Is it possible to figure out from a WSDL, what is the kind of webservice?
Document/literal
Document/encoded
RPC/literal
RPC/encoded
If yes, how?
If you are using PHP, you can use the Zend framework's Zend_Soap_AutoDiscover class.
Otherwise, look at the Response:
Document style response contains schema definitions, whilst RPC does not
Literal contains name attributes, whilst encoded does not
Aside:
The pairing is usually RPC/encoded or Document/literal, as Document/encoded is not WS-I compliant. Document/literal is most common of all types.
So for example these are both of type Document/literal as they contain both schema definitions and name attributes:
http://www.w3schools.com/xml/tempconvert.asmx?wsdl
https://webapi.allegro.pl/uploader.php?wsdl
Reference:
Examples of all three valid combinations: https://www.ibm.com/support/knowledgecenter/en/SSB27H_6.2.0/fa2ws_ovw_soap_syntax_lit.html
Related
I am wondering if anybody knows if wiremock has support for WS-Policy in regards to SOAP webservices?
What I'm after is to give wiremock a WSDL that has some WS-Policy in it, that contains the "reciepe" for what the response should look like. Ie timestamp in the header, signed body, etc.
So, ideally I'd just specify the soap body and wiremock would apply the WS-Policy and add the necessary signatures.
I found this github issue that mentioned SOAP support, but the impression I got from that support was that it was just an arbitrary text response without having actual SOAP understanding/processing.
Would it be possible to plug-in Apache CXF to get proper JAX-WS/WS-Policy support if I were so inclined? Or would it be difficult to offload response processing to a third party library?
No such support I'm afraid. SOAP requires a lot of tooling to in test contexts.
I posted my solution to this problem in another similar question. The crux of it was some hand crafted SOAP manipulation and WireMocks CustomRequest matchers.
I am developing SOAP web service using annotation i.e. #WebService, #WebMethod and XML annotation for request and response entities. The web server generates the WSDL contract which the client uses. I am not able to set any xml restriction on the response elements, say for example i want top set a String element to max length to 50 characters. As I am not writing the WSDL/XSD manually is there a way to define this through annotation so the the server includes in the generated WSDL.
JAX-WS web service uses JAXB for data binding. Unfortunately, the default JAXB reference implementation does not support JAXB facet. So with the default implementation, you cannot use annotation to specify string element maxlength restriction. However, you can check out JAXB-Facets project, which does exactly what you want.
Can somebody explain to me the differences between Document and RPC style webservices? Apart from JAX-RPC, the next version is JAX-WS, which supports both Document and RPC styles. I also understand document style webservices are meant for Asynchronous communication where a client would not block until the response is received.
Either way, using JAX-WS I currently annotate the service with #Webservice, generate the WSDL and from that WSDL I generate the client side artifacts.
Once the artifacts are received, in both styles, I invoke the method on the port. Now, this does not differ in RPC style and Document style. So what is the difference and where is that difference visible?
Similarly, in what way does SOAP over HTTP differ from XML over HTTP? After all SOAP is also XML document with SOAP namespace.
Can some body explain me the differences between a Document style and
RPC style webservices?
There are two communication style models that are used to translate a WSDL binding to a SOAP message body. They are:
Document & RPC
The advantage of using a Document style model is that you can structure the SOAP body any way you want it as long as the content of the SOAP message body is any arbitrary XML instance. The Document style is also referred to as Message-Oriented style.
However, with an RPC style model, the structure of the SOAP request body must contain both the operation name and the set of method parameters. The RPC style model assumes a specific structure to the XML instance contained in the message body.
Furthermore, there are two encoding use models that are used to translate a WSDL binding to a SOAP message. They are: literal, and encoded
When using a literal use model, the body contents should conform to a user-defined XML-schema(XSD) structure. The advantage is two-fold. For one, you can validate the message body with the user-defined XML-schema, moreover, you can also transform the message using a transformation language like XSLT.
With a (SOAP) encoded use model, the message has to use XSD datatypes, but the structure of the message need not conform to any user-defined XML schema. This makes it difficult to validate the message body or use XSLT based transformations on the message body.
The combination of the different style and use models give us four different ways to translate a WSDL binding to a SOAP message.
Document/literal
Document/encoded
RPC/literal
RPC/encoded
I would recommend that you read this article entitled Which style of WSDL should I use? by Russell Butek which has a nice discussion of the different style and use models to translate a WSDL binding to a SOAP message, and their relative strengths and weaknesses.
Once the artifacts are received, in both styles of communication, I
invoke the method on the port. Now, this does not differ in RPC style
and Document style. So what is the difference and where is that
difference visible?
