I was wondering if someone could explain the differences in a SOAP request/response of a Web service with the following wsdl binding style/use:
Document/literal
RPC/literal
wrapped document style
Thanks in advance
This article from IBM DeveloperWorks [Which style of WSDL should I use?] has an excellent explanation of the differences between these binding styles. In a nutshell, the only differences are the values of the SOAP binding "style" attribute ("rpc" or "document") in the WSDL file and the way the message arguments and return values are defined (and thus how they appear in the SOAP messages themselves):
[Note the reordering of items from the question to emphasize relationships]
RPC/literal - WSDL message element defines arguments and return value(s) of operations.
PROS: simple WSDL, operation name appears in SOAP message, WS-I compliant.
CONS: difficult to validate since arguments are defined in WSDL not XSD.
Document/literal - WSDL message parts are references to elements defined in XML Schema.
PROS: easily validated with XSD, WS-I compliant but allows breakage.
CONS: complicated WSDL, SOAP message does not contain operation name.
Document/literal wrapped (or "wrapped document style") - WSDL message input has single input and output parameters and input refers to XSD element with same local name as WSDL operation.
PROS: easily validated, SOAP message contains operation name, WS-I compliant.
CONS: most complicated WSDL (not an official style but a convention).
In my experience, #3 (Document/literal Wrapped) is very common in large enterprise projects because it is both Microsoft and OSS friendly and it is well suited for a top-down development model (e.g. WSDL/XSD first, then generate code artifacts). Microsoft invented it [1] and popular Java/OSS tools (Axis2, JAX-WS) support it explicitly.
The "real world" difference likely comes down to which styles are supported — and how well — by the tools of your choice.
Related
This is not Java specific question, but let's have an example in Java: It is a standard practice in the Java world to add xmime:expectedContentTypes="*/* to base64 elements to enable MTOM processing on the server side - it results in the #XmlMimeType annotation, use of DataHandlers instead of byte arrays etc. While this description is of course greatly simplified, xmime:expectedContentTypes="*/* is usually recognized as 'MTOM ready' by the developers (and more importantly also by the implementing libraries) when seen in the schema. From what I've gathered from the examples, the situation is the same in the C# world.
It does however make no sense to me - the attribute specifies what kind of data we might actually expect in the XML, not that it can be used together with MTOM. I have also not found any direct connection between expected content type and MTOM in any RFC or similar document for SOAP 1.1.
My question can be phrased in two ways:
How does the service make clear that it accepts / serves binary data as MTOM attachments in the request / response?
How does the client correctly recognize that the binary data can be sent / obtained by using MTOM attachments for the given service?
It seems you are slightly confused between attachments, SOAP Attachment and MTOM.
SOAP-Attachment was first introduced in December 2000 as a W3C note (not a specification) and defined an extension to the transport binding mechanisms defined in SOAP 1.1. In particular, this note defined:
a binding for a SOAP 1.1 message to be carried within a MIME multipart/related message in such a way that the processing rules for the SOAP 1.1 message are preserved.The MIME multipart mechanism for encapsulation of compound documents can be used to bundle entities related to the SOAP 1.1 message such as attachments.
In simple terms, it defined a mechanism for multiple documents (attachments) to be associated with SOAP message in their native formats using a multipart mime structure for transport. This was achieved using a combination of "Content-Location" and "Content-ID" headers along with a set of rules for interpreting the URI that was referred to by "Content-Location" headers.
A SOAP message in this format can be visualized as below (encapsulated as multipart/mime):
This is also the format that you might have worked with when you used SAAJ, but is not recommended anymore, unless you are working with legacy code. The W3C note was later revised to a "feature" level in 2004 (along with SOAP 1.2) and was eventually superseded by SOAP MTOM mechanism.
SOAP Message Transmission Optimization Mechanism (MTOM) is officially defined as not one, but three separate features that work together to deliver the functionality:
"Abstract SOAP Transmission Optimization Feature" describes an abstract feature for optimizing the transmission and/or wire format of the SOAP message by selectively encoding portions of the message, while still presenting an XML infoset to the SOAP application.
"An optimized MIME Multipart/Related serialization of SOAP Messages" describes an Optimized MIME Multipart/Related Serialization of SOAP Messages implementing the Abstract SOAP Transmission Optimization Feature in a binding independent way.
"HTTP SOAP Transmission Optimization Feature" describes an implementation of the Abstract Transport Optimization Feature for the SOAP 1.2 HTTP binding.
If you read the second document, you will realize that "attachments" has been replaced with XML binary optimized "packages" or XOP.
A XOP package is created by placing a serialization of the XML Infoset inside of an extensible packaging format (such a MIME Multipart/Related, see [RFC 2387]). Then, selected portions of its content that are base64-encoded binary data are extracted and re-encoded (i.e., the data is decoded from base64) and placed into the package. The locations of those selected portions are marked in the XML with a special element that links to the packaged data using URIs.
