AwsHandlerResolver.java

package com.nash.tradeinbooks.webservice.client;

import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
import java.util.Set;
import java.util.TimeZone;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.namespace.QName;
import javax.xml.soap.SOAPBody;
import javax.xml.soap.SOAPException;
import javax.xml.soap.SOAPMessage;
import javax.xml.ws.handler.Handler;
import javax.xml.ws.handler.HandlerResolver;
import javax.xml.ws.handler.MessageContext;
import javax.xml.ws.handler.PortInfo;
import javax.xml.ws.handler.soap.SOAPHandler;
import javax.xml.ws.handler.soap.SOAPMessageContext;

import org.apache.commons.codec.binary.Base64;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

public class AwsHandlerResolver implements HandlerResolver {
	private String awsSecretKey;

	public AwsHandlerResolver(String awsSecretKey) {
		this.awsSecretKey = awsSecretKey;
	}

	@SuppressWarnings("unchecked")
	public List<Handler> getHandlerChain(PortInfo portInfo) {
       List<Handler> handlerChain = new ArrayList<Handler>();

       QName serviceQName = portInfo.getServiceName();
       if(serviceQName.getLocalPart().equals("AWSECommerceService")) {
    	   handlerChain.add(new AwsHandler(awsSecretKey));
       }

       return handlerChain;
	}

	private static class AwsHandler implements SOAPHandler<SOAPMessageContext> {
        private byte[] secretBytes;

        public AwsHandler(String awsSecretKey) {
			secretBytes = stringToUtf8(awsSecretKey);
		}

		public void close(MessageContext messagecontext) {
		}

		public Set<QName> getHeaders() {
		    return null;
		}

		public boolean handleFault(SOAPMessageContext messagecontext) {
		    return true;
		}

		public boolean handleMessage(SOAPMessageContext messagecontext) {
			Boolean outbound = (Boolean) messagecontext.get(MessageContext.MESSAGE_OUTBOUND_PROPERTY);
			if (outbound) {
				try {
			    	SOAPMessage soapMessage = messagecontext.getMessage();
			    	SOAPBody soapBody = soapMessage.getSOAPBody();
			    	Node firstChild = soapBody.getFirstChild();

			        String timeStamp = getTimestamp();
			    	String signature = getSignature(firstChild.getLocalName(), timeStamp, secretBytes);

			    	appendTextElement(firstChild, "Signature", signature);
			    	appendTextElement(firstChild, "Timestamp", timeStamp);
				} catch(SOAPException se) {
					throw new RuntimeException("SOAPException was thrown.", se);
				}
		    }
		    return true;
		}

		private String getSignature(String operation, String timeStamp, byte[] secretBytes) {
			try {
				String toSign = operation + timeStamp;
				byte[] toSignBytes = stringToUtf8(toSign);

				Mac signer = Mac.getInstance("HmacSHA256");
				SecretKeySpec keySpec = new SecretKeySpec(secretBytes, "HmacSHA256");

				signer.init(keySpec);
				signer.update(toSignBytes);
				byte[] signBytes = signer.doFinal();

				String signature = new String(Base64.encodeBase64(signBytes));
				return signature;
			} catch(NoSuchAlgorithmException nsae) {
				throw new RuntimeException("NoSuchAlgorithmException was thrown.", nsae);
			} catch(InvalidKeyException ike) {
				throw new RuntimeException("InvalidKeyException was thrown.", ike);
			}
	    }

		private String getTimestamp() {
			Calendar calendar = Calendar.getInstance();
			SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
			dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
			return dateFormat.format(calendar.getTime());
	    }

		private byte[] stringToUtf8(String source) {
			try {
				return source.getBytes("UTF-8");
			} catch (UnsupportedEncodingException e) {
				// This will never happen.  UTF-8 is always available.
				throw new RuntimeException("getBytes threw an UnsupportedEncodingException", e);
			}
		}

		private void appendTextElement(Node node, String elementName, String elementText) {
	    	Element element = node.getOwnerDocument().createElement(elementName);
	    	element.setTextContent(elementText);
	    	node.appendChild(element);
		}
	}
}