SAAJ Coffee Supplier Service - The J2EE 1.4 Tutorial

SAAJ Coffee Supplier Service

In contrast to the JAX-RPC service, the SAAJ supplier service does not register in a publicly accessible registry. It simply implements the arrangements that the supplier and the Coffee Break have made regarding their exchange of XML documents. These arrangements include the kinds of messages they will send, the form of those messages, and the kind of messaging they will do. They have agreed to do request-response messaging using the SAAJ API (the javax.xml.soap package).

The Coffee Break servers send two kinds of messages:

Requests for current wholesale coffee prices
Customer orders for coffee

The SAAJ coffee supplier responds with two kinds of messages:

Current price lists
Order confirmations

All the messages they send conform to an agreed-upon XML structure, which is specified in a DTD for each kind of message. This allows them to exchange messages even though they use different document formats internally.

The four kinds of messages exchanged by the Coffee Break servers and the SAAJ supplier are specified by the following DTDs:

request-prices.dtd
price-list.dtd
coffee-order.dtd
confirm.dtd

These DTDs can be found at <INSTALL>/j2eetutorial14/examples/cb/saaj/dtds/. The dtds directory also contains a sample of what the XML documents specified in the DTDs might look like. The corresponding XML files for the DTDs are as follows:

request-prices.xml
price-list.xml
coffee-order.xml
confirm.xml

Because of the DTDs, both parties know ahead of time what to expect in a particular kind of message and can therefore extract its content using the SAAJ API.

Code for the client and server applications is in this directory:

<INSTALL>/j2eetutorial14/examples/cb/saaj/src/ 

SAAJ Client

The Coffee Break servers, which are the SAAJ clients in this scenario, send requests to their SAAJ supplier. The SAAJ client application uses the SOAPConnection method call to send messages.

SOAPMessage response = con.call(request, endpoint); 

Accordingly, the client code has two major tasks. The first is to create and send the request; the second is to extract the content from the response. These tasks are handled by the classes PriceListRequest and OrderRequest.

Sending the Request

This section covers the code for creating and sending the request for an updated price list. This is done in the getPriceList method of PriceListRequest, which follows the DTD price-list.dtd.

The getPriceList method begins by creating the connection that will be used to send the request. Then it gets the default SOAPFactory object to be used for creating Name objects, and the default MessageFactory object to be used for creating the SOAPMessage object msg.

SOAPConnectionFactory scf = 
  SOAPConnectionFactory.newInstance();
SOAPConnection con = scf.createConnection();
SOAPFactory soapFactory = SOAPFactory.newInstance();

MessageFactory mf = MessageFactory.newInstance();
SOAPMessage msg = mf.createMessage(); 

The next step is to access the message's SOAPBody object, to which the message's content will be added.

SOAPBody body = msg.getSOAPBody(); 

The file price-list.dtd specifies that the topmost element inside the body is request-prices and that it contains the element request. The text node added to request is the text of the request being sent. Every new element that is added to the message must have a Name object to identify it, and this object is created by the SOAPFactory method createName. The following lines of code create the top-level element in the SOAPBody object body. The first element created in a SOAPBody object is always a SOAPBodyElement object.

Name bodyName = soapFactory.createName("request-prices",
  "RequestPrices", "http://sonata.coffeebreak.com");
SOAPBodyElement requestPrices =
  body.addBodyElement(bodyName); 

In the next few lines, the code adds the element request to the element request-prices (represented by the SOAPBodyElement requestPrices). Then the code adds a text node containing the text of the request. Next, because there are no other elements in the request, the code calls the method saveChanges on the message to save what has been done.

Name requestName = soapFactory.createName("request");
SOAPElement request = 
  requestPrices.addChildElement(requestName);
request.addTextNode("Send updated price list.");

msg.saveChanges(); 

With the creation of the request message completed, the code sends the message to the SAAJ coffee supplier. The message being sent is the SOAPMessage object msg, to which the elements created in the previous code snippets were added. The endpoint is the URI for the SAAJ coffee supplier, http://localhost:8080/saaj-coffee-supplier/getPriceList. The SOAPConnection object con is used to send the message, and because it is no longer needed, it is closed.

