bookorderimpl.java

来自「java web services how to program」· Java 代码 · 共 111 行

// Fig. 15.17: BookOrderImpl.java
// Class BookOrderImpl is the implementation of the BookOrder
// Web service, which determines the price of a book, based on
// that book's ISBN and the quantity of books to order.
package com.deitel.jws1.services;

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

public class BookOrderImpl 
   implements com.deitel.jws1.services.BookOrder {

   private Connection connection; // connection to database

   // constructor to initialize database connection
   public BookOrderImpl()
   {
      // load JDBC driver and establish 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" ) );
      }

      // 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

   // obtain price of book based on book's ISBN and quantity
   public double orderBook( String ISBN, int quantity )
   {
      // detemine book availability, then determine price
      try {

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

         // make query to determine number of available books
         ResultSet resultSet = statement.executeQuery( "SELECT" +
            " quantity, price FROM books WHERE isbn = " + ISBN );

         int availableBookCount = 0;

         // obtain quantity associated with isbn from database 
         if ( resultSet != null ) {
            resultSet.next();
            availableBookCount = resultSet.getInt( "quantity" );
         }

         // determine whether quantity exceeds number of 
         // available books in database
         if ( availableBookCount < quantity ) {
            statement.close();
            return -1;
         }
         else {

            // determine price for one book
            double pricePerBook = resultSet.getDouble( "price" );
            int newQuantity = availableBookCount - quantity;

            // update database to decrement number of books
            statement.execute( "UPDATE books " +
               "SET quantity = " + newQuantity + 
               " WHERE isbn = " + ISBN );
            statement.close();

            return pricePerBook * quantity;
         }
      }

      // handle exception in executing Statement
      catch ( SQLException sqlException ) {
         sqlException.printStackTrace();
         return -1;
      }

   } // end method orderBook
   
} // end class BookPriceImpl