In simple terms, this means that instead of encapsulating data as "attachment" in a multipart/mime message, the data is now referred to by a "pointer" or links. The following diagrams may assist in understanding:
Now that we have the background, let us come back to your questions.
How does the service make clear that it accepts / serves binary data as MTOM attachments in the request / response?
It does not. There is no concept of an attachment with MTOM, and thus a server can't declare that it accepts attachments.
How does the client correctly recognize that the binary data can be sent / obtained by using MTOM attachments for the given service?
Like I said above, there is no way for a client to do this as "attachments" are not supported.
Having said that, there is yet another W3C spec on XML media types that states:
The xmime:contentType attribute information item allows Web services applications to optimize the handling of the binary data defined by a binary element information item and should be considered as meta-data. The presence of the xmime:contentType attribute does not changes the value of the element content.
When you enable MTOM using xmime:contentType and xmime:expectedContentTypes="application/octet-stream (* should not be used), the generated WSDL will have an entry like this:
<element name="myImage" xmime:contentType="xsd:base64Binary" xmime:expectedContentTypes="application/octet-stream"/>
This is server's way of declaring that it can receive an XML binary optimized package (which could be broken down into multipart MIME message).
When the client sees the above, the client knows server can accept XML binary optimized packages and generates appropriate HTTP requests as defined Identifying XOP Documents:
XOP Documents, when used in MIME-like systems, are identified with the "application/xop+xml" media type, with the required "type" parameter conveying the original XML serialization's associated content type.
Hope that helps!
I do want to build a generic gateway from a nested map (generated from binary data stream) to SOAP- clients.
Background: a non-java-application which needs to call SOAP-Services can't generate json or SOAP/XML, but easily generate a custom protocol (which is under our control).
So a proxy is needed. That proxy should not be rewritten on every change of the WSDL or rollout of the next Webservice.
My plan is:
to have url, port and service-name (url:port/service-name) as "strict" defined parameters of that proxy,
to have the SOAP Action as a "strict" defined parameter
to request (possibly cached) the wsdl of url:port/service-name?wsdl and initiate the stub-call dynamically (cached),
to fill the values, which are present in the nested map, to that stub
call the SOAP-Service
convert the answer back to that binary protocol.
If some necessary values are missing it should send the equivalent of a SOAP-Error.
All that of course with small (affordable) latency, high stability, absolute minimal deployment downtime (for updates) and quite some load.
I see several possibilities:
a) Using a ESB like WSO2ESB. There I would implement the stream format as a special input format adapter, convert it to internal XMLStream (at least the json-adapters seem to work that way) and send it to mediator. That mediator would try something like in
http://today.java.net/pub/a/today/2006/12/13/invoking-web-services-using-apache-axis2.html "Creating a Dynamic Client" and call the SOAP-Service directly.
b) using a MOM-Middleware like ApacheMQ with Camel,
c) reduce it to something like Apache Karaf and CXF
I'm a bit lost between all those possibilities, and those are just more or less arbitrary samples of each kind.
Thoughts to a):
minus: It feels a bit odd to have no ESB-Target, since the mediator would directly call the given SOAP-Requests
minus: I wonder if internally converting into XML-Stream would not cost extra time and resources
minus: changing the code needs restart of the WSO2ESB as far as I got it
plus: instead of url, port, service-name I could define symbolic names which are resolved using the ESB -- iff that doesn't take extra milliseconds.
For b) I have not yet checked how easily those format conversions are in Camel and if SOAP-Service-Requests fit into Message Sending and Queueing.
I did already some searches to that topic but it's really confusing because of the overlapping scopes of quite different products. I thought it to be a standard problem but apparently there are no obvious solutions - at least I didn't find them.
I do hope to get a clue which of those solutions could lead into trouble or much work (and which into easy success), and I hope that there is some reason in my approach.
Thanks for any qualified comments!
Marco
I'm using GWT-RPC to get the client data and my requirement is to parse the payload to retrieve the data inside. I need to log or persist this data for metrics/monitoring purpose.
I'm using the Servlet Filter to intercept the HTTP requests. I can see that the request looks something like this -
5|0|7|http://localhost:8080/testproject|
29F4EA1240F157649C12466F01F46F60|com.test.client.GreetingService|
greetServer|java.lang.String|myInput1|myInput2|1|2|3|4|2|5|5|6|7|
Is there any standard mechanism to parse this data? I'm afraid writing my own code to parse this is not a good solution as this request payload is going to be complex when we pass custom objects to/from RPC and GWT-RPC internal parsing mechanism could change in future, which can break my code. I came across this, but not sure if it is robust/maintained.
Is there any alternative? Any pointers will be appreciated.
