Is there a way today within the Jersey API to decouple a client request from the response and asynchronously send back a response?
I guess I am looking for an alternative to the startAsync() method of a HTTPRequest object within Jersey - havent seen something of that sort yet, although I have come across the Atmosphere project - which looks somewhat promising, but are there any other options?
If you are looking for a client-side async api, look at AsyncWebResource in Jersey client API.
If you mean suspending the request processing on the server side, we are adding that only in Jersey 2.0.
Related
From what I understand the Spark Framework for Java makes it very easy to run a restful server that accepts, POST, GET, etc..
Is there an easy way to send a POST out using the spark library?
The idea is to handle requests asynchronously and to respond via a callback. That callback requires an asynchronous post to come from my application to another web server.
You'll have to add another library to act as the rest client. Spark is intended to be a rest server.
I was going thru Soap vs Rest on net and found most of them says Soap supports asynchronous call while Rest does not but did not get any concrete example of that. Can anybody help me here?
Here is one of the resources i was referring to
http://web.archive.org/web/20120421084456/http://www.prescod.net/rest/rest_vs_soap_overview/
http://searchsoa.techtarget.com/tip/REST-vs-SOAP-How-to-choose-the-best-Web-service
http://seanmehan.globat.com/blog/2011/06/17/soap-vs-rest/
As per my understanding both should be synchronous. In both cases client makes a call to web service either thru soap or rest, client waits till response comes back from service. So how come soap supports asynchronous behaviour while rest does not?
REST is purely an HTTP transport based call and you will receive a response say 200 OK
on the other side,
SOAP uses two varieties,
Synchronous Messaging over HTTP
Asynchronous Messaging over HTTP
With synchronous messaging, the Requestor makes a request and the transport layer code blocks waiting for a response from the Provider. The Requestor receives the response on the same HTTP connection that the Requestor initially established to send the request. Synchronous exchange is usually easier to implement and requires that the Provider be able to generate a response in a short time, specifically in a time less than the HTTP timeout value(generally 120sec).
[A single HTTP Connection is used that itself behaves Synchronously]
With asynchronous messaging, the Requestor is able to release transport specific resources once the request is acknowledged by the responder, knowing that a response will eventually be received. When the Provider completes the processing of the message it sends a response back to the Requestor over a new HTTP connection.
[Here we utilize two HTTP Connections to implement an asynchronous messaging
first HTTP Connection is used that for sending the Request and receiving an acknowledgement HTTP Response 200/OK
second HTTP Connection is used for receiving the callback and responding HTTP Response 200/OK]
Rijoy
https://soascribbles.wordpress.com/
SOAP defines a reply approach that allows for asynchronous computing, like a callback mechanism. You can achieve the same with REST but there is no specification for it, so you would have to build it yourself.
Here is an example using JAX-WS 2.0 demonstrating the feature.
I found useful information in Wikipedia WS-Addressing, which has a link for this W3C Specification.
In the past I also developed in SAP ESB designer which allowed for asynchronous service interface methods. Although I never used that feature, that tool was fully compliant with SOAP specification and I am pretty sure it would work just like the Java example above, since the WSDL was used to generate JAX-WS server based. If I have time next week I will use that option to so see what happens and post it here.
You should also check this answer which address pertinent aspects of this approach.
I have created a REST service which actually calls an async method to interact with DB layer and made our service asynchronous. I feel it is possible to implement asynchronous service in REST API. But in that case you need to have a call back service which will check whether the process has been completed in regular interval.
I'd like to synchronize the state to all the clients interested in particular entity changes. So I'd like to achieve something like:
exposing CRUD API on entity (via HTTP/REST and websockets)
and routing the response (of the modifying calls) to websockets topic
So technically, I'd be interested in ideas to mix spring-data-rest with spring websockets implementation to achieve something like spring-data-websocket.
There are a two solutions coming to my mind, and in fact both would be:
spring-data-rest to expose my entities via REST/HTTP API
websocket controllers (used for the modification calls on entities)
The websocket controllers would look like this:
#Controller
public class EntityAWebSocketController {
#MessageMapping("/EntityA/update")
#SendTo("/topic/EntityA/update")
public EntityA update(EntityA entityA) throws Exception {
// persist,....
return entityA;
}
}
Scenario 1: Websocket API called from REST/HTTP API
Rules:
client request is always REST/HTTP API
response is REST/HTTP API for all the operations
moreover for modifying operations the websocket message comes as well
Technically, could be achieved, by:
calling the websocket controllers from the spring-rest-data events (namely in the AfterCreateEvent, AfterSaveEvent, AfterLinkSaveEvent, AfterDeleteEvent)
Still the solution seems quite sick to me, as I'd need to go for:
client A --HTTP request--> Server (spring-data-rest controller)
Server (AfterXXXEvent in the spring-data-rest controller) --websocket message--> Spring websocket controller
Spring websocket controller --websocket message via topic--> all Clients interested in the topic
Server (spring-data-rest controller) --HTTP response--> client A
Scenario 2: Websocket API independent from REST API
Rules:
client request is REST/HTTP API for non-modifying operations only
response is REST/HTTP API for non-modifying operations only
client sends websocket message for all the modifying operations
websocket message is sent to client for all the modifying operations only
Well, if no other ideas come up, I'd go for the later one, but still, it would be great if I could have somehow generated C(R)UD methods exposed via websockets as well, something like spring-data-websockets and handle only the routes in my implementation.
