Make Perl speak JMS (3)

Finally I will implement a Perl web service client. The tool I pick is SOAP::Lite (v0.55).

SOAP::Lite comes with a handy tool similar to wsdl2java called stubmaker. Run our WSDL through the tool and it generates a Perl module MessageRoutingService.pm. This module wrapps the call to the single RouteMessage API defined in the WSDL. Following code shows how to use this module:

my @dest = ( 
 SOAP::Data->name(protocol=>'jms'),
 SOAP::Data->name(category=>'queue'),
 SOAP::Data->name(server=>'my_jms_server'),
 SOAP::Data->name(port=>'7222'),
 SOAP::Data->name(target=>'my_queue'),
 SOAP::Data->name(user=>'user_a'),
 SOAP::Data->name(password=>'password_a') );

my @content = (SOAP::Data->name(content=>'Hello World'));
my @route_request = (SOAP::Data->name(destination=>\SOAP::Data->value(@dest)),
 SOAP::Data->name(request=>\SOAP::Data->value(@content)));

my $result = MessageRoutingService->RouteMessage(@route_request);
print $result->{content};

Sounds easy? There is a small catch here. The generated stub module needs a little tweak. Somehow it misses the URI namespace for the top method wrapper element .

my %methods = (
 RouteMessage => {
  endpoint => 'http://localhost:8080/common_router',
  soapaction => 'http://www.simple.code/router/action/RouteMessage',
  uri => '',
  parameters => [
   SOAP::Data->new(name => 'document', type => '', attr => {}),
  ],
 },
);

Without the URI, the method in the request looks like

 <RouteMessage xmlns="">

which is obviously wrong. After I manually add the URI in the stub to make it look like

my %methods = (
 RouteMessage => {
  endpoint => 'http://localhost:8080/common_router',
   soapaction => 'http://www.simple.code/router/action/RouteMessage',
   uri => 'http://www.simple.code/router/action/RouteMessage',
   parameters => [
    SOAP::Data->new(name => 'document', type => '', attr => {}),
   ],
  },
);

Now the request becomes

<RouteMessage xmlns="http://www.simple.code/router/action/RouteMessage">

and it is happily accpted by the Java Axis server.

Make Perl speak JMS (2)

Now the WSDL is ready, I can start to implement the WS server in Java. The tool of choice is Apache Axis 1.2.1.

With the wsdl2java tool, it is straight forward to generate the codes from the WSDL file. Because we will only use the server code, so we only need to change one class HttpBindingImpl.java.

private MessageRouter mRouter = new MessageRouter();

public code.simple.www.router._2005._11._7.RouteResponseType routeMessage
 (code.simple.www.router._2005._11._7.RouteRequestType document)
 throws java.rmi.RemoteException
{
 try
 {
  return mRouter.routeMessage(document);
 }
 catch(Exception ee)
 {
  throw new RemoteException("Failed to route the message", ee);
 }
}

Here we just forward the request to the MessageRouter class and let it handle the details.

Axis provides several different ways to deploy the web services. The most convenient way is to use JWS file but it has certain limitations. Here I choose to use the WSDD file and embed the Axis engine in the Tomcat servlet container. As of how to integrate Axis with a servlet container, I could not find a good documentation. Eventually I figured it out and here is the code

protected void doPost(HttpServletRequest req, HttpServletResponse resp) 
 throws ServletException, IOException
{
 PrintWriter pw = null;
 try
 {
  pw = resp.getWriter();
  resp.setContentType(CONTENT_TYPE);

  String reqMsg = readContent(req.getReader());
  mLogger.info("Got WS request:\n" + reqMsg);
  MessageContext msgContext = new MessageContext(mAxisServer);
  msgContext.setRequestMessage(new Message(reqMsg));
  msgContext.setTargetService("MessageRouterPort");

  String respMsgStr = null;
  try
  {
   mAxisServer.invoke(msgContext);
   respMsgStr = msgContext.getResponseMessage().getSOAPPartAsString();
  }
  catch (AxisFault fault)
  {
   Message respMsg = msgContext.getResponseMessage();
   if (respMsg == null)
   {
    respMsg = new Message(fault);
    ((org.apache.axis.SOAPPart)respMsg.getSOAPPart()).
     getMessage().setMessageContext(msgContext);
   }
   respMsgStr = respMsg.getSOAPPartAsString();
  }

  mLogger.info("Got WS response:\n" + respMsgStr);
  pw.write(respMsgStr);
 }
 catch (Exception me)
 {
  mLogger.error(me);
  throw new ServletException(me);
 }
 finally
 {
  if (pw != null)
  {
   pw.close();
  }
 }
}

public void init(ServletConfig cfg) throws ServletException
{
 super.init(cfg);
 EngineConfigurationFactory factory = 
  EngineConfigurationFactoryFinder.newFactory(cfg);
 EngineConfiguration config = factory.getServerEngineConfig();
 mAxisServer = new AxisServer(config);
}