Use the RPC class from GWT.
You'll have to provide the serialization policy, whose strong name is passed in a request header.
Decoding responses is harder. You can use com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.ResponseReader along with a com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader but you'll need to have the JsParser from gwt-dev.jar in the classpath; and you cannot have gwt-dev.jar in a web application as it contains the servlet API (among others); so you'll have to extract the relevant classes from gwt-dev.jar to use them in your web app.
Note that in both cases, you'll reconstruct the same objects as will be deserialized for processing the request "for real", or were serialized as the result of the request processing.
All-in-all, you'll probably have better luck and better performances with using AOP on the methods of your RemoteServiceServlets.
I'm not sure, if that is what you're looking for, but a standard way to log the parsed parameters would be to override AbstractRemoteServiceServlet's onAfterRequestDeserialized(RPCRequest rpcRequest): RPCRequest contains the service method, with all its parameter values, the parsed RpcToken etc. in the form of nice Java objects.
I am using Resteasy and GWT. For certain reasons, as many others have similar motivations, I am not using GWT-RPC for some of the functionality of the software I am working on.
I need to pass POJOs between GWT client and server by marshalling/demarshalling the POJOs into/from JSON.
OK, easier said than done because I need the POJO-JSON converters on both sides to match.
Q1. Is there a standard POJO notation in JSON? Is there an ietf RFC or ISO or ECMA that specifies the format of POJO notation in JSON? Or is it a free for all, libertarian anarchy?
Q2. Do Jettison and Jackson (when used with JAXB) and Autobeans produce the same JSON for POJOs?
Q3. This is the most crucial question. You can ignore the other questions above but you MUST answer this. Give me a combination pair of server-side and GWT client side JSONizer/deJSONizer that works together. For example, can I use Autobeans on client-side and use JAXB-jettison on server side and expect the JSONized POJO notation to be the same?
Q4. Is it possible to use JAXB-Jettison or JAXB-Jackson on GWT client-side by including the java source code for JAXB, Jettison/Jackson in the whatever.gwt.xml file? Are there parts of JAXB, Jettison/Jackson source code that might e.g., depend on reflection, or non-serializable, etc that would not make it possible to use JAXB + Jettison/Jackson in GWT client code? If possible, please explain how?
~
I should clarify concerning Q1:
I am not asking about RFC for JSON. I am asking about JSON POJO format. When a POJO is converted to JSON, everybody does it their own way - so, I am thinking that there should be an RFC to standardise the way and format a POJO is converted to JSON. Is there a standard or not? !!I hope your answers should not quote me the RFC for JSON!!
~
What about
Someone needs to tell me about
badgerfish on GWT client
and GWT client-server matched JSON-RPC.
There is no standard for mapping, but I would claim there is obvious simple mapping, given simplicity of JSON format, and de facto standard of Java Beans (i.e. mapping of set/get methods to logical property names). One of few exceptions is Jettison.
Jettison is not as much a JSON/POJO library as it is JSON<->XML library: it converts JSON to XML API calls (and vice versa), to allow use of XML tools such as JAXB for XML data binding, on JSON. But the cost here is that JSON it produces and consumes has extra complexity which is only needed to work with XML APIs. And this is what makes it non-standard compared to the usual straight-forward bindings like used by Jackson, GSON, Flex-json and other "native" JSON libs.
I would recommend not using Jettison unless you really, really must for some reason. Not even if you produce both XML and JSON -- usually you are better off mapping JSON to/from POJOs using JSON tools, and XML separate to/from POJOs (using JAXB etc).
Jettison was intended to bridge the gap between (then) more mature XML tools and newish JSON format. But there isn't much benefit nowadays when there are dozens of mature JSON libraries available.
JSON is just a subset of JavaScript, it was "invented" by Douglas Crockford. Here is the RFC for application/json: http://www.ietf.org/rfc/rfc4627.txt?number=4627. So any of your server side solutions should create the same result.
We are using RestyGwt ( http://restygwt.fusesource.org/ ) on the clientside and it works like charm. Its JSON encoding style is compatible with the default Jackson Data Binding so it should work with Jackson as well.
I'm developing a new application for the company.
The application have to exchange data from and to iPhone.
Company server side uses .NET framework.
For example: the class "Customer" (Name, Address etc..) for a specific CustomerNumber should be first downloaded from server to iphone, stored locally and then uploaded back to apply changes (and make them available to other people). Concurrency should not be a problem (at least at this time...)
In any case I have to develop both the server side (webservice or whatever) and the iPhone app.
I'm free to identify the best way to do that (this is the application "number ONE" so it will become the "standard" for the future).
So, what do you suggest me ?
Use SOAP web services (XML parsing etc..) or user JSON ? (it seems lighter...)