URL endpoint = new URL(url);
SOAPMessage response = con.call(msg, endpoint);
con.close(); 

When the call method is executed, the Application Server executes the servlet PriceListServlet. This servlet creates and returns a SOAPMessage object whose content is the SAAJ supplier's price list. (PriceListServlet is discussed in Returning the Price List.) The Application Server knows to execute PriceListServlet because we map the given endpoint to that servlet.

Extracting the Price List

This section demonstrates (1) retrieving the price list that is contained in response, the SOAPMessage object returned by the method call, and (2) returning the price list as a PriceListBean.

The code creates an empty Vector object that will hold the coffee-name and price elements that are extracted from response. Then the code uses response to access its SOAPBody object, which holds the message's content.

Vector list = new Vector();

SOAPBody responseBody = response.getSOAPBody(); 

The next step is to retrieve the SOAPBodyElement object. The method getChildElements returns an Iterator object that contains all the child elements of the element on which it is called, so in the following lines of code, it1 contains the SOAPBodyElement object bodyEl, which represents the price-list element.

Iterator it1 = responseBody.getChildElements(); 
while (it1.hasNext()) {
  SOAPBodyElement bodyEl = (SOAPBodyElement)it1.next(); 

The Iterator object it2 holds the child elements of bodyEl, which represent coffee elements. Calling the method next on it2 retrieves the first coffee element in bodyEl. As long as it2 has another element, the method next will return the next coffee element.

  Iterator it2 = bodyEl.getChildElements();
  while (it2.hasNext()) {
    SOAPElement child2 = (SOAPElement)it2.next(); 

The next lines of code drill down another level to retrieve the coffee-name and price elements contained in it3. Then the message getValue retrieves the text (a coffee name or a price) that the SAAJ coffee supplier added to the coffee-name and price elements when it gave content to response. The final line in the following code fragment adds the coffee name or price to the Vector object list. Note that because of the nested while loops, for each coffee element that the code retrieves, both of its child elements (the coffee-name and price elements) are retrieved.

    Iterator it3 = child2.getChildElements();
    while (it3.hasNext()) {
      SOAPElement child3 = (SOAPElement)it3.next();
      String value = child3.getValue();
      list.addElement(value);
    }
  }
} 

The final code fragment adds the coffee names and their prices (as a PriceListItem) to the ArrayList priceItems, and prints each pair on a separate line. Finally it constructs and returns a PriceListBean.

ArrayList priceItems = new ArrayList();
for (int i = 0; i < list.size(); i = i + 2) {
  priceItems.add(
    new PriceItemBean(list.elementAt(i).toString(), 
    new BigDecimal(list.elementAt(i + 1).toString())));
  System.out.print(list.elementAt(i) + "        ");
  System.out.println(list.elementAt(i + 1));
}

Date today = new Date();
Date endDate = DateHelper.addDays(today, 30);
Calendar todayCal = new GregorianCalendar();
todayCal.setTime(today);
Calendar cal = new GregorianCalendar();
cal.setTime(endDate);
plb = new PriceListBean();
plb.setStartDate(todayCal);
plb.setPriceItems(priceItems);
plb.setEndDate(cal); 

Ordering Coffee

The other kind of message that the Coffee Break servers can send to the SAAJ supplier is an order for coffee. This is done in the placeOrder method of OrderRequest, which follows the DTD coffee-order.dtd.

Creating the Order

As with the client code for requesting a price list, the placeOrder method starts by creating a SOAPConnection object, a SOAPFactory object, and a SOAPMessage object, and accessing the message's SOAPBody object.

