Review of new Http client API (original) (raw)

Michael McMahon michael.x.mcmahon at oracle.com
Tue Aug 21 06:57:23 PDT 2012

Sam,

Thanks for the comments. Some discussion below.

On 17/08/12 00:13, Sam Pullara wrote:

I suggest that you make it a more fluent API rather than having multiple callback methods in your callback interface. As it stands it isn't compatible with lambdas. You might take some inspiration for the asynchronous callbacks from my work porting Twitter's Future/Promise to JDK8:

I agree with the above. In a previous version of the API the main callback was lambda compatible. Originally we used HttpResponse to encapsulate everything related to a response including errors. But, some preferred to keep HttpResponse aligned to an actual response from a server in all cases. There might be other ways to get around that by combining HttpResponseHeadersHandler.{onError(), onHeaders()} back into a single method. Maybe, drop the onError() method and add the exception/throwable as a parameter to onHeaders()

But, we also wanted to provide notification of body data (through the sub-interface HttpResponseHandler). Keeping the two interfaces distinct meant that applications could get asynchronous notification of the response headers, but then possibly read the response body in a blocking manner. Or alternatively, applications can use the handler to be notified of both headers and body.

So, if we revert HttpResponseHeadersHandler back to having a single method, the sub-interface now would have two methods (instead of three).

One way around that could be to have two unrelated interfaces:

interface HttpResponseHeadersHandler { public void onHeaders(HttpResponse response, Exception e); }

interface HttpResponseBodyHandler { public void onBodyPart(HttpResponse resp, ByteBuffer buffer, boolean last); }

// Then a HttpResponseBodyHandler would be added to HttpClient.sendRequest() as below:

public void sendRequest(HttpRequest, HttpResponseHeadersHandler, HttpResponseBodyHandler);

Both of the interfaces would be lambda compatible (again) though at the cost of having to specify two separate handlers. So, the following might be how it could be used (and using a builder for HttpClient)

HttpClient client = HttpClient.createBuilder() .setAsynchronousChannelGroup (..) .setCookieManager(..) .setDefaultTimeout(..) .setProxy(...) .addFilter(...) .buildClient();

HttpRequest request = client.createRequest(new URI("http://www.foo.com/")) .setBody("Hello world".getBytes()) .setMethod(HttpMethod.POST);

client.sendRequest ( request,

 // handle headers
 (HttpResponse response, Exception e) ->  {
if (response.getResponseCode() != 200) {
    // handle error response
}
// handle normal case
 },

 // handle body
 (HttpResponse response, ByteBuffer buf, boolean last) ->  {
// handle data in buf
 }

);

It seems fairly readable still, I think.

Another thing that this usage points to, is the usefulness of being able to hang some user context off of the HttpResponse or HttpRequest objects. That would be the only way to share some user state between the two handlers above, in this Lambda style.

https://github.com/spullara/java-future-jdk8

Another consideration might be to make sure that it is compatible with an implementation that is using SPDY under the covers for connectivity as I suspect that HTTP as a wire protocol has peaked though the HTTP semantics will survive. Right. This is important. One area where there will be changes is with pipe-lining. We need to ensure that our pipe-lining API is not restricted to only Http 1.1 pipe-lining Are you aware of other areas that could have an impact on the API?

Thanks Michael.

Sam

On Tue, Aug 14, 2012 at 5:01 AM, Michael McMahon <michael.x.mcmahon at oracle.com> wrote: Hi,

(apologies for sending this again) We have just published a draft of a proposed new Http client API [1] for JDK 8. This message has been cc'd to jdk8-dev so that as many people as possible know about it, but the discussion will be on the net-dev list (net-dev at openjdk.java.net). So, folks will have to join that list [2], in order to take part. Thanks, Michael. [1]http://cr.openjdk.java.net/~michaelm/httpclient/v0.3/ [2]http://mail.openjdk.java.net/mailman/listinfo/net-dev

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