Sunday, June 14, 2009

Truly Dynamic Web Services on WebLogic using JAX-WS

In my last blog (a long time ago I know) I talked about the potential for using JAX-WS on WebLogic 10.3 to fulfil the 8 key values that I believe are important for Web Service based Messaging. I've been using JAX-WS in WebLogic a lot over the last half a year and I've been very impressed with its power. As promised, I'm now (finally) going to describe the results of my experiments, with JAX-WS Providers/Dispatchers specifically, to see if they can achieve 8 out of 8 on my scorecard. Does JAX-WS give me the power and freedom I desire when doing web services?

For the experiment, I have used a Customer based web service example, like I've used before. Using an Interface-First approach, I created a WSDL and associated XSD Schema for a fictitious "Change Customer Information" HTTP SOAP web service. Then I created the Java Web Service (JWS) implementing a JAX-WS Provider interface, rather than using a strongly-typed JAX-WS Service Endpoint Interface (SEI). To test out the integration between the WebLogic's JAX-WS runtime and WebLogic's Security sub-system, I included a WS-Policy in my WSDL to force service consumer applications to provide a WS-Security UserToken (username/password) in the SOAP header for authentication.

My code for the Provider is shown below:
@WebServiceProvider(
serviceName="CustomerInfoChangeService",
targetNamespace="testns:custinfochngsvc",
portName="CustomerInfoChangeServiceSOAP",
wsdlLocation="/WEB-INF/wsdls/CustomerInfoChangeService.wsdl"
)
@ServiceMode(value=Service.Mode.PAYLOAD)
public class CustomerInfoChangeService implements Provider<Source> {
private final static String XSD_NMSPC = "testns:custinfo";
@Resource
private WebServiceContext context;

public Source invoke(Source request) {
try {
// Check some security stuff
System.out.println("Service invoked with principal: " +
context.getUserPrincipal().getName());
System.out.println("Is in Administrators group? " +
context.isUserInRole("Administrators"));

// Process request
Transformer transformer = TransformerFactory.newInstance().newTransformer();
StreamResult sysOutStream = new StreamResult(System.out);
System.out.println("Changing following customer info:");
transformer.transform(request, sysOutStream);
System.out.println();

// INVOKE REAL XML PROCESSING AND CUSTOMER DB UPDATE LOGIC HERE

// Construct response
String responseText = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
"<CustomerInfoChangeAcknowledgement xmlns=\"" + XSD_NMSPC + "\">" +
" <Ack>SUCCESS</Ack>" +
" <Comment>Successfully processed change for customer</Comment>" +
"</CustomerInfoChangeAcknowledgement>";
return new StreamSource(new StringReader(responseText));
} catch (Exception e) {
throw new WebServiceException("Error in Provider JAX-WS service", e);
}
}
}

I bundled this Provider JWS into a plain WAR archive and deployed to WebLogic. I then created the service consumer code as a standalone Java application. The code for this client, which uses the JAX-WS Dispatch API to locate and invoke the remote Web Service, is shown here:
public class CustomerInfoChangeClient {
private final static String WSDL_URL_SUFFIX = "?WSDL";
private final static String WSDL_NMSP = "testns:custinfochngsvc";
private final static String WSDL_SRVC_PORT = "CustomerInfoChangeServiceSOAP";
private final static String WSDL_SRVC_NAME = "CustomerInfoChangeService";
private final static String XSD_NMSP = "testns:custinfo";
private final static String USERNAME = "weblogic";
private final static String PASSWORD = "weblogic";

public static void main(String[] args) {
if (args.length <= 0) {
throw new IllegalArgumentException("Must provide endpoint URL arg");
}

try {
new CustomerInfoChangeClient(args[0]);
} catch (Exception e) {
e.printStackTrace();
}
}

public CustomerInfoChangeClient(String endpointURL) throws IOException,
SAXException, TransformerException, ParserConfigurationException {
// Construct request
String requestText = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
"<CustomerInfo xmlns=\"" + XSD_NMSP + "\">" +
" <Id>1</Id>" +
" <Address1>6</Address1>" +
" <PostCode>AB1 2YZ</PostCode>" +
"</CustomerInfo>";
Source request = new StreamSource(new StringReader(requestText));

// Invoke service operation, adding appropriate credentials
Service service = Service.create(new URL(endpointURL + WSDL_URL_SUFFIX),
new QName(WSDL_NMSP, WSDL_SRVC_NAME));
Dispatch<Source> dispatcher = service.createDispatch(new QName(
WSDL_NMSP, WSDL_SRVC_PORT), Source.class, Service.Mode.PAYLOAD);
Map<Object, String> rc = ((BindingProvider) dispatcher).
getRequestContext();
List<CredentialProvider> credProviders = new
ArrayList<CredentialProvider>();
credProviders.add(new ClientUNTCredentialProvider(USERNAME.getBytes(),
PASSWORD.getBytes()));
rc.put(WSSecurityContext.CREDENTIAL_PROVIDER_LIST, credProviders);
//rc.put(BindingProvider.USERNAME_PROPERTY, USERNAME);
//rc.put(BindingProvider.PASSWORD_PROPERTY, PASSWORD);
Source response = dispatcher.invoke(request);

// Process response
Transformer transformer = TransformerFactory.newInstance().
newTransformer();
StreamResult sysOutStream = new StreamResult(System.out);
System.out.println("Change customer service result:");
transformer.transform(response, sysOutStream);
System.out.println();
}
}

Notice that I have not used any generated XML-to-Java classes for the parameters and return values from within the client or in the service itself. Once compiled and run, the client application works completely as expected, and successfully authenticates with the remote web service using the specified username/password WS-Security credentials.