SOAPConnectionFactory scf =
  SOAPConnectionFactory.newInstance();
SOAPConnection con = scf.createConnection();
SOAPFactory soapFactory = SOAPFactory.newInstance();

MessageFactory mf = MessageFactory.newInstance();
SOAPMessage msg = mf.createMessage();

SOAPBody body = msg.getSOAPBody(); 

Next, the code creates and adds XML elements to form the order. As is required, the first element is a SOAPBodyElement, which in this case is coffee-order.

Name bodyName = soapFactory.createName("coffee-order", "PO", 
  "http://sonata.coffeebreak.com"); 
SOAPBodyElement order = body.addBodyElement(bodyName); 

The application then adds the next level of elements, the first of these being orderID. The value given to orderID is extracted from the OrderBean object passed to the OrderRequest.placeOrder method.

Name orderIDName = soapFactory.createName("orderID");
SOAPElement orderID = order.addChildElement(orderIDName);
orderID.addTextNode(orderBean.getId()); 

The next element, customer, has several child elements that give information about the customer. This information is also extracted from the Customer component of OrderBean.

Name childName = soapFactory.createName("customer");
SOAPElement customer = order.addChildElement(childName);

childName = soapFactory.createName("last-name");
SOAPElement lastName = customer.addChildElement(childName);    
lastName.addTextNode(orderBean.getCustomer().getLastName());

childName = soapFactory.createName("first-name"); 
SOAPElement firstName = customer.addChildElement(childName);    
firstName.addTextNode(orderBean.getCustomer().getFirstName());

childName = soapFactory.createName("phone-number"); 
SOAPElement phoneNumber = customer.addChildElement(childName);      
phoneNumber.addTextNode(
  orderBean.getCustomer().getPhoneNumber());

childName = soapFactory.createName("email-address"); 
SOAPElement emailAddress = 
  customer.addChildElement(childName); 
emailAddress.addTextNode(
  orderBean.getCustomer().getEmailAddress()); 

The address element, added next, has child elements for the street, city, state, and zip code. This information is extracted from the Address component of OrderBean.

childName = soapFactory.createName("address");
SOAPElement address = order.addChildElement(childName);

childName = soapFactory.createName("street");
SOAPElement street = address.addChildElement(childName);
street.addTextNode(orderBean.getAddress().getStreet());

childName = soapFactory.createName("city");   
SOAPElement city = address.addChildElement(childName); 
city.addTextNode(orderBean.getAddress().getCity());

childName = soapFactory.createName("state");
SOAPElement state = address.addChildElement(childName);
state.addTextNode(orderBean.getAddress().getState());

childName = soapFactory.createName("zip");
SOAPElement zip = address.addChildElement(childName);
zip.addTextNode(orderBean.getAddress().getZip()); 

The element line-item has three child elements: coffeeName, pounds, and price. This information is extracted from the LineItems list contained in OrderBean.

for (Iterator it = orderBean.getLineItems().iterator();
    it.hasNext(); ) {
  LineItemBean lib = (LineItemBean)it.next();

  childName = soapFactory.createName("line-item");
  SOAPElement lineItem = order.addChildElement(childName);

  childName = soapFactory.createName("coffeeName");
  SOAPElement coffeeName = 
    lineItem.addChildElement(childName);
  coffeeName.addTextNode(lib.getCoffeeName());

  childName = soapFactory.createName("pounds");
  SOAPElement pounds = lineItem.addChildElement(childName);
  pounds.addTextNode(lib.getPounds().toString());

  childName = soapFactory.createName("price");
  SOAPElement price = lineItem.addChildElement(childName);
  price.addTextNode(lib.getPrice().toString());
}

// total
childName = soapFactory.createName("total");
SOAPElement total = order.addChildElement(childName);
total.addTextNode(orderBean.getTotal().toString());  

With the order complete, the application sends the message to the endpoint http://localhost:8080/saaj-coffee-supplier/orderCoffee and closes the connection.

