Spring/Hibernate CRUD not working (MySQL)

Question

I am trying to make a simple Spring/Hibernate/MySQL CRUD but it is not working :/ I got:

HTTP Status 500 - Internal Server Error

Type Exception Report

Message: Request processing failed; nested exception is java.lang.IllegalArgumentException: org.hibernate.hql.internal.ast.QuerySyntaxException: employees is not mapped [from employees order by last_name]

Description: The server encountered an unexpected condition that prevented it from fulfilling the request.

Here's my code:

Employee.java

package com.employeemanager.entity;

import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="employees")
public class Employee {

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id")
private int id;

@Column(name="first_name")
private String firstName;

@Column(name="last_name")
private String lastName;

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

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

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


public Employee(){

}
public Employee(String firstName){

}
public Employee(String firstName,Set<Project> projects){
    this.firstName=firstName;
    this.projects=projects;
}

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public String getFirstName() {
    return firstName;
}

public void setFirstName(String firstName) {
    this.firstName = firstName;
}

public String getLastName() {
    return lastName;
}

public void setLastName(String lastName) {
    this.lastName = lastName;
}

public String getEmail() {
    return email;
}

public void setEmail(String email) {
    this.email = email;
}

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}


}

EmployeeDAO.java

package com.employeemanager.dao;

import java.util.List;

import com.employeemanager.entity.Employee;

public interface EmployeeDAO {

public List<Employee> getEmployees();

public void saveEmployee(Employee theEmployee);

public Employee getEmployee(int theId);

public void deleteEmployee(int theId);


}

EmployeeDAOImpl.java

package com.employeemanager.dao;

import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;


import com.employeemanager.entity.Employee;

@Repository
public class EmployeeDAOImpl implements EmployeeDAO {


@Autowired
private SessionFactory sessionFactory;


@Override
public List<Employee> getEmployees() {

    Session currentSession=sessionFactory.getCurrentSession();
    List<Employee> employeeList=
            currentSession.createQuery("from employees order by 
last_name").getResultList();
    return employeeList;
}

@Override
public void saveEmployee(Employee theEmployee) {

    Session currentSession=sessionFactory.getCurrentSession();
    currentSession.saveOrUpdate(theEmployee);

}


@Override
public Employee getEmployee(int theId) {

Session currentSession=sessionFactory.getCurrentSession();

Employee theEmployee=currentSession.get(Employee.class, theId);

return theEmployee;

}


@Override
public void deleteEmployee(int theId) {

    Session currentSession=sessionFactory.getCurrentSession();

    Employee employee=((Employee) 
currentSession.load(Employee.class,theId));
    if(null!=employee){
         this.sessionFactory.getCurrentSession().delete(employee);
    }
}

}

EmployeeService.java

package com.employeemanager.service;

import java.util.List;

import com.employeemanager.entity.Employee;

public interface EmployeeService {

public List<Employee> getEmployees();

public void saveEmployee(Employee theEmployee);

public Employee getEmployee(int theId);

public void deleteEmployee(int theId);


}

EmployeeServiceImpl.java

package com.employeemanager.service;

import java.util.List;

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

import com.employeemanager.entity.Employee;
import com.employeemanager.dao.EmployeeDAO;

@Service
public class EmployeeServiceImpl implements EmployeeService {

@Autowired
private EmployeeDAO employeeDAO;

@Override
@Transactional
public List<Employee> getEmployees() {

    return employeeDAO.getEmployees();
}

@Override
@Transactional
public void saveEmployee(Employee theEmployee) {

    employeeDAO.saveEmployee(theEmployee);
}

@Override
@Transactional
public Employee getEmployee(int theId) {

    return employeeDAO.getEmployee(theId);
}

@Override
@Transactional
public void deleteEmployee(int theId) {

    employeeDAO.deleteEmployee(theId);

}

}

EmployeeController.java

package com.employeemanager.controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

import com.employeemanager.entity.Employee;
import com.employeemanager.entity.Project;
import com.employeemanager.service.EmployeeService;
import com.employeemanager.service.ProjectService;

@Controller
@RequestMapping("/employee")
public class EmployeeController {

@Autowired
private EmployeeService employeeService;

@Autowired
private ProjectService projectService;

@GetMapping("/list")
public String listEmployees(Model theModel){


    List<Employee> theEmployees=employeeService.getEmployees();

    theModel.addAttribute("employees",theEmployees);

    return"employees-list";
}

@GetMapping("/addEmployeeForm")
public String addEmployeeForm(Model theModel){

    Employee theEmployee=new Employee();
    List<Project> theProjects=projectService.getProjects();
    theModel.addAttribute("projects",theProjects);

    theModel.addAttribute("employee",theEmployee);

    return"employee-form";
}

@PostMapping("/saveEmployee")
public String saveEmployee(@ModelAttribute("employee") Employee theEmployee)
{

    employeeService.saveEmployee(theEmployee);

    return "redirect:/employee/list";
}

@GetMapping("/updateEmployeeForm")
public String updateEmployeeForm(@RequestParam("employeeId") int theId,
                                Model theModel){

    Employee theEmployee=employeeService.getEmployee(theId);
    theModel.addAttribute("employee",theEmployee);

    return"employee-form";
}

@GetMapping("/deleteEmployee")
public String deleteEmployee(@RequestParam("employeeId") int theId){
    employeeService.deleteEmployee(theId);
    return"redirect:/employee/list";
}

}

Do you have any ideas how to resolve this problem? Thank you for all your help :)

Answer 1

I think that there is an error in EmployeeDAOImpl.java. Change "employees" to "Employee" and "last_name" to "lastName" (names should be the same as in the mapped class(Employee.java))

Just change:

@Override
public List<Employee> getEmployees() {

Session currentSession=sessionFactory.getCurrentSession();
List<Employee> employeeList=
        currentSession.createQuery("from employees order by 
last_name").getResultList();
return employeeList;
}

to:

@Override
public List<Employee> getEmployees() {

Session currentSession=sessionFactory.getCurrentSession();
List<Employee> employeeList=
        currentSession.createQuery("from Employee order by 
lastName").getResultList();
return employeeList;
}

and tell us if it worked :)

Answer 2

If you are using HQL, then java Entity names should be used instead of real table names:

@Repository
public class EmployeeDAOImpl implements EmployeeDAO {

    @Override
    public List<Employee> getEmployees() {
        Session currentSession = sessionFactory.getCurrentSession();
        return currentSession.createQuery("from Employee order by last_name").getResultList();
    }
}

Answer 3

Change your HQL from this:

from employees order by last_name

To this:

from Employee e order by e.lastName

In HQL you should use namings the same as your mapped class.