Parameter 0 of constructor in X required a bean of type 'Y' that could not be found

Issue

Whenever I run my Spring Boot app to connect to an AWS database I get the error saying

Parameter 0 of constructor in services.UserService required a bean of type 'repositories.UserRepository' that could not be found.

My current project structure is like this:

Here are the individual files:

User.kt:

package entities

import org.springframework.data.annotation.Id
import javax.persistence.Entity
import javax.persistence.GeneratedValue
import javax.persistence.GenerationType
import javax.persistence.Table

@Entity
@Table(name = "users")
data class User(
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    val id: Long?,
    val name: String
)

UserRepository.kt:

package repositories

import entities.User
import org.springframework.data.jpa.repository.Query
import org.springframework.data.repository.CrudRepository
import org.springframework.stereotype.Component
import org.springframework.stereotype.Repository

@Repository
interface UserRepository : CrudRepository<User, Long>{
    @Query("SELECT * FROM users")
    fun getAllUsers(): List<User>
}

UserService.kt:

package services

import entities.User
import org.springframework.stereotype.Service
import repositories.UserRepository

@Service
class UserService(val database: UserRepository) {

    fun getAllUsers(): List<User> = database.getAllUsers()

    fun post(user: User){
        database.save(user)
    }
}

UserController.kt:

package controllers

import entities.User
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.PostMapping
import org.springframework.web.bind.annotation.RestController
import services.UserService

@RestController
class UserController(val userService: UserService) {

    @GetMapping
    fun index() = "TEST"

    @PostMapping("/users/add")
    fun addUser(user: User){
        userService.post(user)
    }

    @GetMapping("/users/all")
    fun getAllUsers() = userService.getAllUsers()
}

TutortekApplication.kt:

package com.karbal.tutortek

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.context.annotation.ComponentScan

@SpringBootApplication(scanBasePackages = ["controllers", "entities", "repositories", "services"])
class TutortekApplication

fun main(args: Array<String>) {
    runApplication<TutortekApplication>(*args)
}

What am I missing to make this work?

Solution

Move the packages "controllers", "entities", "repositories" and "services" to com.karbal.tutortek. With this you may get rid of scanBasePackages = ["controllers", "entities", "repositories", "services"] and use only @SpringBootApplication as follows:

package com.karbal.tutortek

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.context.annotation.ComponentScan

@SpringBootApplication
class TutortekApplication

fun main(args: Array<String>) {
    runApplication<TutortekApplication>(*args)
}

@SpringBootApplication encapsulates @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations with their default attributes. The default value for @ComponentScan means that all the sub packages on the package the @ComponentScan is used are scanned. That is why it is usually a good practice to include the main class in the base package of the project.

Answered By - João Dias