The deployment descriptor for the servlet is:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app >
 <servlet>
  <servlet-name>MessageRoutingServlet</servlet-name>
  <servlet-class>code.simple.MessageRoutingServlet</servlet-class>
  <init-param>
   <param-name>servletId</param-name>
   <param-value>defaultServlet</param-value>
  </init-param>
 </servlet>

 <servlet-mapping>
  <servlet-name>MessageRoutingServlet</servlet-name>
  <url-pattern>/*</url-pattern>
 </servlet-mapping>
</web-app>

Make Perl speak JMS (1)

To add JMS capability to Plum, I need to find a way to let Perl talk "JMS". Unfortunately there is no standard wire protocol for JMS. The JMS spec. defines the Java API but not the wire protocol. This is understandable as JMS is a Java centric system. Some JMS implementations, such as JBoss 3.x and 4.x, just use the Java serialization as their wire protocol. Others may use their propriate formats. This is an effort to define a generic XML protocol that can be utilized by different JMS implementations, but it is not there yet.

For now, a relatively simple way is to create a web service in Java which will route any requests to JMS server. Then one can make any lanaguage to speak JMS as long as they can consume the web service. Of course the limitation is that only text message will be supported.

Here is my try. I created a simple web service which is defined by following WSDL:

<?xml version="1.0" encoding="UTF-8"?>
<definitions name="MessageRouter" 
 targetNamespace="http://www.simple.code/router.wsdl/2005/11/7"
 xmlns:wsdlns="http://www.simple.code/router.wsdl/2005/11/7"
 xmlns:router="http://www.simple.code/router/2005/11/7"
 xmlns:xsd="http://www.w3.org/2001/XMLSchema"
 xmlns:stk="http://schemas.microsoft.com/soap-toolkit/wsdl-extension"
 xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
 xmlns="http://schemas.xmlsoap.org/wsdl/">

 <types>
  <xsd:schema targetNamespace="http://www.simple.code/router/2005/11/7" 
   elementFormDefault="qualified">

  <xsd:complexType name="DestinationType">
   <xsd:sequence>
    <xsd:element name="protocol" type="xsd:string"/>
    <xsd:element name="category" type="xsd:string"/>
    <xsd:element name="server" type="xsd:string"/>
    <xsd:element name="port" type="xsd:long"/>
    <xsd:element name="target" type="xsd:string"/>
    <xsd:element name="user" type="xsd:string" minOccurs="0"/>
    <xsd:element name="password" type="xsd:string" minOccurs="0"/>
   </xsd:sequence>
  </xsd:complexType>

  <xsd:complexType name="MessageHeadType">
   <xsd:sequence>
    <xsd:element name="header" type="xsd:string" maxOccurs="unbound"/>
   </xsd:sequence>
  </xsd:complexType>

  <xsd:complexType name="MessageBodyType">
   <xsd:sequence>
    <xsd:element name="content" type="xsd:string"/>
   </xsd:sequence>
  </xsd:complexType>

  <xsd:complexType name="RouteRequestType">
   <xsd:sequence>
    <xsd:element name="destination" type="router:DestinationType"/>
    <xsd:element name="head" type="router:MessageHeadType" minOccurs="0"/>
    <xsd:element name="request" type="router:MessageBodyType"/>
   </xsd:sequence>
  </xsd:complexType>

  <xsd:complexType name="RouteResponseType">
   <xsd:sequence>
    <xsd:element name="response" type="router:MessageBodyType"/>
   </xsd:sequence>
  </xsd:complexType>

  <xsd:element name="RouteRequest" type="router:RouteRequestType"/>
  <xsd:element name="RouteResponse" type="router:RouteResponseType"/>

  </xsd:schema>
 </types>

 <message name="RouteRequest">
  <part name="document" element="router:RouteRequest"/>
 </message>

 <message name="RouteResponse">
  <part name="document" element="router:RouteResponse"/>
 </message>

 <portType name="MessageRouterPortType">
  <operation name="RouteMessage">
   <input message="wsdlns:RouteRequest" />
   <output message="wsdlns:RouteResponse" />
  </operation>
 </portType>

 <binding name="HttpBinding" type="wsdlns:MessageRouterPortType">
  <stk:binding preferredEncoding="UTF-8" />
  <soap:binding style="document" 
   transport="http://schemas.xmlsoap.org/soap/http" />
  <operation name="RouteMessage">
   <soap:operation 
    soapAction="http://www.simple.code/router/action/RouteMessage" 
    style="document"/>
   <input>
    <soap:body use="literal"/>
   </input>
   <output>
    <soap:body use="literal"/>
   </output>
  </operation>
 </binding>

 <service name="MessageRoutingService">
  <port name="MessageRouterPort" binding="wsdlns:HttpBinding">
   <soap:address
    location="http://localhost:8080/common_router" />
  </port>
 </service>

</definitions>