Is it clear to me how to "upload" data using SOAP (very long to code the xml soap envelope ... I would avoid) but how can I do the same using JSON ?
The application needs to use date values (for example: last_visit_date etc..) what about date in Json ?
JSON has several advantages over XML. Its a lot smaller and less bloated, so you will be passing much less data over the network - which in the case of a mobile device will make a considerable difference.
Its also easier to use in javascript code as you can simply pass the data packet directly into a javascript array without any parsing, extracting and converting, so it is much less CPU intensive too.
To code with it, instead of an XML library, you will want a JSON library. Dates are handled as you would with XML - encode them to a standard, then let the library recognise them. (eg here's a library with a sample with dates in it)
Here's a primer.
Ah, the big question: JSON or XML?
In general, I would prefer XML only when I need to pass around a lot of text, since XML excels at wrapping and marking up text.
When passing around small data objects, where the only strings are small (ids, dates, etc.), I would tend to use JSON, as it is smaller, easier to parse, and more readable.
Also, note that even if you choose XML, that does not by any means mean you need to use SOAP. SOAP is a very heavy-weight protocol, designed for interoperability between partners. As you control both the client and server here, it doesn't necessarily make sense.
Consider how you'd be consuming the results on the iPhone. What mechansim would you use to read the web service response? NSXMLParser?
How you consume the data would have the biggest impact on how your serve it.
Are JSON and SOAP your only options? What about RESTful services?
Take a look at some big players on the web that have public APIs that are accessible by iPhone clients:
Twitter API
FriendFeed API
Also, review the following related articles:
How to parse nested JSON on iPhone
RESTful WCF service that can still use SOAP
Performance of REST vs SOAP
JSON has following advantages:
it can encode boolean and numeric values ... in XML everything is a string
it has much clearer semantics ... in json you have {"key":"someValue"}, in XML you can have <data><key>someValue</key></data> or <data key="someValue" /> ... any XML node must have a name ... this does not always make sense ... and children may either represent properties of an object, or children, which when occuring multiple times actually represent an array ... to really understand the object structure of an XML message, you need its corresponding schema ... in JSON, you need the JSON only ...
smaller and thus uses less bandwidth and memory during parsing/generation ...
apart from that, i see NO difference between XML and JSON ... i mean, this is so interchangable ... you can use JSON to capture the semantics of SOAP, if you want to ...
it's just that SOAP is so bloated ... if you do want to use SOAP, use a library and generators for that ... it's neither fun nor interesting to build it all by hand ...
using XML RPC or JSON RPC should work faster ... it is more lightweight, and you use JSON or XML at will ... but when creating client<->server apps, a very important thing in my eyes, is to abstract the transport layer on both sides ... your whole business logic etc. should in no way depend on more than a tiny interface, when it comes to communication, and then you can plug in protocols into your app, as needed ...
There are more options than just SOAP vs JSON. You can do a REST-based protocol (Representational State Transfer) using XML. I think it's easier use than SOAP and you get a much nicer XSD (that you design.) It's rather easy for almost any client to access such services.
On the other hand, JSON parsers are available for almost any language and make it really easy to call from JavaScript if you'll use them via AJAX.
However, SOAP can be rather powerful with tons of standardized extensions that support enterprise features.
You could also use Hessian using HessianKit on the iPhone side, and HessianC# on the server side.
The big bonuses are:
1. Hessian in a binary serialization protocol, so smaller data payloads, good for 3G and GSM.
2. You do not need to worry about format in either end, transport is automated with proxies.
So on the server side you just define an C# interface, such as:
public interface IFruitService {
int FruitCount();
string GetFruit(int index);
}
Then you just subclass CHessianHandler and implement the IFruitService, and your web service is done.
On the iPhone just write the corresponding Objective-C protocol:
#protocol IFruitService
-(int)FruitCount;
-(NSString*)GetFruit:(int)index;
#end
That can then be access by proxy by a single line of code:
id<IFruitService> fruitService = [CWHessianConnection proxyWithURL:serviceURL
protocol:#protocol(IFruitService)];
Links:
HessianKit : hessiankit
I would certainly go with JSON, as others already noted - it's faster and data size is smaller. You can also use a data modelling framework like JSONModel to validate the JSON structure, and to autoconvert JSON objects to Obj-C objects.
JSONModel also includes classes for networking and working with APIs - also includes json rpc methods.
Have a look at these links:
http://www.jsonmodel.com - the JSONModel framework
http://json-rpc.org - specification for JSON APIs implementation
http://www.charlesproxy.com - the best tool to debug JSON APIs
http://json-schema.org - tool to define validation schemas for JSON, useful along the way
Short example of using JSONModel:
http://www.touch-code-magazine.com/how-to-make-a-youtube-app-using-mgbox-and-jsonmodel/
Hope these are useful