Home > Articles > Web Development

Taking Advantage of SOAP Extensibility

Let's take a look at how SkatesTown can use SOAP extensibility to its benefit. It turns out that SkatesTown's partners are demanding some type of proof that certain items are in SkatesTown's inventory. In particular, partners would like to have an e-mail record of any inventory checks they have performed.

Al Rosen got the idea to use SOAP extensibility in a way that allows the existing inventory check service implementation to be reused with no changes. SOAP inventory check requests will include a header whose element name is EMail belonging to the http://www.skatestown.com/ns/email namespace. The value of the header will be a simple string containing the e-mail address to which the inventory check confirmation should be sent.

Service Requestor View

Service requestors will have to modify their clients to build a custom SOAP envelope that includes the EMail header. Listing 3.5 shows the necessary changes. The e-mail to send confirmations to is provided in the constructor.

Listing 3.5  Updated Inventory Check Client

package ch3.ex3;

import org.apache.axis.client.ServiceClient;
import org.apache.axis.message.SOAPEnvelope;
import org.apache.axis.message.SOAPHeader;
import org.apache.axis.message.RPCElement;
import org.apache.axis.message.RPCParam;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;

 * Inventory check web service client
public class InventoryCheckClient {
     * Service URL
    String url;

     * Email address to send confirmations to
    String email;
     * Point a client at a given service URL
    public InventoryCheckClient(String url, String email) {
        this.url = url;
        this.email = email;
     * Invoke the inventory check web service
    public boolean doCheck(String sku, int quantity) throws Exception {
        // Build the email header DOM element
        DocumentBuilderFactory factory = 
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document doc = builder.newDocument();
        Element emailElem = doc.createElementNS(
            "http://www.skatestown.com/", "EMail");

        // Build the RPC request SOAP message
        SOAPEnvelope reqEnv = new SOAPEnvelope();
        reqEnv.addHeader(new SOAPHeader(emailElem));
        Object[] params = new Object[]{ sku, new Integer(quantity), };
        reqEnv.addBodyElement(new RPCElement("", "doCheck", params));
        // Invoke the inventory check web service
        ServiceClient call = new ServiceClient(url);
        SOAPEnvelope respEnv = call.invoke(reqEnv);
        // Retrieve the response
        RPCElement respRPC = (RPCElement)respEnv.getFirstBody();
        RPCParam result = (RPCParam)respRPC.getParams().get(0);
        return ((Boolean)result.getValue()).booleanValue();

To set a header in Axis, you first need to build the DOM representation for the header. The code in the beginning of doCheck() does this. Then you need to manually construct the SOAP message that will be sent. This involves starting with a new SOAPEnvelope object, adding a SOAPHeader with the DOM element constructed earlier, and, finally, adding an RPCElement as the body of the message. At this point, you can use ServiceClient.invoke() to send the message.

When the call is made with a custom-built SOAP envelope, the return value of invoke() is also a SOAPEnvelope object. You need to pull the relevant data out of that envelope by getting the body of the response, which will be an RPCElement. The result of the operation will be the first RPCParam inside the RPC response. Knowing that doCheck() returns a boolean, you can get the value of the parameter and safely cast it to Boolean.

As you can see, the code is not trivial, but Axis does provide a number of convenience objects that make working with custom-built SOAP messages straightforward. Figure 3.5 shows a UML diagram with some of the key Axis objects related to SOAP messages.

Figure 3.5 Axis SOAP message objects.

Service Provider View

The situation on the side of the Axis-based service provider is a little more complicated because we can no longer use a simple JWS file for the service. JWS files are best used for simple and straightforward service implementations. Currently, it is not possible to indicate from a JWS file that a certain header (in this case the e-mail header) should be processed. Al Rosen implements three changes to enable this more sophisticated type of service:

  • He moves the service implementation from the JWS file to a simple Java class.

  • He writes a handler for the EMail header.

  • He extends the Axis service deployment descriptor with information about the service implementation and the header handler.

Moving the service implementation is as simple as saving InventoryCheck.jws as InventoryCheck.java in /WEB-INF/classes/com/skatestown/services. No further changes to the service implementation are necessary.

Building a handler for the EMail header is relatively simple, as Listing 3.6 shows. When the handler is invoked by Axis, it needs to find the SOAP message and lookup the EMail header using its namespace and name. If the header is present in the request message, the handler sends a confirmation e-mail of the inventory check. The implementation is complex because to produce a meaningful e-mail confirmation, the handler needs to see both the request data (SKU and quantity) and the result of the inventory check. The basic process involves the following steps:

  1. Get the request or the response message using getRequestMessage() or getResponseMessage() on the Axis MessageContext object.

  2. Get the SOAP envelope by calling getAsSOAPEnvelope().

  3. Retrieve the first body of the envelope and cast it to an RPCElement because the body represents either an RPC request or an RPC response.

  4. Get the parameters of the RPC element using getParams().

  5. Extract parameters by their position and cast them to their appropriate type. As seen earlier in Listing 3.5, the response of an RPC is the first parameter in the response message body.

