Processing Request/Response Messages of a Web Service Using Handler Chain

Here is the ant script build.xml to package the EAR. Note that Web.xml and application.xml should be available before building the EAR.

build.xml

<project name="webservices-handler" default="all" basedir=".">
<!--  set global properties for this build  -->
<property environment="env" />
<property name="compiler" value="modern" />
<property name="debug" value="yes" />
<property name="deprecation" value="yes" />
<property name="build.compiler" value="${compiler}" />
<property name="source" value="." />
<property name="build" value="${source}/build" />
<property name="war_file" value="BalanceEnquiry.war" />
<property name="ear_file" value="BalanceEnquiry.ear" />
<property name="namespace" value="http://www.bea.com" />
<property name="client.classes.dir" value="{source}/clientclasses" />
<target name="all" depends="clean, war, ear" />
<target name="clean">
<delete dir="${build}" />
<delete file="${source}/${ear_file}" />
<delete file="${war_file}" />
</target>
<target name="war">
<delete dir="${build}" />
<mkdir dir="${build}" />
<mkdir dir="${build}/WEB-INF" />
<mkdir dir="${build}/WEB-INF/classes" />
<javac srcdir="${source}" includes="AuthenticationHandler.java,
                          BalanceEnquiryService.java"
                          destdir="${build}/WEB-INF/classes" />
<copy todir="${build}/WEB-INF">
<fileset dir="${source}">
<include name="web-services.xml" />
<include name="web.xml" />
</fileset>
</copy>
<jar jarfile="${war_file}" basedir="${build}" />
</target>
<target name="ear" depends="war">
<delete dir="${build}" />
<mkdir dir="${build}" />
<mkdir dir="${build}/META-INF" />
<copy todir="${build}">
<fileset dir="${source}">
<include name="${war_file}" />
</fileset>
</copy>
<copy todir="${build}/META-INF">
<fileset dir="${source}">
<include name="application.xml" />
</fileset>
</copy>
<jar jarfile="${source}/${ear_file}" basedir="${build}" />
</target>
</project>

The ant script creates a WAR and then packages the EAR.

Deploy the generated EAR in Weblogic server. The following is the client to invoke the BalanceEnquiryService.

Client.java

import org.apache.axis.client.Call;
import org.apache.axis.client.ServiceFactory;
import org.apache.axis.client.Service;
import org.apache.axis.MessageContext;
import org.apache.axis.attachments.Attachments;
import org.apache.axis.message.SOAPEnvelope;

import javax.xml.namespace.QName;
import javax.xml.soap.SOAPBody;
import javax.xml.soap.SOAPBodyElement;
import javax.xml.soap.SOAPConnection;
import javax.xml.soap.SOAPConnectionFactory;
import javax.xml.soap.SOAPElement;
import javax.xml.soap.SOAPHeader;
import javax.xml.soap.SOAPHeaderElement;
import javax.xml.soap.SOAPMessage;
import javax.xml.soap.SOAPPart;
import javax.xml.namespace.QName;
import javax.xml.rpc.ParameterMode;
import javax.xml.soap.AttachmentPart;
import javax.xml.soap.MessageFactory;
import javax.xml.soap.Name;
import javax.xml.rpc.ParameterMode;

import java.net.URL;
import java.util.Iterator;


public class Client
{
   private static String TARGET_NAMESPACE = "http://www.bea.com";
   private static QName xsdFloat = new
                  QName("http://www.w3.org/2001/XMLSchema", "float");
   public static org.apache.axis.message.SOAPEnvelope env = null;
   public static SOAPMessage message = null;
   public static void main(String[] argv) throws Exception
   {
      Client client = new Client();
      env = client.constructSOAPEnvelope();
      client.constructHeader(env);
      client.constructBody(env);
      System.setProperty( "javax.xml.rpc.ServiceFactory",
                          "org.apache.axis.client.ServiceFactory" );

      String url =
     "http://localhost:7001/BalanceEnquiry/BalanceEnquiryService";
     ServiceFactory factory =
         (org.apache.axis.client.ServiceFactory)ServiceFactory.
              newInstance();
      QName serviceName   = new QName(TARGET_NAMESPACE,
         "BalanceEnquiryService");

      Service service = 
         (org.apache.axis.client.Service)factory.
          createService(serviceName);
      Call call = (org.apache.axis.client.Call)service.createCall();
      call.setTargetEndpointAddress(url);
      SOAPEnvelope result = call.invoke(env);
      System.out.println(result);
   }
   public SOAPEnvelope constructSOAPEnvelope() throws Exception
   {
      org.apache.axis.message.SOAPEnvelope env = new
         org.apache.axis.message.SOAPEnvelope();
      return env;
   }
   public void constructHeader(SOAPEnvelope envelope) throws Exception
   {
      SOAPHeader header = envelope.getHeader();
      Name headerElementName =
         envelope.createName("AccountDetails","",
                             "http://schemas.xmlsoap.org/soap/
                                     envelope/");
      SOAPHeaderElement headerElement =
         header.addHeaderElement(headerElementName);
      headerElement.setMustUnderstand(false);
      headerElement.addNamespaceDeclaration("soap",
         "http://schemas.xmlsoap.org/soap/envelope/");
      SOAPElement accNo = headerElement.addChildElement("accountNo");
      accNo.addTextNode("12345");
      SOAPElement pinNo = headerElement.addChildElement("pin");
      pinNo.addTextNode("6789");
   }

   public void constructBody(SOAPEnvelope envelope) throws Exception
   {
      SOAPBody body = envelope.getBody();
      Name bodyRootElementName =
         envelope.createName("getBalance","",
                             "http://schemas.xmlsoap.org/soap/
                                     encoding/");
      SOAPBodyElement bodyRootElement =
         body.addBodyElement(bodyRootElementName);
      SOAPElement bodyElement =
         bodyRootElement.addChildElement("param0");
      bodyElement.addAttribute(envelope.createName("xsi:type"),
                                                   "xsd:string");
      bodyElement.addTextNode("12");
   }
}

If there is a client side handler available, make the following changes:

1. Import the following two classes.

   import javax.xml.rpc.handler.HandlerInfo;
   import javax.xml.rpc.handler.HandlerRegistry;
   

2. Include the following lines before call.invoke().

   QName portName = new QName( "http://bea.com/", 
                               "HelloWorldServicePort");
   HandlerRegistry registry = service.getHandlerRegistry();
   List handlerList = new ArrayList();
   handlerList.add( new HandlerInfo( ClientHandler.class, null,
                    null ) );
   registry.setHandlerChain( portName, handlerList );
   

Conclusion

We hope this article helps you understand more about the the Handler chain mechanism and its usage in Web Services.

About the Authors

Nandhini Arumugam holds a Masters degree in Computer Applications from PSG College of Technology, Coimbatore. She has been working as a software engineer in the Telecom and Mobile Solutions Lab, Hewlett-Packard, Bangalore for more than one year. The domain of her experience includes Web Services and J2EE-related technologies. She can be reached at nandhini.arumugam@hp.com.

Jeyarani Venkatasamy holds a Masters degree in Computer Applications from Sri Sarada College for Women, Tirunelveli. She has been working as a senior sofware engineer in the Telecom and Mobile Solutions Lab, Hewlett-Packard, Bangalore for more than one year. The domain of her experience includes Web Services, Java, and J2EE-related technologies. She can be reached at jeyarani.venkatasamy@hp.com.