Google AppEngine Webservice from Google.

A Great article for creating Google AppEngine -

http://code.google.com/appengine/articles/soap.html

NOTE: I got this code from the SITE above. I just copied the code, so that it is not lost even if the code is removed from Google.
========================================================================
HOW TO: Build a SOAP Server and a SOAP Client on Google App Engine

Mitch Rudominer
February 2011
SDK: 1.4.2
======================================================================

We'll keep things very simple. Our class will only expose two simple methods: sayHello() and sayGoodbye().

package com.example;
public class Greeter {
public String sayHello(String name){
return "Hello, " + name+ "!";
}
public String sayGoodbye(String name){
return "Goodbye, " + name + "!";
}
}


3. Add the javax.jws.WebService annotation to the class, and the javax.jws.WebMethod annotation to each of the methods you wish to expose through SOAP.

package com.example;
import javax.jws.WebMethod;
import javax.jws.WebService;

@WebService
public class Greeter {
@WebMethod
public String sayHello(String name){
return "Hello, " + name+ "!";
}
@WebMethod
public String sayGoodbye(String name){
return "Goodbye, " + name + "!";
}
}

As of version 1.4.2 Google App Engine does not support the use of JAX-WS in a SOAP server. (It is supported in a SOAP client.) As we'll see below, in order to complete the SOAP server we will have to directly use javax.xml.soap and JAX-B. So then why did we bother to add the JAX-WS annotations? As we'll see, we can take advantage of the the JAX-WS tool wsgen to generate a WSDL file and the JAX-B POJOs that will be of use to us in our SOAP server. The annotations are needed for that reason.

4. Run wsgen on the annoted class. This tool is now included in the JDK. My JDK includes the version from JAX-WS RI 2.1.6. (You can discover the version by typing wsgen -version.) Because wsgen has several command-line arguments, I have written a Linux shell script called runwsgen.sh to execute it. If you are not using Linux, you will have to translate this script to your OS scripting language. Place the following script in the root directory of the project (i.e. the parent directory of war and src) and execute it from there.

class=com.example.Greeter
clpth='./war/WEB-INF/classes'
resourcedir='./war'
outsourcedir='./src'
outdir='./war/WEB-INF/classes'
wsgen -cp "$clpth" -wsdl -keep -r "$resourcedir" -d "$outdir" -s "$outsourcedir" $class

I'll now go through the results of executing this script while at the same time explaining what each of the arguments mean.

* class=com.example.Greeter – defines the main argument of the wsgen command to be our annotated class.
* clpth='./war/WEB-INF/classes' – tells wsgen where to find com/example/Greeter.class. WSGEN does not operate on Java source files but rather on Java class files.
* resourcedir='./war' – tells wsgen where to put the generated WSDL file GreeterService.wsdl and the associated XML schema document GreeterService_schema1.xsd. Notice the command line argument -wsdl was used to tell wsgen to generate a WSDL. I put the two files in the war directory because I want them to be included in the war file to be deployed on App Engine. Putting the files in that directory allows the SOAP client to access them from there.

* outsourcedir='./src' – tells wsgen where to put the generated Java source files. Notice the command line argument -keep, which tells wsgen to keep the generated Java source files. WSGEN generated four Java classes in the package com.example.jaxws:
1. SayGoodbye
2. SayGoodbyeResponse
3. SayHello
4. SayHelloResponse

These are POJOs with JAX-B annotations corresponding to the request and response for each of the methods in Greeter.java that we annoted with @WebMethod. I chose to put the generated source files into the src directory so that they would become part of the source code for my project.



* outdir='./war/WEB-INF/classes.' – tells wsgen where to put the generated class files. Actually I don't need the generated class files at all because Eclipse will compile the generated Java source files for me. But I chose to let wsgen put the class files into their proper place in WEB-INF/classes anyway.

