xdocs/0_94/transport_howto.html - axis-axis2-java-core - Git at Google

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 <h1>How to write your own Axis2 transport</h1>

 <h2>Prologue</h2>

 <p>To stop you from reinventing the wheel I will quickly list the transports
 that are already supported in Axis2 with a small description before we get
 started.</p>

 <p></p>
 <ul>
   <li><b>HTTP</b> - In the HTTP transport, the transport Listener is a
     Servlet or a Simple HTTP server provided by Axis2. The transport Sender
     uses sockets to connect and send the SOAP Message. Currently we have the
     commons-httpclient based HTTP Transport sender as the default
   transport.</li>
   <li><b>TCP</b> This is the most simple transport, but needs addressing
     support to be functional.</li>
   <li><b>SMTP</b> This can work off a single email account or a mailserver.
     The Mail Transport Receiver is a tread that checks for emails in fixed
     time intervals.</li>
 </ul>

 <p>To understand the rest of this document you will need some understanding
 of the Architecture of Axis2. Therefor if you are not familiar with the
 Architecture of Axis2 you will have to first read the <a
 href="Axis2ArchitectureGuide.html">Axis2 Architecture Guide</a> before you
 read any further.</p>

 <h2>Introduction</h2>

 <p>Broadly speaking a transport inside Axis2 can be classified as a way of
 getting a messages that arrive though some channel into the Axis2 engine. The
 core of Axis2 is transport independent. All data that is transport
 specific is striped out of the incoming message and inserted into the
 MessageContext and on the outgoing message all transport specific information
 like headers are added and sent.</p>

 <p>To write your own transport you will need to primarily write two classes,
 one is the TransportSender and the other is the TransportReceiver. To
 register a transport with Axis2 you will need to put two entries in the
 axis2.xml file. One for the transport receiver and the other for the
 transport sender. We will walk though the process of adding the entries in
 the relevent sections.</p>

 <h2>Transport Receiver</h2>

 <p>Any message that is comming into Axis2 needs to go though a transport
 receiver. All information about how the message is received at the Axis2
 server from the wire [or by snail mail for that matter:)] is isolated inside
 the transport receiver. It extracts the data that is coming on the wire and
 transforms it into a state that the Axis2 server understands.</p>

 <p>So now that we have some background information about how transports work
 inside Axis2 with out further delay why don't we dive into some coding and
 start building out own transport.</p>

 <p></p>

 <p>To get things stared you will first need to extend from the
 org.apache.Axis2.transport.TransportListener class and write you own
 transport listener. To create an engine to process the MessageContext we need
 a configuration context. The following code fragment will do this. This
 should ideally be only done once for the lifetime of the Transport
 receiver.</p>

 <p><source>
 <pre>try {
         //Create a factory
         ConfigurationContextFactory factory = new ConfigurationContextFactory();
         //Use the factory and an Axis2 repository to create a new Configuration Context
         configurationContext = factory.buildConfigurationContext(repository_directory);
 } catch (Exception e) {
         log.info(e.getMessage());
 }</pre>
 </source>
 </p>
 <p>Now we need some kind of a listener to listen to the requests that come
 in. This you will need to implement according to the transport that you are
 trying to build. After a message is received at the receiver you can use the
 following code to process the request and then forward the message context to
 the engine using thing the engine.receive(msgContext) method.{Following code snippet extracted from MailListener as an example}</p>
 <source><pre>AxisEngine engine = new AxisEngine(configurationContext);
 MessageContext msgContext = null;
 // create and initialize a message context
 try {
         TransportInDescription transportIn =
                 reg.getAxisConfiguration().getTransportIn(new QName(Constants.TRANSPORT_NAME));
         TransportOutDescription transportOut =
                 reg.getAxisConfiguration().getTransportOut(new QName(Constants.TRANSPORT_NAME));
         if (transportIn != null &amp;&amp; transportOut != null) {
                 //create Message Context
                 msgContext = new MessageContext(configurationContext, transportIn, transportOut);
                 msgContext.setServerSide(true);
                 msgContext.setProperty(MailSrvConstants.CONTENT_TYPE, message.getContentType());
                 msgContext.setProperty(MessageContext.CHARACTER_SET_ENCODING, message.getEncoding());

