Dynamically calling WebServices

[Will Myers]

Hi,
I'm trying to write a simple(!) application that will call a webservice depending on the arguments passed into the main method. The idea is that the app loads an xml file on start-up and uses that to bind to a webservice, something like:

<?xml version="1.0" encoding="UTF-8"?>
<ws-client>
	<webservice name="SwapOrchestrationEngineService">
		<wsdl>http://localhost:7001/WebServices/Service?WSDL</wsdl>
		<method name="startSwapOrcReqsBySql">
			<params>
				<param position="0" type="java.lang.String"/>
				<param position="1" type="java.lang.String"/>

			</params>
		</method>
	</webservice>
	<webservice name="MtmEngineService">
		<wsdl>http://localh:6002/WebServices/EngineService?WSDL</wsdl>
		<method name="startMtmCalculationsBySql">
			<params>
				<param position="0" type="java.lang.String"/>
			</params>
		</method>
	</webservice>
</ws-client>

The xml file needs to be able to change to accomodate new webservices as when they are added so I don't want to have to rebuild everytime.

Is there a way to do this? Everything I've read so far all involve hard coding a wsdl somwhere and generating the endpoints via a build tool....

[William Brogden]

Don't you expect these new web services to publish their WSDL?

Bill

[Will Myers]

Ths WSDLs are published but what I want to do is write the code once and then if I want to add another webservice later just add to the xml not rebuild the app.

[William Brogden]

Many SOAP toolkits provide tools for automatically creating client-side code by reading a WSDL published by a service.

Now, how do you plan to make any use of an added service without additional programming?

Bill

[Will Myers]

ok, I have got it all working. What I did was 'borrow' the code from here http://faq.javaranch.com/view?WebServicesHowTo#saaj-client.

To access a new web service all I do is add it to the config file and then pass the correct params to the executable jar which loads the config file and calls the web service.

[Will Myers]

In case you are interested here's my code:

public class WebService {

    private static final String CONFIG = "wsclient-config.xml";

    public static void main(String[] args) {

	if (args == null || args.length == 0) {
	    System.out.println("Please pass in the following information: \n");
	    System.out.println("webservice name \nmethod name\nfollowed by a list of args in the correct order");
	    return;
	}

	// load the config
	List<Method> methods = loadConfig(args[0]);

	for (Method method : methods) {
	    if (method.getMethodName().equals(args[1])) {
		// start after the webservice and method name
		String[] argArray = new String[args.length - 2];
		for (int i = 2, x = 0; i < args.length; i++, x++) {
		    method.getParams()[x].setValue(args[i]);
		}
		// right, call the web service
		callWebService(method);
	    }
	}

    }

    public static void callWebService(Method method) {

	try {
	    // First create the connection
	    SOAPConnectionFactory soapConnFactory = SOAPConnectionFactory.newInstance();
	    SOAPConnection connection = soapConnFactory.createConnection();

	    // Next, create the actual message
	    MessageFactory messageFactory = MessageFactory.newInstance();
	    SOAPMessage message = messageFactory.createMessage();

	    SOAPPart soapPart = message.getSOAPPart();
	    SOAPEnvelope envelope = soapPart.getEnvelope();


	    // Create and populate the body
	    SOAPBody body = envelope.getBody();

	    // Create the main element and namespace
	    SOAPElement bodyElement = body.addChildElement(envelope.createName(method.getMethodName(), "ns1", "http://www.xyz.com"));
	    // body.addNamespaceDeclaration(prefix, uri)
	    // Add parameters
	    for (int i = 0; i < method.getParams().length; i++) {
		if (method.getParams()[i].getValue() != null) {
		    bodyElement.addChildElement(method.getParams()[i].getName()).addTextNode(method.getParams()[i].getValue());
		}
	    }

	    // Save the message
	    message.saveChanges();

	    // Check the input

	    System.out.println("\nRequest:\n");
	    message.writeTo(System.out);
	    System.out.println();

	    // Send the message and get the reply
	    SOAPMessage reply = connection.call(message, method.getWsdl());

