Spring mvc works with AdminDaoImpl but not if you implement the AdminDao

[mike molin]

I can persist an admin to the database when i dont implement the interface but when i implement it, i get this error.

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'startController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: se.trix.data.AdminService se.trix.controller.StartController.as; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'adminService': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private se.trix.daoimpl.AdminDaoImpl se.trix.data.AdminService.ar; nested exception is java.lang.IllegalArgumentException: Can not set se.trix.daoimpl.AdminDaoImpl field se.trix.data.AdminService.ar to com.sun.proxy.$Proxy19
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:292)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1185)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475)

adminDao

package se.trix.dao;

import se.trix.model.Admin;


public interface AdminDao {
	
	public void addAdmin(Admin admin);
	
	public boolean doAdminExist(Admin admin);
	
	public boolean addNewAdmin(Admin admin);
	
	public Admin getAdminById(Long id);
	
	public void updateAdmin(Admin admin);
	
	public void deleteAdmin(Long id);
	
	public Admin getAdminFromLoginPage(Long id, String password);
	
	public boolean checkIfUserIsAdmin(Long id, String password);

}

AdminDaoImpl

package se.trix.daoimpl;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

import se.trix.dao.AdminDao;
import se.trix.model.Admin;

@Repository
public class AdminDaoImpl implements AdminDao{

	@PersistenceContext
	private EntityManager em;
	
	@Override
	@Transactional
	public void addAdmin(Admin admin) {
		// TODO Auto-generated method stub
		em.persist(admin);
		
	}

	@Override
	public boolean doAdminExist(Admin admin) {
		// TODO Auto-generated method stub
		return false;
	}

	@Override
	public boolean addNewAdmin(Admin admin) {
		// TODO Auto-generated method stub
		return false;
	}

	@Override
	public Admin getAdminById(Long id) {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public void updateAdmin(Admin admin) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void deleteAdmin(Long id) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public Admin getAdminFromLoginPage(Long id, String password) {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public boolean checkIfUserIsAdmin(Long id, String password) {
		// TODO Auto-generated method stub
		return false;
	}

}

but when i do this it works, but i dont want to to it this way i want to implement the interface

package se.trix.daoimpl;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

import se.trix.dao.AdminDao;
import se.trix.model.Admin;

@Repository
public class AdminDaoImpl {

	@PersistenceContext
	private EntityManager em;
	
	
	@Transactional
	public void addAdmin(Admin admin) {
		// TODO Auto-generated method stub
		em.persist(admin);
		
	}

	
	public boolean doAdminExist(Admin admin) {
		// TODO Auto-generated method stub
		return false;
	}

	
	public boolean addNewAdmin(Admin admin) {
		// TODO Auto-generated method stub
		return false;
	}

	
	public Admin getAdminById(Long id) {
		// TODO Auto-generated method stub
		return null;
	}

	
	public void updateAdmin(Admin admin) {
		// TODO Auto-generated method stub
		
	}

	
	public void deleteAdmin(Long id) {
		// TODO Auto-generated method stub
		
	}

	
	public Admin getAdminFromLoginPage(Long id, String password) {
		// TODO Auto-generated method stub
		return null;
	}

	
	public boolean checkIfUserIsAdmin(Long id, String password) {
		// TODO Auto-generated method stub
		return false;
	}

}

adminservice

package se.trix.data;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import se.trix.daoimpl.AdminDaoImpl;
import se.trix.model.Admin;



@Service
public class AdminService {

	
	@Autowired
	private AdminDaoImpl ar;
	
	public void addAdmin(Admin admin){
		ar.addAdmin(admin);
	}
}

Please can anyone help me with this, it must be a way to get it to work when implementing the interface ?

[Jayesh A Lalwani]

You should code your service to the interface not to the implementation. In other words, in admin service, declare ar as AdminService

[mike molin]

i get the same problem if i code it to the adminservice, as long as i dont implement the interface it works, but as soon as i implement it i get the same error

[Jayesh A Lalwani]

Sorry, my mistake. In AdminService, declare are as AdminDAO, not as AdminDAOImpl

[mike molin]

Thank you so much now it works :-)
But why does it work when i use the Dao and not the DaoImpl

[Jayesh A Lalwani]

When you have an AOP annotation on a class that implements an interface, spring creates a java proxy class that implements the interface. When the proxy is called, it calls the aspect and your class. If your class doesn't implement interface, spring cannot use java proxy, so it falls back to using cglib, which creates a class that extends your class. So, the differrence is when you implement interface spring creates a class that implements the interface, when you don't implement interface, spring creates a class that extends your class

Now, during auto wiring, if it has a proxy class that implements the AdminDAO interface, it cannot inject it I to a property of type admindaoimpl. Once you changed your auto wiring to inject the interface, it worked