I am bit confused about ADO.Net Data Services.
Is it just meant for creating RESTful web services? I know WCF started in the SOAP world but now I hear it has good support for REST. Same goes for ADO.Net data services where you can make it work in an RPC model if you cannot look at everything from a resource oriented view.
At least from the demos I saw recently, it looks like ADO.Net Data Services is built on WCF stack on the server. Please correct me if I am wrong.
I am not intending to start a REST vs SOAP debate but I guess things are not that crystal clear anymore.
Any suggestions or guidelines on what to use where?
In my view ADO.Net data services is for creating restful services that are closely aligned with your domain model, that is the models themselves are published rather then say some form of DTO etc.
Using it for RPC style services seems like a bad fit, though unfortunately even some very basic features like being able to perform a filtered counts etc. aren't available which often means you'll end up using some RPC just to meet the requirements of your customers i.e. so you can display a paged grid etc.
WCF 3.5 pre-SP1 was a fairly weak RESTful platform, with SP1 things have improved in both Uri templates and with the availability of ATOMPub support, such that it's becoming more capable, but they don't really provide any elegant solution for supporting say JSON, XML, ATOM or even something more esoteric like payload like CSV simultaneously, short of having to make use of URL rewriting and different extension, method name munging etc. - rather then just selecting a serializer/deserializer based on the headers of the request.
With WCF it's still difficult to create services that work in a more a natural restful manor i.e. where resources include urls, and you can transition state by navigating through them - it's a little clunky - ADO.Net data services does this quite well with it's AtomPub support though.
My recommendation would be use web services where they're naturally are services and strong service boundaries being enforced, use ADO.Net Data services for rich web-style clients (websites, ajax, silverlight) where the composability of the url queries can save a lot of plumbing and your domain model is pretty basic... and roll your own REST layer (perhaps using an MVC framework as a starting point) if you need complete control over the information i.e. if you're publishing an API for other developers to consume on a social platform etc.
My 2ø worth!
Using WCF's rest binding is very valid when working with code that doesn't interact with a database at all. The HTTP verbs don't always have to go against a data provider.
Actually, there are options to filter and skip to get the page like feature among others.
See here:
Related
We have an established WCF SOAP service. Its interface is defined in WSDL, from which C# classes are generated for our server (customers generate client-side bindings in various languages, from the same WSDL). The WSDL has a current version, which we can change a bit, and old versions, which we can't change or drop without a deprecation period, consultation etc. The SOAP requests tend to be complicated, having multiple XML namespaces within the same request.
The WCF SOAP service has a lot of "smarts" in it, and provides exactly the kinds of fetching and reporting facilities that we need for a new Web application that we need to make. We hope to use AngularJS for the client side of that. But these complex SOAP requests aren't easy to make in JavaScript world. If only we had a REST service, we could use angular Resource service. If not that, then a server that spoke JSON, albeit in an RPC style like SOAP, would run a fairly close second.
I've had various ideas for how the impedance mismatch between our server and client might be mitigated. But nothing sounds quick or easy.
I've thought of: -
Write a new REST service. Exactly what the client-side wants, but a serious piece of new development.
WebHttpBinding looks to offer something. But seems to me like it requires C# markup of custom attribute (how to achieve when our C# is generated from WSDL) and possibly wouldn't support our complex types
Obtain or write loads of client-side JS to abstract away calling SOAP services. But, unless this can be auto-generated from the WSDL, it's a huge amount of client-side code to write.
Write an IDispatchMessageFormatter for the server, to accept some JSON format of messages that I invent. Sounds hard, especially as good examples of people implementing and integrating IDispatchMessageFormatter seem hard to come by.
Write a MessageEncoder to swap between JSON and XML. But this isn't really an encoding operation, as became very clear when I tried to write it!
I'm searching for suggestions.
Generally, I recommend a REST service for any AngularJS development and have wrapped a number of legacy systems with Node.js API servers. Of course there is a massive amount of "it depends", but generally most projects will be happier and more productive following that route.
Some Things To Think About
How well does your current SOAP API fit the user interface requirements?
