vieworderservlet.java

java web services how to program

// Fig. 11.26: ViewOrderServlet.java
// ViewOrderServlet enables a user to view the status of orders 
// created by the JAXM applications.
package com.deitel.jws1.jaxm.bookbuyer.sender;

// Java core packages
import java.io.*;
import java.util.*;
import java.sql.*;
import java.text.NumberFormat;

// Java extension packages
import javax.servlet.http.*;
import javax.servlet.*;
import javax.xml.parsers.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;

// W3C XML packages
import org.w3c.dom.*;

public class ViewOrderServlet extends HttpServlet {

   private Connection connection; // connection to database

   // factories for creating XML and applying XSLT
   private DocumentBuilderFactory factory;
   private TransformerFactory transformerFactory;

   // setup database connection for servlet
   public void init( ServletConfig servletConfig ) 
      throws ServletException 
   {
      super.init( servletConfig );

      // initialize connection to database
      try {

         // obtain URL of properties file
         java.net.URL propertyURL = getClass().getResource( 
            "bookStock.properties" );

         // load properties file
         Properties databaseProperties = new Properties();
         databaseProperties.load( new FileInputStream( 
            propertyURL.getPath() ) );

         // load JDBC driver
         Class.forName( databaseProperties.getProperty( 
            "jdbcDriver" ) );

         // establish database connection
         connection = DriverManager.getConnection(
            databaseProperties.getProperty( "databaseURI" ) );

         // create factory to build XML Documents
         factory = DocumentBuilderFactory.newInstance();

         // create factory to apply XSLT
         transformerFactory = TransformerFactory.newInstance();
      } 

      // handle exception if database driver does not exist
      catch ( ClassNotFoundException classNotFoundException ) {
         classNotFoundException.printStackTrace();
      }

      // handle exception in making Connection
      catch ( SQLException sqlException ) {
         sqlException.printStackTrace();
      }

      // handle exception in loading properties file
      catch ( IOException ioException ) {
         ioException.printStackTrace();
      }

   } // end method init

   // invoked upon receiving message
   public void doGet( HttpServletRequest request, 
      HttpServletResponse response ) throws ServletException
   {
      // determine whether order was successful
      try {

         // SQL query to database
         Statement statement = connection.createStatement( 
            ResultSet.TYPE_SCROLL_INSENSITIVE,
            ResultSet.CONCUR_READ_ONLY );

         // make query to extract order information
         ResultSet resultSet = statement.executeQuery( "SELECT" +
            " orderID, isbn, quantity, price FROM orders" );

         Document orderXmlDocument = null;

         // view order information
         if ( resultSet != null )
            orderXmlDocument = createXML( resultSet );

         if ( orderXmlDocument != null )
            applyXSLT( "XSL/viewOrder_XHTML.xsl", 
               orderXmlDocument, response );

         statement.close();
      }

      // handle exception in accessing database
      catch ( SQLException sqlException ) {
         sqlException.printStackTrace();
      }

      // handle exception in applying XSLT
      catch ( IOException ioException ) {
         ioException.printStackTrace();
      }

   } // end method doGet

   // create XML document from ResultSet
   private Document createXML( ResultSet resultSet )
      throws SQLException
   {
      // use ResultSet to build XML document
      try {
         DocumentBuilder builder = factory.newDocumentBuilder();
         Document document = builder.newDocument();

         // create orders root Element
         Element orders = document.createElement( "orders" );
         document.appendChild( orders );

         // store ID, isbn, quantity and price in order Element
         while ( resultSet.next() ) {

            // create order Element for each order
            Element order = document.createElement( "order" );

            // obtain ID, isbn, quantity and price from resultSet
            Integer ID = 
               new Integer( resultSet.getInt( "orderID" ) );
            String isbn = resultSet.getString( "isbn" );
            Integer quantity = 
               new Integer( resultSet.getInt( "quantity" ) );
            Double price = 
               new Double( resultSet.getDouble( "price" ) );

            // create Elements for ID, isbn, quantity and price 
            Element orderID = 
               document.createElement( "orderID" );
            Element orderIsbn = document.createElement( "isbn" );
            Element orderQuantity = 
               document.createElement( "quantity" );
            Element orderPrice = 
               document.createElement( "price" );

            // append elements as children to Element order
            order.appendChild( orderID );
            order.appendChild( orderIsbn );
            order.appendChild( orderQuantity );
            order.appendChild( orderPrice );

            // create NumberFormat to format price to US locale
            NumberFormat priceFormatter = 
               NumberFormat.getCurrencyInstance( Locale.US );

            // store ID, isbn, quantity and price information
            orderID.appendChild( 
               document.createTextNode( ID.toString() ) );
            orderIsbn.appendChild( 
               document.createTextNode( isbn ) );
            orderQuantity.appendChild( 
               document.createTextNode( quantity.toString() ) );
            orderPrice.appendChild( document.createTextNode( 
               priceFormatter.format( price ) ) );

            // append each order Element to root Element orders
            orders.appendChild( order );
         }

         return document;
      }

      // handle exception in parsing
      catch ( ParserConfigurationException parserException ) {
         parserException.printStackTrace();
         return null;
      }

   } // end method createXML

   // apply XSLT style sheet to XML document
   private void applyXSLT( String xslFile, Document xmlDocument,
      HttpServletResponse response ) throws IOException
   {
      // apply XSLT
      try {

         // open InputStream for XSL document 
         InputStream xslStream = 
            getServletContext().getResourceAsStream( xslFile );

         // create StreamSource for XSLT document
         Source xslSource = new StreamSource( xslStream );

         // create DOMSource for source XML document
         Source xmlSource = new DOMSource( xmlDocument );

         // get PrintWriter for writing data to client
         PrintWriter output = response.getWriter();

         // create StreamResult for transformation result
         Result result = new StreamResult( output );

         // create Transformer for XSL transformation
         Transformer transformer =
            transformerFactory.newTransformer( xslSource );

         // transform and deliver content to client
         transformer.transform( xmlSource, result );

      }

      // handle exception transforming content
      catch ( TransformerException transformerException ) {
         transformerException.printStackTrace();
      }

   } // end method applyXSLT

} // end class ViewOrderServlet