When migrating from SOAP based webservices to RESTful, how complicated is the task? I have worked on them individually, but never on any migration. Can any one tell me the points that need to be taken into consideration when doing this? Not sure if its an appropriate question. More like a discussion thing.
The general approach on any situation like that can be to have a middle adapter/layer work between your existing system and newly developed system.
Converting an existing SOAP web service into RESTful web service can be tedious depending upon the complexity of existing system. Rather we can take alternative approach where an REST Adapter can be written that acts as a mediator between existing SOAP system and freshly developed REST web service.
This way can be done with minimum efforts and delivery can be fast. But again it depends on what is the system all about, how complex is current SOAP web service.
So with this approach end client will generate a REST request that will be landed on REST adapter and from Adapter to existing SOAP web service, takes back the response from your SOAP web service converts it back ready for REST client response. Intermediate JSON to XML and XML to JSON conversions can be easily handled.
This approach can be better as if required adapter can be turned off. This
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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the way to solve this using IBM RAD JAX-RPC webservice from a WSDL with an SDO facade, but the article seems to be outdated.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've some confusions about ReST clients and need a bit of help.
For ReST, does the service provider give WSDL document or not? If not, how does the client will know what kind of JSON data to expect? When I invoke the rest client, I will recieve the JSON/XML response in a string format which I'll need to convert it into a Java object(or Javascript, if using on client side) to do any meaningful tasks with the response. So it seems like I, as a client developer, need to know the WSDL or the Schema definition so that I can build a java object similar to the JSON response I'm expecting. But if you go by this answer, generating a client class based on the service definition flies directly in the face of ReST fullness. If that is the case, how do I go about creating my client code?
WADL/Web Application Description Language is not a standard but is gaining popularity for REST APIs contract definition.
The Web Application Description Language (WADL) is a machine-readable
XML description of HTTP-based web applications (typically REST web
services).1 WADL models the resources provided by a service and the
relationships between them.1 WADL is intended to simplify the reuse
of web services that are based on the existing HTTP architecture of
the Web.1[2] It is platform and language independent and aims to
promote reuse of applications beyond the basic use in a web
browser.
For documentation:
https://github.com/wordnik/swagger-core/tree/master/modules/swagger-jaxrs
For client code:
https://github.com/wordnik/swagger-ui
You integrate the library and annotate your resources and online documentation is generated on the fly.
You also need a client for which you can integrate the ui.
The dynamically generated REST client looks something like this:
http://petstore.swagger.wordnik.com/
I have been seeing SOAP is "Heavy Weight" and REST is "Light Weight". On what parameters, we are telling REST is lightweight than SOAP?
We were using IFW model web services in our company earlier. But our management told us to develop all the new APIs going forward in REST. We are backend service providers in my company.
How REST is best useful for us?
What does "lightweight" means in context?
This question seems like repetition but don't understand the terms used.
REST gives you a session less window into a system. It does not track you, it does not care about you. All you have done is send a request which contains..hopefully some id to verify that you can make it. It may return a HTTP status code, it may return some body but ultimately, once the request is complete you are forgotten.
SOAP is heavy in a sense that it describes a "contract" between the remote system and your client. In order for your client to communicate effectively it MUST implement its schema...this is the SOAP skeleton. It describes the calls you can make and the objects you can expect back.
The reason why SOAP is heavy is because of serialization. Upon each SOAP request you typically serialize a java object, send it over HTTP and get a serialized response which is deserialized into an object via reflection...this is heavy. It also means that if the endpoint changes how they work, you must change your contract. You don't have to do this with REST.
With SOAP you run into multi threaded issues.
To answer quickly..
they might mean that a REST service is "lightweight" because you do not need to release changes to clients. You simply make changes to your logic, retaining URLS and the response should remain the same.
With SOAP...if you added a new field to an object, you would have to get the client to implement the new schema. SOAP is pretty old had.
REST is lightweight in that it and relies upon the HTTP standard to do its work. It is great to get a useful web service up and running quickly. If you don't need a strict API definition, this is the way to go. Most web services fall into this category. You can version your API so that updates to the API do not break it for people using old versions(as long as they specify a version). REST essentially requires HTTP and is format-agnostic, so you can use XML, JSON, HTML etc).
But the SOAP will wrap the structure into a SOAP envelope (follows an XML standard). The complexity of the SOAP envelope is based on the used message version and additional Web Service protocols. SOAP is generally transport-agnostic, meaning you don't necessarily need to use HTTP.
It can be pointed out that SOAP was designed for a distributed computing environment whereas REST was designed for a point-to-point environment.
I wonder if it is OK to say that while SOAP gives more security, REST-based API s will be easier on the resources and more scalable? As an example, Twitter, Facebook, Google Drive, Blogger, etc all have REST-based APIs that clients can consume.
Generally REST reduces the size and scope of request payloads by mapping request semantics to the underlying HTTP protocol. For example, SOAP will usually add an envelope (of varying complexity) which utilizes a WSDL (a contract) for both request and response types and service mappings. REST will just use POST, GET, etc to a URL with some HTTP encoded parameters and thus lacks an enforced contract.
There are several aspects of lightweight. SOAP is XML only, while REST allows you to send any payload, such as JSON which is less verbose and simpler than XML. Generally speaking, it takes less memory and less bandwidth to deal with JSON than XML.
On another level, using SOAP you typically describe everything as services. So, you need to define a message schema/structure for each verb and noun i.e. "CreateOrder". In REST, you use the predefined HTTP methods such as POST and put the noun/"resource" in the URI which uses already existing constructs on the HTTP level - not reinventing them in XML.