Here are my observations from the experiment:
  • In the simple example I just used StreamSource for processing the XML request and responses at both ends. However, I could have used other APIs such as DOMSource, JAXBSource, SAXSource, StAXSource from the Java 1.6 standard 'javax.xml.transform' packages instead (and even mixed and matched these for the request and the response).
  • I have used javax.xml.transform.Source for accessing the SOAP request and response messages, instead of javax.xml.soap.SOAPMessage. With Source I can only access the contents of the SOAP Body (refered to as the 'PAYLOAD'). With SOAPMessage, I can choose to access the XML elements of the SOAP Envelope (including SOAP headers) as well (refered to as the 'MESSAGE'). However using SOAPMessage restricts me to only being able to process XML using the W3C DOM API, therefore using Source appeals to me more. When using Source, if I need to access SOAP Headers, I'd probably just use JAX-WS Protocol Handlers anyway, to process these headers before or after my main Provider class is called.
  • I don't need to use WebLogic's WSDLC, JWSC or ClientGen Ant tasks because no "build-time" generation of Java classes (using JAXB) or stubs/skeletons is required. For my service, I could have still optionally used JWSC to generate a deployable WAR file with the appropriate web.xml deployment descriptor auto-generated, but I chose to create these artefacts myself, in a way that I can control, using simple Ant build.xml tasks.
  • To ensure that my JAX-WS service is detected properly by the WebLogic runtime, the key thing I needed to do was create a Servlet definition and mapping entry in my web.xml deployment descriptor for my JWS Provider class (even though a provider class does not actually implement javax.servlet.Servlet). During deployment, the WebLogic Web Service Container automatically detects that the web.xml declared servlet is infact a JWS class and automatically maps the URL specified to an internal WebLogic JAX-WS handling Servlet called "weblogic.wsee.jaxws.JAXWSWebAppServlet". As a result, my transport-protocol agnostic SOAP JWS class is now exposed over HTTP. My web.xml file includes the following:
   <servlet>
<servlet-name>CustomerInfoChangeService</servlet-name>
<servlet-class>test.service.CustomerInfoChangeService</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CustomerInfoChangeService</servlet-name>
<url-pattern>/CustomerInfoChangeService</url-pattern>
</servlet-mapping>
[UPDATE 19-Jun-09: Actually after some further testing, I discovered that if I omit the servlet definition/mapping from my web.xml, the JWS Provider web-app still deploys and runs correctly. WebLogic automatically maps the Provider it discovers on deployment, to a URL which is the Provider class's name (without package name prefix and without .class suffix). This is in-line with the JavaEE 1.5 - Servlet 2.5 spec, where deployment descriptors are now optional. However, it may still be desirable to create a servlet definition/mapping in web.xml to be able to better control the URL of the service).]
  • I would have ideally liked to have included a @RolesAllowed() annotation in my Provider class to help declaratively restrict access to service operations based on role. However, the JAX-WS specification doesn't currently cater for this annotation and WebLogic's JAX-WS implementation does not process this annotation, if its included.
  • In addition to testing authentication using message-level security (eg. a WS-Security user token) I also tested authentication via transport-level security using a client provided HTTP Basic Authentication token (see commented out lines of code in the client app above). In both cases, authentication worked properly, and in my Provider class, when I call context.getUserPrincipal() the proper authenticated principal user object is returned.
  • However, when using context.isUserInRole("Administrators")) in my Provider class, "true" is only returned when using transport-level security, but not when using message-level security. This means that for message-level security, performing programmatic access control is currently limited to checking the user principal object only - the user's roles can't be queried. Here was the security role I defined in web.xml:
    <security-role>
<role-name>Administrators</role-name>
</security-role>
...and here is how I mapped the role to my WebLogic EmbeddedLdap 'Administrators' group in weblogic.xml:
    <security-role-assignment>
<role-name>Administrators</role-name>
<principal-name>Administrators</principal-name>
</security-role-assignment>

So to wrap up, how does JAX-WS in WebLogic 10.3 stack up against my 8 criteria?

Well pretty well actually. I would say 7.75 out of 8. A full score on the first 7 criteria in the list and on the 8th (integration with the host container's Security Framework), just a 1/4 point dropped. This is due to a lack of full flexibility in defining declarative or programmatic access control for a service, when using message-level authentication.


Song for today: Festival by Sigur Rós