                 String soapAction = message.getSOAPActionHeader();
                 msgContext.setWSAAction(soapAction);
                 msgContext.setSoapAction(soapAction);

                 // Here we are trying to set the reply to if it is present in the transport information.
                 msgContext.setReplyTo(new EndpointReference(message.getReplyTo());

                 //Create the SOAP Message -- This code in from the mail transport and will change depending
                 //on how the data is handled in each transport.
                 ByteArrayInputStream bais = new ByteArrayInputStream(message.getContent().toString().getBytes());
                 XMLStreamReader reader = XMLInputFactory.newInstance().createXMLStreamReader(bais);

                 String soapNamespaceURI = "";
                 if(message.getContentType().indexOf(SOAP12Constants.SOAP_12_CONTENT_TYPE) &gt; -1){
                         soapNamespaceURI = SOAP12Constants.SOAP_ENVELOPE_NAMESPACE_URI;
                 }else if(message.getContentType().indexOf(SOAP11Constants.SOAP_11_CONTENT_TYPE) &gt; -1){
                         soapNamespaceURI = SOAP11Constants.SOAP_ENVELOPE_NAMESPACE_URI;
                 }

                 StAXBuilder builder = new StAXSOAPModelBuilder(reader, soapNamespaceURI);

                 SOAPEnvelope envelope = (SOAPEnvelope) builder.getDocumentElement();
                 msgContext.setEnvelope(envelope);
                 if (envelope.getBody().hasFault()) {
                         engine.receiveFault(msgContext);
                 } else {
                         engine.receive(msgContext);
                 }
         } else {
                 throw new AxisFault(Messages.getMessage("unknownTransport",Constants.TRANSPORT_NAME));
         }

 } catch (Exception e) {
         try {
                 if (msgContext != null) {
                         MessageContext faultContext = engine.createFaultMessageContext(msgContext, e);
                         engine.sendFault(faultContext);
                 } else {
                         log.error(e);
                 }
         } catch (AxisFault e1) {
                 log.error(e);
         }
 }</pre>
 </source>
 <p>Now we have the coding in place and we need to let Axis2 know about our
 new transport receiver. How we do this is by addind an entry into the
 axis2.xml file. If you need to pass any properties for the transport to
 operate it can also be done through the axis2.xml file.</p>
 <source><pre>   &lt;transportReceiver name="TRANSPORT_NAME" class="org.apache.Axis2.transport.TRANSPORT_NAME.TRANSPORT_LISTNER_CLASS"&gt;
         &lt;parameter name="PROPERTY_NAME" locked="false"&gt;PROPERTY_VALUE&lt;/parameter&gt;
         &lt;parameter name="PROPERTY_NAME_2" locked="false"&gt;PROPERTY_VALUE_2&lt;/parameter&gt;
   &lt;/transportReceiver&gt;
   </pre>
 </source>
 <p>Using a code fragment like
 Utils.getParameterValue(transportOut.getParameter(MailSrvConstants.SMTP_USER))
 we can extract the parameters that we insert into the axis2.xml file.</p>

 <p>So as you can see getting a new transport receiver up and running is a
 task that requires very little effort.</p>

 <h2>Transport Sender</h2>

 <p>Any message that is to be sent out from Axis2 is sent through the
 Transport Sender. The Transport Sender needs to be extended from the
 org.apache.Axis2.transport.AbstractTransportSender class.</p>