Then there is the effort it takes to adapt to change. A small change in SOAP requires you to redefine the schema, redefine the wsdl and handle versions. In rest, in the best of worlds, there is a degree of dynamic coded into the API (links to referenced resources, among other things), so that some changes can be implemented and takes effect directly.
All the heavy weight strictness of SOAP of course has a valid reason for existence. It's less likely two implementations have different interpretations of the API, than in a loosely defined REST API. SOAP also allows you to implement skeleton code in various languages based on a WSDL. In some complex scenarios, this is actually almost the only productive way to work with SOAP. Marshalling and unmarshalling between objects and serialized XML is rather heavy and adds to the heavyness of SOAP.
Is there any way to consume a SOAP based Spring web service without generating stubs on the client (as suggested by umpteen threads pointing to JAX-WS)?
Here is my complete scenario:
I have 2 web applications, say APP1 & APP2, both of which have Spring support. APP2 exposes it's APIs as Spring-WS that accept POJOs (Reqeust and Response objects) via. SOAP. Now, I want to call these web services from APP1, but would like to avoid having to create stubs using the WSDL frmo APP2. Is this possible?
For more detail, here is one of my web service's operation:
#PayloadRoot(localPart = "CreateNewRequest", namespace = "myNameSpace")
public CreateNewReqResponse createNewRequest( CreateNewReqRequest requestObj ) throws Exception
{
NewCase newCase = this.localSpringService.createNewCase( requestObj.getParam1(), requestObj.getParam2() );
CreateNewReqResponse response = this.objectFactory.createCreateNewReqResponse();
CreateNewReqResponseObject responseObject = this.objectFactory
.createCreateNewReqResponseObject();
if( null != newCase )
{
responseObject.setParam1( newCase.getParam1() );
responseObject.setParam2( newCase.setParam2() );
}
responseObject.setCaseRequestedDate( caseRequestedDate );
}
response.setResponseObject( responseObject );
return response;
}
Now, as you can see, the web service method accepts CreateNewReqRequest and returns CreateNewReqResponse. What I am trying to figure out is how can I call this web service from APP1, which does not have any clue about these classes - CreateNewReqRequest and CreateNewReqResponse? Is there no other way other than creating stubs in APP1 (from the WSDL) using JAX-WS?
Both the applications in question are our own (that is we have developed them) but run on different servers, because of which APP1 can not call the web service directly - cross-domain policy. Hence, I will writing a servlet in APP1 which will consume the web service exposed by APP2.
At the end of they day SOAP is simple a protocol on top of HTTP. So if you wish to forgo the usage of JAX-WS, you could start using raw http connections and hand code the SOAP requests and manually parse the SOAP Response on your own. This would simply mean you are re - inventing the wheel which is JAX-WS Client stubs.
So If you absolutely want to avoid Stub creation, have a go it at with HTTP post and get Messages at the WSDL end point URL.
What the client Stub does is simply abstract out that implementation for you. i.e. you will not have to deal with nitty gritty of SOAP/WSDL and http connection, you would be dealing with SOAP at a higher level, i.e through Java Objects.
You could also look into other libraries such as Apache CXF or Axis, but even there you will have to generate client stubs.
Thus the question you want to ask is, Do you want to really go in and manually muck around with http connections and SOAP XMLs or let the a framework take do that grunt work for you.
Reply to Nitin's comment follows below
To answer your questions, 1. Yes you will have to re-create the stubs if the WSDL changes, if you are not using the stubs but parsing everything manually you will have to change that code. So effectively there is no difference between the two. Your program will have to change if the WSDL (i.e. the contract between client and service) changes. This would be same even for REST, i.e. if the contract published by the service changes(Maybe the parameters, or the action etc), you will have to Change your client code. There is no escaping that. Hopefully, the public Webservices would have been designed in such a way to allow future modification, and such modifications wouldn't happen overnight thus giving you enough time to modify your code. This issue has nothing to do with how the web service has been implemented i.e. Spring Web Service has nothing to do with.
You seem to be missing the point of the Client stubs that a SOAP framework like JAX-WS, Axis, CXF generate for you. The Client Stub is one way to talk to the Web service. It is not the only way. The Client stub is the preferred method, because it abstracts outout the nitty gritties of handling SOAP calls manually. So, rather then you re inventing the wheel and implementing a SOAP(XML) parsing library, you can concentrate your efforts on the actual application that you are writing. In your actual program you would only have to deal with POJOs and never have to worry about how the SOAP magic happens i.e. how to convert your data and package it up in a SOAP message, send that SOAP Message to the Service using a HTTP connection, handle the response, Parse the response SOAP Message and retrieve the data you care about. All of this you avoid by using the POJOs. You set the properties for request, make a method call to the client stub service method, and recieve an object, everything else is you don't have to worry about (ideally).
I hope this clear things up a bit.
Take a look at WebServiceTemplate class.
I am developing a web service in java and Metro that requires a lot of information to be passed. For example, something like xml describing all the attributes of a customer.
I am wondering if there is some standard way in which to pass the data in a document. Currently I have been passing the data as a string parameter named 'customerXML'.
Any suggestions appreciated. FYI I have defined another restful ws using RestEasy which works great using input/output streams, but am looking for a way to leverage soap-based web services to expose similar functionality.
JAX WS is perfect for this requirement, It works on SOAP
My hypothesis is that there isn't a standard way to pass xml documents to a soap-based web service without coding the entire SOAP message yourself. Hence I do not think there is an easy way to do so and one reason why RESTful web services are gaining acceptance. The best way to do it using SOAP based web services is to pass the document as a string parameter and validate/parse within your server code.