Parameter 0 of constructor in ‘ ‘ required a bean of type ‘ ‘ that could not be found

I am creating a spring boot application, wherein any client can submit the request, these request can be GET, PUT, POST, DELETE.

But while creating this application, I am getting the following errors:

***************************
APPLICATION FAILED TO START
***************************

Description:

Parameter 0 of constructor in com.idr.springboot.service.PersonService required a bean of type 'com.idr.springboot.dao.PersonDao' that could not be found.

The following candidates were found but could not be injected:
    - User-defined bean


Action:

Consider revisiting the entries above or defining a bean of type 'com.idr.springboot.dao.PersonDao' in your configuration.

The structure of my application is:

PersonDao.java

package com.idr.springboot.dao;

import com.idr.springboot.model.Person;
import java.util.UUID;


public interface PersonDao {

    int insertPerson(UUID id, Person person);

    default int insertPerson(Person person) {
        UUID id = UUID.randomUUID();
        return insertPerson(id, person);
    }


}

PersonService.java

package com.idr.springboot.service;

import com.idr.springboot.dao.PersonDao;
import com.idr.springboot.model.Person;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;

@Service
public class PersonService {


    private final PersonDao personDao;

    @Autowired
    public PersonService(@Qualifier("fake demo") PersonDao personDao) {
        this.personDao = personDao;
    }


    public int addPerson(Person person) {
        return personDao.insertPerson(person);
    }
}

I know that many questions with the following error, are already been asked, but still I am not able to solve this.

Parameter 0 of constructor in com.idr.springboot.service.PersonService required a bean of type 'com.idr.springboot.dao.PersonDao' that could not be found.

I have tried to annotate PersonDao.java with @Service, @Repository, @Component, but still I am getting the same error.

I have even tried solutions from these SO answers :

(1) Parameter 0 of constructor in required a bean of type ‘java.lang.String’ that could not be found

(2) Spring – Error Parameter 0 of constructor in Service required a bean of type Configuration that could not be found

(3) Parameter 0 of constructor in ….. Spring Boot

But still I am not able to resolve my issue.

Answer

By adding the qualifier @Qualifier("fake demo") to public PersonService(@Qualifier("fake demo") PersonDao personDao) a bean with that qualifier is searched to be injected in PersonService which does not exist. You can declare this qualifier as well on PersonDao or remove it. I would recommend removing it. In addition you should annotate PersonDao with @Repository and extend interface org.springframework.data.repository.Repository.