我和我的同事们正在做一个SpringBoot项目，我们同时工作，我们都连接到同一个mysql数据库。问题是，过了一段时间，我们中的一些人将不再能够连接，错误是太多的连接，现在我和数据库管理员谈过，他将最大连接数提高到500（在此之前大约为150），但我们仍然收到错误，如何修复此错误？我们使用的唯一配置属性如下：

spring.datasource.url= ...
spring.datasource.username= ...
spring.datasource.password= ...
spring.datasource.hikari.maximum-pool-size=25

也许jpa每次执行查询时都会打开一个新的连接，但没有关闭它？我不知道，我对此一无所知
编辑：我被要求展示一些关于与数据库交互的代码，下面是：

@Autowired
private EmployeeDAO employeeDAO;
@Autowired
private LogDAO logDAO;
@Autowired
private ContrattoLavoroDAO contrattoLavoroDAO;

    @Override
    public void deleteEmployeeById(Long idEmployee, String username) {
        contrattoLavoroDAO.deleteContrattoByEmpId(idEmployee);
        employeeDAO.deleteById(idEmployee);
        LogEntity log = new LogEntity();
        LocalDateTime date = LocalDateTime.now();
        log.setData(date);
        log.setUser(username);
        log.setCrud("delete");
        log.setTabella("Employees");
        log.setDescrizione("l'utente " + username + " ha rimosso il dipendente con matricola " + idEmployee);
        logDAO.save(log);
    }

下面是DAO的模型：

public interface ContrattoLavoroDAO extends JpaRepository<ContrattoLavoroEntity, Long> {

    @Modifying
    @Query(value = "DELETE contratto_lavoro, employee_contratto FROM contratto_lavoro" + " INNER JOIN"
            + " employee_contratto ON employee_contratto.id_contratto = contratto_lavoro.id_contratto" + " WHERE"
            + " contratto_lavoro.id_contratto = ?1", nativeQuery = true)
    public void deleteContrattoByEmpId(Long empId);
}