	    System.out.println("\nResponse:\n");
	    reply.writeTo(System.out);
	    System.out.println();


	    connection.close();
	} catch (Exception e) {
	    System.out.println(e);
	}

    }

    public static List<Method> loadConfig(String name) {

	List<Method> method = new ArrayList<Method>();
	String wsdl = null;

	DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();

	try {
	    DocumentBuilder builder = builderFactory.newDocumentBuilder();

	    // look for the config file passed in
	    String config = System.getProperty(CONFIG);

	    if (config == null) {
		config = "wsclient-config.xml";
	    }
	    Document document = builder.parse(new FileInputStream(config));

	    // get the root ie. <ws-client>...
	    Element root = document.getDocumentElement();
	    // now get the <webservice> nodes
	    NodeList nodes = root.getChildNodes();

	    for (int i = 0; i < nodes.getLength(); i++) {
		Node node = nodes.item(i);
		if (node instanceof Element) {
		    Element wsElement = (Element) node;
		    if (wsElement.getAttribute("name") != null && wsElement.getAttribute("name").equals(name)) {

			NodeList wsNodes = wsElement.getChildNodes();
			for (int x = 0; x < wsNodes.getLength(); x++) {
			    Node n = wsNodes.item(x);
			    if (n instanceof Element) {
				Element e = (Element) n;

				if (e.getNodeName().equals("wsdl")) {
				    wsdl = e.getTextContent();
				}
				if (e.getNodeName().equals("method")) {
				    Method m = new Method();
				    m.setWsdl(wsdl);
				    m.setWsName(name);
				    m.setMethodName(e.getAttribute("name"));
				    NodeList mNodes = e.getChildNodes();
				    for (int z = 0; z < mNodes.getLength(); z++) {
					Node n1 = mNodes.item(z);
					if (n1 instanceof Element) {
					    Element e1 = (Element) n1;

					    // param list
					    NodeList pNodes = e1.getChildNodes();
					    List<Param> params = new ArrayList<Param>();
					    for (int y = 0; y < pNodes.getLength(); y++) {
						Node n2 = pNodes.item(y);
						if (n2 instanceof Element) {

						    Element e2 = (Element) n2;
						    Param param = new Param();
						    int position = Integer.parseInt(e2.getAttribute("position"));
						    param.setName(e2.getAttribute("name"));
						    param.setType(e2.getAttribute("type"));
						    param.setPosition(position);
						    params.add(position, param);
						}
					    }
					    m.setParams(params.toArray(new Param[0]));
					}
				    }

				    method.add(m);
				}
			    }
			}
		    }
		}
	    }

	    return method;
	} catch (ParserConfigurationException e) {
	    throw new RuntimeException(e);
	} catch (FileNotFoundException e) {
	    throw new RuntimeException(e);
	} catch (SAXException e) {
	    throw new RuntimeException(e);
	} catch (IOException e) {
	    throw new RuntimeException(e);
	}

    }

}

public class Method {

    private String wsdl;
    private String wsName;
    private String methodName;
    private Param[] params;

....getters and setters
}

public class Param {

    private String name;
    private String type;
    private int position;
    private String value;

...getters and setters
}

and the config file:

<?xml version="1.0" encoding="UTF-8"?>
<ws-client>
	<webservice name="SwapOrchestrationEngineService">
		<wsdl>http://localhost:6002/EssWebServices/SwapOrchestrationEngineService?WSDL</wsdl>
		<method name="startSwapOrcReqsBySql">
			<params>
				<param position="0" type="java.lang.String" name="sql"/>
				<param position="1" type="java.lang.String" name="engineOverrides"/>

			</params>
		</method>
	</webservice>
	<webservice name="MtmEngineService">
		<wsdl>http://localhost:6002/EssWebServices/MtmEngineService?WSDL</wsdl>
		<method name="startMtmCalculationsBySql">
			<params>
				<param position="0" type="java.lang.String" name="sql"/>
			</params>
		</method>
	</webservice>
</ws-client>