Previews the results of a transform.
The API accepts a
PreviewTransformRequest object as a request and returns a
PreviewTransformRequest takes a single argument: a valid transform config.
When executing a
PreviewTransformRequest in the following manner, the client waits
PreviewTransformResponse to be returned before continuing with code execution:
PreviewTransformResponse response = client.transform() .previewTransform(request, RequestOptions.DEFAULT);
Synchronous calls may throw an
IOException in case of either failing to
parse the REST response in the high-level REST client, the request times out
or similar cases where there is no response coming back from the server.
In cases where the server returns a
5xx error code, the high-level
client tries to parse the response body error details instead and then throws
ElasticsearchException and adds the original
ResponseException as a
suppressed exception to it.
PreviewTransformRequest can also be done in an asynchronous fashion so that
the client can return directly. Users need to specify how the response or
potential failures will be handled by passing the request and a listener to the
asynchronous preview-transform method:
The asynchronous method does not block and returns immediately. Once it is
ActionListener is called back using the
if the execution successfully completed or using the
onFailure method if
it failed. Failure scenarios and expected exceptions are the same as in the
synchronous execution case.
A typical listener for
preview-transform looks like:
PreviewTransformResponse contains the preview documents