I want to download xsd specifications from a web service and automatic converting (serialize) these schemas to classes (visual studio - vb.net). If the organization that is responsible for the xsd schemas alter them in a way that only my class corresponding to the xsd have to be altered (not the rest of my code) I would like to automatic update my xsd corresponding class. Is this possible? If so, can somebody tell me how to do it?
Thanks!
I use vs2010. What I want to do is: call a web service where I can send in an input parameter to the service which specifies the xsd I want to retrieve (the service is GetShemaDefenition and returns an object with the schema specification in a string property of the object). I den have to read the xsd string from the string property and convert this to a class representation of this xsd specification. Is it possible to do this automatically? I have done this manually by using xsd.exe. If the owner organization of the xsd has altered the xsd specification, I have to test if there is a new specification, and if there is I have to build a new class representation of this xsd? Is it possible to do what I want? And how would I know if it has been a big change in the xsd which also affect other parts of my code, not just the class representation of the xsd?
Tanks a lot for your reply! So what you are saying, if I understand you correct, is that there is not a good solution for automating this functionality because if the xsd change I most likely (in some occasions’) have to change my code manually? So I have to choose, either in my application or in my intermediate service? But what is the purpose for providing the xsd in a web service? What can I use the web service for? I just wondering, maybe it is clear but I am new to web services and is eager to learn more.
Update:
Thanks! But can you explain a little bit more. What I have to do is: I use one web service where one of the properties is a string. The string is an XML inside a CDATA block. The organization which provides the web service will not pares the xml inside the CDATA block but instead forward this to another organization that will use the xml data. The organization which uses the xml data specifies the xsd schem that I have to follow to generate my xml correct. This is the xsd schema I can get from another web service. I don’t really understand what I can do with this xsd file from the web service. What can I do with it and why do I want to download it from the web service, when I can’t use it automatically? Because I have to manually do the changes when the xsd changes I can easily download the xsd schema from the organization’s home page and make the new class with xsd.exe. I understand there is something I don’t understand :o), can you pleas clarify?
What visual studio version you are using?, Normally you can click on the project's references and Add Web service. In this case Visual studio creates automatically the objects required to consume the service. you can update it any time by a right click on the reference.
However if it is very likely to change often, One solution is to implement an adapter class. use create an interface that provides the same functionality and call the actual web service. In your application you use only the proxy class and not the Web Service. Later when the web service interface changes all you have to do is to change the internals of this intermediate class.
Update:
you can use this tool to create you object model in code. Then you can compile your new object model and use it in you application. There are many complications in what you want to do and the bottom line is; when the object model changes, your code will fail. There is absolutely no way to imagine how the interface will change so while you can do all that automatically there is nothing to do if the name of a function changes.
However the answer to your situation is indirection. If you can't guaranty the stability of a external service. Why not create a stable intermediate service that calls the actual one? this way in future you don't need to touch you application. All you have to do is to modify the intermediate service while keeping it's interface compatible.
Related
I am trying to learn, how to create a custom NiFi controller service. To start off, I thought of mimicking the DBCPConnectionPool controller service by simply copying the original source code of DBCPConnectionPool service. To implement the same, I generated a maven archetype from "nifi-service-bundle-archetype" and got the following project structure
However, when i generated the archetype from 'nifi-processor-bundle-archetype , I got the following structure: -
I understand that in case of processor I simply need to write my code in MyProceesor.java present under nifi-ListDbTableDemo-processors folder and then create a nar file out of it. But in case of controller service, I have 4 folders generated. I can see two java files i.e.
StandardMyService.java present under nifi-DbcpServiceDemo folder
MyService.java present under nifi-DbcpServiceDemo-apifolder
Now, why is there two java files generated in case of custom controller service, while there was only one java file generated in case of custom processor. Also, Since I am trying to mimick the DBCPConnectionPool service, in which java file out of two should I copy the original source code of DBCPConnectionPool service.
Please guide me from scratch, the steps that I need to follow to create a custom service equivalent to that of DBCPConnectionPool service.
MyService.java under nifi-DbcpServiceDemo-api is an interface which be implemented by the StandardMyService.java under nifi-DbcpServiceDemo. Once the implementation is done, you have to use nifi-DbcpServiceDemo-api as dependency in the processor bundle which needs to work with this custom controller Service.
