What is Spring Web Services (WS)?
Spring Web Services (Spring-WS) is a product of the Spring community focused on creating document-driven Web services. Spring Web Services aims to facilitate contract-first SOAP service development, allowing for the creation of flexible web services using one of the many ways to manipulate XML payloads. The product is based on Spring itself, which means you can use the Spring concepts such as dependency injection as an integral part of your Web service.
Source: Spring WS Reference 2.0
What is Contract-First development?
When creating Web services, there are two development styles: Contract Last and Contract First. When using a contract-last approach, you start with the Java code, and let the Web service contract (WSDL, see sidebar) be generated from that. When using contract-first, you start with the WSDL contract, and use Java to implement said contract.For an in-depth look of Spring WS, I suggest my readers to visit the Spring WS Reference 2.0 and the Spring WS API 2.0.0.RC2
Source: Spring WS Reference 2.0
We begin by defining our requirements. We have a magazine business. Our business partner has clients that needs to subscribe with our magazine. To expose this feature, we decided to use a web service. Our contract is that the clients will send the following information:
subscription code name emailOur web service will send a reply if the subscription is successful or not. The reply will contain the following elements:
status code descriptionSince all web services are ultimately XML message, we need to define the format of our messages. We will create an XSD file. If you're not familiar with XSD, please see the excellent XSD tutorial w3schools.com XML Schema Tutorial.
Here's our XSD document:
subscription.xsd
This XSD is comprised of simple and complex element types. Each simple element has been assigned with restriction. In this way we can filter data even before it comes to our service. It's also a good way to validate XML data. Spring WS will handle the validation based on these restrictions.
When the client sends a request, we receive an XML document. Using Java's object-oriented approach and XML approach is not really convenient when manipulating information. Therefore we will use marshalling techniques to map the XML document with a corresponding Java object.
First let's see the actual XML document that is sent to us by the client:
Take note that this XML format is not arbitrary! The client has to honor the format that we declared in the XSD document.
Let's map this document to a SubscriptionRequest class:
SubscriptionRequest
For every request sent by the client, we send a response. We declare a SubscriptionResponse object:
Our marshaller will automatically convert this class into an XML document. If you look at the XSD file, we have declared a subscriptionResponse element.
This has been declared so that the client who is reading our WSDL will see what kind of response he will receive. Hence, the Contract-First development.
When the client receives a response, this is what he actually gets:
Our class has been automatically converted to XML.
To convert Java objects to XML and vice-versa we use Castor as our marshaller/unmarshaller implementation. For more info about Castor, check the reference guide Castor XML Mapping. There are other marshallers available, such as JAXB and JiBX. Check the Spring WS Reference Guide Chapter 8. Marshalling XML using O/X Mapper for more info.
To use Castor we need to declare a mapping file:
castor-mapping.xml
We're done with our contract. We now start the actual development!
The programming model of Spring WS 2 is similar with the programming model of Spring 3 MVC. Keep that in mind. In Spring MVC, to declare a controller, we mark the name of the class with @Controller and @RequestMapping. For example:
In Spring WS, we have a corresponding controller as well. Actually, it's called an endpoint. To declare an endpoint, we mark it with @Endpoint. For example:
In Spring MVC, to expose a method for a particular request, we add the @RequestMapping annotation and the associated URI template value and the type of method. For example:
In Spring WS, to expose a method for a particular service request, we add the @PayloadRoot annotation and the associated localPart and namespace values. For example:
The method is also annotated with @ResponsePayload, indicating that the return value ( SubscriptionResponse) is used as the payload of the response message. The method takes a SubscriptionRequest as a parameter, annotated with @RequestPayload. This means that the payload of the message is passed on this method as a DOM element. If you have omitted these two annotations, you will encounter a "java.lang.IllegalStateException: No adapter for endpoint".
Let's now declare our SubscriptionEndpoint class:
SubscriptionEndpoint
This endpoint has one method named processSubscription. It takes a SubscriptionRequest and delegates the processing to a SubscriptionService. If the subscription is successful a SUCCESS response is sent. If it failed, a FAILURE response is sent.
Here's the SubscriptionService:
SubscriptionService
We're done with the Spring WS part. We now start the Spring MVC development.
What we're adding here are just basically a single controller and single JSP file to display our subscribers. Here's a screenshot of our subscribers list:
Here's the controller:
MainController
This controller declares a single mapping:
/main/subscribersThis mapping delegates the call to the SubscriptionService. This is the same service that's utilized by Spring WS earlier!
