects( val projectRepository: ProjectRepository ) { operator fun invoke( currentUser: User ): Either<ProjectError, Projects> = projectRepository.getAll(currentUser) }
26. @Component class ObtainProjects( val projectRepository: ProjectRepository ) { operator fun invoke( currentUser: User ): Either<ProjectError, Projects> = projectRepository.getAll(currentUser) }
27. @Repository class ProjectRepository( private val projectDataSource: ProjectDataSource ) { fun getAll( currentUser: User ): Either<ProjectError, Projects> = TryLogger { Projects( projects = projectDataSource .findByOwner( userEntity = currentUser.mapToEntity() ) .mapToDomain() ) }.toEither { ProjectError.DbStorageError } }
28. @Repository class ProjectRepository( private val projectDataSource: ProjectDataSource ) { fun getAll( currentUser: User ): Either<ProjectError, Projects> = TryLogger { Projects( projects = projectDataSource .findByOwner( userEntity = currentUser.mapToEntity() ) .mapToDomain() ) }.toEither { ProjectError.DbStorageError } }
29. /**/ Projects( projects = projectDataSource .findByOwner( userEntity = currentUser.mapToEntity() ) .mapToDomain() ) /**/ fun User.mapToEntity(): UserEntity = UserEntity( _id = this.id, name = this.name, email = this.email, username = this.username )
30. @Repository class ProjectRepository( private val projectDataSource: ProjectDataSource ) { fun getAll( currentUser: User ): Either<ProjectError, Projects> = TryLogger { Projects( projects = projectDataSource .findByOwner( userEntity = currentUser.mapToEntity() ) .mapToDomain() ) }.toEither { ProjectError.DbStorageError } }
31. interface ProjectDataSource : MongoRepository<ProjectEntity, String> { fun findByOwner( userEntity: UserEntity ): List<ProjectEntity> }
32. interface ProjectDataSource : MongoRepository<ProjectEntity, String> { fun findByOwner( userEntity: UserEntity ): List<ProjectEntity> }
33. @Repository class ProjectRepository( private val projectDataSource: ProjectDataSource ) { fun getAll( currentUser: User ): Either<ProjectError, Projects> = TryLogger { Projects( projects = projectDataSource .findByOwner( userEntity = currentUser.mapToEntity() ) .mapToDomain() ) }.toEither { ProjectError.DbStorageError } }
34. @Repository class ProjectRepository( private val projectDataSource: ProjectDataSource ) { fun getAll( currentUser: User ): Either<ProjectError, Projects> = TryLogger { Projects( projects = projectDataSource .findByOwner( userEntity = currentUser.mapToEntity() ) .mapToDomain() ) }.toEither { ProjectError.DbStorageError } }
35. sealed class DomainError( val message: String ) sealed class ProjectError( message: String ) : DomainError(message, field) { object DbStorageError : ProjectError( message = "Error accessing to the db” ) class NotFound( field: String ) : ProjectError(message = "$field not found”) }
36. @Component class ObtainProjects( val projectRepository: ProjectRepository ) { operator fun invoke( currentUser: User ): Either<ProjectError, Projects> = projectRepository.getAll(currentUser) }
37. @RestController class ProjectController( private val obtainProjects: ObtainProjects ) { @GetMapping("/projects") fun getProjectsEndpoint( authentication: Authentication ) = obtainProjects( authentication.getCurrentUser() ).fold( ifRight = { ResponseEntity.ok(it.mapToApi()) }, ifLeft = { it.toErrorApi() } ) }
38. fun ProjectError.toErrorApi(): ResponseEntity<String> = when (this) { ProjectError.DbStorageError -> ResponseEntity.status(HttpStatus.SERVICE_UNAVAILABLE) is ProjectError.NotFound -> ResponseEntity.status(HttpStatus.NOT_FOUND }.body(createErrorMessage(this)) fun createErrorMessage( projectError: ProjectError ): String = projectError.toJson()
39. fun ProjectError.toErrorApi(): ResponseEntity<String> = when (this) { ProjectError.DbStorageError -> ResponseEntity.status(HttpStatus.SERVICE_UNAVAILABLE) is ProjectError.NotFound -> ResponseEntity.status(HttpStatus.NOT_FOUND }.body(createErrorMessage(this)) fun createErrorMessage( projectError: ProjectError ): String = projectError.toJson()
40. Authentication
41. @RestController class ProjectController( private val obtainProjects: ObtainProjects ) { @GetMapping(“/projects”) // @Secured({"ROLE_ADMIN", "ROLE_USER"}) // @PreAuthorize(“hasRole(‘ADMIN')") fun getProjectsEndpoint( authentication: Authentication ) = obtainProjects( authentication.getCurrentUser() ).fold( ifRight{ ResponseEntity.ok(it.mapToApi()) }, ifLeft = { it.toErrorApi() } ) }
42. class JwtTokenFilter( private val jwtTokenProvider: JwtTokenProvider) : OncePerRequestFilter() { @Throws(ServletException::class, IOException::class) override fun doFilterInternal( httpServletRequest: HttpServletRequest, httpServletResponse: HttpServletResponse, filterChain: FilterChain ) { val token = jwtTokenProvider.resolveToken(httpServletRequest) if (token == null) { filterChain.doFilter(httpServletRequest, httpServletResponse) return } if (jwtTokenProvider.validateToken(token)) { val auth = jwtTokenProvider.getAuthentication(token) SecurityContextHolder.getContext().authentication = auth } filterChain.doFilter(httpServletRequest, httpServletResponse) } }
43. if (jwtTokenProvider.validateToken(token)) { val auth = jwtTokenProvider.getAuthentication(token) SecurityContextHolder.getContext().authentication = auth } @GetMapping(“/projects”) fun getProjectsEndpoint( authentication: Authentication )