Listing 3.6  E-mail Header Handler

package com.skatestown.services;

import java.util.Vector;
import org.apache.axis.* ;
import org.apache.axis.message.*;
import org.apache.axis.handlers.BasicHandler;
import org.apache.axis.encoding.SOAPTypeMappingRegistry;
import bws.BookUtil;
import com.skatestown.backend.EmailConfirmation;

 * EMail header handler
public class EMailHandler extends BasicHandler
     * Utility method to retrieve RPC parameters
     * from a SOAP message.
    private Object getParam(Vector params, int index)
        return ((RPCParam)params.get(index)).getValue();
     * Looks for the EMail header and sends an email
     * confirmation message based on the inventory check
     * request and the result of the inventory check
    public void invoke(MessageContext msgContext) throws AxisFault
            // Attempt to retrieve EMail header
            Message       reqMsg = msgContext.getRequestMessage();
            SOAPEnvelope  reqEnv = reqMsg.getAsSOAPEnvelope();
            SOAPHeader    header = reqEnv.getHeaderByName(
                "EMail" );
            if (header != null)
                // Mark the header as having been processed
                // Get email address in header
                String email = (String)header.getValueAsType(
                // Retrieve request parameters: SKU & quantity
                RPCElement reqRPC = (RPCElement)reqEnv.getFirstBody();
                Vector params = reqRPC.getParams();
                String sku = (String)getParam(params, 0);
                Integer quantity = (Integer)getParam(params, 0);
                // Retrieve inventory check result
                Message respMsg = msgContext.getResponseMessage();
                SOAPEnvelope respEnv = respMsg.getAsSOAPEnvelope();
                RPCElement respRPC = (RPCElement)respEnv.getFirstBody();
                Boolean result = (Boolean)getParam(
                                                respRPC.getParams(), 0);
                // Send confirmation email
                EmailConfirmation ec = new EmailConfirmation(
                ec.send(email, sku,
                        quantity.intValue(), result.booleanValue());
        catch(Exception e)
            throw new AxisFault(e);
     * Required method of handlers. No-op in this case
    public void undo(MessageContext msgContext)

It's simple code, but it does take a few lines because several layers need to be unwrapped to get to theRPC parameters. When all data has been retrieved, the handler calls the e-mail confirmation backend, which, in this example, logs e-mails "sent" to /resources/email.log.

Finally, adding deployment information about the new header handler and the inventory check service involves making a small change to the Axis Web services deployment descriptor. The book example deployment descriptor is in /resources/deploy.xml. Working with Axis deployment descriptors will be described in detail in Chapter 4.

Listing 3.7 shows the five lines of XML that need to be added. First, the e-mail handler is registered by associating a handler name with its Java class name. Following that is the description of the inventory check service. The service options identify the Java class name for the service and the method that implements the service functionality. The service element has two attributes. Pivot is an Axis term that specifies the type of service. In this case, the value is RPCDispatcher, which implies that InventoryCheck is an RPC service. The output attribute specifies the name of a handler that will be called after the service is invoked. Because the book examples don't rely on an e-mail server being present, instead of sending confirmation this class writes messages to a log file in /resources/email.log.

Listing 3.7  Deployment Descriptor for Inventory Check Service

<!-- Chapter 3 example 3 services -->
<handler name="Email" class="com.skatestown.services.EMailHandler"/>
<service name="InventoryCheck" pivot="RPCDispatcher" response="Email">
   <option name="className" value="com.skatestown.services.InventoryCheck"/>
   <option name="methodName" value="doCheck"/>

Putting the Service to the Test

With all these changes in place, we are ready to test the improved inventory check service. There is a simple JSP test harness in ch3/ex3/index.jsp that is modeled after the JSP test harness we used for the JWS-based inventory check service (see Figure 3.6).

Figure 3.6 Putting the enhanced inventory check Web service to the test.

SOAP on the Wire

With the help of TCPMon, we can see what SOAP messages are passing between the client and the Axis engine. We are only interested in seeing the request message because the response message will be identical to the one before the EMail header was added.

Here is the SOAP request message with the EMail header present:

POST /bws/services/InventoryCheck HTTP/1.0
Content-Length: 482 
Host: localhost
Content-Type: text/xml; charset=utf-8
SOAPAction: "/doCheck"

<?xml version="1.0" encoding="UTF-8"?>
      <e:EMail xmlns:e="http://www.skatestown.com/ns/email">
      <ns1:doCheck xmlns:ns1="AvailabilityCheck">
         <arg0 xsi:type="xsd:string">947-TI</arg0>
         <arg1 xsi:type="xsd:int">1</arg1>

There are no surprises in the SOAP message. However, a couple of things have changed in the HTTP message. First, the target URL is /bws/services/InventoryCheck. This is a combination of two parts: the URL of the Axis servlet that listens for SOAP requests over HTTP (/bws/services) and the name of the service we want to invoke (InventoryCheck). Also, the SOAPAction header, which was previously empty, now contains the name of the method we want to invoke. The service name on the URL and the method name in SOAPAction are both hints to Axis about the service we want to invoke.

That's all there is to taking advantage of SOAP custom headers. The key message is one of simple yet flexible extensibility. Remember, the inventory check service implementation did not change at all!

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020