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Writing a simple java client which uses soap messages for bunch of provided WSDL and XSD files?

I want to write a java client to use some medical api. On there website they have uploaded a bunch of WSDL files and corresponding XSD files, along with documentation explaining the SOAP messages format to consume each service.
In past I have used REST API of Amazon and Azure to write java client but this seems to be different.
I have read about JAX-WS and also tried to create a dynamic web project in Eclipse using Tomcat but nothing working (https://wiki.eclipse.org/Creating_a_Java_Web_Service_Client).
Could some one explain me basic steps on how to write a simple java
client to **consume these WSDL and XSD files using SOAP messages** and
point me to really good tutorial where I can understand the underlying
concepts?
Till now:
I read about basic wsdl and xsd structure.
Tried to use Postman and SoapUI to make service call to these services.
But struggling to make first step towards making a simple java client project to interact with these services.

I would recommend you go check SAAJ API

How to use WSDL url to create a request for data

I have a WSDL url(http:localhost:8080/userdata?wsdl) and I want to create a request to this webservice so I can fetch the data for further processing. Can I do this without wsimport?
If I have to create package from wsimport, how I can create a client which will use generated classes to create the XML request?
If I can do this without wsimport , how I can create a client which will create the XML request?
New to webservices, links to documentation would be appreciated. I am trying to understand this at the moment http://java.dzone.com/news/5-techniques-create-web-servic

You can use CXF wsdl2Java to generate a client code for the web service.
Once you run the wsdl2java , you will get a set of java classes generated for you. You can then use those classes to call the services without any explicit conversion of XML - the underlying framework will do it for you automatically. You can start with http://cxf.apache.org/docs/how-do-i-develop-a-client.html
I proposed CXF while you can look for many other alternatives - However, i have found CXF to be very feature rich and will help you in developing/working with web services.

On top of what Akhilesh said you can also create a Dynamic client for invoking WSDL. I have done it recently and i found it a little bit better then using CXF as dynamic client does not generate any code whatsoever. You just pass in the parameters to it and it does all the job for you. You can find a "shell" to build your own client HERE

How does a wsimport generated client work?

Before anything else, I want you to know that I can already connect to the web service server. I'm asking this question because I want to gain a deeper knowledge on how a wsimport generated client works. Based from my research, wsimport uses JAXWS. Please note that I have no knowledge from JAXWS.
I generated my client using wsimport. The WSDL I used is from an Axis2 web service and was automatically generated by Axis2. The classes below are the results of wsimport:
Under com.datamodel.xsd
DataBeanRequest.java
DataBeanResponse.java
ObjectFactory.java
package-info.java
Under com.service
MyWebService.java
MyWebServicePortType.java
MyMethod.java
MyMethodResponse.java
ObjectFactory.java
package-info.java
With the classes above, I can that tell that com.datamodel.xsd contains the beans used by the web service server (excluding ObjectFactory and package-info). Meanwhile, MyMethod and MyMethodResponse are also beans used to set the request and response parameter of the web service method/operation.
Below are my questions: (You don't really have to answer all of it if you don't know the answers on some of my questions. :) And please feel free to share any info that you think I might find useful.)
Am I correct with
Am I correct with my assumptions above?
What are the function of the other classes?
I inspected MyWebService and it contains an annotation referring to the absolute location of the WSDL I used to generate the client. What is the relevance of specifying the wsdllocation in the client? How does the client use that info?
I noticed that the actual URL of the web service is not declared in any of the classes generated. How does the client know where it needs to connect to?
Was the WSDL file annotated so that the client can read the URL on the WSDL file upon connection? If so, then does it mean that the WSDL file is always read when a new connection must be established?
Since there's a need for me to compile my application and install it on a different server, the will become invalid. Can I set it to a relative path instead of an absolute path? How? (Answer: Yes, it can be set to a relative path. The wsimport command has a wsdllocation attribute wherein the value of the wsdllocation can be specified.)
What if I need to connect to an HTTPS. How can I set the server certificate?
Is there any difference when I generate my client using wsimport and when I generate it using Axis2 or Apache CXF.

