I am reading Professional XML
By: Bill Evjen; Kent Sharkey; Thiru Thangarathinam; Michael Kay; Alessandro Vernet; Sam Ferguson
Chapter SOAP & WSDl focusses on,
After you have found the service you want to consume, the act of discovery should bring you to the location of the Web service's WSDL file. The WSDL file is an XML description of the Web service's interface. After you have found the WSDL file of the Web service, you can create a proxy class (or your environment automatically creates one for you) that enables you to send messages back and forth to the Web service.
What is the proxy class in para above means and by whom it gets instantiated?
Is the Web Method which I wish to invoke through the SOAP constructed message format is also a method of the object of the proxy class?
The WSDL file is the technical contract which defines the communication interface with a service.
The "proxy class" in your citation, is just the logical representation of the service in your program. You can do this class by yourself, or have it made automatically. Most IDEs out there allow you to import a WSDL and they will generate most of the code needed to communicate with the service. The import tool will most likely create classes with methods and variables that correspond directly to operations and types in the WSDL file.
Your application instantiates the class and you call the methods you need to call by just filling the data as parameters and receiving the response in return. The class handles Object to SOAP message conversion for you. Keep in mind that even though it looks very similar to local function call, it is not - it is not nearly as fast and it involves network communication risks. It is quite possible to have communication errors that you need to handle.
Related
I'm almost new to web services in Java.
Our company has previously used IBM Process Server to handle the interactions between SCA objects. Due to some reasons we've decided to give up IBM Process Server and therefore we started to migrate our current integrations to EJB.
Just to make myself more clear I've attached a simple schema describing my current task. This is a process deployed at IBM Process Server:
I need to develop an EJB, which also acts as a JAX-WS web service and receives an SDO DataObject from the JAX-WS client service, then makes some additional logic and sends the SOAP-request to another web service.
I'm totally don't know how to make my EJB receive a DataObject via SOAP. I have a WSDL-file, describing SOAP request and response formats.
I also found an article, describing the way to solve this using IBM RAD JAX-RPC webservice from a WSDL with an SDO facade, but the article seems to be outdated.
Is there any way to create the service without using JAXB-bounded POJOs, but with SDO? In case of no, how to handle it using JAXB in a proper way? Thanks in advance.
Solved!
During my searchings I figured out, that it's neccessary to generate a bean skeleton, change all the web methods signatures to receive and return JAXB-binded POJOs, generated from WSDL and then transforming it to Data Objects if needed.
JAXB takes care of the all marshalling/unmarshalling staff. I just needed to RTFM a little bit.
I'm starting to choose a way to create my webservice, so i found 2 ways to do it:
1) Using the package javax.jws, with annotation #WebService:
#WebService(...)
public class MyServiceImpl {
2) The other way is using javax.ws, with annotation #Path:
#Path("/MyService")
public class MyServiceImpl
In my understand using the second solution is more simple, because when i need to create the Client i just need make a HTTP call (GET/POST). Using the first solution i need create a WSDL client, more complex solution.
So, I would like to know which is the advantage in use FIRST SOLUTION.
The SOAP/WSDL style is useful when a formal contract must be established to describe the interface that the web service offers.The Web Services Description Language (WSDL) describes the details such as messages, operations, bindings, and location of the web service.
Also the SOAP/WSDL style is useful when the application architecture needs to handle asynchronous processing and invocation (e.g. using JAX-WS the assynchronous clients can be created).
The disadvantages of SOAP/WSDL style are
its complexity: tools are required to create a client
heavier on Bandwidth : SOAP requires a heavy XML wrapper arround each request or response
complicated security rules
The advantages of REST style are
simplicity: REST client can be accessed from any browser (however, this is only true for GET method. Data creation request requires also the XML wrapper).
lighter on Bandwidth : data on the wire are usually bare xml elements (not wrapped within the <Envelope><Body> tags).
REST application security rules can be setup using the http standards: the administrator (or firewall) can discern the intent of each message by analyzing the HTTP command used in the request.
For example, a GET request can always be considered safe because it can't, by definition, modify any data.
