Implementation

Rather than build a module to fetch stock quotes, OTN developers used an existing Web Service. The Web Service WSDL URL is http://services.xmethods.net/soap/urn:xmethods-delayed-quotes.wsdl, and that's just about all the developers need to access the service. Here's why: Oracle9i JDeveloper provides a wizard that can parse the WSDL file and generate the Java code that a client needs to invoke the service's methods. In this case, the generated Java class is StockQuoteServiceStub. It provides code for connecting to the service and wrapper methods that a client can call to interact with the service. Following is some of the code from the generated stub class that connects to the service and wraps the getQuote method.

/**
 * Generated by the Oracle9i JDeveloper Web Services Stub/Skeleton Generator.
 * Date Created: Fri Apr 19 15:45:47 IST 2002
 * WSDL URL: http://services.xmethods.net/soap/urn:xmethods-delayed-quotes.wsdl
 *
 * net.xmethods.services.stockquote.StockQuote web service
 */
public class StockQuoteServiceStub {
  public String endpoint = "http://66.28.98.121:9090/soap";  
  private OracleSOAPHTTPConnection m_httpConnection = null;  

  public StockQuoteServiceStub() {
    m_httpConnection = new OracleSOAPHTTPConnection();
  }
  public Float getQuote(String symbol)
      throws Exception {
    Float returnVal = null;
    URL endpointURL = new URL(endpoint);
    Call call = new Call();
    call.setSOAPTransport(m_httpConnection);
    call.setTargetObjectURI("urn:xmethods-delayed-quotes");
    call.setMethodName("getQuote");
    call.setEncodingStyleURI(Constants.NS_URI_SOAP_ENC);
    Vector params = new Vector();
    params.addElement(new Parameter("symbol", String.class, symbol, null));
    call.setParams(params);
    Response response = call.invoke(endpointURL,
                                   "urn:xmethods-delayed-quotes#getQuote");
    if(!response.generatedFault()) {
      Parameter result = response.getReturnValue();
      returnVal = (Float)result.getValue();
    }
    else {
      Fault fault = response.getFault();
      throw new SOAPException(fault.getFaultCode(), fault.getFaultString());
    }
    return returnVal;
  }

Because the FBS uses several Web Services, the developers chose to centralize most of the service-related client code in one class, WebServicesHelper. Following is some of the code from WebServicesHelper that calls the getQuote method provided by the remote Web Service.

public class WebServicesHelper {


...

  public WebServicesHelper() {

  ...

    // Initialize stock quote service stub
    stockService = new StockQuoteServiceStub();
  }



  public StockRate fetchStockRate(String symbol)
      throws WebServiceAccessException {
    float rate;
    try {
      rate = stockService.getQuote(symbol).floatValue();
    } catch (Exception ex) {
      throw new WebServiceAccessException(" Stock Quote service error : "
                                          + ex.toString());
    }
    return new StockRate(symbol, new Date(), rate, (float) (rate + 0.5));
  }

To demonstrate a different apporach, the FBS accesses another third-party Web Service via an API provided by that third party. Specifically, the FBS uses Google Search APIs to fetch financial news. Here is the code from WebServicesHelper.java that makes the connection and fetches the data.

package oracle.otnsamples.ibfbs.admin.helper;
...
import com.google.soap.search.GoogleSearch;
import com.google.soap.search.GoogleSearchFault;
import com.google.soap.search.GoogleSearchResult;
import com.google.soap.search.GoogleSearchResultElement;

...
public class WebServicesHelper {
  private GoogleSearch search = null;
  ...
  public WebServicesHelper() {
    // Initialize Google Search and set the key
    search = new GoogleSearch();
    search.setKey(ConnectionParams.googleSearchKey);
    // Initialize stock quote service stub
    stockService = new StockQuoteServiceStub();
  }

  /**
   * This method retrieves the latest news for a particular symbol by accessing
   * the news webservice.
   *
   * @param symbol Stock symbol
   * @param maxResults maximum number of results for the symbol
   * @return news news for given symbol
   * @exception WebServiceAccessException if accessing webservice fails
   * @since 1.0
   */
  public Collection fetchLatestNews(String symbol, String companyName,
                                    int maxResults)
      throws WebServiceAccessException {
    ArrayList newsList = new ArrayList();
    News      news     = null;
    Date      today    = new Date();
    int julianDate  = this.toJulian(today);
    // Set the search string
    search.setQueryString(new StringBuffer().append("intitle:")
                                            .append(companyName)
                                            .append(" finance stock news")
                                            .append(" daterange:")
                                            .append(julianDate-30)
                                            .append("-")
                                            .append(julianDate).toString());
    // Set the maximum number of results returned
    search.setMaxResults(maxResults);
    try {
      // Search
      GoogleSearchResult          searchResult = search.doSearch();
      GoogleSearchResultElement[] result       =
        searchResult.getResultElements();
      // Number of matching results
      int noofresults = searchResult.getEndIndex();
      for (int i = 0; i < noofresults; i++) {
        news = new News(null, today, symbol, removeHTML(result[i].getTitle()),
                        URLEncoder.encode(result[i].getURL()));
        newsList.add(news);
      }
    } catch (GoogleSearchFault ex) {
      throw new WebServiceAccessException(" Stock News service error : "
                                          + ex.toString());
    }
    return newsList;
  }

Each instance of the FBS represents a unique stock exchange. When an FBS user buys or sells a particular stock, the order is sent to the corresponding stock exchange as a simplified message. If the stock is not traded in the current exchange, the FBS forwards the order to another FBS, and so on until the trade is executed. FBS instances pass orders around via Web Services. See ExchangeStub.java, Exchange.java, ExchangeHome.java, ExchangeBean.java, and Exchange.wsdl for implemenation details.