44. Is this the real life?
45. @Component class UploadVideo( val projectRepository: ProjectRepository, val storageService: StorageService, val videoRepository: VideoRepository ) { operator fun invoke(newVideo: NewVideo): Either<ProjectError, Video> = binding { if (!validateVideo(newVideo)) ProjectError.VideoFormatError.left().bind() val project = projectRepository[newPhoto.projectId] .bind() .toEither { ProjectError.NotFound("project") } .bind() val videoStorageInfo = storageService .storePhoto( generateName(project.id), video ).bind() photoRepository.add(VideoToStore( filename = videoStorageInfo.filename, videoUrl = videoStorageInfo.url, owner = newVideo.owner, projectId = projectId )).bind() }
46. @Component class UploadVideo( val projectRepository: ProjectRepository, val storageService: StorageService, val videoRepository: VideoRepository ) { operator fun invoke(newVideo: NewVideo): Either<ProjectError, Video> = binding { if (!validateVideo(newVideo)) ProjectError.VideoFormatError.left().bind() val project = projectRepository[newPhoto.projectId] .bind() .toEither { ProjectError.NotFound("project") } .bind() val videoStorageInfo = storageService .storePhoto( generateName(project.id), video ).bind() photoRepository.add(VideoToStore( filename = videoStorageInfo.filename, videoUrl = videoStorageInfo.url, owner = newVideo.owner, projectId = projectId )).bind() }
47. @Component class UploadVideo( val projectRepository: ProjectRepository, val storageService: StorageService, val videoRepository: VideoRepository ) { operator fun invoke(newVideo: NewVideo): Either<ProjectError, Video> = binding { if (!validateVideo(newVideo)) ProjectError.VideoFormatError.left().bind() val project = projectRepository[newPhoto.projectId] .bind() .toEither { ProjectError.NotFound("project") } .bind() val videoStorageInfo = storageService .storePhoto( generateName(project.id), video ).bind() photoRepository.add(VideoToStore( filename = videoStorageInfo.filename, videoUrl = videoStorageInfo.url, owner = newVideo.owner, projectId = projectId )).bind() }
48. @Component class UploadVideo( val projectRepository: ProjectRepository, val storageService: StorageService, val videoRepository: VideoRepository ) { operator fun invoke(newVideo: NewVideo): Either<ProjectError, Video> = binding { if (!validateVideo(newVideo)) ProjectError.VideoFormatError.left().bind() val project = projectRepository[newPhoto.projectId] .bind() .toEither { ProjectError.NotFound("project") } .bind() val videoStorageInfo = storageService .storePhoto( generateName(project.id), video ).bind() photoRepository.add(VideoToStore( filename = videoStorageInfo.filename, videoUrl = videoStorageInfo.url, owner = newVideo.owner, projectId = projectId )).bind() }
49. @Component class UploadVideo( val projectRepository: ProjectRepository, val storageService: StorageService, val videoRepository: VideoRepository ) { operator fun invoke(newVideo: NewVideo): Either<ProjectError, Video> = binding { if (!validateVideo(newVideo)) ProjectError.VideoFormatError.left().bind() val project = projectRepository[newPhoto.projectId] .bind() .toEither { ProjectError.NotFound("project") } .bind() val videoStorageInfo = storageService .storePhoto( generateName(project.id), video ).bind() photoRepository.add(VideoToStore( filename = videoStorageInfo.filename, videoUrl = videoStorageInfo.url, owner = newVideo.owner, projectId = projectId )).bind() }
50. @Component class UploadVideo( val projectRepository: ProjectRepository, val storageService: StorageService, val videoRepository: VideoRepository ) { operator fun invoke(newVideo: NewVideo): Either<ProjectError, Video> = binding { if (!validateVideo(newVideo)) ProjectError.VideoFormatError.left().bind() val project = projectRepository[newPhoto.projectId] .bind() .toEither { ProjectError.NotFound("project") } .bind() val videoStorageInfo = storageService .storePhoto( generateName(project.id), video ).bind() photoRepository.add(VideoToStore( filename = videoStorageInfo.filename, videoUrl = videoStorageInfo.url, owner = newVideo.owner, projectId = projectId )).bind() }
51. Find me I am very social! jorge@karumi.com @flipper83 Questions? https://greach.contestia.es