Are you experienced with Express, Sinatra, Flask or other micro-framework that allow rapid development of REST APIs? I find I can build a solid Node.js Express API server in a couple of hours and then extend it as I build the AngularJS application out.
How experienced are you with AngularJS? It's a more advanced project to build a complex data layer client-side.
Six Reasons Why REST is Important for AngularJS
It's much faster to write Angular code using $resource and $http. Get the API right is a good recommendation for effective AngularJS development. Indeed, you could argue that AngularJS is designed for REST, and that's why plain JavaScript works for the model (see 2).
Angular's plain-old JavaScript object data model works well with a REST API that speaks JSON that matches the user interface. However, issues arise when there isn't a good fit- Angular doesn't have a formal data model so you end up writing an lot of code trying to rationalize your API to work well with Angular. 3rd party libraries like breeze.js may offer some solution, but it's still awkward.
You can scale easily with caching. It's easy to add Redis or memcache or Varnish or other common HTTP caching solutions into the mix. Resource-based abstractions are perfect for caching strategies due to the transparency and idempotency of a REST api.
Loose coupling of front-end and server- it will be easier to support changes to the backend if you migrate off SOAP or need to integrate with other services.
It's generally easier to test JSON APIs separately from AngularJS logic, so your test suites will be simpler and more effective.
Your new REST API will be easier to leverage for future AngularJS and JSON-oriented projects.
I hope that helps.
Cheers,
Nick
I have just started evaluating whether or not I should be using OData influenced wcf data services or a standard WCF service application as the primary data source for Silverlight applications. I would like your thoughts on which is a better way under what situation/circumstance. What is lighter over the wire, easier to maintain, etc.
What I have gathered so far is:
There are no Wcf data service templates in VS2010 that I know of, and I will need to create a asp.net web project first and then add a wcf data service, so its going to affect how I structure my projects.
WCF Data services expose actual table names over the service. I don't know yet of a way I can alias them and I'm not sure its a good idea to let the world know my table structure
In a standard wcf service I will need to write linq queries against the EF or Domain service classes on the service side, while in a data service I can move that processing logic to the client.
At first glance examining the classes exposed by the wcf data services seem easier to read and understand than those exposed by the EF
Do add your thoughts on this..
Thanks for your time.
There are no Wcf data service
templates in VS2010 that I know of,
Not project template - just an item template (for use inside an ASP.NET web site or web app). WCF DataServices are very tightly coupled to HTTP, so they only make sense in a web site/app.
WCF Data services expose actual table
names over the service.
NO ! At least not necessarily. The whole point of EF is that you can decouple the actual physical structure of your database from the (conceptual) model that gets exposed. You can totally rename entities, you can map several entities onto a single table, split up an entity over several tables, you can leave out attributes - anything you like!
At first glance examining the classes
exposed by the wcf data services seem
easier to read and understand than
those exposed by the EF
I doubt it - because by default, WCF Data Services will use a Linq-to-SQL or EF model as their basis, really. You can make that as simple or as complicated as you like.
Using a "regular" WCF service allows you to use the netTcpBinding for much faster performance (thanks to binary message encoding vs. textual messages for other bindings), when using your Silverlight 4 app in a company-internal network (doesn't work for internet scenarios) - not something you can do with WCF DataServices.
The main difference in my opinion is the SOAP vs. REST difference:
SOAP (traditional WCF) is oriented towards methods - you think and design your system in terms of methods - things you can do (GetCustomer, SaveOrder etc.)
REST (the WCF DataServices approach) is all about resources, e.g. you have your resources and collections of resources (e.g. Customers) and you expose those out to the world, with standard HTTP verbs (GET, POST, PUT, DELETE) instead of separate specific methods that you define
So both approaches have their pros and cons. I guess the most important question is: what kind of app are you creating, and what kind of user audience are you targetting?
Update:
for intranet / internal apps, I would think the advantage of a netTcpBinding (binary encoding) would justify using a classic WCF service - also for data-intensive apps, I personally find a method-based approach (GetCustomer, SaveCustomer) to be easier to use and understand
for a public-facing app, using HTTP and being as interoperable as possible is probably your major concern, so in that scenario, I'd probably favor the WCF Data Service - easy to use, easy to understand URLs for the user
I was thinking about the architecture of a web application that I am planning on building and I found myself thinking a lot about a core part of the application. Since I will want to create, for example, an android application to access it, I was already thinking about having an API.
