booktitleproxyservlet.java

java web services how to program

// Fig. 14.7: BookTitleProxyServlet.java.
// BookTitleProxyServlet uses JAXM and SAAJ to invoke the Book
// Titles Web service.
package com.deitel.jws1.j2me.servlet;

// Java core packages
import java.io.*;
import java.util.Iterator;

// Java extension packages
import javax.servlet.*;
import javax.servlet.http.*;
import javax.xml.soap.*;
import javax.xml.messaging.*;

public class BookTitleProxyServlet extends HttpServlet {

   private SOAPConnectionFactory soapConnectionFactory;
   private URLEndpoint urlEndpoint;
   private MessageFactory messageFactory;

   // initialize BookTitleProxyServlet
   public void init() throws ServletException
   {
      // create factory objects
      try {

         // factory for establishing point-to-point connections
         soapConnectionFactory = 
            SOAPConnectionFactory.newInstance();

         // factory for building SOAP messages
         messageFactory = MessageFactory.newInstance();
      }

      // handle exception in initializing factory objects
      catch ( SOAPException exception ) {
         throw new ServletException( exception.getMessage() );
      }

      String endpoint = 
         getServletConfig().getInitParameter( "SERVICE_URL" );

      // define Web-service URL
      urlEndpoint = new URLEndpoint( endpoint );

   } // end constructor

   // use JAXM to invoke remote Web service
   public void doGet( HttpServletRequest request, 
      HttpServletResponse response ) throws ServletException,
      IOException
   {
      // invoke Web service and convert result to String array
      try {
         SOAPMessage responseMessage = sendSoapRequestMessage();

         // store response message in String array
         String titles[] = 
            handleSoapResponseMessage( responseMessage );

         DataOutputStream out = new DataOutputStream( 
            new BufferedOutputStream( 
               response.getOutputStream() ) );

         // send String to client
         for ( int i = 0; i < titles.length; i++ ) {
            for ( int j = 0; j < titles[ i ].length(); j++ )
               out.writeChar( titles[ i ].charAt( j ) );
            out.writeChar( '\n' );
         }

         out.close();
      }

      // handle exception in sending or receiving SOAP message
      catch( SOAPException exception ) {
         throw new IOException( exception.getMessage() );
      }

      // handle exception in populating bookTitles String array
      catch ( ArrayIndexOutOfBoundsException exception ) {
         throw new IOException( exception.getMessage() );
      }

   } // end method doGet

   // invoke remote Web service by sending SOAP request
   private SOAPMessage sendSoapRequestMessage()
      throws SOAPException
   {
      // use SOAPConnectionFactory to create SOAP connection
      SOAPConnection soapConnection = 
            soapConnectionFactory.createConnection();

      // use MessageFactory to create SOAP message
      SOAPMessage soapRequestMessage = 
         messageFactory.createMessage();

      // send SOAP message to Web service
      SOAPMessage soapResponseMessage = soapConnection.call( 
         soapRequestMessage, urlEndpoint );

      soapConnection.close();

      return soapResponseMessage;

   } // end method sendSoapRequestMessage

   // convert SOAP message returned by Web service to array of 
   // Strings, in which each String represents a book title
   private String[] handleSoapResponseMessage( 
      SOAPMessage soapResponseMessage ) throws SOAPException
   {
      // obtain references to response message elements
      SOAPPart responsePart = soapResponseMessage.getSOAPPart();
      SOAPEnvelope responseEnvelope = responsePart.getEnvelope();
      SOAPBody responseBody = responseEnvelope.getBody();

      // obtain Iterator of all child elements of element Body
      Iterator responseBodyChildElements = 
         responseBody.getChildElements();

      // extract element titles from SOAP message element Body
      SOAPBodyElement titlesElement =
         ( SOAPBodyElement ) responseBodyChildElements.next();

      // extract number of book titles from element Titles
      int bookCount = Integer.parseInt( 
         titlesElement.getAttributeValue(
            responseEnvelope.createName( "bookCount" ) ) );

      // create array of Strings that represent book titles
      String bookTitles[] = new String[ bookCount ];

      // use Iterator to obtain child elements of element Titles
      Iterator titleIterator = 
         titlesElement.getChildElements( 
            responseEnvelope.createName( "title" ) );

      // store each book title in bookTitles String array
      int i = 0;
      while ( titleIterator.hasNext() ) {
         SOAPElement titleElement =
            ( SOAPElement ) titleIterator.next();
         bookTitles[ i++ ] = titleElement.getValue();
      }

      return bookTitles;

   } // end method handleSoapResponseMessage

} // end class BookTitleProxyServlet