booktitlesimpl.java

java web services how to program

// Fig. 11.2: BookTitlesImpl.java.
// Class BookTitlesImpl handles the logic for the Book Titles
// Web service, which returns a list of book titles that are
// stored in a database.
package com.deitel.jws1.services;

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

public class BookTitlesImpl {

   private Connection connection; // connection to database

   // constructor to initialize database connection
   public BookTitlesImpl()
   {
      // load JDBC driver and establish connection to database
      try {

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

      // 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 constructor

   // service to obtain titles of books listed in database
   public String[] getBookTitles()
   {
      // obtain book titles from database and return title list
      try {
         String[] bookTitles = null;

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

         // use SQL query to obtain book titles from database
         ResultSet resultSet = 
            statement.executeQuery( "SELECT title FROM titles" );

         // use ResultSet to create book-title list
         if ( resultSet != null ) {

            // instantiate book-title list according to number
            // of titles stored in ResultSet
            List list = new ArrayList();

            // store each ResultSet item in book-title list
            for ( int i = 0; resultSet.next(); i++ )
               list.add( resultSet.getObject( "title" ) );
            bookTitles = 
               ( String[] ) list.toArray( new String[ 0 ] );
         }

         statement.close();

         return bookTitles;
      }

      // handle exception in executing Statement
      catch ( Exception sqlException ) {
         sqlException.printStackTrace();
         return null;
      }

   } // end method getBookTitles

   // terminate connection to database
   protected void finalize()
   {
      // close database connection
      try {
         connection.close();
      }

      // handle if connection cannot be closed
      catch ( SQLException sqlException ) {
         sqlException.printStackTrace();
      }

   } // end method finalize

} // end class BookTitlesImpl