Reading responsesedit

The Response object, either returned by the synchronous performRequest methods or received as an argument in ResponseListener#onSuccess(Response), wraps the response object returned by the http client and exposes some additional information.

Response response = restClient.performRequest("GET", "/");
RequestLine requestLine = response.getRequestLine(); 
HttpHost host = response.getHost(); 
int statusCode = response.getStatusLine().getStatusCode(); 
Header[] headers = response.getHeaders(); 
String responseBody = EntityUtils.toString(response.getEntity()); 

Information about the performed request

The host that returned the response

The response status line, from which you can for instance retrieve the status code

The response headers, which can also be retrieved by name though getHeader(String)

The response body enclosed in an org.apache.http.HttpEntity object

When performing a request, an exception is thrown (or received as an argument in ResponseListener#onFailure(Exception) in the following scenarios:

IOException
communication problem (e.g. SocketTimeoutException)
ResponseException
a response was returned, but its status code indicated an error (not 2xx). A ResponseException originates from a valid http response, hence it exposes its corresponding Response object which gives access to the returned response.
Note

A ResponseException is not thrown for HEAD requests that return a 404 status code because it is an expected HEAD response that simply denotes that the resource is not found. All other HTTP methods (e.g., GET) throw a ResponseException for 404 responses unless the ignore parameter contains 404. ignore is a special client parameter that doesn’t get sent to Elasticsearch and contains a comma separated list of error status codes. It allows to control whether some error status code should be treated as an expected response rather than as an exception. This is useful for instance with the get api as it can return 404 when the document is missing, in which case the response body will not contain an error but rather the usual get api response, just without the document as it was not found.

Note that the low-level client doesn’t expose any helper for json marshalling and un-marshalling. Users are free to use the library that they prefer for that purpose.

The underlying Apache Async Http Client ships with different org.apache.http.HttpEntity implementations that allow to provide the request body in different formats (stream, byte array, string etc.). As for reading the response body, the HttpEntity#getContent method comes handy which returns an InputStream reading from the previously buffered response body. As an alternative, it is possible to provide a custom org.apache.http.nio.protocol.HttpAsyncResponseConsumer that controls how bytes are read and buffered.