5. Put the SOAP request URL into the WSDL file. Take a look at the generated GreeterService.wsdl file. I'm not going to explain the contents of this file in any detail. The primary thing to know about the WSDL file is that it, along with the associated XML Schema document, describes the XML that must be sent in a SOAP request and the XML that should be expected in a SOAP response. Another role of the WSDL is to specify the URL to where SOAP requests should be sent. Notice that in the generated WSDL file the URL is represented by a place-holder: 'REPLACE_WITH_ACTUAL_URL'. Replace this string with the actual URL of your SOAP server. We are going to use the HelloSoapServerServlet that was automatically generated by the Google Eclipse plugin to serve SOAP requests. In the automatically generated web.xml file this servlet has been mapped to the URL path /hellosoapserver. We are going to deploy our application to App Engine running on appspot.com. So the actual URL that should go into the WSDL file is .appspot.com/hellosoapserver. For example if our app ID were greeter-soap-example then the actual URL would be http://greeter-soap-example .appspot.com/hellosoapserver.







6. Write an adapter class to adapt between a signature that uses the JAX-B POJOs that were generated by wsgen and the signature of your real business logic methods. In our case we need to adapt between one signature that uses SayHello, SayHelloResponse, SayGoodbye, and SayGoodbyeResponse—to the signature of Greeter.java that takes Strings as inputs and yields Strings as outputs. The class GreeterAdapter does that for us. This step would not be necessary if JAX-WS for SOAP servers were supported on App Engine, but it currently is not. Here is the code for GreeterAdapter. (We have not included any comments for the sake of brevity.)

package com.example;
import com.example.jaxws.SayGoodbye;
import com.example.jaxws.SayGoodbyeResponse;
import com.example.jaxws.SayHello;
import com.example.jaxws.SayHelloResponse;
public class GreeterAdapter {
private Greeter greeter = new Greeter();

public SayHelloResponse sayHello(SayHello request){
String name = request.getArg0();
String responseGreeting = greeter.sayHello(name);
SayHelloResponse response = new SayHelloResponse();
response.setReturn(responseGreeting);
return response;
}

public SayGoodbyeResponse sayGoodbye(SayGoodbye request){
String name = request.getArg0();
String responseGreeting = greeter.sayGoodbye(name);
SayGoodbyeResponse response = new SayGoodbyeResponse();
response.setReturn(responseGreeting);
return response;
}
}

7. Write a SOAPHandler class that implements the following method:

public SOAPMessage handleSOAPRequest(SOAPMessage request);

SOAPMessage is a class from javax.xml.SOAP that represents a SOAP request or response message. The purpose of handleSOAPRequest() is to accept a SOAPMessage representing a request for one of the methods annoted with @WebMethod, either sayHello() or sayGoodbye(), use JAX-B to generate the appropriate POJO, either a SayHello object or a SayGoodbye object, and forward the call on to the appropriate method in GreeterAdapter, either sayHello() or sayGoodbye(). Again, this step would not be necessary if JAX-WS on the server side was supported on App Engine.

In order to be able to distinguish whether the request is for sayHello() or sayGoodbye(), SOAPHandler will need to make use of the XML element names of the SOAP elements corresponding to each of these methods. These names may be found in one of two places. Firstly, the names may be found in the JAX-B annotations of the generated POJO classes. For example if we look in SayHello.java we find the following annotation:

@XmlRootElement(name = "sayHello", namespace = "http://example.com/").

And if we look in SayGoodby.java we find the following annotation:

XmlRootElement(name = "sayGoodbye", namespace = "http://example.com/").

The second place where the XML element names may be found is in the generated XSD file. If we look in GreeterService_schema1.xsd we see:





Here is the code for GreeterSOAPHandler.java. Again there are no comments for conciseness.

package com.example;
import java.util.Iterator;
import javax.xml.bind.JAXB;
import javax.xml.namespace.QName;
import javax.xml.soap.MessageFactory;
import javax.xml.soap.SAAJResult;
import javax.xml.soap.SOAPBody;
import javax.xml.soap.SOAPElement;
import javax.xml.soap.SOAPException;
import javax.xml.soap.SOAPFault;
import javax.xml.soap.SOAPMessage;
import javax.xml.transform.dom.DOMSource;
import com.example.jaxws.SayGoodbye;
import com.example.jaxws.SayHello;

public class GreeterSOAPHandler {

private static final String NAMESPACE_URI = "http://example.com/";
private static final QName SAY_HELLO_QNAME = new QName(NAMESPACE_URI, "sayHello");
private static final QName SAY_GOODBYE_QNAME = new QName(NAMESPACE_URI, "sayGoodbye");

