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I'm developing a gateway that will be located between mobile web apps and web services on backend systems. The purpose of this gateway is to protect web apps against changes to backend web service api's, to introduce concurrency, transform messages, buffering, etc.
My proposed architecture is as follows:
Platform independent mobile web apps using PhoneGap (done)
Gateway is a web service using Scala for business logic and ZeroMQ for message passing (new)
Backends are existing web services (existing)
The gateway is purely responsible passing, translation, aggregation, etc. of messages and does not need to keep state or do user authentication at this point - it's simply responsible for being a single interface that knows how to talk to mobile apps on the one side and one or more services on the other side.
I'm strongly considering using Scala as the development language because it seems well suited for this type of application, but what would be the correct architecture for such a Scala service? I looked at frameworks such as Lift and Play and also considered doing a simple "java" based web service and just use Scala as to implement my business logic. I believe strongly in keeping things as simple as possible. I'm wary of complicated setups and thousands of lines of dead code in frameworks that may never be used. On the other side, limiting oneself to a 'role your own' solution and creating a lot of work and having to maintain code that may have been part of existing solutions is also not ideal.
Some things to consider: I'm the architect and developer, but my knowledge of Scala is limited to the first half of "Programming in Scala, Second Edition". Also, my time is very limited. Still, I want to get this right the first time.
I'm hoping that some clever gent or dame will provide me with insights to this type of solution and maybe a link or two to get started quick. I really need to get going FAST, but hope that the experience or insights of another professional could help me avoid pitfalls along the way. Any insights to development environments and tools will also be helpful. I have to develop on Mac (company rules) but will be deploying on Ubuntu server. I'm currently juggling between installs of Eclipse or Idea as IDE's and the scala compiler or sbt for building.
UPDATE
Thanks for all the potential answers below. I had a look at each and every suggestion and all of them have merit. The problem is now to bet on the right horse. Spray is possibly the simplest solution to the problem, but I also found Finagle. It seams like a stunning solution to my problem. I'm a bit concerned that it is built on top of Netty instead of Akka. Does anyone see any problem with that. I was hoping to keep my solution as purely Scala as possible, but Finagle appears to be the most mature of the lot. Any ideas?
It might be worth taking a look at Akka, which provides a lightweight framework for writing concurrent, fault-tolerant applications on the JVM, as well as useful built-in abstractions for writing web services. In addition, the Spray project looks like it could be useful for your purposes, providing HTTP server and client libraries on top of Akka (Although, unlike Akka itself, I haven't used this so myself so can't vouch for it).
If you're using a web service that is purely for other services, then an Akka based service like Spray or Blueeyes is probably your best bet. You can use Jerkson to do the JSON mapping to and from your case classes and use Akka-Camel to link to ZeroMQ.
As mistertim says, Akka is a good option. I'm biased, but I think Lift and its RestHelper is a fantastic way to go also (I've built several APIs for iPhone apps using Lift). Beyond those, I know several people who are very happy with Unfiltered.
Unfiltered is very interesting option if you want to keep it lightweight, as is not a full blown web framework.
To be honest, the documentation can use more detail, but to provide a web service you just write:
object MyService extends unfiltered.filter.Plan {
def intent = {
case req # GET(Path ("/myendpoint")& Params(params)) =>
for {
param1<-params("param1")
param2<-params("param2")
} yield ResponseString(yourMethod(param1,param2))
}
override def main(args:Array[String]) = unfiltered.jetty.Http.anylocal.filter(MyService).run();
}
Very useful if you don't want to use a framework and don't want to mix java/java annotations with Scala (otherwise, you have the usual java solutions)
Still, I would recommend to look into Akka if you think you think actors will fit your problem
If your system is middle-ware and get the things done quickly, then Spray will be a best. Spray was developed on top of Akka. Akka has ZeroMQ support.
in future if you are going to add some other web like module along with your middle-ware, then choosing Lift + Akka will be better because, Lift also provides Spray like web service stuff + it will be easy to start developing other modules.
You can choose SBT as your build, there are some project templates, template generation tools available, so you can get the project build very quickly.
In my experience , SBT + InteliJ Idea works well, have a look on sbt-idea plugin
Spray Project Template
Lift Project Template Generator
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I've just started learning Scala, and the first thing I'm going to implement is a tiny web application. I've been using Erlang for the last year to implement server-side software, but I've never wrote web applications before. It will be a great experience.
Are there web-frameworks for Scala except for Lift?
Don't get me wrong, Lift looks awesome. I just want to know how many frameworks there are so that I can then choose between them. It's always a good to have a choice, but I the only thing I found was Lift.
I'm very interested in Scala, but I have not used it yet, so with that caveat, the frameworks I am aware of that are not mentioned in HRJ's answer (Lift, Sweet, Slinky) are:
Scalatra, previously Step (on GitHub)
Play 2 (on GitHub)
Pinky
I wrote a blog post about this.
