[[java-rest-high-x-pack-ml-get-datafeed]]
=== Get Datafeed API

The Get Datafeed API provides the ability to get {ml} datafeeds in the cluster.
It accepts a `GetDatafeedRequest` object and responds
with a `GetDatafeedResponse` object.

[[java-rest-high-x-pack-ml-get-datafeed-request]]
==== Get Datafeed Request

A `GetDatafeedRequest` object gets can have any number of `datafeedId` entries.
However, they all must be non-null. An empty list is the same as requesting for all datafeeds.

["source","java",subs="attributes,callouts,macros"]
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include-tagged::{doc-tests}/MlClientDocumentationIT.java[x-pack-ml-get-datafeed-request]
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<1> Constructing a new request referencing existing `datafeedIds`, can contain wildcards
<2> Whether to ignore if a wildcard expression matches no datafeeds.
 (This includes `_all` string or when no datafeeds have been specified)

[[java-rest-high-x-pack-ml-get-datafeed-execution]]
==== Execution

The request can be executed through the `MachineLearningClient` contained
in the `RestHighLevelClient` object, accessed via the `machineLearningClient()` method.

["source","java",subs="attributes,callouts,macros"]
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include-tagged::{doc-tests}/MlClientDocumentationIT.java[x-pack-ml-get-datafeed-execute]
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<1> The count of retrieved datafeeds
<2> The retrieved datafeeds

[[java-rest-high-x-pack-ml-get-datafeed-execution-async]]
==== Asynchronous Execution

The request can also be executed asynchronously:

["source","java",subs="attributes,callouts,macros"]
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include-tagged::{doc-tests}/MlClientDocumentationIT.java[x-pack-ml-get-datafeed-execute-async]
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<1> The `GetDatafeedRequest` to execute and the `ActionListener` to use when
the execution completes

The method does not block and returns immediately. The passed `ActionListener` is used
to notify the caller of completion. A typical `ActionListener` for `GetDatafeedResponse` may
look like

["source","java",subs="attributes,callouts,macros"]
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include-tagged::{doc-tests}/MlClientDocumentationIT.java[x-pack-ml-get-datafeed-listener]
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<1> `onResponse` is called back when the action is completed successfully
<2> `onFailure` is called back when some unexpected error occurs