The reason why controller services are implemented this way is:
We will be hiding the actual implementation from the processor bundle because it need not depend on the implementation.
Tomorrow you write a new controller service implementation, say StandardMyServiceTwo which again implements MyService because only the implementation varies from StandardMyService and other members remains the same and can be shared. This new controller service can be introduced transparently without making any changes on the processor bundle.
Example:
The best example is the record reader/writer controller services. If you look at the nifi-record-serialization-services-bundle in nifi, they have different implementation for serializing records of JSON, Grok, avro, CSV data formats but they all are actually implementing one API - nifi-record-serialization-service-api And hence for the processors which want to use the Record Reader or Record Writer, instead of having the actual implementations as its dependency, they rather can have the api as its dependency.
So tomorrow you can add add a new implementation in the record-serialization-services-bundle for a new data format without touching anything on the processors bundle.
For you references, please take a look at the following links which would help you in writing the custom controller service from scratch
http://www.nifi.rocks/developing-a-custom-apache-nifi-controller-service/
https://github.com/bbende/nifi-dependency-example
I am working on a project where the customer has changed the way they are generating the wsdls that we consume. When I generate the service reference with using the original wsdl it appears that the DataContract attributes are being used in the reference.cs class. When I use the new wsdl it looks like the XmlSerializer attributes are being used.
This causes a problem because the Order of the elements is being enforced by the XmlElement attribute. From what I have read, the VS service generator will do this if there are schema elements used in the wsdl that are either ignored or forbidden.
Is there any way automated or other means that will highlight where these errors might be?
Thanks
I have a WSDL file from a published ASMX web service. What I am after
is creating a mock service that mimics the real service for testing purposes.
From the WSDL, I used SvcUtil.exe to generate code. Apparently it also generates
the server side interface.
Well the issue is that it generates very chunky interfaces. For example, a method
int Add(int, int) is showing up in the generated .cs file as AddResponse Add(AddRequest). AddRequest and AddResponse have a AddRequestBody and AddRequestResponse and so on.
The issue is that, to implement, I need to create the body and response instances for each method, even when I just want to return a simple int result.
Why can't it generate the method signature properly? Is there a better way of generating WCF Server side interface/contracts from WSDL?
The message structure you are describing is caused by two things:
better interoperability across web service stacks and their programming models (RPC vs messaging);
flexibility to accommodate new parameters into existing web services.
You are not the first one to complain about it, or the last. It's a WSDL binding style commonly called the document/literal wrapped pattern. It produces document/literal web services and yet also supports an RPC programming style. It's very "WS interoperability friendly", so to speak...
The WS-I Basic profile specifies that the soap:body must have only one child element and in this case it's a wrapper for the operation name that's being invoked. The parameters of the call are packed into only one element as a best practice since it's more flexible to later changes. In case of WCF you usualy end up with a MessageContract which has one MessageBodyMember which wraps all the parameters.
Basically, you are seeing the results of web service battles fought long time ago.
Here is some extra reading on the subject (and that's just the tip of the iceberg):
Which style of WSDL should I use?
RPC/Literal and Freedom of Choice
My Take on the Document/Literal 'Wrapped' Idiom
I found an issue but it refers to the BETA version of VS 2010. I am interested in knowing if this issue has been fixed in RTM?
Basically it states (saw it via EF 4 Self Tracking Entities does not work as expected )
Make certain to reuse the
Self-Tracking Entity template’s
generated entity code on your client.
If you use proxy code generated by Add
Service Reference in Visual Studio or
some other tool, things look right for
the most part, but you will discover
that the entities don’t actually keep
track of their changes on the client.
I am very used to using Add Service Reference, and its always worked great for me in the past but of course I wasn't using STE (Self tracking entities). Is this problem still apparent with VS 2010 RTM and the STE template?
If I do create the proxy via code instead of add service then all the classes won't be created will they?
This is not an issue and it never was an issue. It is absolutly expected and correct behavior. STEs are classes which contains data and logic (the logic tracks changes).
When adding service reference your client proxy code is generated from service's metadata. Metadata are exposed in form WSDL. WSDL is XML based description of the service which also contains XSD description of transfered data types. XSD can describe only data format but not related logic implemented by the type. By default all unknown data types described in WSDL are generated on the client. So when you generate client proxy with all data types by Add service reference the tracking logic is lost.