To summarise, some of the options are:
Lift
Sweet
Slinky
I finally found that none were suitable for me, and developed my own little "framework". (It is not open-source yet).
I like Lift ;-)
Play is my second choice for Scala-friendly web frameworks.
Wicket is my third choice.
Following is a dump of frameworks. It doesn't mean I actually used them:
Coeus. A traditional MVC web framework for Scala.
Unfiltered. A toolkit for servicing HTTP requests in Scala.
Uniscala Granite.
Gardel
Mondo
Amore. A Scala port of the Ruby web framework Sinatra
Scales XML. Flexible approach to XML handling and a simplified way of interacting with XML.
Belt. A Rack-like interface for web applications built on top of Scalaz-HTTP
Frank. Web application DSL built on top of Scalaz/Belt
MixedBits. A framework for the Scala progamming language to help build web sites
Circumflex. Unites several self-contained open source projects for application development using the Scala programming language.
Scala Webmachine. Port of Basho's webmachine in Scala, a REST-based system for building web applications
Bowler. A RESTful, multi-channel ready Scala web framework
Try Play Framework, which also support Scala.
One very interesting web framework with commercial deployment is Scalatra, inspired by Ruby's Sinatra. Here's an InfoQ article about it.
I find Unfiltered very interesting https://github.com/unfiltered/unfiltered.
It's mentioned in IttayD's list.
Here is a presentation about it http://unfiltered.lessis.me/#0
and the video http://code.technically.us/post/942531598/doug-tangren-presents-the-unfiltered-toolkit-for
Also here there is an article with more info http://code.technically.us/post/998251172/holding-the-parameter
It must be noted that there is also a considerable interest in Wicket and Scala. Wicket fits Scala suprisingly well. If you want to take advantage of the very mature Wicket project and its ecosystem (extensions) plus the concise syntax and productivity advantage of Scala, this one may be for you!
See also:
Some prosa
Presentation
Some experience with Wicket and Scala
Announcments with reference to the project for the glue code to bind Scala closures to models
Play is pretty sweet.
It is now production ready. It incorporates: a cool template framework,automatic reloading of source files upon safe, a composable action system, akka awesomeness, etc.
Its part of the Typesafe Stack.
Having used it for two projects, I can say that it works pretty smoothly and it should be something to consider next time you are looking to learn new web frameworks.
I tend to use JAX-RS using Jersey (you can write nice resource beans in Scala, Java or Groovy) to write RESTul web applications. Then I use Scalate for the rendering the views using one of the various template languages (JADE, Scaml, Ssp (Scala Server Pages), Mustache, etc.).
There's a new web framework, called Scala Web Pages. From the site:
Target Audience
The Scala Pages web framework is likely to appeal to web programmers who come from a Java background and want to program web applications in Scala. The emphasis is on OOP rather than functional programming.
Characteristics And Features
Adheres to model-view-controller paradigm
Text-based template engine
Simple syntax: $variable and <?scp-instruction?>
Encoding/content detection, able to handle international text encodings
Snippets instead of custom tags
URL Rewriting
Prikrutil, I think we're on the same boat. I also come to Scala from Erlang. I like Nitrogen a lot so I decided to created a Scala web framework inspired by it.
Take a look at Xitrum. Its doc is quite extensive. From README:
Xitrum is an async and clustered Scala web framework and web server on top of Netty and Hazelcast:
It fills the gap between Scalatra and Lift: more powerful than Scalatra and easier to use than Lift. You can easily create both RESTful APIs and postbacks. Xitrum is controller-first like Scalatra, not view-first like Lift.
Annotation is used for URL routes, in the spirit of JAX-RS. You don't have to declare all routes in a single place.
Typesafe, in the spirit of Scala.
Async, in the spirit of Netty.
Sessions can be stored in cookies or clustered Hazelcast.
jQuery Validation is integrated for browser side and server side validation.
i18n using GNU gettext, which means unlike most other solutions, both singular and plural forms are supported.
Conditional GET using ETag.
Hazelcast also gives:
In-process and clustered cache, you don't need separate cache servers.
In-process and clustered Comet, you can scale Comet to multiple web servers.
Follow the tutorial for a quick start.
There's also Pinky, which used to be on bitbucket but got transfered to github.
By the way, github is a great place to search for Scala projects, as there's a lot being put there.
I'd like to add my own efforts to this list. You can find out more information here:
brzy framework
It's in early development and I'm still working on it aggressively. It includes features like:
A focus on simplicity and extensibility.
Integrated build tool.
Modular design; some initial modules includes support for scalate, email, jms, jpa, squeryl, cassandra, cron services and more.
Simple RESTful controllers and actions.
Any and all feedback is much appreciated.
