Spring-Data Project is not receiving my Get/Post "404 not found"

I finished creating a simple Spring-boot project in which I can enter users and through the Get command it returns me the name (from a list of identical names) with the oldest entry date. Unfortunately, every time I ask for Get it returns this ERROR:

D:\>curl -G  localhost:8080/demo/first?=Biagio
{"timestamp":"2020-10-04T22:46:35.996+00:00","status":404,"error":"Not Found","message":"","path":"/demo/first"}

And to each of my POST / Add requests like this ERROR:

D:\>curl localhost:8080/demo/add -d name=Giovanni -d email=giovanni@gmail.com -d surname=Jackie
{"timestamp":"2020-10-04T22:40:51.928+00:00","status":404,"error":"Not Found","message":"","path":"/demo/add"}

Below I enter the interested parties of my project to try to get something out of it, because I have been stuck for days now

AccessingDataMysqlApplication.java

package com.example.accessingdatamysql;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.ComponentScan;
@SpringBootApplication
public class AccessingDataMysqlApplication {
public static void main(String[] args) {
SpringApplication.run(AccessingDataMysqlApplication.class, args);
}
}

MainController.java

package com.example.accessingdatamysql.rest;
import javax.persistence.NoResultException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import com.example.accessingdatamysql.model.UserDto;
import com.example.accessingdatamysql.service.UserService;
@RestController
@RequestMapping("/demo")
public class MainController {
@Autowired
private UserService userService;
@Transactional
//@RequestMapping(value = "/add/", method = RequestMethod.POST)
@PostMapping(path="/demo/add")
public String addNewUser(@PathVariable("name") String name, @PathVariable("email") String email,
@PathVariable("surname") String surname) {
UserDto n = new UserDto();
n.setName(name);
n.setSurname(surname);
n.setEmail(email);
userService.create(n);
return "User Saved in DB";
}
@SuppressWarnings({ "rawtypes", "unchecked" })
//@RequestMapping(value = "/fetchUser/{name}", method = RequestMethod.GET)
@GetMapping("/demo/first")
public ResponseEntity<UserDto> fetchUser(@PathVariable("name") String name) {
System.out.println(name);
try {
UserDto namefound = userService.findFirstByName(name);
System.out.println("Name found");
ResponseEntity<UserDto> user = new ResponseEntity<UserDto>(namefound, HttpStatus.OK);
return user;
} catch(NoResultException ne) {
System.out.println("User not found");
return new ResponseEntity("User not found with name : " + name, HttpStatus.NOT_FOUND);
}
}
}

UserService.java

package com.example.accessingdatamysql.service;
import org.springframework.stereotype.Service;
import com.example.accessingdatamysql.model.UserDto;
@Service
public interface UserService {
UserDto findFirstByName(String name);
void create(UserDto user);
}

UserServiceImpl.java

package com.example.accessingdatamysql.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
import com.example.accessingdatamysql.model.UserDto;
import com.example.accessingdatamysql.model.UserEntity;
import com.example.accessingdatamysql.repo.UserRepository;
import com.example.accessingdatamysql.util.UserMapper;
@Service
public class UserServiceImpl implements UserService {
@Autowired
private UserRepository userRepository;
@Autowired
UserMapper mapper;
@Override
public UserDto findFirstByName(String name) {
UserEntity entity = userRepository.findFirstByName(name);
return mapper.toDtoMapper(entity);
}
@Override
public void create(UserDto user) {
UserEntity entity = mapper.toEntityMapper(user);
userRepository.create(entity);
}
}

UserMapper.java

package com.example.accessingdatamysql.util;
import org.mapstruct.Mapper;
import com.example.accessingdatamysql.model.UserDto;
import com.example.accessingdatamysql.model.UserEntity;
@Mapper(componentModel = "spring")
public interface UserMapper {	
public UserEntity toEntityMapper (UserDto user);	
public UserDto toDtoMapper (UserEntity userEntity);
}

UserRepository.java

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

UserRepositoryImpl.java

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

UserDto.java

package com.example.accessingdatamysql.model;
import java.io.Serializable;
import java.sql.Timestamp;
public class UserDto implements Serializable {
/**
* 
*/
private static final long serialVersionUID = -7621330660870602403L;
/**
* 
*/
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Timestamp getTimestamp() {
return timestamp;
}
public void setTimestamp(Timestamp timestamp) {
this.timestamp = timestamp;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getSurname() {
return surname;
}
public void setSurname(String surname) {
this.surname = surname;
}
private Timestamp timestamp;
private String email;
private String surname;
}

If you need I can also insert User.java and the pom, but the pom has no problems as the dependencies are all correct.

You have an additional demo in your path descriptions for GET and POST methods, you should remove it:

@GetMapping("/demo/first")
@PostMapping(path = "/demo/first")

It should be :

@GetMapping("/first")
@PostMapping(path = "/first")

This because you have already defined demo in the RequestMapping annotation in the class level.