URL endpoint = new URL(url);
SOAPMessage reply = con.call(msg, endpoint);
con.close(); 

Because we map the given endpoint to ConfirmationServlet, the Application Server executes that servlet (discussed in Returning the Order Confirmation) to create and return the SOAPMessage object reply.

Retrieving the Order Confirmation

The rest of the placeOrder method retrieves the information returned in reply. The client knows what elements are in it because they are specified in confirm.dtd. After accessing the SOAPBody object, the code retrieves the confirmation element and gets the text of the orderID and ship-date elements. Finally, it constructs and returns a ConfirmationBean with this information.

SOAPBody sBody = reply.getSOAPBody();
Iterator bodyIt = sBody.getChildElements();
SOAPBodyElement sbEl = (SOAPBodyElement)bodyIt.next();
Iterator bodyIt2 = sbEl.getChildElements();

SOAPElement ID = (SOAPElement)bodyIt2.next();
String id = ID.getValue();

SOAPElement sDate = (SOAPElement)bodyIt2.next();
String shippingDate = sDate.getValue();

SimpleDateFormat df = 
  new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy");
Date date = df.parse(shippingDate);
Calendar cal = new GregorianCalendar();
cal.setTime(date);
cb = new ConfirmationBean(id, cal);  

SAAJ Service

The SAAJ coffee supplier--the SAAJ server in this scenario--provides the response part of the request-response paradigm. When SAAJ messaging is being used, the server code is a servlet. The core part of each servlet is made up of three javax.servlet.HttpServlet methods: init, doPost, and onMessage. The init and doPost methods set up the response message, and the onMessage method gives the message its content.

Returning the Price List

This section takes you through the servlet PriceListServlet. This servlet creates the message containing the current price list that is returned to the method call, invoked in PriceListRequest.

Any servlet extends a javax.servlet class. Being part of a web application, this servlet extends HttpServlet. It first creates a static MessageFactory object that will be used later to create the SOAPMessage object that is returned.

public class PriceListServlet extends HttpServlet { 
  static MessageFactory messageFactory = null; 

  static { 
    try { 
      messageFactory = MessageFactory.newInstance();
    } catch (Exception ex) { 
      ex.printStackTrace();
    } 
  }; 

Every servlet has an init method. This init method initializes the servlet with the configuration information that the Application Server passed to it.

public void init(ServletConfig servletConfig) 
    throws ServletException { 
  super.init(servletConfig);
} 

The next method defined in PriceListServlet is doPost, which does the real work of the servlet by calling the onMessage method. (The onMessage method is discussed later in this section.) The Application Server passes the doPost method two arguments. The first argument, the HttpServletRequest object req, holds the content of the message sent in PriceListRequest. The doPost method gets the content from req and puts it in the SOAPMessage object msg so that it can pass it to the onMessage method. The second argument, the HttpServletResponse object resp, will hold the message generated by executing the method onMessage.

In the following code fragment, doPost calls the methods getHeaders and putHeaders, defined immediately after doPost, to read and write the headers in req. It then gets the content of req as a stream and passes the headers and the input stream to the method MessageFactory.createMessage. The result is that the SOAPMessage object msg contains the request for a price list. Note that in this case, msg does not have any headers because the message sent in PriceListRequest did not have any headers.

public void doPost(HttpServletRequest req, 
    HttpServletResponse resp) 
    throws ServletException, IOException { 
  try { 
    // Get all the headers from the HTTP request 
    MimeHeaders headers = getHeaders(req);

    // Get the body of the HTTP request 
    InputStream is = req.getInputStream();

    // Now internalize the contents of the HTTP request 
    // and create a SOAPMessage 
    SOAPMessage msg = 
      messageFactory.createMessage(headers, is); 

Next, the code declares the SOAPMessage object reply and populates it by calling the method onMessage.