As I feel like I'd have to manually expose (via *WebSocketControllers) all the CUD methods for all my entities. And I might be too lazy for that.
Ideas?
Scenario 2 talks about, in the last step, a single client.But I thought your requirement was for a topic since you wanted multiple clients.
If I wanted to complete 2 for your stated requirement, then you might want to maintain a list of clients and implement your own queue or use a ForkJoinPool to message all your clients listening in on your WebSockets. Having said that, A topic is definitely more elegant here but overall looks too complicated with different interfaces
For all messages from client to server, just go with a simple wire protocol and use a collection to parameterize, it could be
RParam1.......
At the server, you need a controller to map these to different requests(and operations). Somehow does not look like too much work.
Hope this helps.
The same architecture has bugged my mind for a while now and it will be a long story if I want to mention all the drawbacks and advantages of it so let me jump into the implementation.
The second scenario is valid, but as you mentioned its better to perform the crud actions on same websocket session. This shall remove the need for HTTP handshakes on every request, and reduces the body size of messages, therefore you will have better latency. Meanwhile, you already have a persisting connection to a server, so why not make good use out of it?
I searched around for a while and after 6 years from your question, I still couldn't find any websocket protocols that can make this happen, so I decided to work on that by myself cause I needed it for another dummy project.
Another advantage of such protocol could be that it doesn't require much changes to your already written controllers. So it should be able to support Spring Framework (for example) annotations and make websocket endpoints out of it.
The hard part about implementing such protocol in another framework like spring is that as its not nice to create ServletRequest and ServletResponse and convert them to your own websocket protocol, you loose some advantages. For example, any http filter you have written in your application till that moment, will be meaningless because its not really easy to pass your websocket messages through those filters.
About the protocol itself: I decided everything to be passed through json format, alongside a unique id for each request so we can map callbacks on client side to the request id. And of course there is a filter chain to add your filters to it.
Another hard to deal thing here is Spring Security as that too works like http filters in some cases. In my own lib I could finally handle annotations like #PreAuthorize but if you are using antMatchers in your HTTP Security Config, it would be a problem.
Therefore, creating websocket adapter to call http controllers will have many drawbacks.
You can check out the project here: Rest Over Websocket. Its written for Spring Boot.
I'm looking for a way of implementing a simple API to receive log messages (for various events across various systems).
We've concluded an HTTP get request is the most open (lowest barrier to entry) for the different code bases and systems that would need to post to this server.
The server itself needs to provide an HTTP GET api where I would send a message e.g. logging.internal/?system=email&message=An email failed
However we'd like this to be non blocking so any application can throw information to this server and never have to wait (not slowing any production systems).
Does anyone know of any framework to implement this in Java, or an appropriate approach?
In java, for the server, you can use any implementation of JAX-RS for the Restful part, and when processing the message, just call an asynchronous EJB method ( http://docs.oracle.com/javaee/6/tutorial/doc/gkkqg.html ), which will do the longer processing.
This will allow the RESTful request to return as fast as possible.
In this case, the only blocking part will be the http request/response.
If you want to make it less blocking, issue the RESTful request from the client in an Async method as well (or a Message Driven Bean if using Java EE 5).
I am looking for a way to setting up a JSON proxy client in a spring framework way.
We are going to use Spring MVC on the server side. We don't like XML as they are overkill and heavy. JSON seem to be a lightweight and effective message container for us.
However, I've search around and read http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/remoting.html many times and I don't find any hits to put my spring client into a JSON client.
They provided RMI, Http, JAX-WS, SOAP and others. But nothing related to as a client of MVC (which I guess it could be common as we don't want to write it twice)
RestTemplate looks good but I am wonder is it the suggested way to do in spring 3.0.
The RestTemplate is indeed the preferred way of accessing rest services.
I've been in the same position as you - looking through the Spring docs for how to implement a simple JSON client API. I ended up implementing it myself, as I only needed it for a few RPC-like calls to another webapp. IIRC Jax-RS has this capability so you might want to invest in implementing it - for my needs it seemed overkill.
All there is to it:
write a simple method to perform the HTTP GET to the JSON web service and return a String (I used Apache HttpClient)
pass the String to Jackson to deserialize into a Java object (see mapper.readValue())
This assumes you already know what kind of object you expect to get back from a given JSON web service.
As an aside, the other thing I needed from my Spring MVC JSON web service was the ability to do JSONP (cross site callback) for consumption in the browser with JQuery (note: JSONP is not secure so use at your own risk). The automagic Spring JSON webservices that Bozho outlined does not provide an option for JSONP. The easiest way to provide JSONP is to implement a simple servet filter.