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Web Client API and Rest API

As I have understood we use Web services(Rest/Soap) so that a piece of code with some functionality written in one language(say Java) can be used by other programmer no matter the language(say Python) he is developing the application over the internet.
One of the projects I came across uses EWS web services to create,delete appointments on our Outlook 365. The application is developed in Java and a JAVA EWSAPI.jar file is included in the library path(which contains class files like appointment.class,Meeting.class etc) to connect to EWS server and create meetings .
My confusion is suppose we were developing the application in Python, so for that do we have another API (say EWSPython.pythonextension). So then how developing a web service helped us.
I understand API defines the set the methods available and how can they be called with argument.
Please clear my doubts.

I think that you have misunderstood the aim of webservices. We need webservices to make their calls (clients) a platform independent interface which means that once you have created your webservice using any technology (java for your case here) now anyone can call this service by creating a client using any language like python, C#, C++, Ruby, ........... in that case a service which was built by Java will be consumed or called by an application or client created using python and vice versa.

JAVA EWSAPI.jar file is a API Client Library.
What is a client library?
A client library, sometimes called a helper library, is a set of code that application developers can add to their development projects. It provides chunks of code that do the basic things an application needs to do in order to interact with the API. For example, a client library may:
Provide boiler-plate code needed to create an HTTP request and to process the HTTP response from the API.
Include classes that correspond with the elements or data types that the API expects. For example, a Java client library can return native Java objects in the response from the API.
Handle user authentication and authorisation.
How is that useful?
Looking at the developer who’s using the API: With a REST API or any web service API, the developer could be using any of a number of programming languages to make the API calls.
Wouldn’t it be great if we could give them some code in their own language, to help them get started with the API? That’s what a client library does. It helps to reduce the amount of code the application developers have to write, and ensures they’re using the API in the best supported manner.
For more information:
https://ffeathers.wordpress.com/2015/10/25/what-is-an-api-client-library/

Advice on implementing JAX-WS web services to be consumed by non-Java (PHP) endpoint

I am a Java SE programmer and exploring implementing JAX-WS web services for the purpose of integrating with our web server. To this date, I have not had experience with web-services thus would like to get everyone’s expert opinion.
The background is that my company has a POS system developed and hosted in-house using Java SE. We are planning for e-commerce capabilities, which will be implemented in HTML/PHP, via external web development company and hosted externally.
Thus we are exploring implementing JAX-WS web services on our endpoint for the purpose of integrating with our e-commerce server running PHP endpoint.
I’ve done some research and my understanding is that:
it is possible to implement JAX-WS without Java EE containers
JAX-WS Web Services Without Java EE Containers
it is possible to mix end-point technologies, and specifically in my case JAX-WS as our endpoint and PHP SoapClient on our e-commerece end-point
PHP SOAP Client to consume JAX-WS with Basic Http Authentication
Using PHP SoapClient with Java JAX-WS RI (Webservice)
I am now wondering what’s is the proper approach when discussing implementation with the external web development company that is building our e-commerce platform. Most web sites and forums’ examples assumes Java on both endpoints and that both endpoints are implemented by the same developer/team.
Based on my limited understudying, I gather the process would be:
Me/my company creating the web service (coding the web services methods in Java)
Me/my company creating the server program
The wsdl generated from the URI (http://:/md5WebService?wsdl )of my server program is then used as the interface contract between our internal POS system and the external e-commerce platform
The web development company that is implementing the e-commerce platform then uses the wsdl to implement the PHP SoapClient endpoint on their side.
And in the case where our internal POS system need to consume a web services created by the external web development company, they will pass me the wsdl and I use that to make the call to them.
Is this the correct way to do proceed?
Many thanks.
Cheers,
Arthur

In Java you have actually two ways to start your design of your web service. You can either create the WSDL (Web Service Description Language) contract first (contract first approach) and then let Java or some framework tools create Java skeleton classes for you which you can use to implement the logic of each operation or you can start by code first approach and implement each web method and its logic and then let Java or some external framework tools generate the WSDL contract for you.
Either way you start, the result should be very similar and platform independent. The standard message format used for WSDL based web services is SOAP (Simple Object Access Protocol) which is based on XML (eXtensible Markup Language) which is by definition platform and programming language neutral.
So, after implementing your service and starting a server for the WS endpoint adding ?wsdl to the end of the endpoint URL should return the WSDL contract to the invoker, which can be used to create client side stubs for the required programming language which furthermore simplify the sending and receiving of messages from and to the web service. Note however that creating stub files might not be needed as all the information may be parsed from the WSDL contract directly. As of lack of knowledge concerning PHP I can't give details on how to call a WS from PHP directly or if stub file creation is required/recommended.
In order to call an other WS from your service you need to create a WS client within one of your web methods and invoke one or more of the operations offered by the remote WS and process the response within your web method.
As I am not sure if you are using any (Java) frameworks like f.e. Apache CXF I am not giving any code examples here. For integrating external web services within your service you might also have a look at Apache Camel which offers integration support for numerous Java based frameworks including CXF. Here your web service is treated as a Consumer while other external services you need to invoke are handled as Producers. The interaction between your internal and the external services is modeled here within a route where you can apply various Enterprise Integration Patterns (EIP) like splitting multiple elements contained within a response into distinct objects which you furthermore can process in parallel.
In general your enumeration of steps involved does look right if you follow the code first approach but as mentioned earlier you can also start by defining your contract first. Depending on your knowledge of the WSDL/XSD syntax (the less you know the exact syntax the more you should use code first approach), crating the contract first might enable PHP side integration sooner while you still develop the internal logic of your implementation.