Here's the JSP file:
We're done will all our classes. What's left are the XML configurations. We start by declaring the web.xml file:
web.xml
All request are handled by Spring MVC's DispatcherServlet. In a stand-alone Spring WS, we use the MessageDispatcherServlet instead. But since we're now integrating both, we need a way to resolve our dispatchers hierarchy.
As an alternative to the MessageDispatcherServlet, you can wire up a MessageDispatcher in a standard, Spring-Web MVC DispatcherServlet. By default, the DispatcherServlet can only delegate to Controllers, but we can instruct it to delegate to a MessageDispatcher by adding a WebServiceMessageReceiverHandlerAdapter to the servlet's web application context:I suggest to read the Spring WS 2 reference for a thorough description of this integration.
Spring WS 2 Reference 5.3.2. Wiring up Spring-WS in a DispatcherServlet
If you examine carefully the servlet element, we've declared an init-param. This is required to dynamically convert WSDLs regardless where you deploy it. There's no need to manually set the URL of your WSDL anymore, though you still can.
In the web.xml we declared a servlet-name spring. By convention, we must declare a spring-servlet.xml as well.
spring-servlet.xml
By convention, we must declare an applicationContext.xml as well.
applicationContext.xml
These beans activate Spring's annotation support for Spring 3 MVC. At the bottom portion we import an external configuration file spring-ws.xml. This contains all the Spring WS specific configuration. In a normal Spring project, it's typical to have multiple XML configs. To lessen the XML hell experience, it's advisable we group related configurations in their owned XML file.
Here's spring-ws.xml:
spring-ws.xml
This configuration uses the latest Spring WS 2.0.0 RC2 features (unlike if you're still using 1.5.9).
What's new with Spring WS 2.0.0 RC2?
The most important new feature in this release is the update of the Spring-WS XML namespace, which now contains <sws:annotation-driven/> and <sws:interceptors/> elements (similar to the Spring-MVC namespace), and <sws:static-wsdl/> and <sws:dynamic-wsdl/> for exporting your WSDLs.It's worth mentioning in the spring-ws.xml, we're using a pluggable endpoint adapter
Source: SpringSource Forum: Spring Web Services 2.0.0 RC2 released
DefaultMethodEndpointAdapterand a marshalling method processor
MarshallingPayloadMethodProcessorIf you visit some of the popular Spring WS tutorials, they still use the old GenericMarshallingMethodEndpointAdapter. However, this is already deprecated in favor of a pluggable adapter.
Class GenericMarshallingMethodEndpointAdapterThat concludes our Spring WS development. We've managed to setup a simple Spring 3 WS application using the latest Spring WS 2.0.0.RC2 build. We've utilized the latest annotation features. We've also leveraged Spring 3 MVC's programming model.
Deprecated. as of Spring Web Services 2.0, in favor of DefaultMethodEndpointAdapter and MarshallingPayloadMethodProcessor.
See Spring WS API 2.0.0 GenericMarshallingMethodEndpointAdapter
To test the application, you will need to deploy it in a server, like Tomcat. For the client, unless you know how to develop a Web Service client, I advise my readers to use Soap UI for testing. They have a free version at http://soapui.org/. It's also one of the recommended tools at the official Spring Web Services site at http://static.springsource.org/spring-ws/sites/2.0/resources.html.
Here's a sample screenshot using SOAP UI to test the application:
To access the service endpoint, use the following URL:
http://localhost:8080/spring-ws/krams/wsTo access the WSDL, use the following URL (you can use Firefox to check this out):
http://localhost:8080/spring-ws/krams/ws/subscription.wsdlTo access the subscribers page, use the following URL:
http://localhost:8080/spring-ws/krams/main/subscribersThe best way to learn further is to try the actual application.
Download the project
You can access the project site at Google's Project Hosting at http://code.google.com/p/spring-ws-2-0-0-rc2-tutorial/
You can download the project as a Maven build. Look for the spring-ws.zip in the Download sections.
You can run the project directly using an embedded server via Maven.
For Tomcat: mvn tomcat:run
For Jetty: mvn jetty:run
If you want to learn more about Spring MVC and integration with other technologies, feel free to read my other tutorials in the Tutorials section.
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Thanks for this excellent tutorial !
ReplyDelete@Jose, thanks for comment. You might want to check the spring-ws-si project in the Spring Integration 2: Integrating a JDBC and WS System tuorial. It uses JAXB instead of Castor for marshalling. I'm planning to make a guide for it. But bassically it's the same idea
ReplyDeleteI really have to say, that your tutorial is SUPERB!