Given the fact that I will want to have an external API to my application from day one, is it a good idea to use that API as an interface between the interface layer (web) and the business layer of my application? This means that even the main interface of my application would access the data through the API. What are the downsides of this approach? performance?
In more general terms, if one is building a web application that is likely to need to be accessed in different ways, is it a good architectural design to have an API (web service) as the interface between the interface layer and business layer? Is REST a good "tool" for that?
Sounds like you've got two questions there, so my answer is in two parts.
Firstly, should you use an API between the interface layer and the business layer? This is certainly a valid approach, one that I'm using in my current project, but you'll have to decide on the benefits yourself, because only you know your project. Possibly the largest factor to consider is whether there will be enough different clients accessing the business layer to justify the extra development effort in developing an API? Often that simply means more than 1 client, as the benefits of having an API will be evident when you come to release changes or bug fixes. Also consider the added complexity, the extra code maintenance overhead and any benefits that might come from separating the interface and business layers such as increased testability.
Secondly, if you implement an API, should you use REST? REST is an architecture, which says as much about how the remainder of your application is developed as it does the API. It's no good defining resources at the API level that don't translate to the Business Layer. Rest tends to be a good approach when you want lots of people to be able to develop against your API (like NetFlix for example). In the case of my current project, we've gone for XML over HTTP, because we don't need the benefits that Rest generally offers (or SOAP for that matter).
In general, the rule of thumb is to implement the simplest solution that works, and without coding yourself into a corner, develop for today's requirements, not tomorrow's.
Chris
You will definitely need need a Web Service layer if you're going to be accessing it from a native client over the Internet.
There are obviously many approaches and solutions to achieve this however I consider the correct architectural guideline to follow is to have a well-defined Service Interface on the Server which is accessed by the Gateway on the client. You would then use POCO DTO's (Plain old DTO's) to communicate between the endpoints. The DTO's main purpose is to provide optimal representation of your web service over the wire, it also allows you to avoid having to deal with serialization as it should be handled transparently by the Client Gateway and Service Interface libraries.
It really depends on how to big your project / app is whether or not you want want to go through the effort to mapping your DTO's to the client and server domain models. For large applications the general approach would be on the client to map your DTO's to your UI Models and have your UI Views bind to that. On the server you would map your DTO's to your domain models and depending on the implementation of the service persist that.
REST is an architectural pattern which for small projects I consider an additional overhead/complexity as it is not as good programattic fit compared to RPC / Document Centric web services. In not so many words the general idea of REST is to develop your services around resources. These resources can have multiple representations which your web service should provide depending on the preferred Content-Type indicated by your HTTP Client (i.e. in the HTTP ACCEPT HEADER). The canonical urls for your web services should also be logically formed (e.g. /customers/reports/1 as opposed to /GetCustomerReports?Id=1) and your web services would ideally return the list of 'valid states your client can enter' with each response. Basically REST is a nice approach promoting a loosely-coupled architecture and re-use however requires more effort to 'adhere' to than standard RPC/Document based web services whose benefits are unlikely to be visible in small projects.
If you're still evaluating what web service technology you should use, you may want to consider using my open source web framework as it is optimized for this task. The DTO's that you use to define your web services interface with can be re-used on the client (which is not normally the case) to provide a strongly-typed interface where all the serialization is taken for you. It also has the added benefit of enabling each web service you create to be called by SOAP 1.1/1.2, XML and JSON web services automatically without any extra configuration so you can choose the most optimal end point for every client scenario, i.e. Native Desktop or Web App, etc.
My recent preference, which is based on J2EE6, is to implement the business logic in session beans and then add SOAP and RESTful web services as needed. It's very simple to add the glue to implement the web services around those session beans. That way I can provide the service that makes the most sense for a particular user application.
