DatabaseWrapper.java 文件源码

/**
 * Use this for COUNT() and similar sql queries which are guaranteed to return a result
 */
@Nonnull
@CheckReturnValue
public <T> T selectSqlQuerySingleResult(@Nonnull final String queryString,
                                        @Nullable final Map<String, Object> parameters,
                                        @Nonnull final Class<T> resultClass) throws DatabaseException {
    final EntityManager em = this.databaseConnection.getEntityManager();
    try {
        final Query q = em.createNativeQuery(queryString);
        if (parameters != null) {
            parameters.forEach(q::setParameter);
        }
        em.getTransaction().begin();
        final T result = resultClass.cast(q.getSingleResult());
        em.getTransaction().commit();
        return setSauce(result);
    } catch (final PersistenceException | ClassCastException e) {
        final String message = String.format("Failed to select single result plain SQL query %s with %s parameters for class %s on DB %s",
                queryString, parameters != null ? parameters.size() : "null", resultClass.getName(), this.databaseConnection.getName());
        throw new DatabaseException(message, e);
    } finally {
        em.close();
    }
}