The place where you can find the difference is the "RESPONSE"!
RPC Style:
package com.sample;
import java.util.ArrayList;
import javax.jws.WebService;
import javax.jws.soap.SOAPBinding;
import javax.jws.soap.SOAPBinding.Style;
#WebService
#SOAPBinding(style=Style.RPC)
public interface StockPrice {
public String getStockPrice(String stockName);
public ArrayList getStockPriceList(ArrayList stockNameList);
}
The SOAP message for second operation will have empty output and will look like:
RPC Style Response:
<ns2:getStockPriceListResponse
xmlns:ns2="http://sample.com/">
<return/>
</ns2:getStockPriceListResponse>
</S:Body>
</S:Envelope>
Document Style:
package com.sample;
import java.util.ArrayList;
import javax.jws.WebService;
import javax.jws.soap.SOAPBinding;
import javax.jws.soap.SOAPBinding.Style;
#WebService
#SOAPBinding(style=Style.DOCUMENT)
public interface StockPrice {
public String getStockPrice(String stockName);
public ArrayList getStockPriceList(ArrayList stockNameList);
}
If we run the client for the above SEI, the output is:
123
[123, 456]
This output shows that ArrayList elements are getting exchanged between the web service and client. This change has been done only by the changing the style attribute of SOAPBinding annotation. The SOAP message for the second method with richer data type is shown below for reference:
Document Style Response:
<ns2:getStockPriceListResponse
xmlns:ns2="http://sample.com/">
<return xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xsi:type="xs:string">123</return>
<return xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xsi:type="xs:string">456</return>
</ns2:getStockPriceListResponse>
</S:Body>
</S:Envelope>
Conclusion
As you would have noticed in the two SOAP response messages that it is possible to validate the SOAP response message in case of DOCUMENT style but not in RPC style web services.
The basic disadvantage of using RPC style is that it doesn’t
support richer data types and that of using Document style is that it
brings some complexity in the form of XSD for defining the richer
data types.
The choice of using one out of these depends upon the
operation/method requirements and the expected clients.
Similarly, in what way SOAP over HTTP differ from XML over HTTP? After
all SOAP is also XML document with SOAP namespace. So what is the
difference here?
Why do we need a standard like SOAP? By exchanging XML documents over HTTP, two programs can exchange rich, structured information without the introduction of an additional standard such as SOAP to explicitly describe a message envelope format and a way to encode structured content.
SOAP provides a standard so that developers do not have to invent a custom XML message format for every service they want to make available. Given the signature of the service method to be invoked, the SOAP specification prescribes an unambiguous XML message format. Any developer familiar with the SOAP specification, working in any programming language, can formulate a correct SOAP XML request for a particular service and understand the response from the service by obtaining the following service details.
Service name
Method names implemented by the service
Method signature of each method
Address of the service implementation (expressed as a URI)
Using SOAP streamlines the process for exposing an existing software component as a Web service since the method signature of the service identifies the XML document structure used for both the request and the response.
An RPC style web service uses the names of the method and its parameters to generate XML structures representing a method’s call stack. Document style indicates the SOAP body contains an XML document which can be validated against pre-defined XML schema document.
A good starting point : SOAP Binding: Difference between Document and RPC Style Web Services
In WSDL definition, bindings contain operations, here comes style for each operation.
Document : In WSDL file, it specifies types details either having inline Or imports XSD document, which describes the structure(i.e. schema) of the complex data types being exchanged by those service methods which makes loosely coupled. Document style is default.
Advantage:
Using this Document style, we can validate SOAP messages against predefined schema. It supports xml datatypes and patterns.
loosely coupled.
Disadvantage: It is a little bit hard to get understand.
In WSDL types element looks as follows:
<types>
<xsd:schema>
<xsd:import schemaLocation="http://localhost:9999/ws/hello?xsd=1" namespace="http://ws.peter.com/"/>
</xsd:schema>
</types>
The schema is importing from external reference.
RPC :In WSDL file, it does not creates types schema, within message elements it defines name and type attributes which makes tightly coupled.
<types/>
<message name="getHelloWorldAsString">
<part name="arg0" type="xsd:string"/>
</message>
<message name="getHelloWorldAsStringResponse">
<part name="return" type="xsd:string"/>
</message>
Advantage: Easy to understand.
Disadvantage:
we can not validate SOAP messages.
tightly coupled
RPC : No types in WSDL
Document: Types section would be available in WSDL
The main scenario where JAX-WS RPC and Document style are used as follows:
The Remote Procedure Call (RPC) pattern is used when the consumer views the web service as a single logical application or component with encapsulated data. The request and response messages map directly to the input and output parameters of the procedure call.
