The 5W's of descriptive epidemiology:
Net over the wire. In this article, we intend to show how simple technology coupled with a document-centric approach can be used to deliver valuable business services without the use of proprietary middle-ware or the complexities of the web services stack.
The Web Service way The best way to introduce this approach is to contrast it with a simple web service example. Imagine a simple Weather Service exposing a web method called "WeatherQuery" that returned the temperature and pressure wrapped in an object.
Web services providers and consumers(CXF, Spring Ws, JAX B). Estimated: $79, - $, a year Please note that all salary figures are approximations based upon third party submissions to SimplyHired or its affiliates. View Amit Nagar’s profile on LinkedIn, the world's largest professional community. Information Technology and Services. Current: - Worked with RESTful Web services using JAX-WS (Jersey Title: Full Stack J2EE/Cloud Developer. Moldova remains Europe's poorest economy, but has made steps toward expanding its market access by signing and ratifying an Association Agreement with the EU in , which fully entered into force in July after ratification by all EU member states.
In most cases people take existing code and use a tool to expose a method and generate some WSDL. Unfortunately things are not quite that simple, WSDL is a broad standard, in fact broad enough to be open to interpretation. In our case we found. Net enforced a document approach and our java tools assumed the opposite, RPC.
We also found issues with mixtures of namespaces, inclusion of schemas and tools splitting the WSDL into separate parts. In short the technology starts to distract from the actual problem we are trying to solve. To compound the issue, we also found inconsistencies within tools for web services.
We became very weary of something that may be kludged to work today, but may break tomorrow if a more complicated web method were needed in later version of the service. Instead of thinking about the parameters of the request and the type of the return, we can think of the request as a document that embodies the type of request along with its parameters.
Think of that document as something that represents part of the contract for the business process you are trying to model. If we take the same WeatherQuery method, and describe it in an element normal XML we might see something like - Also as a document, the return type may look like - Now we can define a simple class design that represents the same fields as the documents - The interesting thing about these two documents is that they are relatively easy to serialize and deserialize in both.
Net, the built-in XML serialization with some annotations does the job well. Here is the C for the same classes - Java is not so lucky. It has no built in tools for XML serialization: With this shift, we are able to think about multiple document types using the same entry-point into the system giving us a more extensible approach.
Coding the Java server The technologies we used for a Java implementation of the service are that of the serialization library XStream, and any servlet container, as we chose to host the services inside a Servlet.
XStream is open source: Our servlet should implement the doPost rather than doGet method. It is a matter of preference though - as long as its the same on client and server. When a request comes in, we deserialize the XML into a command object using XStream and appropriately handle it.
Net server The server technologies for. Net's built-in XML serialization. Net port of XStream that makes things simpler still, but we have not experimented with that, and we have heard of another port about to be launched on the open source world.
Coding the Java client See http: The former may be attractive if you want to create a test web form for the service. Net client For the. Net client you'll need just the framework and this can be either version 1. Making it extensible and compatible The beauty of simply POSTing XML that represents commands is that we can add more commands later without changing our messages implementation.
Schema validation, if performed at runtime, gives a developer a sense of safety that is not appropriate. A failure may still happen - the wrong XML could be sent. There would be a schema invalid exception message raised.
Alternatively with the XML mapped to a class's design, there would either be a correct object, or it would be missing some fields. In that situation, a real exception could be thrown with a real reason, that could easily be turned into a clear XML reply message for the consumer.
The key difference is that an exception is raised only if required information is missing - anything else could change. Inherently in this design, there is the possibility that elements could be added to the XML fields to the class that make it possible to move the API notionally forward a notch.
With some careful testing, the service could support consumers sending older versions of the request documents.
An API change, as well as being "extra field" level, could also be more far reaching: It may be better to encode the version number into the URL though: You may be doing this to side-step the corporate standards police.
Extending it to Messaging Leveraging Tibco Rendezvous, we were able to send the same XML representations of requests around for execution against an implicitly asynchronous service. We did not try MQ Series but it should work too.I am deciding on the implementation of Web Service Client in Java.
I've generated Axis client in Eclipse and JAS-WS client with wsimport. Both solutions work and now I have to choose one to go forward.
Web services providers and consumers(CXF, Spring Ws, JAX B). Estimated: $79, - $, a year Please note that all salary figures are approximations based upon third party submissions to SimplyHired or its affiliates.
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