What good open source REST webservice technology is out there? - web-services

Question

I'm looking for an alternative to the awesome .NET (WCF) REST capabilities.
Why?
I have deep interest in open source technology, but when it comes to webservices I do not have any experience except with .NET webservices.
Besides, I'm currently using a lot of Java and Python, and I am moving away from the Microsoft technology stack.
Please suggest alternatives in any programming language, but explain why it's good or better for some reasons. (this reason may be be tightly related with the choice of language)
What do I want to know?
Ease of use
Installation
Configuration
Generation capabilities
IDE integration
Deployment
Learning curve
Pros and cons
etc.

Answer 1

Spring 3.0 REST:
Spring uses annotation based controllers, which can be used to bind a url to a method in the controller. Annotations are used to differentiate between GET methods and POST methods.
#RequestMapping(value="/hotels/{hotel}/bookings/{booking}",
method=RequestMethod.GET)
public String getBooking(#PathVariable("hotel") long hotelId,
#PathVariable("booking") long bookingId, Model model) {
Hotel hotel = hotelService.getHotel(hotelId);
Booking booking = hotel.getBooking(bookingId);
model.addAttribute("booking", booking);
return "booking";
}
Under the hood, the variable "hotel" in the URI string is converted to a long in the parameter list, as is booking. Spring REST can also marshal JSON objects into custom classes using this same technique. Note that this method is annotated as RequestMethod.GET, which means it's invoked for GET requests but not POST requests.
Spring 3.0 REST makes it easier to create RESTful Web services by eliminating the need to reinvent the wheel or marshal/unmarshal JSON text by hand from/to Java objects.
There is a demo here on the SpringSource Blog titled REST In Spring MVC. The learning curve is low, but getting the demo to work may take some time thanks to dependencies. Once you get setup and have a working demo, the hardest part should be over.
For IDE integration, check out Spring Roo. I've not used it, but I've heard it has some features that integrate with Eclipse IDE to make your life easier.
Restlets:
Restlets were designed solely for REST. As a result, the overhead is a lot lower than Spring 3.0. Restlets are better suited for cases where you don't have a GUI, and where you aren't concerned with MVC. Restlets can easily serve as both a server and a client. It also has an embedded server you can run, which eliminates the need for a container like Jetty or Tomcat.
I've had very little exposure to Python, but from what I've seen of Google App Engine's implementation of the webApp framework, the Router concept feels very similar. Those with a Python background may find the learning curve to be a lot lower:
#Override
public Restlet createInboundRoot() {
Router router = new Router(getContext());
getConnectorService().getClientProtocols().add(Protocol.FILE);
// Serve the files generated by the GWT compilation step.
Directory dir = new Directory(getContext(), LocalReference.createFileReference(new File("war/")));
router.attachDefault(dir);
router.attach("/contacts/123", ContactServerResource.class);
return router;
}
It uses GWT on the client-side; I prefer to take that part out as it reminds me too much of Java Swing. While some people may find that advantageous, my personal preference is to stick with the technologies that feel more like the Web.
Below is a simple example of a REST server using the standalone mode. The server runs on port 8182, and it listens for GET requests. It has a similar annotation-based model as the Spring REST framework, which also helps split up the different HTTP methods and point them at different methods in your classes. This is a very basic "Hello World" REST example:
public class FirstServerResource extends ServerResource {
public static void main(String[] args) throws Exception {
// Create the HTTP server and listen on port 8182
new Server(Protocol.HTTP, 8182, FirstServerResource.class).start();
}
#Get
public String toString() {
return "hello, world";
}
}
Check out the Restlet Web Site for more information and examples of the Restlets framework. Restlets has a slightly less learning curve than Spring because it's targeted to REST; as a result, it doesn't contain all of the extra functionality included with Spring that can sometimes make finding an answer to a problem difficult. Restlets are definitely the way to go if you're looking for something lightweight.
Both of these two frameworks will run in Tomcat, Jetty, as well as on Google App Engine.

