[Spring Boot] Get user information with Rest API (beginner)

Things necessary

1. entity class (Employee.java)
2. Repository interface (EmployeeRepository.java)
3. main class (first called class, SampleApplication.java)
4. RestController class (Con.java)
5. application.properties (DB information retention file)
6. build.gradle (mainly dependencies)

Source code

Employee.java

@Entity
@Table(name="m_emp")
public class Employee {
    @Id
    @Column(name="empno")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;
    private String empname;
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getEmpname() {
        return empname;
    }
    public void setEmpname(String empname) {
        this.empname = empname;
    }
}

EmployeeRepository.java

@Repository
public interface EmployeeRepository extends JpaRepository<Employee, Long> {
}

SampleApplication.java

@SpringBootApplication
public class SampleApplication {
    public static void main(String[] args) {
        SpringApplication.run(SampleApplication.class, args);
    }
}

Con.java

@RestController
public class Con {
    @Autowired
    EmployeeRepository empRepository;
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public String index(Model model) {
        List<Employee> emplist=empRepository.findAll();
        model.addAttribute("emplist", emplist);
        return emplist.toString();
    }
}

application.properties

spring.datasource.url=jdbc:mysql://localhost:3306/db name
spring.datasource.username=root
//No password required if no password is specified in brew install
#spring.datasource.password=mysql
spring.datasource.driverClassName=com.mysql.cj.jdbc.Driver
spring.jpa.database=MYSQL
spring.jpa.hibernate.ddl-auto=update

build.gradle

plugins {
    id 'org.springframework.boot' version '2.1.8.RELEASE'
    id 'io.spring.dependency-management' version '1.0.8.RELEASE'
    id 'java'
}

group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

configurations {
    developmentOnly
    runtimeClasspath {
        extendsFrom developmentOnly
    }
    compileOnly {
        extendsFrom annotationProcessor
    }
}

repositories {
    mavenCentral()
}

dependencies {
        compile('org.springframework.boot:spring-boot-starter-data-jpa')
        compile('org.springframework.boot:spring-boot-starter-thymeleaf')
        compile('org.springframework.boot:spring-boot-starter-web')
        runtime('org.springframework.boot:spring-boot-devtools')
        runtime('mysql:mysql-connector-java')
        compileOnly('org.projectlombok:lombok')
        implementation('org.springframework.boot:spring-boot-starter-tomcat')
        testCompile('org.springframework.boot:spring-boot-starter-test')
}