 <p>The following bit of code from the abstract transport sender will call the
 Transport Sender that you wrote.</p>
 <source><pre>// If an EPR is present then the message is going on a diffrent channel.
 if (epr != null) {
         out = openTheConnection(epr, msgContext);
         OutputStream newOut = startSendWithToAddress(msgContext, out);
         if (newOut != null) {
                 out = newOut;
         }
         writeMessage(msgContext, out);
         finalizeSendWithToAddress(msgContext, out);
         } else {
         out = (OutputStream) msgContext.getProperty(MessageContext.TRANSPORT_OUT);
         if (out != null) {
                 startSendWithOutputStreamFromIncomingConnection(msgContext, out);
                 writeMessage(msgContext, out);
                 finalizeSendWithOutputStreamFromIncomingConnection(msgContext, out);
         } else {
                 throw new AxisFault(
                         "Both the TO and Property MessageContext.TRANSPORT_WRITER is Null, No way to send response.");
         }
 }</pre>
 </source>
 <p>So depending on whether your transport is using the same channel to send
 the responce or using a different channel you will need to implement a
 sub-set of the methods from the abstract class.</p>

 <p>After implementing the necessary methods you can let Axis2 know about your
 new transport sender by adding an entry to the axis2.xml file like you did
 for the Transport Receiver.</p>
 <source><pre>   &lt;transportSender name="TRANSPORT_NAME" class="org.apache.Axis2.transport.TRANSPORT_NAME.TRANSPORT_SENDER_CLASS"&gt;
         &lt;parameter name="PROPERTY_NAME" locked="false"&gt;PROPERTY_VALUE&lt;/parameter&gt;
         &lt;parameter name="PROPERTY_NAME_2" locked="false"&gt;PROPERTY_VALUE_2&lt;/parameter&gt;
   &lt;/transportSender&gt;
   </pre>
 </source>
 <p>Have a look at org.apache.Axis2.transport.mail.MailTransportSender for a
 very simple Transport Sender. Also have a look at
 org.apache.Axis2.transport.http.CommonsHTTPTransportSender which is used to
 send HTTP responses.</p>

 <p>Once we have written our transport receiver and our transport sender, and
 inserted the needed entries into the axis2.xml file we are done. It is as
 simple as that. :-)</p>
 </body>
 </html>
	<html>
	<head>
	<meta http-equiv="Content-Type" content="">
	<title></title>
	</head>

	<body>
	<h1>How to write your own Axis2 transport</h1>

	<h2>Prologue</h2>

	<p>To stop you from reinventing the wheel I will quickly list the transports
	that are already supported in Axis2 with a small description before we get
	started.</p>

	<p></p>
	<ul>
	<li><b>HTTP</b> - In the HTTP transport, the transport Listener is a
	Servlet or a Simple HTTP server provided by Axis2. The transport Sender
	uses sockets to connect and send the SOAP Message. Currently we have the
	commons-httpclient based HTTP Transport sender as the default
	transport.</li>
	<li><b>TCP</b> This is the most simple transport, but needs addressing
	support to be functional.</li>
	<li><b>SMTP</b> This can work off a single email account or a mailserver.
	The Mail Transport Receiver is a tread that checks for emails in fixed
	time intervals.</li>
	</ul>

	<p>To understand the rest of this document you will need some understanding
	of the Architecture of Axis2. Therefor if you are not familiar with the
	Architecture of Axis2 you will have to first read the <a
	href="Axis2ArchitectureGuide.html">Axis2 Architecture Guide</a> before you
	read any further.</p>

	<h2>Introduction</h2>

	<p>Broadly speaking a transport inside Axis2 can be classified as a way of
	getting a messages that arrive though some channel into the Axis2 engine. The
	core of Axis2 is transport independent. All data that is transport
	specific is striped out of the incoming message and inserted into the
	MessageContext and on the outgoing message all transport specific information
	like headers are added and sent.</p>

	<p>To write your own transport you will need to primarily write two classes,
	one is the TransportSender and the other is the TransportReceiver. To
	register a transport with Axis2 you will need to put two entries in the
	axis2.xml file. One for the transport receiver and the other for the
	transport sender. We will walk though the process of adding the entries in
	the relevent sections.</p>