We've had good luck doing something like this on a project. Our web services mainly do standard content management, with a high proportion of reads (GET) to writes (PUT, POST, DELETE). So if your logic layer is similar, this is a very reasonable approach to consider.
In one case, we have a video player app on Android (Motorola Droid, Droid 2, Droid X, ...) which is supported by a set of REST web services off in the cloud. These expose a catalog of video on demand content, enable video session setup and tear-down, handle bookmarking, and so on. REST worked out very well for this.
For us one of the key advantages of REST is scalability: since RESTful GET responses may be cached in the HTTP infrastructure, many more clients can be served from the same web application.
But REST doesn't seem to fit some kinds of business logic very well. For instance in one case I wrapped a daily maintenance operation behind a web service API. It wasn't obvious what verb to use, since this operation read data from a remote source, used it to do a lot of creates and updates to a local database, then did deletes of old data, then went off and told an external system to do stuff. So I settled on making this a POST, making this part of the API non-RESTful. Even so, by having a web services layer on top of this operation, we can run the daily script on a timer, run it in response to some external event, and/or have it run as part of a higher level workflow.
Since you're using Android, take a look at the Java Restlet Framework. There's a Restlet edition supporting Android. The director of engineering at Overstock.com raved about it to me a few years ago, and everything he told us was true, it's a phenomenally well-done framework that makes things easy.
Sure, REST could be used for that. But first ask yourself, does it make sense? REST is a tool like any other, and while a good one, not always the best hammer for every nail. The advantage of building this interface RESTfully is that, IMO, it will make it easier in the future to create other uses for this data - maybe something you haven't thought of yet. If you decide to go with a REST API your next question is, what language will it speak? I've found AtomPub to be a great way for processes/applications to exchange info - and it's very extensible so you can add a lot of custom metadata and yet still be eaily parsed with any Atom libraries. Microsoft uses AtomPub in it's cloud [Azure] platform to talk between the data producers and consumers. Just a thought.
Assume a situation where a data will never be queried directly. AKA, there will always be some filtering logic and/or business logic that must occur.
When is a good reason to use data services outside of ajax/js?
Please don't site this page http://msdn.microsoft.com/en-us/data/bb931106.aspx
Your essentially asking what layer of abstraction should I use, WCF Data Services is built on top of WCF and aims to simplify the process of creating a REST based service that is consumable by anything on the web. It takes away a lot of the plumbing and configuration required to do this with a standard WCF service. The querying feature is another big plus and something that is difficult to get right with standard WCF.
So in short:
If you want to quickly build a loosely typed service that wraps an existing data model and enables querying support give WCF Data Services a go.
If you want full control over the service contract or the flexibility of exposing the service over any protocol, stick with plain old WCF.
There a lot of different ways a Silverlight application can connect back to it’ server. Including
WCF - Windows Communication Foundation
REST (see also)
ADO.NET Data Services (or is this just REST?)
POX - Plain Old XML (E.g basic xml)
RIA services
For each of these please say what it’s for and when you would or wouldn’t use it. I am not looking for a great level of details just a set of “rules of thumb” for choosing between them.
(The problem is when designing your first Silverlight application knowing what to use when you don’t have time to learn all of them.)
If I was to replace Silverlight with WPF in this question what effect would it have on your answers? (I am assuming with WPF that due to firewalls and admin policies a direct connect to the database is not an option.)
My two (euro) cents:
WCF seems best suited when the service can be viewed as the business layer of the application, that is, when your service has "intelligent" operations like "CalculateDiscountForClient".
ADO.NET Data Services (indeed, just a REST implementation) seems appropriate when your application is basically data-centric and the service is simply a front-end for the database. That is, all your service methods are of type GetCustomers, CreateInvoice, etc.
RIA services is a very new technology that I haven't experimented with yet, but it seems to be useful to create applications in which the Silverlight part and the service are very tightly coupled: you define your service classes and methods in the service project, and they are automatically replicated to the Silverlight project in design time. Also, you can define both WCF-style "action" methods and ADO.NET Data Services-style "data" methods. Looks promising.
Use POX if there is a chance that you change the client part from Silverlight to any other technology (for example HTML+AJAX) in the future, since it is the most interoperable option.