    SOAPMessage reply = null;
    reply = onMessage(msg); 

If reply has anything in it, its contents are saved, the status of resp is set to OK, and the headers and content of reply are written to resp. If reply is empty, the status of resp is set to indicate that there is no content.

    if (reply != null) { 

      /*
       * Need to call saveChanges because we're 
       * going to use the MimeHeaders to set HTTP 
       * response information. These MimeHeaders
       * are generated as part of the save.
       */
      if (reply.saveRequired()) { 
        reply.saveChanges(); 
      }

      resp.setStatus(HttpServletResponse.SC_OK);
      putHeaders(reply.getMimeHeaders(), resp); 

      // Write out the message on the response stream 
      OutputStream os = resp.getOutputStream(); 
      reply.writeTo(os); 
      os.flush(); 
    } else {
      resp.setStatus(
        HttpServletResponse.SC_NO_CONTENT);
    }
  } catch (Exception ex) { 
    throw new ServletException( "SAAJ POST failed: " +
      ex.getMessage()); 
  } 
} 

The methods getHeaders and putHeaders are not standard methods in a servlet, as init, doPost, and onMessage are. The method doPost calls getHeaders and passes it the HttpServletRequest object req that the Application Server passed to it. It returns a MimeHeaders object populated with the headers from req.

static MimeHeaders getHeaders(HttpServletRequest req) {

  Enumeration headerNames = req.getHeaderNames(); 
  MimeHeaders headers = new MimeHeaders();

  while (headerNames.hasMoreElements()) { 
    String headerName = (String)headerNames.nextElement(); 
    String headerValue = req.getHeader(headerName);

    StringTokenizer values = 
      new StringTokenizer(headerValue, ","); 
    while (values.hasMoreTokens()) {
      headers.addHeader(headerName,
        values.nextToken().trim());
    }
  }
  return headers; 
} 

The doPost method calls putHeaders and passes it the MimeHeaders object headers, which was returned by the method getHeaders. The method putHeaders writes the headers in headers to res, the second argument passed to it. The result is that res, the response that the Application Server will return to the method call, now contains the headers that were in the original request.

static void putHeaders(MimeHeaders headers,
    HttpServletResponse res) {

  Iterator it = headers.getAllHeaders(); 
  while (it.hasNext()) { 
    MimeHeader header = (MimeHeader)it.next();

    String[] values = headers.getHeader(header.getName()); 
    if (values.length == 1) 
      res.setHeader(header.getName(), header.getValue()); 
    else { 
      StringBuffer concat = new StringBuffer(); 
      int i = 0; 
      while (i < values.length) { 
        if (i != 0) {
          concat.append(',');
        }
        concat.append(values[i++]); 
      }
      res.setHeader(header.getName(), concat.toString()); 
    } 
  } 
} 

The method onMessage is the application code for responding to the message sent by PriceListRequest and internalized into msg. It uses the static MessageFactory object messageFactory to create the SOAPMessage object message and then populates it with the supplier's current coffee prices.

The method doPost invokes onMessage and passes it msg. In this case, onMessage does not need to use msg because it simply creates a message containing the supplier's price list. The onMessage method in ConfirmationServlet (see Returning the Order Confirmation), on the other hand, uses the message passed to it to get the order ID.

public SOAPMessage onMessage(SOAPMessage msg) { 
  SOAPMessage message = null; 
  

  try { 
    SOAPFactory soapFactory = SOAPFactory.newInstance();
    message = messageFactory.createMessage();

    SOAPBody body = message.getSOAPBody();

    Name bodyName = soapFactory.createName("price-list",
      "PriceList", "http://sonata.coffeebreak.com");
    SOAPBodyElement list = body.addBodyElement(bodyName);

    Name coffeeN = soapFactory.createName("coffee");
    SOAPElement coffee = list.addChildElement(coffeeN);

