What is the best technique to push notifications from the cloud to a client? REST does not seem to support this. In particular, I have JSON objects representing world state going to the cloud and want to be able to notify a client when that state changes.
All HTML5 implementations I've seen support full duplex communication via WebSockets.
If you're using Google App Engine you can use the Channel API. https://developers.google.com/appengine/docs/java/channel/
If you're using JBoss you can use the Errai Framework. http://errai.github.io/
I'm sure there are a lot of other options out there. And there's always email.
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Could anybody explain advantage of using json-rpc over json-api and vice-versa? First and second format are JSON-based, but where I should use one, and where is another?
Note: I may come across a little biased. I am the author of the Json-RPC.net server library.
Json-RPC is a remote procedure call specification. There are multiple libraries you can use to communicate using that protocol. It is not REST based, and is transport agnostic. You can run it over HTTP as is very common, you can also use it over a socket, or any other transport you find appropriate. So it is quite flexible in that regard. You can also do server to client along with client to server requests with it by hosting the RPC server on either the client or the server.
Json-API is a specification for building REST APIs. There are multiple libraries you can use to get started with it. In contrast to Json-Rpc it requires you to host it on an HTTP server. You cannot invoke functions on the client with it. You cannot run it over a non-http transport protocol. Being REST based, it excels at providing information about Resources. If you want an API that is based around the idea of Create, Read, Update, Delete on some collections of resources, then this may be a good choice.
Json-API is going to be better if your API is resource-based, and you want your API to be browsable by a human without setting up documentation for it. Though that human would likely need to be in the software engineering field to make any sense of it.
Json-RPC is going to be better if your API is function based, or you want the flexibility it provides. Json-RPC can still be used to manipulate Resources by creating Create, Read, Update, and Delete functions for your resources, but you don't get the browsability with it not being REST based. It can still be explored (not browsed) by a human by generating documentation based off of the functions you expose.
A popular example of something that uses Json-Rpc is BitCoin.
There are a lot of popular REST-based API's and Json-API is a spec with a bunch of tools to help you do REST right.
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Note: Neither of those (Json-RPC, or Json-API) are good when you consider for developer time, performance, or efficiently using network resources.
If you care about performance, efficiency, or developer time then take a look at Google's gRPC which is fantastic in those regards, and can still reduce developer time more than using a REST API as client and server code can be generated from a protocol definition file.
I read "Those who would like to enjoy the binding, presentation model structuring, testing capabilities, toolkit independence, and all the other benefits of OpenDolphin, but prefer REST (or other) remoting for data access, can use OpenDolphin with the in-memory configuration"
But I could not find any further hints in the docs?
I can't rely on sticky sessions in my load balanced webserver.
Therefore I need to plugin something different for the http session state.
Is there a opendolphin config property prepared for this? If not are there any plugin points available?
since OpenDolphin and Dolphin Platform use the remote presentation model pattern to synchronize presentation models between client and server you need a state on the server. Currently this state is defined in the session. As you said it's no problem to use load balancing with sticky sessions to provide several server instances. If you need dynamic updates between the clients a distributed event bus like hazelcast will help.
Therefore I need to plugin something different for the http session
state.
What do you need? With the last version (0.8.6) of Dolphin Platform you can access the http client in the client API and provide custom headers or cookies. Will this help? Can you please tell us what you need or open an issue at the Dolphin Platform github repo?
I'm working on a desktop application that uses API keys for Twitter but AFAIK, AIR applicatioons are easy to decompile. I want the processing of the API requests to be client-side, not server-sided. At most, I want to keep the dependency onto the server to as low as possible.
What I'm thinking is sending the API from the server to the AIR app on the first run. I've already seen Shared secret with API in an Ajax Adobe AIR app but my question is a bit different in that, I want to know how secure ELS is?
How does Adobe work it's way to storing stuff into the ELS? Does it go through multiple encryption sessions before finally getting stored somewhere on the computer?
Anything that an application on the user's desktop can read, can also be read by the user himself. They can get the key by using a proxy (like Charles) when you send it from or to the server; or they can read it with a debugger when AIR writes it to the ELS.
If I'm not mistaken, Twitter's API keys are public anyway (its only purpose is to track how you are using their API). Are you worried that a user might use your key for their own application? If they do that, all you have to do is get a new Twitter key.
I have few questions regarding HornetQ:
What are differences between HornetQ core API and the JMS API ?
is there any advantage or disadvantage on using one of these ?
Is it true to say if I use the core API and then I decide to
change my Messaging Bus (let's say to ActiveMQ) then I have to
change all my codes ?
HornetQ Core API is a proprietary API from HornetQ, while the JMS API is a standard API defined by the Java Community Process.
There are a few features that are not supported on JMS API, that are available through core-api:
It's not possible to have multiple consumers on a single topic subscription (say if you wanted to have multiple consumers to scale it better)
It's more generic on how you create the subscription. You just create a queue within an address. Very simple.
We have a nice API for asynchronous confirmations. No need to block ever if you use this feature.
The advantage on the JMS is portability. Your code stays the same if you decide to move between providers.
The disadvantage on JMS is that it lacks some features and it's a bit verbose, what's under works on JMS 2 JSR right now.
Yes, because as I have said here, Hornetq-core api is a proprietary API, hence it will only work on HornetQ. The same way as some message systems will have a proprietary API.
If you encapsulate your Messaging access you can minimize that a lot though where you could just replace a single class on your system using standard OO techniques.
What I would like to do is create a canvas that will show a network map. It's not really a network map but in terms of explaining it the network map example works best to not bog you down with details that don't pertain to my question.
On the network map I want to display routes the traffic takes. These routes change in time, sometimes as frequently as multiple times per minute. On the server side I have a log file to which each route change is appended as it happens.
I know how to create the canvas, I know how to draw my routes onto the canvas.
Is it possible to have the server push an update to the canvas without requiring a page reload/refresh, essentially requiring no user interaction at all? The routes drawn just automagically change?
This would need to work on IIS so a jscript or .Net based solution would be necessary. I won't be able to install PHP, Python, Ruby etc.
Thanks in advance for any insights you can provide.
I recommend that you look at a WebSockets solution to push the information from the server to the client (JavaScript). When you receive the update you can update the canvas as required.
Technologies you should look at if your preferred server technology is .NET would be a service like Pusher, who I work for, and our .NET APIs which let you push updates to the client via our REST API.
If you would prefer to host your own realtime infrastructure then you could look at WebSync (which is actually a Comet technology) which integrates with IIS and also XSockets. There are also a number of realtime technologies on this guide which may interest you. If you've any further questions just let me know.
Server-Sent Events: http://www.html5rocks.com/en/tutorials/eventsource/basics
( Server-sent events is a technology for providing push notifications from a server to a browser client in the form of DOM events. The Server-Sent Events EventSource API is now being standardized as part of HTML5[1] by the W3C. )
Yes, I've done this before (with an ajax-based drawing application). It's very possible. Send packets of information via AJAX (JSON or something), interpret them, and draw them on the client's canvas element. This is trivial to design (and easy to implement using something like jQuery). It seems that you already figured out you need to have a server-side script that pushes information to a web page and a web page that actually draws stuff on the canvas. That's essentially all it is.