Parameter 0 of constructor in com.example.service.QuestionService required a bean of type 'com.example.Dao.QuestionDao' that could not be found

Question

Description:

Parameter 0 of constructor in com.example.service.QuestionService required a bean of type 'com.example.Dao.QuestionDao' that could not be found.

Action:

Consider defining a bean of type 'com.example.Dao.QuestionDao' in your configuration.

I couldn't solve this problem for last 2 days ..........If anyone know please help me...

`Controller:

@RestController
@RequestMapping("question")
public class QuestionController<Question> {

    private QuestionSerice questionService;
    public QuestionController (QuestionService questionService)
    { this.questionService = questionService;
    }
    // ------Read Operation----
    @GetMapping("allQuestions")

        public List<com.example.model.Question> getAllQuestions () {
        return questionService.getAllQuestions();
    }
    @GetMapping("category/{category}")
    public List<com.example.model.Question> getQuestionsByCategory (@PathVariable String category) {
    return questionService.getQuestionsByCategory( category);
    }
    //------Create Operation---
    @PostMapping("create")
    public String createQuestion (@RequestBody Question question) {
    return questionService.createQuestion ((com.example.model.Question) question);
    }
}

QuestionDao:

@Repository
public interface QuestionDao extends JpaRepository<Question, Integer>{
List<Question> findByCategory (String category);
}

Service:

@Service
public class QuestionService {

    
    private QuestionDao questionDao;
    

    public QuestionService(QuestionDao questionDao) {
        this.questionDao = questionDao;
    }


    public List<Question> getAllQuestions() {
        return questionDao.findAll();
        
    }

    public String createQuestion(Question question) {
         questionDao.save(question) ;
         return "Sucess";
    }

    public List<Question> getQuestionsByCategory(String category) {
        
        return questionDao.findByCategory(category);
    }
    
    
}

Dao: @Repository public interface QuestionDao extends JpaRepository<Question,Integer>{

List<Question> findByCategory(String category);

} model:

@Data
@Entity
@Table(name = "question")
public class Question {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "questionTitle")
    private String questionTitle;

    @Column(name = "option1")
    private String option1;

    @Column(name = "option2")
    private String option2;

    @Column(name = "option3")
    private String option3;

    @Column(name = "option4")
    private String option4;

    @Column(name = "rightAnswer")
    private String rightAnswer;

    @Column(name = "difficultylevel")
    private String difficultylevel;

    @Column(name = "category")
    private String category;
}

main:

@SpringBootApplication
@ComponentScan(basePackages={"com.example.controller","com.example.demo","com.example.Dao","com.example.model","com.example.service"})
public class QuizMaker1Application {

    private QuestionDao questionDao;
    public static void main(String[] args) {
        SpringApplication.run(QuizMaker1Application.class, args);
    }
    

   
}

Answer 1

First of all remove ComponentScan annotation from QuizMaker1Application. It is not required for spring boot application to find beans in root directory.

Then remove private QuestionDao questionDao; from QuizMaker1Application. It's not used there, so it's not required.

This should be fine to start and find beans and repository.

If it will not work. Try adding @EnableJpaRepositories("com.example.dao") to QuizMaker1Application.

Answer 2

I made a mistake during the package creation

this is a wrong way to create a package -----

com.example.Quizmaker1Application
com.example.controller
|
QuestionController.class
com.example.service
|
QuestionService.class
com.example.dao
|
QuestionDao.class
com.example.model
|
Question.class

this is a correct way to create a package -----

com.example.Quizmaker1Application
|
   com.example.Quizmaker1Application.controller
   |
   QuestionController.class
|
   com.example.Quizmaker1Application.service
   |
   QuestionService.class
|
   com.example.Quizmaker1Application.dao
   |
   QuestionDao.class
|
   com.example.Quizmaker1Application.model
   |
   Question.class