Examples of this type the RPC pattern might include a payment service or a stock quote service.
The document-based pattern is used in situations where the consumer views the web service as a longer running business process where the request document represents a complete unit of information. This type of web service may involve human interaction for example as with a credit application request document with a response document containing bids from lending institutions. Because longer running business processes may not be able to return the requested document immediately, the document-based pattern is more commonly found in asynchronous communication architectures. The Document/literal variation of SOAP is used to implement the document-based web service pattern.
I think what you are asking is the difference between RPC Literal, Document Literal and Document Wrapped SOAP web services.
Note that Document web services are delineated into literal and wrapped as well and they are different - one of the primary difference is that the latter is BP 1.1 compliant and the former is not.
Also, in Document Literal the operation to be invoked is not specified in terms of its name whereas in Wrapped, it is. This, I think, is a significant difference in terms of easily figuring out the operation name that the request is for.
In terms of RPC literal versus Document Wrapped, the Document Wrapped request can be easily vetted / validated against the schema in the WSDL - one big advantage.
I would suggest using Document Wrapped as the web service type of choice due to its advantages.
SOAP on HTTP is the SOAP protocol bound to HTTP as the carrier. SOAP could be over SMTP or XXX as well. SOAP provides a way of interaction between entities (client and servers, for example) and both entities can marshal operation arguments / return values as per the semantics of the protocol.
If you were using XML over HTTP (and you can), it is simply understood to be XML payload on HTTP request / response. You would need to provide the framework to marshal / unmarshal, error handling and so on.
A detailed tutorial with examples of WSDL and code with emphasis on Java: SOAP and JAX-WS, RPC versus Document Web Services
Document
Document style messages can be validated against predefined schema.
In document style, SOAP message is sent as a single document.
Example of schema:
<types>
<xsd:schema> <xsd:import namespace="http://example.com/"
schemaLocation="http://localhost:8080/ws/hello?xsd=1"/>
</xsd:schema>
</types>
Example of document style soap body message
<message name="getHelloWorldAsString">
<part name="parameters" element="tns:getHelloWorldAsString"/>
</message>
<message name="getHelloWorldAsStringResponse">
<part name="parameters"> element="tns:getHelloWorldAsStringResponse"/>
</message>
Document style message is loosely coupled.
RPC
RPC style messages use method name and parameters to generate XML structure.
messages are difficult to be validated against schema.
In RPC style, SOAP message is sent as many elements.
<message name="getHelloWorldAsString">
<part name="arg0"> type="xsd:string"/>
</message>
<message name="getHelloWorldAsStringResponse">
<part name="return"
> type="xsd:string"/>
</message>
Here each parameters are discretely specified,
RPC style message is tightly coupled, is typically static, requiring changes to the client when the method signature changes
The rpc style is limited to very simple XSD types such as String and Integer, and the resulting WSDL will not even have a types section to define and constrain the parameters
Literal
By default style. Data is serialized according to a schema, data type not specified in messages but a reference to schema(namespace) is used to build soap messages.
<soap:body>
<myMethod>
<x>5</x>
<y>5.0</y>
</myMethod>
</soap:body>
Encoded
Datatype specified in each parameter
<soap:body>
<myMethod>
<x xsi:type="xsd:int">5</x>
<y xsi:type="xsd:float">5.0</y>
</myMethod>
</soap:body>
Schema free
What is meant by Message Format in WebService
I have been told that Message Format can be of two styles (RPC / Document )
Please tell me what is meant by Message Format and how it is actually related to the Web services ??
Message Exchanging Formats means the way in which the client XML structure should look like so that the provider can understand the document. there are 4 MEF's:
RPC-Encoded
RPC-literal
document-encoded (This combination is not recommended by WS-I BP 1.0 & 2.0)
document-literal
RPC-encoded is the default MEF for the JAX-RPC API and document-literal is the default MEF for the JAX-WS API
does RPC/Literal and Freedom of Choice help? or Which style of WSDL should I use?
What is WSDL? How is it related to SOAP? Where does REST fit in all of that?
A WSDL is an XML document that describes a web service. It actually stands for Web Services Description Language.
SOAP is an XML-based protocol that lets you exchange info over a particular protocol (can be HTTP or SMTP, for example) between applications. It stands for Simple Object Access Protocol and uses XML for its messaging format to relay the information.
REST is an architectural style of networked systems and stands for Representational State Transfer. It's not a standard itself, but does use standards such as HTTP, URL, XML, etc.
Example: In a simple terms if you have a web service of calculator.