    Name coffeeNm1 = soapFactory.createName("coffee-name");
    SOAPElement coffeeName = 
      coffee.addChildElement(coffeeNm1);
    coffeeName.addTextNode("Arabica");

    Name priceName1 = soapFactory.createName("price"); 
    SOAPElement price1 = coffee.addChildElement(priceName1);
    price1.addTextNode("4.50");

    Name coffeeNm2 = soapFactory.createName("coffee-name"); 
    SOAPElement coffeeName2 =
      coffee.addChildElement(coffeeNm2);
    coffeeName2.addTextNode("Espresso");

    Name priceName2 = soapFactory.createName("price"); 
    SOAPElement price2 = coffee.addChildElement(priceName2);
    price2.addTextNode("5.00");

    Name coffeeNm3 = soapFactory.createName("coffee-name"); 
    SOAPElement coffeeName3 =
      coffee.addChildElement(coffeeNm3);
    coffeeName3.addTextNode("Dorada");

    Name priceName3 = soapFactory.createName("price"); 
    SOAPElement price3 = coffee.addChildElement(priceName3);
    price3.addTextNode("6.00");

    Name coffeeNm4 = soapFactory.createName("coffee-name"); 
    SOAPElement coffeeName4 =
      coffee.addChildElement(coffeeNm4);
    coffeeName4.addTextNode("House Blend");

    Name priceName4 = soapFactory.createName("price"); 
    SOAPElement price4 = coffee.addChildElement(priceName4);
    price4.addTextNode("5.00");

    message.saveChanges();

  } catch(Exception e) { 
    logger.severe("onMessage: Exception: " + e.toString()); 
  } 
  return message; 
}  

Returning the Order Confirmation

ConfirmationServlet creates the confirmation message that is returned to the call method that is invoked in OrderRequest. It is very similar to the code in PriceListServlet except that instead of building a price list, its onMessage method builds a confirmation containing the order number and shipping date.

The onMessage method for this servlet uses the SOAPMessage object passed to it by the doPost method to get the order number sent in OrderRequest. Then it builds a confirmation message containing the order ID and shipping date. The shipping date is calculated as today's date plus two days.

public SOAPMessage onMessage(SOAPMessage message) {

  SOAPMessage confirmation = null;

  try {

    // Retrieve orderID from message received
    SOAPBody sentSB = message.getSOAPBody();
    Iterator sentIt = sentSB.getChildElements();
    SOAPBodyElement sentSBE = (SOAPBodyElement)sentIt.next();
    Iterator sentIt2 = sentSBE.getChildElements();
    SOAPElement sentSE = (SOAPElement)sentIt2.next();

    // Get the orderID test to put in confirmation
    String sentID = sentSE.getValue();

    // Create the confirmation message
    confirmation = messageFactory.createMessage();
    SOAPBody sb = message.getSOAPBody();

    SOAPFactory soapFactory = SOAPFactory.newInstance();

    Name newBodyName = soapFactory.createName("confirmation",
      "Confirm", "http://sonata.coffeebreak.com");
    SOAPBodyElement confirm = sb.addBodyElement(newBodyName);

    // Create the orderID element for confirmation
    Name newOrderIDName = soapFactory.createName("orderId");
    SOAPElement newOrderNo =
      confirm.addChildElement(newOrderIDName);
    newOrderNo.addTextNode(sentID);

    // Create ship-date element
    Name shipDateName = soapFactory.createName("ship-date");
    SOAPElement shipDate = 
      confirm.addChildElement(shipDateName);

    // Create the shipping date
    Date today = new Date();
    long msPerDay = 1000 * 60 * 60 * 24;
    long msTarget = today.getTime();
    long msSum = msTarget + (msPerDay * 2);
    Date result = new Date();
    result.setTime(msSum);
    String sd = result.toString();
    shipDate.addTextNode(sd);

    confirmation.saveChanges();

  } catch (Exception ex) {
    ex.printStackTrace();
  }
  return confirmation;
} 

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