From: vasudevram Date: 2007-08-25T01:15:03+09:00 Subject: Re: Advice on bulding a web service On Aug 24, 6:44 pm, Doug Livesey wrote: > Jeremy Wells wrote: > > Doug Livesey wrote: > > Hallo. > > I need to build a web server (it'll be RESTful & everything), but am not > > sure about the best way to proceed. > > It will be a single instance app, that needs to strictly control > > concurrency, ie only one instance of an object can be manipulated at > > once. > > The built-in web service support of a full-fledged Rails app is not what > > I'm after. > > Basically, I want to be able to set the service going, then have other > > apps calling it (I'll probably use JSON) for data. At first, setting it > > off in a command prompt will do (sadly, I work in Windows). > > What I'm after, really, is advice on the best libraries to use, and > > maybe pointers to tutorials that achieve the sort of thing that I'm > > after. > > Thanks in advance, > > Doug. > > > maybe you'd enjoy campinghttp://code.whytheluckystiff.net/camping/ > > Cheers for that -- I don't think (after a quick semi-peruse of the page) > that this is for writing web servers (that receive & send JSON, for > example, & never render to a screen). > Although please correct me if I'm wrong. > No, the app I have in mind could well become quite complex internally -- > it's just a web service, not a web site. > Although, Camping does look rather cool! > Cheers again, > Doug. > -- > Posted viahttp://www.ruby-forum.com/. You have at least a couple of options for the web server (I'm assuming you're mainly interested in writing your app, not implementing a web server): 1. WEBRick 2. Mongrel Both of these support 'servlets' - not the same as Java servlets, as in, not the exact same API as the servlet API, but something roughly similar (though their API's are much simpler and smaller in size). In outline, do something like this: - Create an instance of a server (see the WEBrick / Mongrel docs for the exact class name). - Write your app-specific classes, each of which you want to expose as a REST resource, i.e. give them Ruby methods corresponding to the HTTP methods GET, POST, PUT, DELETE, etc. - Write a 'controller' class that reads the request URI and decides which of your app-specific classes to delegate the request to. E.g. in its doGET method, delegate to the 'get' method of the appropriate class (determined by checking the incoming request URI). If the method is GET, the parameters in the URI should be passed as arguments to your class's 'get' method, including an optional one that says what format the client wants the response in (e.g.: HTML/XML/JSON). - 'Mount' this class on the server. - Start the server. - For each request that comes in, your controller gets control, does as said above (delegates the request), and then the the return value from the appropriate method of your class, as HTML/XML/JSON. is sent to the client as the response. Note: The above approach is for if you have multiple app-specific classes / instances that you want to expose as REST resources. If you have only one, things can be simpler - the 'controller' class itself can be the main or only app-specific class. Then, in its doGET method, just return the representation of the resource, appropriately formatted (as HTML/XML/JSON). On the client end, you'll have to read and parse the response, and do whatever you want to, with it. (If your client is a browser, you may not have to do anything. Just let the user interact with the server using the browser, e.g. clicking links in the response.) E.g. Display it, allow the user to interact with the data shown, including clicking links that trigger new REST requests, etc. For parsing the XML you can use REXML, for JSON, there's a JSON library for Ruby (ruby-json? - GIYF). For sending the requests, use open-uri or Net:HTTP. (The WEBrick and Mongrel API's provide support for some of the above steps, i.e. creating the server and mounting your classes on it. The rest is app-specific and up to you.) The book "RESTful Web Services" from O'Reilly, by Leonard Richardson and Sam Ruby, is a great resource for what you're trying to do (IMO). I got it recently and have read some of it. If you can, get it, then it should be a snap to do what you need. Also read the WEBRick or Mongrel docs for their server and servlet classes. GIYF again ... The book authors mention some limitations with open-uri for REST work (doesn't support all HTTP methods, among other things), which they fix by writing another library - rest-open-uri - on top of it, which you can probably get from the source code link for the book at the book's web page on the O'Reilly site. Also, 'Enterprise Integration with Ruby' by Maik Schmidt, from the Pragmatic Bookshelf, has some good examples of writing WEBrick servlets. HTH Vasudev ----------------------------------------- Vasudev Ram http://www.dancingbison.com http://jugad.livejournal.com http://sourceforge.net/projects/xtopdf -----------------------------------------