ReplyDeleteAll the other tutorials on spring webservices don't compare to yours, you explain exactly what is needed to explain, thank you :)
@Anonymous, thank for the comment :) I appreciate it
ReplyDeleteGood post, facing the same issue.
ReplyDeleteNo adapter for endpoint
Is your endpoint annotated with @Endpoint, or does it implement a supported interface like MessageHandler or PayloadEndpoint?
Great Tutorial!
ReplyDeleteI have tried to adapt it to run in Spring Roo. I get the WSDL, but once I post to the URL I get 404.
Do you know if there any reason for this?
very useful tutorial!
ReplyDeleteThanks for the tutorial.
ReplyDeleteI have created all and I get an exception.
Could you help me please?
http://forum.springsource.org/showthread.php?117083-java.lang.IllegalStateException-No-adapter-for-endpoint
@Anonymous, this is a common issue with Spring WS. In my experience it could mean you're missing the @Endpoint annotation or the @RequestPayload annotation in your method arguments
ReplyDeleteReally gud tutorial
ReplyDelete@krams - Thanks so much for sharing this tutorial. It is very clear and I have attempted to follow your steps to add MVC to an existing SpringWS service to allow a more simple method to monitor the health of the service. I had little to change to integrate MVC, but the Listener fails quietly:
ReplyDeleteApr 27, 2012 4:28:12 PM org.apache.catalina.core.StandardContext start
SEVERE: Error listenerStart
Apr 27, 2012 4:28:12 PM org.apache.catalina.core.StandardContext start
SEVERE: Context [/BlahService] startup failed due to previous errors
I have tweaked my logging but find no more to point to the issue. Woudl you have a recommendation on how to debug this?
Hey,
ReplyDeleteI launched your source code and noticed what generated WSDL has empty soapAction :(
I tried to access services using SoapUI, but cannot figure out the URL for the action. Tried all the possible URLs including the obvious http://localhost:8080/krams/ws/subscriptionRequest/ but all I get is 404.
Any ideas how to add soapAction to WSDL ? also figuring out the URL of the action would be great ?
By the way the URLs you provided at the end of your post are wrong, for example your WSDL is accessible at http://localhost:8080/krams/ws/subscription.wsdl (exclude the "spring-ws" part).
Simply superb!!
ReplyDeletejust the kind of tutorial I am looking for.
Keep posting such stuff.
It works for me in Eclipse STS, thanks a lot for the great tutorial.
ReplyDeleteNow I want to use my own location instead of http://krams915.blogspot.com/ws/schema/oss But it does not resolve in the browser, so how can we know what to place there?
Hi,
ReplyDeleteI can access wsdl file but cannot access endpoint that has
http://localhost:8080/spring-ws/krams/ws url. And get HTTP-404 error.
Krams Your tutorial is awsome ! However i have a question, how i can add subscribers? under which address?
ReplyDeleteHi Kram.. how should i import this project into eclipse that i can get working copy..
ReplyDeletethanks in advance...
Sir this error comes while running the project ::: Error occurred during deployment: Exception while loading the app : java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'messageDispatcher' defined in ServletContext resource [/WEB-INF/mvc-ws-integration.xml]: Cannot resolve reference to bean 'defaultMethodEndpointAdapter' while setting bean property 'endpointAdapters' with key [0]; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'defaultMethodEndpointAdapter' defined in ServletContext resource [/WEB-INF/spring-ws.xml]: Initialization of bean failed; nested exception is java.lang.NoClassDefFoundError: org/exolab/castor/xml/XMLException. Please see server.log for more details.
ReplyDeleteSres:
ReplyDeleteThe tutorial is very buene but I have the drawback that return a list, if it is eaten with soapUI or from the same JAVA if it returns the list but when consumed from. NET returns null, eye single to the list of other types of variable type I have problem or is that springws and beaver-mapping is not compatible with. NET:
Code castor-mapping:
Code XSD:
Thank you thank you thank you thank you.
ReplyDeleteReally fantastic.
ReplyDeleteThank you! Great tutorial!
ReplyDeleteHi Krams - I'd like to seek a help from you for this code.
ReplyDeleteWhen I run on browser for
http://localhost:8080/spring-ws/krams/ws - I don't see any output.
http://localhost:8080/spring-ws/krams/main/subscribers - I only see blank data with header
Subscribers
Id Name Email
I have read your blog its very attractive and impressive. I like it your blog.
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