Spring-Data Mysql cannot find the name in the DB

I'm new to Spring-Data Mysql, I created a little method to make it give me a name from a list of names, it returns me the name with the oldest entry date. Unfortunately when I do the get it returns me this :

D:\>curl -G localhost:8080/demo/first  -d name=Biagio
{"timestamp":"2020-10-02T09:29:33.704+00:00","status":404,"error":"Not Found","message

I've tried them all a little but so far I can't be successful. Below is the method and the relative controller

UserRepositoryImpl.java

package com.example.accessingdatamysql;
import javax.persistence.EntityManager;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Root;
import org.springframework.stereotype.Component;
@Component
public class UserRepositoryImpl implements UserRepository {
private final EntityManager em;
public UserRepositoryImpl(EntityManager entityManager) {
this.em = entityManager;
}
@Override
public User findFirstByName(String name) {
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<User> criteria = builder.createQuery(User.class);
Root<User> root = criteria.from(User.class);
criteria.select(root).where(builder.equal(root.get("name"), name));
criteria.orderBy(builder.asc(root.get("timestamp")));
TypedQuery<User> query = em.createQuery(criteria).setMaxResults(1);
return query.getSingleResult();
}
@Override
//	per la creazione//
public void create(User entity) {
em.persist(entity);	
}
}

mainController.java

package com.example.accessingdatamysql;
import javax.persistence.NoResultException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
@Controller 
@RequestMapping(path="/demo") 
public class MainController {
@Autowired 
private UserRepository userRepository;
@Transactional
@PostMapping(path="/add")
public @ResponseBody String addNewUser (@RequestParam String name
, @RequestParam String email,@RequestParam String surname) 
{
User n = new User();
n.setName(name);
n.setSurname(surname);
n.setEmail(email);
userRepository.create(n);
return "Saved";
}
@GetMapping("/first")
User one(@RequestParam String name) {
System.out.print(name);
try { return userRepository.findFirstByName(name); 
} catch (NoResultException nre) { 
return null; } 
}
}

I add User and UserRepository.java for everything

User.java

package com.example.accessingdatamysql;
import java.sql.Timestamp;
import java.time.Instant;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity 
public class User {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;
public String name;
private String email;
private String surname;
@Column(name="stmp", columnDefinition = "TIMESTAMP (6)")
Timestamp timestamp = Timestamp.from(Instant.now());
public void setTimestamp(Timestamp timestamp) {
this.timestamp = timestamp;
}
public Timestamp getTimestamp() {
return timestamp;
}
public String getSurname() {
return surname;
}
public  void setSurname(String surname) {
this.surname = surname;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}

UserRepository.java

package com.example.accessingdatamysql;
import org.springframework.stereotype.Repository;
@Repository
public interface UserRepository {
User findFirstByName(String name);
void create(User entity);
}

EDIT: I insert the database referenced by this small project:

+----+---------------------+--------+----------------------------+---------+
| id | email               | name   | stmp                       | surname |
+----+---------------------+--------+----------------------------+---------+
| 32 | mirketto90@yahoo.it | Mirko  | 2020-10-01 12:31:47.827000 | NULL    |
| 36 | biagio@gmail.com    | Biagio | 2020-10-01 16:31:31.687000 | Vaso    |
| 37 | biagio@gmail.com    | Biagio | 2020-10-01 16:31:50.077000 | Vaso    |
| 38 | biagio@gmail.com    | Biagio | 2020-10-01 18:35:45.992000 | Vaso    |
+----+---------------------+--------+----------------------------+---------+

the first things I see are the following:

• Your method for /demo/first is not public.
• The proper way to call this endpoint should be curl localhost:8080/demo/first?name=Biagio -H "Accept: application/json"

You should be able to verify the endpoint localhost:8080/demo/first?name=Biagio using your browser, as it submits GET requests by default.

I managed to reproduce this issue, you should remove the class-level mapping and provide full path on the method in MainController:

@RestController
public class MainController {
    @Autowired
    private UserRepository userRepository;

    @Transactional
    @PostMapping("/demo/add")
    public @ResponseBody String addNewUser (
            @RequestParam String name,
            @RequestParam String email,
            @RequestParam String surname) 
    {
        User n = new User();
        n.setName(name);
        n.setSurname(surname);
        n.setEmail(email);
        userRepository.create(n);
        return "Saved";
    }

    @GetMapping("/demo/first")
    public User one(@RequestParam String name) {
        System.out.print(name);
        return userRepository.findFirstByName(name); 
    }
}

The following curl requests should succeed:

curl -X GET localhost:8080/demo/first?name=Biagio
curl -G localhost:8080/demo/first?name=Biagio
curl -G localhost:8080/demo/first -d name=Biagio

Update<br/>
The following fix is also working without leading slashes in the method-level mappings:

@Controller
@RequestMapping("/demo") // trailing slash optional, could be "/demo/"
public class MainController {
    @Autowired
    private UserRepository userRepository;

    @Transactional
    @PostMapping("add") // no leading slash
    public @ResponseBody String addNewUser (/* ... */) {
    // ...
    }

    @GetMapping("first") // no leading slash
    public User one(@RequestParam String name) {
        return userRepository.findFirstByName(name); 
    }
}