Exists API

It uses GetRequest just like the Get API. All of its optional arguments are supported. Since exists() only returns true or false, we recommend turning off fetching _source and any stored fields so the request is slightly lighter:

GetRequest getRequest = new GetRequest(
    "posts", 
    "1");    
getRequest.fetchSourceContext(new FetchSourceContext(false)); 
getRequest.storedFields("_none_");                            

When executing a GetRequest in the following manner, the client waits for the boolean to be returned before continuing with code execution:

boolean exists = client.exists(getRequest, 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 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.

Executing a GetRequest 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 exists method:

client.existsAsync(getRequest, RequestOptions.DEFAULT, listener); 

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 exists looks like:

ActionListener<Boolean> listener = new ActionListener<Boolean>() {
    @Override
    public void onResponse(Boolean exists) {
        
    }

    @Override
    public void onFailure(Exception e) {
        
    }
};

A variant of the exists request is existsSource method which has the additional check that the document in question has stored the source. If the mapping for the index has opted to remove support for storing JSON source in documents then this method will return false for documents in this index.