	<h2>Transport Receiver</h2>

	<p>Any message that is comming into Axis2 needs to go though a transport
	receiver. All information about how the message is received at the Axis2
	server from the wire [or by snail mail for that matter:)] is isolated inside
	the transport receiver. It extracts the data that is coming on the wire and
	transforms it into a state that the Axis2 server understands.</p>

	<p>So now that we have some background information about how transports work
	inside Axis2 with out further delay why don't we dive into some coding and
	start building out own transport.</p>

	<p></p>

	<p>To get things stared you will first need to extend from the
	org.apache.Axis2.transport.TransportListener class and write you own
	transport listener. To create an engine to process the MessageContext we need
	a configuration context. The following code fragment will do this. This
	should ideally be only done once for the lifetime of the Transport
	receiver.</p>

	<p><source>
	<pre>try {
	//Create a factory
	ConfigurationContextFactory factory = new ConfigurationContextFactory();
	//Use the factory and an Axis2 repository to create a new Configuration Context
	configurationContext = factory.buildConfigurationContext(repository_directory);
	} catch (Exception e) {
	log.info(e.getMessage());
	}</pre>
	</source>
	</p>
	<p>Now we need some kind of a listener to listen to the requests that come
	in. This you will need to implement according to the transport that you are
	trying to build. After a message is received at the receiver you can use the
	following code to process the request and then forward the message context to
	the engine using thing the engine.receive(msgContext) method.{Following code snippet extracted from MailListener as an example}</p>
	<source><pre>AxisEngine engine = new AxisEngine(configurationContext);
	MessageContext msgContext = null;
	// create and initialize a message context
	try {
	TransportInDescription transportIn =
	reg.getAxisConfiguration().getTransportIn(new QName(Constants.TRANSPORT_NAME));
	TransportOutDescription transportOut =
	reg.getAxisConfiguration().getTransportOut(new QName(Constants.TRANSPORT_NAME));
	if (transportIn != null && transportOut != null) {
	//create Message Context
	msgContext = new MessageContext(configurationContext, transportIn, transportOut);
	msgContext.setServerSide(true);
	msgContext.setProperty(MailSrvConstants.CONTENT_TYPE, message.getContentType());
	msgContext.setProperty(MessageContext.CHARACTER_SET_ENCODING, message.getEncoding());

	String soapAction = message.getSOAPActionHeader();
	msgContext.setWSAAction(soapAction);
	msgContext.setSoapAction(soapAction);

	// Here we are trying to set the reply to if it is present in the transport information.
	msgContext.setReplyTo(new EndpointReference(message.getReplyTo());

	//Create the SOAP Message -- This code in from the mail transport and will change depending
	//on how the data is handled in each transport.
	ByteArrayInputStream bais = new ByteArrayInputStream(message.getContent().toString().getBytes());
	XMLStreamReader reader = XMLInputFactory.newInstance().createXMLStreamReader(bais);

	String soapNamespaceURI = "";
	if(message.getContentType().indexOf(SOAP12Constants.SOAP_12_CONTENT_TYPE) > -1){
	soapNamespaceURI = SOAP12Constants.SOAP_ENVELOPE_NAMESPACE_URI;
	}else if(message.getContentType().indexOf(SOAP11Constants.SOAP_11_CONTENT_TYPE) > -1){
	soapNamespaceURI = SOAP11Constants.SOAP_ENVELOPE_NAMESPACE_URI;
	}

	StAXBuilder builder = new StAXSOAPModelBuilder(reader, soapNamespaceURI);

	SOAPEnvelope envelope = (SOAPEnvelope) builder.getDocumentElement();
	msgContext.setEnvelope(envelope);
	if (envelope.getBody().hasFault()) {
	engine.receiveFault(msgContext);
	} else {
	engine.receive(msgContext);
	}
	} else {
	throw new AxisFault(Messages.getMessage("unknownTransport",Constants.TRANSPORT_NAME));
	}

