from a non technical intermediary I got a question for a number of files (.xsd and .wsdl) for an external organization that wil be using our webservice.
This is de first time for me that i've written a webservice for an external party that wil be using a different technique other than .NET (it will be java).
as read in the post: How to generate XSD files for web service I think only sending the wsdl file wil be sufficient.
Can someone tell me if i'm right. If not so. How do i generate a fitting xsd with this wsdl?
For what I know, exposing WSDL is enough.
Every language able to read wsdl could create proxies, wrappers and/or classes to make it easier to access/consume your webservice.
As described in Wikipedia page
The WSDL describes services as collections of network endpoints, or
ports. The WSDL specification provides an XML format for documents for
this purpose. The abstract definitions of ports and messages are
separated from their concrete use or instance, allowing the reuse of
these definitions. A port is defined by associating a network address
with a reusable binding, and a collection of ports defines a service.
Messages are abstract descriptions of the data being exchanged, and
port types are abstract collections of supported operations. The
concrete protocol and data format specifications for a particular port
type constitutes a reusable binding, where the operations and messages
are then bound to a concrete network protocol and message format. In
this way, WSDL describes the public interface to the Web service.
WSDL
is often used in combination with SOAP and an XML Schema to provide
Web services over the Internet. A client program connecting to a Web
service can read the WSDL file to determine what operations are
available on the server. Any special datatypes used are embedded in
the WSDL file in the form of XML Schema. The client can then use SOAP
to actually call one of the operations listed in the WSDL file using
XML or HTTP.
Just expose a test url to them. You should do that anyway for them to be able to really test things as they develop their client. After this is done it's just a matter of getting them to retrieve http://[insert url]?wsdl
Related
I am currently working on a Java SOAP client that consumes the SOAP Web Services from a large ecommerce provider (Magento). On that server, I want to be able to talk to multiple instances (in this case stores). Now normally, one would get the WSDL file and generate the classes with it. However, on that server, each instance has its own WSDL file that may or may not be identical in structure. What is the strategy for me as the client. Should I generate Java classes for each WSDL file? Would that give me too many packages? Are these packages permanent or temporary for a request? Should I forego creating classes and just use the harder approach: some SOAP Client (any recommendations?) along with HttpUrlConnection?
Go through this
You need to create the object (http://magentohost/api/V2_soap?wsdl=1) once and this will have all the information required for the webservices and its structure as well.
I have meta data that can be used to describe several hundred new web services and would like to dynamically create WSDL files from within my own Java class. I see many ways to do this when you have Java methods you want to expose as web services. Unfortunately that approach does not work for me as I have a single runtime method that can service many different operations and services. It's dynamic and as such does not have static classes that can be bound via map.xml. My plan is to generate WSDL files that will allow incoming SOAP envelopes to be received via HTTP POST, recognized, transformed and handled by my existing method.
This is to allow web service access is a 20 year old proprietary dynamically callable back end. I am certain that the meta data for each service can be easily presented to the outside world as web services and operations.
I could always write a custom builder by appending text to a StringBuilder but that least desirable choice. It would be far more reliable if there was an API I could use that would take in the essential items and attributes and when complete, validate and render a properly formed WSDL file.
I would like this to be generic and not require proprietary add on classes from others like what I might find in WebSphere.
In such case I would consider implementing web service using Provider API (standard part of JAX-WS).
In the end we built a WSDL generator using the .NET 4 System.Xml.Schema and System.Web.Services.Description namespaces. The generated WSDL is used in both Java and .NET to build client and server interface classes. It took a while but we have most of the services up and running, and they are totally platform agnostic.
I prefer to use Spring Web Services. Where it can take an XSD with reasonable defaults and turn it into a WSDL.
See sws:dynamic-wsdl in http://docs.spring.io/spring-ws/site/reference/html/server.html#server-automatic-wsdl-exposure
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
Im a little confused on the varying definitions and implementations of web services available as implementations. Need some clarification please.
Ones I have used till now:
If a vendor gives me a specific format of XML that I can send populated with data to request and I make a simple HTTP POST over the internet passing in the XML String as the payload, is this a web service call ? If so, is there a specific name to it, this kind of web service ? Because obviously, it does not use anything like Axis, WSDL or SOAP to establish this connection.
A variant of this is If the vendor gives me an XSD, I use JAXB to make a java class out of it and pass in the serialized version of the object, which eventually works out to be the same as option 1.
RESTful web service: Vendor gives me a URL like http://restfulservice/products and I can make HTTP Requests to the URL and depending on what HTTP verb I use, the appropropriate action is called and the response sent over the wire.
Ones I have only read about\ have a vague idea about
SOAP. How does this work?.. Ive read the W3Schools tutorial and I undertsand that there is a very specific form of XML that is standardized according to W3C standards that we use to pass the same kind of messages as we did in option 1. But how does this work in real life? Vendor sends me what? Do I generate classes? Do I serialize some objects and http post them over to an address? Or do the generated objects themselves have connection methods that will do them for me?