Answer 2

If you are using Java and you are familiar with Spring, then you should certainly take a look at Spring MVC 3.x. This version moves away from the ugly XML configuration, and its syntax is very similar to JAX-RS's specs. That said, if you know Spring, then learning Spring MVC 3.0 is going to be minimal. However, if you are having trouble understanding with IoC pattern and what not, then it is going to be a long painful experience. :)
Keep in mind, Spring MVC 3.x is not pure REST, and it will never be in the future at all, based on the Spring MVC developers. Their take was there are already so many good REST implementations and there's no point of making Spring MVC 3.x totally RESTful.
Another option I will certainly recommend to you is Jersey. Jersey is pure REST, in another word, it is an implementation of JAX-RS. Jersey took me 30 minutes to learn. In my opinion, the annotations are so much more powerful and richer than Spring MVC 3.x. The annotations from Spring MVC 3.x seem pretty vanilla to me. Jersey will automatically generate the WADL for you, although it is pretty basic... but having one is better than not having one. You can certainly customize your WADL if you want. (By the way, WADL is REST's version of WSDL, if you don't know what that means). Jersey basically detects your package containing all the Resource classes and generates the WADL based on the configurations you have, pretty neat stuff. The last thing I want to point out is Jersey has a great test framework for you to easily test your Restful web service. In another word, their test framework allows your unit test to easily fire up Grizzly or in-memory server to test your web service. It is certainly one of the best I have ever use thus far. Here's a very easy tutorial for you get your feet wet: http://www.vogella.de/articles/REST/article.html . It is really THAT easy. :)
FYI, I have used both Spring MVC 3.x and Jersey.

Answer 3

ServiceStack is one of the more recent developments. I haven't done much with it yet, but it seems pretty sweet so far.

Answer 4

Ruby and Rails (Ruby on Rails) have great support for RESTful service. In fact Rails supports and encourages design and develop in RESTful manner.
Thanks to ruby's strong DSL feature, writing REST service is very straightforward and easy. Since you have python experience, learning ruby might be easy.
Refer to this guide to have an impression how rest urls (called routes in rails) are defined.
Other Ruby web frameworks such as Sinatra also do a good job on this.
BTW, the best things is that both ruby and rails are open source, and the ruby community is awesome and very active.

Answer 5

There's RESTSharp as a REST/HTTP client (open-source project) and OpenRasta

Answer 6

I welcome you to check out servicestack.net it is designed for simplicity and speed and introduces very low artificial concepts where it is able to maintain a very DRY and succinct API and automatically works out of the box without any configuration or code-gen.
It encourages best practices as it is modelled around Martin Fowlers Gateway and DTO pattern for developing remote services.
The equivalent code for the Spring.NET example above would be
Configuration (in AppHost)
Routes.Add<Booking>("/hotels/{HotelId}/bookings/{BookingId}");
C# Code
public class BookingService : RestServiceBase<Booking>
{
public IHotelService hotelService { get; set; } //auto-injected by IOC
public object OnGet(Booking request)
{
var hotel = hotelService.GetHotel(request.HotelId);
var booking = hotel.GetBooking(request.BookingId);
return booking;
}
}
A similar example to the booking service can be seen by the live Northwind Web Services demo.
That's all the configuration and code (exc DTO) you need to write for that service and it is automatically available via JSON, XML, JSV, CSV, SOAP 1.1/1.2 and HTML endpoints and formats automatically without any extra configuration required.
Checkout the Hello World example for more info on all the endpoints and formats provided as well as the auto generated /metadata and documentation pages.

Answer 7

There is an open source framework entirely developed for RESTful web services which is called Recess
It's not very old, but got good attention from the industry. Alcatel-Lucene already arranged a competition on TopCoder for developing some of their services using this framework.
Check out details at Recess web site