	} catch (Exception e) {
	try {
	if (msgContext != null) {
	MessageContext faultContext = engine.createFaultMessageContext(msgContext, e);
	engine.sendFault(faultContext);
	} else {
	log.error(e);
	}
	} catch (AxisFault e1) {
	log.error(e);
	}
	}</pre>
	</source>
	<p>Now we have the coding in place and we need to let Axis2 know about our
	new transport receiver. How we do this is by addind an entry into the
	axis2.xml file. If you need to pass any properties for the transport to
	operate it can also be done through the axis2.xml file.</p>
	<source><pre> <transportReceiver name="TRANSPORT_NAME" class="org.apache.Axis2.transport.TRANSPORT_NAME.TRANSPORT_LISTNER_CLASS">
	<parameter name="PROPERTY_NAME" locked="false">PROPERTY_VALUE</parameter>
	<parameter name="PROPERTY_NAME_2" locked="false">PROPERTY_VALUE_2</parameter>
	</transportReceiver>
	</pre>
	</source>
	<p>Using a code fragment like
	Utils.getParameterValue(transportOut.getParameter(MailSrvConstants.SMTP_USER))
	we can extract the parameters that we insert into the axis2.xml file.</p>

	<p>So as you can see getting a new transport receiver up and running is a
	task that requires very little effort.</p>

	<h2>Transport Sender</h2>

	<p>Any message that is to be sent out from Axis2 is sent through the
	Transport Sender. The Transport Sender needs to be extended from the
	org.apache.Axis2.transport.AbstractTransportSender class.</p>

	<p>The following bit of code from the abstract transport sender will call the
	Transport Sender that you wrote.</p>
	<source><pre>// If an EPR is present then the message is going on a diffrent channel.
	if (epr != null) {
	out = openTheConnection(epr, msgContext);
	OutputStream newOut = startSendWithToAddress(msgContext, out);
	if (newOut != null) {
	out = newOut;
	}
	writeMessage(msgContext, out);
	finalizeSendWithToAddress(msgContext, out);
	} else {
	out = (OutputStream) msgContext.getProperty(MessageContext.TRANSPORT_OUT);
	if (out != null) {
	startSendWithOutputStreamFromIncomingConnection(msgContext, out);
	writeMessage(msgContext, out);
	finalizeSendWithOutputStreamFromIncomingConnection(msgContext, out);
	} else {
	throw new AxisFault(
	"Both the TO and Property MessageContext.TRANSPORT_WRITER is Null, No way to send response.");
	}
	}</pre>
	</source>
	<p>So depending on whether your transport is using the same channel to send
	the responce or using a different channel you will need to implement a
	sub-set of the methods from the abstract class.</p>

	<p>After implementing the necessary methods you can let Axis2 know about your
	new transport sender by adding an entry to the axis2.xml file like you did
	for the Transport Receiver.</p>
	<source><pre> <transportSender name="TRANSPORT_NAME" class="org.apache.Axis2.transport.TRANSPORT_NAME.TRANSPORT_SENDER_CLASS">
	<parameter name="PROPERTY_NAME" locked="false">PROPERTY_VALUE</parameter>
	<parameter name="PROPERTY_NAME_2" locked="false">PROPERTY_VALUE_2</parameter>
	</transportSender>
	</pre>
	</source>
	<p>Have a look at org.apache.Axis2.transport.mail.MailTransportSender for a
	very simple Transport Sender. Also have a look at
	org.apache.Axis2.transport.http.CommonsHTTPTransportSender which is used to
	send HTTP responses.</p>

	<p>Once we have written our transport receiver and our transport sender, and
	inserted the needed entries into the axis2.xml file we are done. It is as
	simple as that. :-)</p>
	</body>
	</html>