How to use

createStreamFromIterator

method

in

org.springframework.data.util.StreamUtils

@Override
public Stream<T> stream() {
  return StreamUtils.createStreamFromIterator(doStream());
}

  @Override
  protected Object doExecute(final AbstractJpaQuery query, Object[] values) {
    if (!SurroundingTransactionDetectorMethodInterceptor.INSTANCE.isSurroundingTransactionActive()) {
      throw new InvalidDataAccessApiUsageException(NO_SURROUNDING_TRANSACTION);
    }
    Query jpaQuery = query.createQuery(values);
    // JPA 2.2 on the classpath
    if (streamMethod != null) {
      return ReflectionUtils.invokeMethod(streamMethod, jpaQuery);
    }
    // Fall back to legacy stream execution
    PersistenceProvider persistenceProvider = PersistenceProvider.fromEntityManager(query.getEntityManager());
    CloseableIterator<Object> iter = persistenceProvider.executeQueryWithResultStream(jpaQuery);
    return StreamUtils.createStreamFromIterator(iter);
  }
}

@Override
public Stream<T> stream() {
  return StreamUtils.createStreamFromIterator(doStream());
}

@SuppressWarnings("unchecked")
<E> Stream<E> findStream() {
  if (queryType == QUERY) {
    return StreamUtils.createStreamFromIterator(((Query<E>) queryInstance).findIterate());
  }
  throw new IllegalArgumentException("query not supported!");
}

@SuppressWarnings("unchecked")
<E> Stream<E> findStream() {
  if (queryType == QUERY) {
    return StreamUtils.createStreamFromIterator(((Query<E>) queryInstance).findIterate());
  }
  throw new IllegalArgumentException("query not supported!");
}

/**
 * Only provides types that are also annotated with {@link Table}.
 */
@Override
public Iterable<? extends TypeInformation<?>> getPersistentEntityTypes() {
  return StreamUtils
      .createStreamFromIterator(super.getPersistentEntityTypes().iterator())
      .filter((typeInfo) -> typeInfo.getType().isAnnotationPresent(Table.class))
      .collect(Collectors.toList());
}

/**
 * Only provides types that are also annotated with {@link Table}.
 */
@Override
public Iterable<? extends TypeInformation<?>> getPersistentEntityTypes() {
  return StreamUtils
      .createStreamFromIterator(super.getPersistentEntityTypes().iterator())
      .filter((typeInfo) -> typeInfo.getType().isAnnotationPresent(Table.class))
      .collect(Collectors.toList());
}

protected Object executeStream(N1qlQuery query, Class<?> typeToRead) {
 logIfNecessary(query);
 return StreamUtils.createStreamFromIterator(executeCollection(query, typeToRead).iterator());
}

/**
 * Returns a {@link Stream} backed by the given {@link CloseableIterator} and forwarding calls to
 * {@link Stream#close()} to the iterator.
 *
 * @param iterator must not be {@literal null}.
 * @return
 * @since 2.0
 */
public static <T> Stream<T> createStreamFromIterator(CloseableIterator<T> iterator) {
  Assert.notNull(iterator, "Iterator must not be null!");
  return createStreamFromIterator((Iterator<T>) iterator).onClose(() -> iterator.close());
}

private Stream<String> getColumnNameStream(String prefix) {
  return StreamUtils.createStreamFromIterator(entity.iterator()) //
      .flatMap(p -> getColumnNameStream(p, prefix));
}

private Stream<String> getColumnNameStream(String prefix) {
  return StreamUtils.createStreamFromIterator(entity.iterator()) //
      .flatMap(p -> getColumnNameStream(p, prefix));
}

protected Object executeStream(N1qlQuery query, Class<?> typeToRead) {
 logIfNecessary(query);
 return StreamUtils.createStreamFromIterator(executeCollection(query, typeToRead).iterator());
}

/**
 * <p>
 * Execute a retrieval query. The query engine will return this in an iterator, which may need conversion to a single
 * domain entity or a stream.
 * </P>
 *
 * @param query       The query to run
 * @param queryMethod Holds metadata about the query, is paging etc
 * @return Query result
 */
private Object executeFindQuery(final KeyValueQuery<?> query, final QueryMethod queryMethod) {
  Iterable<?> resultSet = this.keyValueOperations.find(query, queryMethod.getEntityInformation().getJavaType());
  if (!queryMethod.isCollectionQuery() && !queryMethod.isPageQuery() && !queryMethod.isSliceQuery() && !queryMethod
      .isStreamQuery()) {
    // Singleton result
    return resultSet.iterator().hasNext() ? resultSet.iterator().next() : null;
  }
  if (queryMethod.isStreamQuery()) {
    return StreamUtils.createStreamFromIterator(resultSet.iterator());
  }
  return resultSet;
}

  @Override
  protected Object doExecute(final AbstractJpaQuery query, Object[] values) {
    if (!SurroundingTransactionDetectorMethodInterceptor.INSTANCE.isSurroundingTransactionActive()) {
      throw new InvalidDataAccessApiUsageException(NO_SURROUNDING_TRANSACTION);
    }
    Query jpaQuery = query.createQuery(values);
    // JPA 2.2 on the classpath
    if (streamMethod != null) {
      return ReflectionUtils.invokeMethod(streamMethod, jpaQuery);
    }
    // Fall back to legacy stream execution
    PersistenceProvider persistenceProvider = PersistenceProvider.fromEntityManager(query.getEntityManager());
    CloseableIterator<Object> iter = persistenceProvider.executeQueryWithResultStream(jpaQuery);
    return StreamUtils.createStreamFromIterator(iter);
  }
}