UPDATE: 2011-09-078, I just posted a major update to version 0.9.1. There's more info at http://brzy.org which includes a screencast.
Both Sweet and Slinky seem to be unmaintanted for about a year. Sweet Maven repo sweetsoftwaredesign.com is dead so there's even no way to download dependencies.
Note: Spiffy is outdated.
<plug>
Spiffy:
is written in Scala
uses the fantastic Akka library and actors to scale
uses servlet API 3.0 for asynchronous request handling
is modular (replacing components is straight forward)
uses DSLs to cut down on code where you don't want it
supports Scalate and Freemarker for templating
Spiffy is a web framework using Scala, Akka (a Scala actor implementation), and the Java Servlet 3.0 API. It makes use of the the async interface and aims to provide a massively parallel and scalable environment for web applications. Spiffy's various components are all based on the idea that they need to be independent minimalistic modules that do small amounts of work very quickly and hand off the request to the next component in the pipeline. After the last component is done processing the request it signals the servlet container by "completing" the request and sending it back to the client.
https://github.com/mardambey/spiffy
</plug>
You could also try Context. It was designed to be a Java-framework but I have successfully used it with Scala also without difficulties. It is a component based framework and has similar properties as Lift or Tapestry.
I have stumbled upon your question a few weeks back, but since then also learned about Circumflex. This is a nice, minimal framework that is therefore easy to learn, and it has pretty good documentation available as well.
Beside it's minimal-ness, it also claims to work well with other libraries and lets you use your own implementation of things when you need it.
I am about to start a new webapp that will be running on P/GAE and reagarding the front end we would like to use one of the mentioned frameworks (GWT, SC, Cap).
Which one do you think is the most developer friendly? It seems that Cappuccino looks stunning but you have to learn Obj-J. Sproutcore seems nicer (since there is only JS) but I could not say I am impressed with the docs plus some of the demos are broken.
GWT on the other hand is very mature but I have the feeling that using Java may slow you down as you cannot use some of the JS quirks on the other hand there is vibrant ecosystem around it.
I think the answer depends on what type of developer are you?
For me, I'm comfortable with Javascript and like the ability to manipulate the browser DOM so that I can implement features that may not be in the framework. That's why I prefer Sproutcore.
Checkout http://www.infoq.com/news/2009/09/sproutcore-1-0.
I have to agree with you that documentation is limited. However, I've found wiki useful and the community really helpful.
GWT is a very nice choice if you're using GAE-Java because then you can develop server-side and client-side in the same language. If you're using Python on the server-side, you won't be able to use GWT's simple RPC calls to serialize objects to/from the browser. It's still a nice framework though.
GWT does allow you to write JS-native code if needed, so you can "use some of the JS quirks" if you need to.
One warning: GWT apps are totally AJAX, so they can't really be seen by search engines (a general problem with AJAX, not with GWT specifically)
So, there are several languages which will allow you to create a website, as long as you configure the server(s) well enough.
To my knowledge, there is:
PHP
ASP.NET
Ruby(on rails, what is
that all about?)
And thusly, my knowledge is limited. Ruby and ASP, I've only heard of, never worked with. If there are other languages, I suppose they have some way to make files containing the needed html. It would then suffice to add a line to the Apache config to associate the file-extension.
And if other languages: are there any notable characteristics about the one(s) you mention?
ANY language can be use to make a dynamic website - you could do it in COBOL or FORTRAN if you were twisted enough. Back in the olden days (about 10 years ago) most dynamic websites were done with CGI scripts - all you needed was a program that could read data from standard input and write data (usually HTML) to standard output.
Most modern languages have libraries and frameworks to make it easier. As well as the languages you have already mentioned, Java, C# and Python are probably the most common in use today.
Typically a web framework will have:
a way of mapping URLs to a class or function to handle the request
a mechanism for extracting data from a request and converting it into an easy to use form
a template system to easily create HTML by filling in the blanks
an easy way to access a database, such as an ORM
mechanisms to handle caching, redirections, errors etc
You can find a comparison of popular web frameworks on wikipedia.
How can you forget Java ? :)
Python
It runs on Windows, Linux/Unix, Mac OS X, and has been ported to the Java and .NET virtual machines.
Python is a perfect scripting language for web applications, e.g. via mod_python for the Apache web server. With Web Server Gateway Interface a standard API has been developed to facilitate these applications. Web application frameworks or application servers like Django, Pylons, TurboGears, web2py and Zope support developers in the design and maintenance of complex applications. Around libraries like NumPy, Scipy and Matplotlib, Python is a standard in scientific computing.
Among the users of Python are YouTube and the original BitTorrent client. Large organizations that make use of Python include Google, Yahoo!, CERN, NASA,and ITA.
This could be for your interest.
Virtually thru CGI all programming languages that produce output may use for web page generation.