What about WSDL? When does a vendor send me WSDL and what do I do with it ? I guess I can generate classes from it. If yes, then what do I do with the generated classes ?
When do I need that axis jar to generate classes from something that the vendor sends ?
As you can see, I have some clear and other mostly vague ideas about the different kinds of web services available. would help if someone ould clarify and\or point to more real-world resources. I've looked a little bit into Java Web Services on the internet and the numerous four letter acronyms that get thrown at me make me dizzy.
Thanks
If a vendor gives me a specific format
of XML that I can send populated with
data to request and I make a simple
HTTP POST over the internet passing in
the XML String as the payload, is this
a web service call ? If so, is there a
specific name to it, this kind of web
service ?
This is still a web service, yes. It doesn't have an "official" name, I usually refer to it as XML-over-HTTP, mainly because I can't think of a better name.
SOAP. How does this work?.. Ive read
the W3Schools tutorial and I
undertsand that there is a very
specific form of XML that is
standardized according to W3C
standards that we use to pass the same
kind of messages as we did in option 1
SOAP provides a standard wrapper layer around the sort of messages you were sending in (1). This wrapper provides information such as an indication as to which operation you are invoking. It can also provide security services, transaction information, and so on. It's a pretty thin layer, usually.
What about WSDL? When does a vendor
send me WSDL and what do I do with it
? I guess I can generate classes from
it. If yes, then what do I do with the
generated classes ?
Again, WSDL is a pretty thin layer, this time around an XML Schema. It defines the operations that SOAP messages will invoke at runtime, as well as the Schema types of the requests and responses. Its a way of formalising the XML document exchange interface.
Say, for example, you had an XML Schema, and have a web service as you described
Using JAXB to generate java source from the schema
Send XML documents conforming to that schema over HTTP to the web service
With WSDL and SOAP, you would extend this a bit :
Write a thin WSDL wrapper around the XML Schema, formalising which operations are available.
Use a WSDL import tool to generate client/server stubs for that WSDL/Schema. In Java, this often incorporates JAXB.
Use a SOAP client/server to invoke the web service
As you can see, it's essentially the same process. The difference is that SOAP/WSDL provides additional information and context to the tools, allowing those tools to do more of the work for you. It's not hugely different, though.
If you get a WSDL document from somewhere, all you really need to know is that it defines a service interface. You run it through your favourite language's binding generator to make some code that you can use to call the service. Typically that means you'll be talking over the wire to the service using SOAP messages over HTTP. SOAP's just a wrapper round sending pretty arbitrary XML messages.
Axis is a library for doing this stuff in Java (both client and server side). I suspect that there are better implementations in other libraries.
I've used Apache CXF to expose about ten java classes as web services.
I've generated clients using CXF, Axis, and .NET.
In Axis and CXF a "Service" or "Locator" is generated.
From this service you can get a "Port".
The "Port" is used to make individual calls to the methods exposed by the web service.
In .NET the "Service" directly exposes the calls to the web service.
Can someone explain the difference between a port, a service, a locator, and an endpoint when it comes to web services?
Axis:
PatientServiceImplServiceLocator locator =
new PatientServiceImplServiceLocator();
PatientService service = locator.getPatientServiceImplPort();
CXF:
PatientServiceImplService locator = new PatientServiceImplService();
PatientService service = locator.getPatientServiceImplPort();
.net:
PatientServiceImplService service = new PatientServiceImplService();
I found the information based on Kevin Kenny's answer, but I figured I'd post it here for others.
A WSDL document defines services as collections of network endpoints, or ports. In WSDL, the abstract definition of endpoints and messages is separated from their concrete network deployment or data format bindings. This allows the reuse of abstract definitions: messages, which are abstract descriptions of the data being exchanged, and port types which are abstract collections of operations. The concrete protocol and data format specifications for a particular port type constitutes a reusable binding. A port is defined by associating a network address with a reusable binding, and a collection of ports define a service. Hence, a WSDL document uses the following elements in the definition of network services:
Types– a container for data type definitions using some type system (such as XSD).
Message– an abstract, typed definition of the data being communicated.
Operation– an abstract description of an action supported by the service.
Port Type–an abstract set of operations supported by one or more endpoints.
Binding– a concrete protocol and data format specification for a particular port type.
Port– a single endpoint defined as a combination of a binding and a network address.
Service– a collection of related endpoints.
I'd hop over to http://www.w3.org/TR/wsdl.html which I think explains Port, Service and Endpoint reasonably well. A locator is an implementation specific mechanism that some WS stacks use to provide access to service endpoints.
I would like to add that <port> and <endpoint> serve the same purpose, but port is used by WSDL 1.1 and endpoint by WSDL 2.0.
As you already mentioned, those terms mean different things in different stacks - there is no one right generic answer for web services.