What does the article below mean by Web Service Definition Language?
Service interfaces are frequently defined using Web Service Definition
Language (WSDL) which is a standard tag structure based on xml
(extensible markup language).
Source: https://www.ibm.com/cloud/learn/soa
I am confused by the word "interface". Interface makes me think it's front end, but that cannot be right.
Is this right? For example, if I build a website application, a directory would include a file (example.xml) which would be written in Web Service Definition Language. The examle.xml file would be used by the computer to request and interoperate data.
You might want to read about the meaning of an interface. In plain words, to interface with something means to interact, or connect, or communicate with something. In the world of web services this means connecting to or communicating with a web service.
So from that point of view, the service has an interface (often the word contract is also used).
To know the specifics of how exactly this interface works it needs to be described to you, i.e. what are the details to connect and interact/communicate. WSDLs are a way to define this, with the advantage of allowing it to be used by tools to generate the necessary code to interact with the web service.
WSDLs are usually used with SOAP web services.
I didn't find anything on Google saying about it.. so, is it possible?
i.e discard the XCode's Storyboard and use Angular 2 to make apps.
PS: Swift isn't discartable for me due frameworks and done backend code. I am using FFT algorythm from Swift's AudioKit Framework.
Angular2 can be used with any compliant web server written in any language. As long as it speaks HTTP correctly it doesn't matter what it's written in.
Angular2 is a front end JavaScript based technology. As long as you have a web viewer that can render HTML and has a standards compliant JavaScript runtime you can make it talk to your back end.
You can wrap it in an app store compatible package but it will still be a JavaScript app and will connect to your backend in the exact same way that it would if you targeted the browser. The difference is it'll be able to leverage certain device specific capabilities. You will communicate with your backend by sending JSON (any format can be used) back and forth.
The key point is that all communication will be in the form of serialized messages only.
Even if your backend were running on the same device, there's no shared memory space.
Of course since a mobile app can persist it's own state locally it might not need a backend at all. This last point is very domain specific.
It could be posibble if you use Vapor as your backend engine. Take a look at Vapor's website for more info.
I have been playing around with the RPC package in Dart which makes it easy to add a Document Discovery service to Dart server.
After a bit of Googling I found out about the API Discovery Service https://developers.google.com/discovery/ which explained how to create client code for a given Discovery Document.
I then found Google Cloud Endpoint which looks like the server end of the a Document Discovery service. Is this true.
My real question is that I would like to use the Document Discovery service on a standard web site that is based on (say) Spring and running (say) an embedded Jetty server? Is this possible or would my application be intertwined with the App Engine Technology?
You application just needs to provide a Document Discovery service.
It shouldn't be to hard to get the information what is expected out of the source of https://pub.dartlang.org/packages/discovery_api_client_generator which is the Dart client which generates Dart client code from discovery documents. As far as I know your service doesn't even need to provide the discovery documents. The discovery_api_client_generator package can also use discovery documents stored locally but the service is of course the preferred way if you want to make it available to everyone.
I would see it as equivalent to SOAP which also allows to create client code from meta-information provided as XML.
Also the shelf_rpc package doesn't need to run on AppEngine or Managed VM. You can run it locally or on any server you want.
I currently have a txt file on a Linux install that I need to access from my app and write back to. The app and the Linux server are on the same subnet and I have full control of both machines (permissions). I've thought about SSHing into the machine but this obviously has its security drawbacks sending raw credentials. Does anyone have any suggestions on what framework to use to create a secure tunnel or perhaps an alternative solution?
Write a simple web service in your language of choice php, python, ruby, etc. And make a simple secure call to your service with the changes.
I have some delphi code which, given a list of items, calculates the total price taking into account any special deals that might apply.
This code is non-trivial to rewrite in another language.
How should I set it up to communicate with a website running on the same server? The website will need to ask it for a price every time the user updates their shopping cart. It's possible that there will be multiple concurrent requests.
The delphi code needs to maintain an in-memory list of special deals, periodically refreshed from a database. So it cannot simply be executed every time or anything as simple as that.
I don't know what the website is written in, or even which http server it runs under, so I'm just looking for ideas or standard methods.
It sounds like the win32 app is already running as a Windows Service on the box. So, if you can't modify that service, you are going to have to deal with whatever way it wants to accept and respond to requests. This could be through sockets or some higher level communication protocol like web services.
You could do a couple of things. Write an assembly that knows how to communicate with the service and have your web site use that assembly. Or you could build a shim service that knows how to communicate with the legacy service, but exposes communication over higher level protocols such as web services. Either way will have the benefit of hiding the concurrency, threading and communications issue behind an easy to call interface, but the latter will make communicating with the service easier for everyone going forward.
If you can modify the delphi app to take an XML request and respond with an XML answer over a TCP socket (ideally using the HTTP protocol), you will be able to make it interoperate with most web server frameworks relatively easily. But the exact details of how to make that integration happen will depend on the language/framework it was written in.
If the web server is on windows you can compile your delphi app as a DLL that can return XML or HTML, taking parameters as part of the URL or a POST operation. Some details on making a Delphi DLL for web servers are here.
It doesn't matter what web server or OS the existing system is running under. What matters is what you want YOUR code to run under. If it is windows then the easiest solution would be to use WebBroker and write a custom ISAPI application, or use SOAP to expose web services. The first method could be used if you wanted to write a rest like API for instance, the second if your web application has the ability to consume web services.
Another option, if you are running both on the same box under IIS, is to create a COM/Automation object which you then invoke via server side scripting (ASP). If the application is an ASP.NET application, then I would use PRISM to port your code into an assembly.
I have done this with a quite complicated workers compensation calculator. I created a windows service using RemObjects Sdk. The calculations are exposed as a soap method so it can be accessed by nearly anything.
It's not necessary to use RemObjects in the service but it makes it much easier to do as it handles a lot of the underlying plumbing. The clients don't need RemObjects, they just need to be able to call soap methods. Nearly any programming langugae can do that.
You could also create an isapi dll for IIS that exposes a soap interface. This would be useful if other websites on different servers needed access to the methods. However I have handled this in my case by opening a port in the firewall to access my windows service.
There is a lot of examples on the web. A couple of places to start reading are About.Com and Dr Bob.
Torn this app into Windows Service. Write Web Service that will communicate with your windows service. You should spend some time designing your Web Service, because this Web Service is going to be your consistent interface, shielding old Delphi app. So in the future whenever you will want to write web app, mobile app, or whatever you will imagine, you will have one consistent interface – XML Web Service.
A popular way to integrate a web application with background services is a message broker.
The message flow would be:
the web application sends a "calculation request" message to a message destination on the message broker, which contains all needed parameters and also a correlation id to match the calculation request with the response from the Delphi service
one (or, in a high availability / load balanced environment more) Delphi services handle the messages: pull the next incoming message, process it by feeding the parameters to the calculation engine, and send a "calculation result message" back to the web server
the web server can either synchronously wait for the response (and discard responses which have no matching correlation ide) and build the result HTML document, or continue with other tasks and asynchronously receive the calculation result in a separate thread, for example in a Ajax based web application
See for an introduction this slideshow about the Dopplr image service:
http://de.slideshare.net/carsonified/dopplr-its-made-of-messages-matt-biddulph-presentation
If you can make it a service (but not a library), you have to do inter-process communication somehow - there are a few ways to do this on Windows:
Sockets directly which is hardest since you have to do marshalling/auth yourself
Shared Memory (yuck!)
RPC which works great but isn't trivial
DCOM which is easier but a pain to configure
WCF - but can you call it from your Windows Service written in Delphi?