Basically, you can use any language (if you are hosting your own server)
Very closely related and very interesting is this article where LISP has been used to build a very succesfull website.
Python has a 3rd party module CherryPy which can be used with or without a http server.
Amongst others: Erlang (YAWS, Mochiweb), Python
JSP has the advantage that it automatically wraps your code in a servlet, compiles that to bytecodes, then uses the just-in-time Java compiler to recompile critical sections into native object code. Not aware of any alternative which allows optimizes your work automatically in this way.
Also allows you to develop and deploy on any combination of Windows, Mac OS X, or Linux.
If you'd like to choose one for the beginning, you should check out PHP first. It gives you the basic clues about how dynamic sites work in general.
After you've become familiar with the basics, I recommend ASP.NET.
Fist off, you should know that ASP.NET is a technology and not a language. (It actually supports any language that can be used on the .NET platform.) Also it is not to be confused with classic ASP. (The old ASP was much more like PHP.)
ASP.NET is very easy to begin with, and after you have some clues about its concepts, you can always dig deeper and customize everything in it. The http://asp.net site is a very good starting point, if you are to learn it. I think it is really worth the effort, because even if you choose not to stick to it, it will give you some interesting ideas and concepts.
I tell you its most important advantages:
The code is compiled (and NOT interpreted like PHP), and it has a very good performance. (In a performace comparsion, it is 10-15 times faster. http://www.misfitgeek.com/pages/Perf_Stat_0809.htm)
It can be run on Windows without effort, and on Linux / Mac / etc using the Mono project.
It implements the Separation of Concerns principle very well.
It has most of the general functionality you'll need built-in. (Such as membership, roles, database management, and so on.)
I am about to start on a college project (a web application) and I have never used a full-fledged IDE such as Eclipse.
Turbo C/C++, Visual Basic 6,Java Basic, a bit of SQL, ASP, etc is the sort of exposure I have.
What things should I keep in mind before starting my project using Eclipse? Are the tools mentioned appropriate for the project?(If not please give a detailed answer)
Designing - UML (Rational Rose)
Language - Google Web Toolkit
Server - Google App Engine
IDE - Eclipse
Version Control - Subversion or Mercurial?
I would definitely recommend Googling first. There are a number of tutorials regarding Eclipse as it is a very popular IDE. A quick Google search of my own brought up all these results: developing web applications in eclipse
As for other things to consider, if you are developing a web application, you'll need:
web server (Tomcat is a popular one)
possibly a database (MySQL is an open source, easy to use DB)
language (I'm assuming you're going with Java since you are using Eclipse)
Of course, you'll also need to consider how you hook everything together and what technologies you want to use to do that. (Hibernate, Spring, etc) Eclipse itself has a ton of plugins to help bring together all these various aspects.
That list from Wikipedia is a good and comprehensive list, but if you are learning or developing on your own machine, you may not necessarily need all of that.
Hope that helps.
Since it is a web application, then start with the looks of it.
First, layout a template of how your pages should look, that is what users see. If it does not look good, the users will think the application (in its entirety) is also not good (it does not matter if the code behind the view is perfect; it will just make a first bad impression).
Start with that and be consistent with the design in all your pages. SiteMesh is a nice tool to dissociate the looks of the page from the functionality you put in it.
Then think what the application will do and what it will use:
you have a database? (use something like MySQL). With what are you going to access it? (IBatis is nice; Hibernate I think is a bit heavy weight for a first project)
you need a server: Tomcat is easy to use;
are you going for a simple Servlet/JSP approach or you want to use a framework (look at Spring or Struts);
try to find the good ways of writing the application, look at service layers, DAO pattern, DTO, MVC. Also, you must understand how HTTP works.
A lot more could be said.
Ah.. and also use a source repository. It’s a must (even if you work alone on this project).
Eclipse can handle all of these tools, but then so can Netbeans.
For your first project with GWT you should read through this tutorial:
http://code.google.com/webtoolkit/tutorials/1.6/gettingstarted.html
If you don't know Java then you will have some learning to do, and unlike Visual Studio your UI won't be just drag and drop, so it will be a bit harder than you are used to.
Subversion is fine, it is a nice source control, and any IDE will work with it.
Depending on your project would determine if GWT is the best choice though.
I expect UML may be overkill, and if you were following an agile methodology you wouldn't use it.
Your best bet is to get the UI done first, just have it appear as you want, and have some fake results, until you are happy with the look and feel.
Then, start to do the wiring to whatever you need on the backend.
Don't mean to be harping on you, but is Eclipse a must? For myself, in the beginning NetBeans turned out to be a really painless introduction to getting a web project up a running fast. I believe in the beginning one will spend a lot less time fighting the IDE with NetBeans.
A lot of the items from your bullet list NB makes super easy to ramp up as well. Just my $0.2