About differences for WPF, the only I can think of, is that for data access, whenever possible I would use direct ADO.NET data connections (properly embedded in a data access layer, LINQ to SQL or the like) instead of ADO.NET Data Services, since it is way more flexible. I must say anyway that I have never developed anything in WPF.
We use RIA, and that's the only one of the options that I know, but I do know it, so here's some of my thoughts.
RIA isn't finished yet. It is being worked on. If you are planning to be finished soon, and you're worried about having to support something that has a potential to change quite a bit, then you might want to consider other options. If this is a new project, and you're going to be supporting it for a long time, RIA will probably get easier to use.
Having said that, I kind of think that there won't be many changes in the way the July Preview of RIA works and the way that a finished version will work. Also the level of support seems to suggest that this will become "The Way" to talk to a server in Silverlight.
Just cause it's worth mentioning, have some links:
http://blogs.msdn.com/brada/ Brad Abrams has an example that he is continually updating.
http://forums.silverlight.net/forums/53.aspx this is where you go to ask questions.
http://www.riaservicesblog.com/Blog/ Colin Blair knows his stuff, and he is very helpful.
I think I would not go POX ever again. If you write WCF so that the service itself is independent of the binding and binding is done in configuration files, then WCF is pretty much agnostic about transport and protocol. It can do SOAP, JSON, REST, or its own form of binary serialization. All of this is in the binding. Internally, WCF only specifies what gets exposed in terms of operation and data contracts (all defined by class, method, and property attributes). WCF gives you tremendous flexibility in this regard, with more to come in 2010.
From the Silverlight side, WCF requires that you write some plumbing code. The .NET frameowrk has the tools to build the proxy in your Silverlight project, but you must be prepared to handle all WCF responses asynchronously, and the proxy cannot catch exceptions thrown by the service.
.NET RIA Services hides all this. It uses WCF under the covers, but that is completely hidden. You don't have to write asynchronous code. You define validation once, mostly declaratively, and it works both server-side and client-side. Release 1 will be targeted for Silverlight, so you don't get the versatility to use the service elsewhere. That scope is supposed to be broadened in later releases.
I don't know enough about ADO.NET Data Services to compare. I suspect the answer would depend on whether you want to expose your data to more than just Silverlight usage.
.NET RIA Services looks like the direction I'd want to go (looking at these issues myself, with a large application in mind). The big issues for me will be implementing a very large collection of functionality in the service layer, and not being able to code directly to the data access layer (we have to be able to run on either SQL Server or Oracle).
Using WPF instead of Silverlight changes everything, depending on where your data resides. It's like the old question of Winforms vs. ASP.NET. With WPF, you're building a Windows client app, and you don't need to use any form of service-based data interface at all, unless your data access forces you into it. You'll still want to separate data and business from presentation code, using MVVM, MVC, or MVP. Other than that, you have the option to treat data access as a layer, rather than a wholy independent tier.
WCF is Microsoft's standard for service communication. I would strongly advise anyone to create a service layer using WCF Web APIs (uses WCF, but tailored specifically for REST), which is coming out this April 2012. WCF Web APIs is currently in preview mode.
Remember these rules of thumb:
- your UI will change faster than your service layer. RESTful services will be around in several years, Silverlight probably won't
- will your services ever be APIs? Well...WCF REST is the way to go
- will you mix JavaScript and Silverlight code? WCF REST will make your life easier
- will you have a mobile component (since Silverlight won't run on iOS or android)...REST is preferred.
Don't tailor to the technology, but the app as a whole.
If you want to create a Silverlight Application and you do not care about other clients, then I would choose RIA Services. It is quite painless to use and you do not need to worry how the connection from the client is made (i.e. no client side configuration necessary). RIA also generates classes for all your entities on the client and you can even share your own "server" code with the client if required (useful for enumerations or extension methods).
Remarks:
I never tried this, but if you really need you can access the RIA Service also with other clients, after all RIA Services are built on top of WCF services.
I do not quite understand Akash Kava's security concerns. You can (and have to) control security on the server-side as you would do with any other service.