Produtos cadastrados desaparecem ao reiniciar o servidor

Oi Antonio, tudo bem?

Verifique o seu "hibernate.hbm2ddl.auto" na classe JPAConfiguration.java está mapeado com "update":

@EnableTransactionManagement
public class JPAConfiguration {

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {

        LocalContainerEntityManagerFactoryBean factoryBean = new LocalContainerEntityManagerFactoryBean();
        JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        factoryBean.setJpaVendorAdapter(vendorAdapter);

        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setUsername("root");
        dataSource.setPassword("");
        dataSource.setUrl("jdbc:mysql://localhost/casadocodigo");
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        factoryBean.setDataSource(dataSource);

        Properties properties = new Properties();
        properties.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL5Dialect");
        properties.setProperty("hibernate.show_sql", "true");
        properties.setProperty("hibernate.hbm2ddl.auto", "update");

        factoryBean.setJpaProperties(properties);
        factoryBean.setPackagesToScan("br.com.casadocodigo.loja.models");

        return factoryBean;
    }

    @Bean
    public JpaTransactionManager transactionManager(EntityManagerFactory emf) {
        return new JpaTransactionManager(emf);
    }


}