it is possible to mix end-point technologies, and specifically in my case JAX-WS as our endpoint and PHP SoapClient on our e-commerece end-point PHP SOAP Client to consume JAX-WS with Basic Http Authentication Using PHP SoapClient with Java JAX-WS RI (Webservice)
This is the exact purpose of introducing webservice concept. You don't have to worry about on which platform or language your client and server is implemented. Client and server will simply exchange xml messages (platform independent) as agreed upon within wsdl.
Go ahead with your understanding.

Consume .NET web services in Java

I have created .NET web services. I want to run it on a remote server and have the Java Applications (clients) contact the server for data. How should I implement the Server such that the Clients can make use of the org.apache.xmlrpc.client.XmlRpcClient package?
I just want the clients to generate a request for data and does not want to have any other dependencies.
Here is a good material on using eclipse for this purpose: http://wso2.org/library/tutorials/creating-web-service-client-3-steps-using-eclipse
Thanks.

Although both are rightfully called "web services" the SOAP based web services usually created in .net are incompatible with web services following the older XML-RPC standard.
In my opinion you can follow 2 routes to solve your problem:
either you go the SOAP route under Java, one of the most common API's for that purpose would be jax-ws - some excellent pointers to tutorials here, in Pascal Thivent's answer
or you transform your .net webservices to XMl-RPC by using xml-rpc.net
Both routes have advantages and disadvantages, it's hard to make that choice for you without knowing more about your project. A priori choosing the SOAP route might look "safer" as there the entire communication will be based on standard components.

If you have the Web Services on the .NET side, you must have a Web Service Description Language (WSDL) (if you are not talking about REST), you can easily create the client classes to consume this Web Service using an IDE, check this link here: http://netbeans.org/kb/docs/websvc/client.html

If you are using Eclipse I suggest you this tutorial to build a simple WS client.
You can adapt this example application to your real needs.
NOTE the example uses an old version of Eclipse, but the wizard is very similar also in newer versions.

J2ME WebServices

I have created J2me application (prototype) and now I have to add web services to it which are written in .Net.
How to do that? I'm looking for the procedure for developing j2me client in which I can pass parameters which are similar as in .Net web service.

As the sreehari explained, first you need to have JAX-RPC API to include in your project. Once you have done that, the next thing comes, How to call web service.
Web Service can be created in any language like Java ( servlets ), PHP or .net, I have worked with all these three. for Java & PHP you can directly call the web-service, while for .net you need to create stubs.
Steps to create stubs. Once you create these stubs, you can simply call it like you call other methods in code and pass the argument ( if necessary ).
Also look at this quetsion How to use web service in J2ME application ?

You will need to use JAX-RPC API to create client for Web services. It doesn't matter in which language the service is implemented. I am not sure on limitations from a J2ME perspective.

Exposing C++ program as a Web Service

How to expose a C++ program as a Web Service?
Or is it a better idea to invoke C++ from Java and expose the resultant Java as a Web Service.
In any case, the C++ program should not undergo any changes.

Consume C++ program in Java WebService end point and expose java webservice
Use JNI to consume C++ program
Nice article from JavaWorld

Interestingly, webservices work on http protocol, which means that you can't "host" a webservice written in C++ without having an http server. Since each web server will have it's own mechanism of writing "hooks" or extensions, the next obvious question is which web server would you like to chose.
Let's say you want IIS on Windows. It's possible to use ISAPI extensions; so you need to know how to write one, which complies with web services standards. Or, alternatively, it's better to learn how to do it in C++ with Visual Studio, which will have lots of built-in stuff to help you get started.
In short, there is no "standard" way of exposing a web service in C++ and you have to be "platform" specific. Windows with IIS has one way of doing it. Apache Axis C++ has another.

You can try c-sevice-interface https://github.com/Taymindis/c-service-interface.
It create a C/C++ program as a service port and listening to NGINX fcgi.
This is a small bridge engine which can handle high load of request, any segfault will not break the engine, it will catch and free the thread, it is built on top NGINX, FCGI. You can setup the proxy, load balance, authentication via NGINX before reach to your interface.
The link shown as below is a wiki to Guide you how to startup from scratch.
https://github.com/Taymindis/backcurl/wiki/How-to-build-BackCurl-for-cpp-Android-development