private MessageFactory messageFactory;
private GreeterAdapter greeterAdapter;

public GreeterSOAPHandler() throws SOAPException {
messageFactory = MessageFactory.newInstance();
greeterAdapter = new GreeterAdapter();
}

public SOAPMessage handleSOAPRequest(SOAPMessage request) throws SOAPException {
SOAPBody soapBody = request.getSOAPBody();
Iterator iterator = soapBody.getChildElements();
Object responsePojo = null;
while (iterator.hasNext()) {
Object next = iterator.next();
if (next instanceof SOAPElement) {
SOAPElement soapElement = (SOAPElement) next;
QName qname = soapElement.getElementQName();
if (SAY_HELLO_QNAME.equals(qname)) {
responsePojo = handleSayHelloRequest(soapElement);
break;
} else if (SAY_GOODBYE_QNAME.equals(qname)) {
responsePojo = handleSayGoodbyeRequest(soapElement);
break;
}
}
}
SOAPMessage soapResponse = messageFactory.createMessage();
soapBody = soapResponse.getSOAPBody();
if (responsePojo != null) {
JAXB.marshal(responsePojo, new SAAJResult(soapBody));
} else {
SOAPFault fault = soapBody.addFault();
fault.setFaultString("Unrecognized SOAP request.");
}
return soapResponse;
}

private Object handleSayHelloRequest(SOAPElement soapElement) {
SayHello sayHelloRequest = JAXB.unmarshal(new DOMSource(soapElement), SayHello.class);
return greeterAdapter.sayHello(sayHelloRequest);
}

private Object handleSayGoodbyeRequest(SOAPElement soapElement) {
SayGoodbye sayGoodbyeRequest =
JAXB.unmarshal(new DOMSource(soapElement), SayGoodbye.class);
return greeterAdapter.sayGoodbye(sayGoodbyeRequest);
}
}

8. Write a doPost(HttpServletRequest req, HttpServletResponse resp) method in HelloSOAPServerServlet.java. This method will do the following things:

1. Construct a SOAPMessage from the XML in the HTTP request.
2. Pass the SOAPMessage to handleSOAPRequest(SOAPMessage request) and obtain a SOAPMessage response.
3. Serialize the SOAPMessage response to the HTTP response

Here is the code for HelloSOAPServerServlet.java.

package com.example;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.StringTokenizer;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.soap.MessageFactory;
import javax.xml.soap.MimeHeaders;
import javax.xml.soap.SOAPException;
import javax.xml.soap.SOAPMessage;

@SuppressWarnings("serial")
public class HelloSOAPServerServlet extends HttpServlet {

static MessageFactory messageFactory;
static GreeterSOAPHandler soapHandler;

static {
try {
messageFactory = MessageFactory.newInstance();
soapHandler = new GreeterSOAPHandler();
} catch (Exception ex) {
throw new RuntimeException(ex);
}
}


@Override
public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
try {
// Get all the headers from the HTTP request
MimeHeaders headers = getHeaders(req);

// Construct a SOAPMessage from the XML in the request body
InputStream is = req.getInputStream();
SOAPMessage soapRequest = messageFactory.createMessage(headers, is);

// Handle soapReqest
SOAPMessage soapResponse = soapHandler.handleSOAPRequest(soapRequest);

// Write to HttpServeltResponse
resp.setStatus(HttpServletResponse.SC_OK);
resp.setContentType("text/xml;charset=\"utf-8\"");
OutputStream os = resp.getOutputStream();
soapResponse.writeTo(os);
os.flush();
} catch (SOAPException e) {
throw new IOException("Exception while creating SOAP message.", e);
}
}

@SuppressWarnings("unchecked")
static MimeHeaders getHeaders(HttpServletRequest req) {
Enumeration headerNames = req.getHeaderNames();
MimeHeaders headers = new MimeHeaders();
while (headerNames.hasMoreElements()) {
String headerName = (String) headerNames.nextElement();
String headerValue = req.getHeader(headerName);
StringTokenizer values = new StringTokenizer(headerValue, ",");
while (values.hasMoreTokens()) {
headers.addHeader(headerName, values.nextToken().trim());
}
}
return headers;
}
}