To overcome this issue you have to do two things:
Create separate assembly and place all your STEs to this assembly. Then share this assembly among all involved layers (yes you have to use Add reference in your client).
Then you can use Add service reference with "Reuse types in referenced assemblies" checked.
I'm working on a simple plug-in framework. WCF client need to create an instance of 'ISubject' and then send back to service side. The 'ISubject' can be extended by the user. The only thing client knows at runtime is ID of a subclass of 'ISubject'.
Firstly, client need to get type information of a specific subclass of 'ISubject'. Secondly, client using reflection to enumerate all members to create a custom property editor so that each member can be asigned with proper value. Lastly, client create an instance of that subclass and send back to service.
The problem is how does client get the type information through WCF communication?
I don't want client to load that assembly where the subclass (of 'ISubject') exists.
Thanks
First, you need to be aware that there is no magic way that WCF will provide any type information to your client in the scenario you have descibed. If you are going to do it, you will have to provide a mechanism yourself.
Next, understand that WCF does not really pass objects from server to client or vice versa. All it passes are XML infosets. Often, the XML infoset passed includes a serialized representation of some object which existed on the sender's side; in this case, if the client knows about that type (i.e. can load the type's metadata from its assembly), it can deserialize the XML to instantiate an identical object on the client side. If the client doesn't have the type metadata, it can't: this is the normal case with WCF unless data contract types are in assemblies shared by both server and client implementations (generally not a good idea).
The way WCF is normally used (for example if the client is implemented using a "Service Reference" in Visual Studio), what happens is that the service publishes WSDL metadata describing its operations and the XML schemas for the operation parameters and return values, and from these a set of types is generated for use in the client implementation. These are NOT the same .NET types as the data contract types used by the service implementation, but they are "equivalent" in the sense that they can be serialized to the same XML data passed over the network. Normally this type generation is done at design time in Visual Studio.
In order to do what you are trying to do, which is essentially to do this type generation at runtime, you will need some mechanism by which the client can get sufficient knowledge of the structure of the XML representing the various types of object implementing ISubject so that it can understand the XML received from the service and generate the appropriate XML the service is expecting back (either working with the XML directly, or deserializing/serializing it in some fashion). If you really, really want to do this, possible ways might be:
some out-of-band mechanism whereby the client is preconfigured with the relevant type information corresponding to each subclass of ISubject that it might see. The link provided in blindmeis's answer is one way to do that.
provide a separate service operation by which the client can translate the ID of the subclass to type metadata for the subclass (perhaps as an XSD schema from which the client could generate a suitable serializable .NET type to round trip the XML).
it would also be feasible in principle for the service to pass type metadata in some format within the headers of the response containing the serialized object. The client would need to read, interpret and act on the type infomation in an appropriate fashion.
Whichever way, it would be a lot of effort and is not the standard way of using WCF. You will have to decide if it's worth it.
I think you might be missing something :)
A major concept with web services and WCF is that we can pass our objects across the network, and the client can work with the same objects as the server. Additionally, when a client adds a service reference in Visual Studio, the server will send the client all the details it needs to know about any types which will be passed across the network.
There should be no need for reflection.
There's a lot to cover, but I suggest you start with this tutorial which covers WCF DataContracts - http://www.codeproject.com/KB/WCF/WCFHostingAndConsuming.aspx
To deserialize an object the receiving side will need to have the assembly the type is defined in.
Perhaps you should consider some type of remoting or proxying setup where the instance of ISubject lives on one side and the other side calls back to it. This may be problematic if you need to marshal large amounts of data across the wire.
wcf needs to know the real object(not an interface!) which should be sent across the wire. so you have to satisfy the server AND the clientproxy side from the WCF service that they know the types. if you dont know the object type while creating the WCF service, you have to find a way to do it in a dynamic way. i use the solution from here to get the knownTypes to my WCF service.
[ServiceContract(SessionMode = SessionMode.Required]
[ServiceKnownType("GetServiceKnownTypes", typeof(KnownTypeHelper))]//<--!!!
public interface IWCFService
{
[OperationContract(IsOneWay = false)]
object DoSomething(object obj);
}
if you have something "universal" like the code above, you have to be sure that whatever your object at runtime will be, your WCF service have to know this object.
you wrote your client create a subclass and sent it back to the service. if you want to do that, WCF(clientproxy and server!) needs to know the real type of your subclass.