Before I answer the questions, some clarification: JAX-WS is a specification for implementing web services in Java. It describes how WSDL artifacts can be mapped to Java classes and how this mapping can be applied using annotations. You can download the specification here. The tool wsimport is part of the reference implementation of this specification and the reference implementation is part of the Java class library. There are several alternative implementations, such as Axis2, CXF or Metro, that enhance the basic JAX-WS support with support for additional standards such as WS-ReliableMessaging or WS-Security.
Now to your questions:
Am I correct with my assumptions above?
Yes, you are.
What are the function of the other classes?
The package-info exists to map the XML namespace used in the web service to the package in which your implementation classes reside. The namespace normally looks different from a Java package name (normally, it is a URL) and this makes the mapping necessary.
The ObjectFactory allows you to create any of the messages sent and received by the service. You need this if you want to hook in code in front of your stub class, provide modified messages or similar things.
I can't see the content of your classes, but if I understand it right MyWebServicePortType is an interface that resembles the portType in your WSDL. That is, it maps the operations and their signatures in the WSDL to Java methods. If you want to provide the service (which you don't, you are asking about the client), you would need to implement this interface. As you implement the client, you simply use it.
Finally, the class MyWebService contains the client stub you need if you want to invoke the web service.
I inspected MyWebService and it contains an annotation referring to
the absolute location of the WSDL I used to generate the client. What
is the relevance of specifying the wsdllocation in the client? How
does the client use that info?
The interface you generated contains the signature of the portType of the service, but it does not explain how you can talk to the service. This is part of the binding in the WSDL. The most basic setting is a document/literal style for the messages using SOAP over HTTP. Other configurations, such as SOAP over JMS, are possible and your client needs to know what protocol to use. Therefore it needs the binding WSDL. Also, as you state later, there is no endpoint address in your Java files. This address is also read from the WSDL.
I noticed that the actual URL of the web service is not declared in
any of the classes generated. How does the client know where it needs
to connect to?
It reads the address from the port of the service in the WSDL. This is located of the end of the WSDL.
Was the WSDL file annotated so that the client can read the URL on the
WSDL file upon connection?
No, the port is a typical element of a concrete web service endpoint. There's nothing special needed here.
If so, then does it mean that the WSDL file is always read when a new
connection must be established?
Well, there could be caching at the client side (I don't know about the details of the reference implementation on this one). From a conceptual point of view: yes, it is.
What if I need to connect to an HTTPS. How can I set the server
certificate
This can be tricky, I can't give you an out-of-the-box answer. I would suggest to read through questions on this topic, such as this one.
Is there any difference when I generate my client using wsimport and
when I generate it using Axis2 or Apache CXF
Yes, there is. wsimport is better, don't use wsdl2java. Here is a description, why.

You asked: I noticed that the actual URL of the web service is not declared in any of the classes generated. How does the client know where it needs to connect to?
If the WSDL was downloaded using a browser and passed as input to wsimport, then the local wsdl file location is embedded into the generated code. That is why you don't see the actual service location in the generated code. It also means if you deleted the local copy of the wsdl file the generated code will not work (when inovked using a main method) .
If the URL of the wsdl was passed as input to wsimport then that URL is embedded in the generated code, which is further used to get the actual service location. The idea is that the WSDL locations are fixed. They are expected to be in a UDDI or as a local file. This allows the actual services to move around and if they do move, you just have to modify the local copy of the wsdl file alone or update the wsdl in the UDDI. [mostly this does not happen as service locations are never IP but DNS names]
This is why it is never a good idea to publish the wsdl in the same server where your webservice is running

Determining methods available in a web service by examining the WSDL file

(I am fairly new to web services, kindly excuse any incorrect terminology)
Given a WSDL URL, how does one determine what methods are available in that web service by looking at the source of the WSDL file?
Also, how does one construct a SOAP response to use with the WSDL file to post data back to the web service?

I think what you ask is how to interpret a wsdl. Following articles[1][2] may help you.
[1] http://wso2.org/library/2873
[2] http://wso2.org/library/2935

Unlike the others, I'm not going to go into details about the WSDL file and how you can read it. You will eventually learn all of that by yourself by reading books, articles, experimenting with web services etc.
What I'm going to do is recommend you a very simple to use, yet powerful tool, than must be in the toolbox of every web service developer (especially someone new to web services): SoapUI.
You create a simple project in SoapUI and point it to the WSDL file of the web service. It will discover the operations, create sample request and response messages, create mocks of the web service and much more.
You can then look at the WSDL code and with the help of what's presented inside SoapUI discover which elements are involved in each method.

Just open this url to WSDL (looks like http://host:port/ddfdgfgd?wsdl) in your browser or download it to file.
Find all WSDL sections portType (portType is similar Java interface). All WSDL port types contains operations linked to input/output messages. These messages linked with XSD elements or types (it depends SOAP encoding type).
Also you can import WSDL with Java with wsimport command line tool and implement client or server side.

How To Use WSDL Url

I wrote a java web service on Netbeans 6.9.1 and deployed on GlassFish 3.0.1
I have a wsdl url like this "http://localhost:8080/web2/service2Service?wsdl".
How can I use this url to access this web service from another java application.
Thanks

You need to generate some Java that represents the client's view of the Web Service and then invoke that Java. Here's an article which explains some of the detail.
Generating client from WSDL in Eclipse
The general idea is that you generate some Java classes from the WSDL. Those classes act as a proxy for the service you want to call. Your java invokes methods on the proxy objects, the generated code creates the appropriate SOAP messages, sends the HTTP request, interprets the response and your code just sees a Java result.
I just use the tooling built into Eclipse, but you will also find other suitable generators, for example in Apache's Axis

1º U must save the content in a "myWebServices.wsdl" file
2º Run your Wsdl converter, all compilers have one of this, normally the name is WDSL.EXE
This process will create a new file with NameSpace or Package with the definitions of webservices built in.
3º Then imports this package or built a library.

Develop web service Client in second application.
You can use Netbeans to create web service client by giving your wsdl url

The document at this url is the actual wsdl (a description of the actual webservice, written in WebService Definfition Language).
The description includes information about the services url, the protocol(s), the method names and and data objects. Your application will use that information to call the remote methods of that service.
The protocol may or may not be SOAP, and without knowing the webservice details, it's quite impossible to recommend a toolset or methodology to use the webservice, there is no general approach. In most cases we see SOAP, for those services I recomment soapUI as a general tool to use and test SOAP based webservices and apache axis to implement java based service consumers.