Java How to Program, 6/e
	ISBN: 0-13-148398-6 © 2005 pages: 1576 Buy the Book!

The following Java tutorial introduces object serialization--Java's built-in mechanism for manipulating objects as streams of bytes. Object serialization provides the foundation for Java's remote method invocation (RMI) capabilties that enable Java programs that are distributed over a network to invoke each others so-called "remote methods." RMI is used frequently in distributed enterprise applications that are built with Java Enterprise Edition (Java EE). In this tutorial, we demonstrate object serialization by writing entire objects to and reading entire objects from files on disk. This tutorial is intended for students and professionals who are already familiar with Java programming. Download the examples for this tutorial here.

[Notes: This tutorial is an excerpt (Section 14.6) of Chapter 14, Files and Streams, from our best-selling textbook Java How to Program, 6/e. This tutorial may refer to other chapters or sections of the book that are not included here. When you purchase this book you also get free access to the Web-based Java Multimedia Cyber Classroom, 6/e, for six months. The Cyber Classroom includes audio descriptions of the examples in Chapters 1-14, solutions to approximately one-half of the end-of-chapter exercises, interactive true/false self-assessment questions and a searchable Web-based e-book. Permission Information: Deitel, Harvey M. and Paul J., JAVA HOW TO PROGRAM, ©2005, pp. 697-706. Electronically reproduced by permission of Pearson Education, Inc., Upper Saddle River, New Jersey.]

Introduction to Object Serialization (Continued)

Fig. 14.18 Sequential file created using ObjectOutputStream.

   1  // Fig. 14.18: CreateSequentialFile.java
   2  // Writing objects sequentially to a file with class ObjectOutputStream.
   3  import java.io.FileOutputStream;        
   4  import java.io.IOException;             
   5  import java.io.ObjectOutputStream;      
   6  import java.util.NoSuchElementException;
   7  import java.util.Scanner;               
   8  
   9  import com.deitel.jhtp6.ch14.AccountRecordSerializable;
   10  
   11  public class CreateSequentialFile
   12  {
   13     private ObjectOutputStream output; // outputs data to file
   14  
   15     // allow user to specify file name
   16     public void openFile()
   17     {
   18        try // open file
   19        {
   20           output = new ObjectOutputStream(           
   21              new FileOutputStream( "clients.ser" ) );
   22        } // end try
   23        catch ( IOException ioException )
   24        {
   25           System.err.println( "Error opening file." );
   26        } // end catch
   27     } // end method openFile
   28  
   29     // add records to file
   30     public void addRecords()
   31     {
   32        AccountRecordSerializable record; // object to be written to file
   33        int accountNumber = 0; // account number for record object
   34        String firstName; // first name for record object
   35        String lastName; // last name for record object
   36        double balance; // balance for record object
   37  
   38        Scanner input = new Scanner( System.in );
   39  
   40        System.out.printf( "%s\n%s\n%s\n%s\n\n",
   41           "To terminate input, type the end-of-file indicator ",
   42           "when you are prompted to enter input.",
   43           "On UNIX/Linux/Mac OS X type <ctrl> d then press Enter",
   44           "On Windows type <ctrl> z then press Enter" );
   45  
   46        System.out.printf( "%s\n%s", 
   47           "Enter account number (> 0), first name, last name and balance.",
   48           "? " );
   49  
   50        while ( input.hasNext() ) // loop until end-of-file indicator
   51        {
   52           try // output values to file
   53           {
   54              accountNumber = input.nextInt(); // read account number
   55              firstName = input.next(); // read first name
   56              lastName = input.next(); // read last name
   57              balance = input.nextDouble(); // read balance
   58  
   59              if ( accountNumber > 0 )
   60              {
   61                 // create new record
   62                 record = new AccountRecordSerializable( accountNumber,
   63                    firstName, lastName, balance );                    
   64                 output.writeObject( record ); // output record        
   65              } // end if
   66              else
   67              {
   68                 System.out.println(
   69                    "Account number must be greater than 0." );
   70              } // end else
   71           } // end try
   72           catch ( IOException ioException )
   73           {
   74              System.err.println( "Error writing to file." );
   75              return;
   76           } // end catch
   77           catch ( NoSuchElementException elementException )
   78           {
   79              System.err.println( "Invalid input. Please try again." );
   80              input.nextLine(); // discard input so user can try again
   81           } // end catch
   82  
   83           System.out.printf( "%s %s\n%s", "Enter account number (>0),",
   84              "first name, last name and balance.", "? " );
   85        } // end while
   86     } // end method addRecords
   87  
   88     // close file and terminate application 
   89     public void closeFile() 
   90     {
   91        try // close file 
   92        {
   93           if ( output != null )
   94              output.close();
   95        } // end try
   96        catch ( IOException ioException )
   97        {
   98           System.err.println( "Error closing file." );
   99           System.exit( 1 );
   100        } // end catch
   101     } // end method closeFile
   102  } // end class CreateSequentialFile

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