Java user authentication using Mysql database and Framework spring boot

Question

good afternoon. I am in the development of a web application using the framework spring boot, Ibernate and jpa with the mysql database. Finally I have a question about the authentication of this user because until now I can only save this user in the database but how can I authenticate it and know if the data in the database is the same that the user is typing in the form? good.. I will show here the only part of the backend because the doubt is all in the backend. this and the part where I used Hibernate.

/**
 Classe de persistência de dados ao banco mysql
 */

package com.web.Models;

import java.io.Serializable;

import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Generatedvalue; import javax.persistence.Generationtype; import javax.persistence.Id; import javax.persistence.Table; import javax.validation.constraints.Notnull;

@Entity @Table(name = "login") public class Login Implements Serializable{

private static final long serialVersionUID = -7123394242940032066L;

@Id
@GeneratedValue(strategy= GenerationType.AUTO)
private long id;

@NotNull
@Column(name = "usuario")
private String usuario;

@NotNull
@Column(name = "senha")
private String senha;


public Login() {

}
public Login(String usuario, String senha, long id) {
    this.usuario = usuario;
    this.senha = senha;
    this.id = id;
}


public long getId() {
    return id;
}
public void setId(long id) {
    this.id = id;
}
public String getUsuario() {
    return usuario;
}
public void setUsuario(String usuario) {
    this.usuario = usuario;
}
public String getSenha() {
    return senha;
}
public void setSenha(String senha) {
    this.senha = senha;
}

}

here the Repository

package com.web.Repository;

import org.springframework.data.repository.Crudrepository; import org.springframework.stereotype.Repository;

import com.web.Models.Login;

@Repository public interface Loginrepository extends Crudrepository{

}

and here the controller the user registration mappings usually work only the user validatorUsuario that does not work yet.

package com.web.Controller;

import org.springframework.Beans.factory.Annotation.Autowired;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.Annotation.Requestbody; import org.springframework.web.bind.Annotation.Requestmapping; import org.springframework.web.bind.Annotation.Requestmethod; import org.springframework.web.bind.Annotation.Responsebody;

import com.web.Models.Login; import com.web.Repository.Loginrepository; import com.web.Util.Log;

import ch.qos.logback.classic.Logger;

@Controller public class Logincontroller { @Autowired Private loginrepository Repository;

@RequestMapping(value="/cadastrarUsuario", method=RequestMethod.GET)
public String form() {
    return "addUser/cadastrarLogin";
}
@RequestMapping(value="/cadastrarUsuario", method=RequestMethod.POST)
public String form(Login login) {
    repository.save(login);
    return "redirect:/cadastrarUsuario";
}


@RequestMapping(value="/validarUsuario", method=RequestMethod.GET)
public String validform() {
    return "validUsuario/validarLogin";
}

because only the part of the controller that I cannot validate this user, I did not create a service class for reasons of exercise of the faculty only with Repository,controller and model, who can help me?

}