OpenSearch/docs/java-rest/high-level/execution.asciidoc

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This file is included by every high level rest client API documentation page
so we don't have to copy and paste the same asciidoc over and over again. We
*do* have to copy and paste the same Java tests over and over again. For now
this is intentional because it forces us to *write* and execute the tests
which, while a bit ceremonial, does force us to cover these calls in *some*
test.
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[id="{upid}-{api}-sync"]
==== Synchronous execution

When executing a +{request}+ in the following manner, the client waits
for the +{response}+ to be returned before continuing with code execution:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-execute]
--------------------------------------------------

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 `4xx` or `5xx` error code, the high-level
client tries to parse the response body error details instead and then throws
a generic `ElasticsearchException` and adds the original `ResponseException` as a
suppressed exception to it.

[id="{upid}-{api}-async"]
==== Asynchronous execution

Executing a +{request}+ 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 {api} method:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-execute-async]
--------------------------------------------------
<1> The +{request}+ to execute and the `ActionListener` to use when
the execution completes

The asynchronous method does not block and returns immediately. Once it is
completed the `ActionListener` is called back using the `onResponse` method
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 +{api}+ looks like:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-execute-listener]
--------------------------------------------------
<1> Called when the execution is successfully completed.
<2> Called when the whole +{request}+ fails.