The disadvantage of REST style is that it still doesn't cover all business requirements
There is no common standard accepted yet for the formal REST service description
REST requests (especially GET method) are not suitable for large amount of data
REST doesn't cover all web services standards, like Transactions, Security, Addressing, Trust, Coordination,
I am first time working with wsdl. I apologize if its a very novice question.
I have a wsdl file for a webservice. I want to create a java console application to consume the service.
I have generated class files using wsimport tool and wsdl. A good number of class file have generated.
I am confused at this point should I need further documentation from webservice provider to implement the service or there is any conversion regarding using the generated files.
Any suggestion would be very helpful.
WSDL file already have whole definition you need, including data-type, request and response wrappers for every method, etc. That mean, that since you have generated the client implementation via wsimport, the only thing you have to do is to import this files into your current java project and use it to access the web-service.
You can find a wide number of examples, how to use this generated client code. Here is one of them. In short, you have two main generated classes, representing web-service: an Interface annotated with #WebService annotation and some service annotated with #WebServiceClient. You just need to get an instance of the intarface from the service, like:
HelloWorldImplService helloService = new HelloWorldImplService();
HelloWorld hello = helloService.getHelloWorldImplPort();
Here us HelloWorld is an interface, which provides all the methods of the web-service from WSDL. And then you'll get it, you can use it to call the web-service. Just don't forget, that you may have to override the default ip-address of the web-service client, if it's not the one you need.
The only additional documentation you may need, is some documentations providing the information about the web-service business purposes, which may be usefull for the developer, whot interacts with this web-service.
Simply you can create a service client object from the class annotated with #WebServiceClient and call the related method with parameters.
WebServiceClient client = new WebServiceClient();
AnswerType answer = client.GetSoap().theMethodYouWantUse(some_parameters);
I created a Web Service using JaxWs. I belive that exist two ways to consume a web service in the client.
using wconsume e putting the generated classes as stubs in the client.
using Dynamic Proxy, whitch means, there wil be no files to be send to client as stubs.
I imagine that the only advantage of this approach is that if the wsdl changed, there will be not need to generat stubs files. However it doesn't look too practical, as I will probably need to change something in the client code and recompiled anyway. I didn't use this tecnichy yet. I found this option when I was reaserching the reason why I need to generate proxy file when developping Java client but I didn't when I using .Net.
Then, I have two question:
What's the difference between stubs and Dynamic Proxy tecnich?
Why .Net client doesn't need proxies files? Or is there the files automaticlly generated and I don't know where to find? Am I loosing performance or security when using stubs versus dynamic proxy?
1.What's the difference between stubs and Dynamic Proxy tecnich?
JAX-RPC is deprecated.
The new standard is JAX-WS.
JAX-WS allows programmers to invoke a web service, as if they were making a local method call.
For this to happen a standard mapping from WSDL to Java has been defined.
This mapping correlates a wsdl:port definition with a Java Interface which is called Service Endpoint Interface (SEI).
The SEI is the Java representation of the web service endpoint.
At runtime JAX-WS creates an instance of a SEI that can be used to make web service calls by simply making method calls on the SEI.
Now the way used to create an instance of a SEI is via the dynamic proxy class.
It is called dynamic proxy since it is created dynamically.
No stubs are need to implement a proxy, but the SEI must already have been implemented in order to be used.
The proxy uses/is based on the stub classes to function, which have been generated by the WSDL.
So the stubs are a prerequisite.
So there is no separation of techniques as you say in your post.
You have misunderstood the concept
I want to build a web services client that takes wsdl link as the input and generates java classes. I know we can do this directly using Netbeans IDE where we provide the wsdl location during project setup. But I want the wsdl location to be provided when the client starts running. How do I do this?
Is the location that will be provided just used to specify the SOAP endpoint (for a web service whose WSDL was known at development time), or will it be a completely arbitrary WSDL?
In the first case, the web service client that was created by Netbeans has methods that accept an alternate SOAP endpoint URL. You can call those to use the client with a server whose location is not hard-coded in the client.
If however, the WSDL describes a completely unrelated service, how are you going to write Java code against it? You cannot use any interfaces derived from the WSDL (because they are not known at development time). You could only have a very generic SOAP client, where the user almost directly types in the XML that will be sent.