WSDL: WSDL tells about the functions that you can implement or exposed to the client. For example: add, delete, subtract and so on.
SOAP: Where as using SOAP you actually perform actions like doDelete(), doSubtract(), doAdd(). So SOAP and WSDL are apples and oranges. We should not compare them. They both have their own different functionality.
Why we use SOAP and WSDL: For platform independent data exchange.
EDIT: In a normal day to day life example:
WSDL: When we go to a restaurant we see the Menu Items, those are the WSDL's.
Proxy Classes: Now after seeing the Menu Items we make up our Mind (Process our mind on what to order): So, basically we make Proxy classes based on WSDL Document.
SOAP: Then when we actually order the food based on the Menu's: Meaning we use proxy classes to call upon the service methods which is done using SOAP. :)
Every time someone mentions SOAP/WSDL, I think of objects and classes defined in xml...
"You use SOAP just the same way that you would any PHP class. However, in this case the class does not exist in the local applications file system, but at a remote site accessed over http."
...
"If we think of using a SOAP service as just another PHP class then the WSDL document is a list of all the available class methods and properties. "
http://www.doublehops.com/2009/07/07/quick-tutorial-on-getting-started-with-soap-in-php/comment-page-1/
..and whenever someone talks about REST I think of HTTP's commands (request methods) like POST, GET and DELETE
SOAP -> SOAP(Simple object access protocal) is the application level protocal created for machine to machine interaction. Protocol defines standard rules. All the parties who are using the particular protocol should adhere to the protocol rules. Like TCP, It unwinds at transport layer, The SOAP protocol will be understood by Application layer( any application which supports SOAP - Axis2, .Net).
WSDL -> SOAP message consist of SoapEnevelope->SoapHeader and SoapBody. It doesn't define what would be message format? what are all the transports(HTTP,JMS) it supports? without this info, It is hard for any client who wants to consume the particular web service to construct the SOAP message. Even if they do, they won't be sure, it'll work all the time. WSDL is the rescue. WSDL (Web Service description Language) defines the operations, message formats and transport details for the SOAP message.
REST -> REST(Representational state transfer) is based on the Transport. Unlike SOAP which targets the actions, REST concerns more on the resources. REST locates the resources by using URL (example -http://{serverAddress}/employees/employeeNumber/12345) and it depends on the transport protocol( with HTTP - GET,POST, PUT, DELETE,...) for the actions to be performed on the resources. The REST service locates the resource based on the URL and perform the action based on the transport action verb. It is more of architectural style and conventions based.
You're not going to "simply" understand something complex.
WSDL is an XML-based language for describing a web service. It describes the messages, operations, and network transport information used by the service. These web services usually use SOAP, but may use other protocols.
A WSDL is readable by a program, and so may be used to generate all, or part of the client code necessary to call the web service. This is what it means to call SOAP-based web services "self-describing".
REST is not related to WSDL at all.
SOAP stands for Simple (sic) Object Access Protocol. It was intended to be a way to do Remote Procedure Calls to remote objects by sending XML over HTTP.
WSDL is Web Service Description Language. A request ending in '.wsdl' to an endpoint will result in an XML message describing request and response that a use can expect. It descibes the contract between service & client.
REST uses HTTP to send messages to services.
SOAP is a spec, REST is a style.
Wikipedia says "The Web Services Description Language is an XML-based language that provides a model for describing Web services". Put another way, WSDL is to a web service, as javadoc is to a java library.
The really sweet thing about WSDL, though, is that software can generate a client and server using WSDL.
Some clear explanations (for SOAP and WSDL) can be found here as well.
Difference between a SOAP message and a WSDL?
REST is light-weight in terms of encoding, much more useful for light weight devices i.e. non strict APIs.
REST is format independent. XML, HTML, JSON all options are available.
REST provides abilities for on 2 point message transfer (not surprising since REST stands for REpresentational State Transfer) where WSDL/SOAP interaction is multiple point message interaction.
REST does not require a new extension for XML messages, where in WSDL/SOAP this is the case.
WSDL/SOAP uses multiple transport protocols, REST relies on only HTTP. Therefore WSDL/SOAP can be used like a RESTful way, however simple requests can be overly complicated/heavy weighted.
A simple analogy: REST is like a motoboy delivers your food easy and quick. XML extended WSDL/SOAP more like UPS delivery, more structured and serious stuff but comes with a cost.
A WSDL document describes a webservice. It specifies the location of the service and the methods of the service using these major elements:
data types using in webservice
data elements for each operation
describe the operations that can be performed and the messages envolved
SOAP (Simple Object Access Protocol) is a messaging protocol that allows programs that run on disparate operating systems to communicate using http and xml.