Java源码——对象序列化（对象的存储及读取）（Object Serialization）

代码如下：

1. 可序列化的实体类（Account）

// Fig. 15.9: Account.java
// Serializable Account class for storing records as objects.
package ch15;
import java.io.Serializable;

public class Account implements Serializable
{
   private int account;
   private String firstName;
   private String lastName;
   private double balance;
   
   // initializes an Account with default values
   public Account() 
   {
      this(0, "", "", 0.0); // call other constructor
   } 
  
   // initializes an Account with provided values
   public Account(int account, String firstName, 
      String lastName, double balance)
   {
      this.account = account;
      this.firstName = firstName;
      this.lastName = lastName;
      this.balance = balance;
   }

   // set account number   
   public void setAccount(int acct)
   {
      this.account = account;
   } 

   // get account number   
   public int getAccount() 
   { 
      return account; 
   } 
   
   // set first name   
   public void setFirstName(String firstName)
   {
      this.firstName = firstName;
   } 

   // get first name   
   public String getFirstName() 
   { 
      return firstName; 
   } 
   
   // set last name   
   public void setLastName(String lastName)
   {
      this.lastName = lastName;
   } 

   // get last name   
   public String getLastName() 
   {
      return lastName; 
   } 
   
   // set balance  
   public void setBalance(double balance)
   {
      this.balance = balance;
   } 

   // get balance   
   public double getBalance() 
   { 
      return balance; 
   } 
} // end class AccountRecordSerializable

2. 使用ObjectOutputStream将对象顺序写入文件

// Fig. 15.10: CreateSequentialFile.java
// Writing objects sequentially to a file with class ObjectOutputStream.
package ch15;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.NoSuchElementException;
import java.util.Scanner;

public class CreateSequentialFile
{
   private static ObjectOutputStream output; // outputs data to file

   public static void main(String[] args)
   {
      openFile();
      addRecords();
      closeFile();
   }

   // open file clients.ser
   public static void openFile()
   {
      try 
      {
         output = new ObjectOutputStream(
            Files.newOutputStream(Paths.get("clients.ser")));
      }
      catch (IOException ioException)
      {
         System.err.println("Error opening file. Terminating.");
         System.exit(1); // terminate the program
      } 
   } 

   // add records to file
   public static void addRecords()
   {
      Scanner input = new Scanner(System.in);

      System.out.printf("%s%n%s%n? ", 
         "Enter account number, first name, last name and balance.",
         "Enter end-of-file indicator to end input.");

      while (input.hasNext()) // loop until end-of-file indicator
      {
         try 
         {
            // create new record; this example assumes valid input
            Account record = new Account(input.nextInt(),
               input.next(), input.next(), input.nextDouble());

            // serialize record object into file
            output.writeObject(record); 
         } 
         catch (NoSuchElementException elementException)
         {
            System.err.println("Invalid input. Please try again.");
            input.nextLine(); // discard input so user can try again 
         } 
         catch (IOException ioException)
         {
            System.err.println("Error writing to file. Terminating.");
            break;
         } 

         System.out.print("? ");
      }
   } 

   // close file and terminate application 
   public static void closeFile() 
   {
      try 
      {
         if (output != null)
            output.close();
      } 
      catch (IOException ioException)
      {
         System.err.println("Error closing file. Terminating.");
      } 
   } 
} // end class CreateSequentialFile

3. 使用ObjectInputStream类从文件中顺序读取对象

// Fig. 15.11: ReadSequentialFile.java
// Reading a file of objects sequentially with ObjectInputStream
// and displaying each record.
package ch15;
import java.io.EOFException;     
import java.io.IOException;      
import java.io.ObjectInputStream;
import java.nio.file.Files;
import java.nio.file.Paths;

public class ReadSequentialFile
{
   private static ObjectInputStream input;

   public static void main(String[] args)
   {
      openFile();
      readRecords();
      closeFile();
   } 

   // enable user to select file to open
   public static void openFile()
   {
      try // open file
      {
         input = new ObjectInputStream(          
            Files.newInputStream(Paths.get("clients.ser")));
      } 
      catch (IOException ioException)
      {
         System.err.println("Error opening file.");
         System.exit(1);
      } 
   }

   // read record from file
   public static void readRecords()
   {
      System.out.printf("%-10s%-12s%-12s%10s%n", "Account",
         "First Name", "Last Name", "Balance");

      try 
      {
         while (true) // loop until there is an EOFException
         {
            Account record = (Account) input.readObject();

            // display record contents
            System.out.printf("%-10d%-12s%-12s%10.2f%n",  
               record.getAccount(), record.getFirstName(), 
               record.getLastName(), record.getBalance());
         } 
      }
      catch (EOFException endOfFileException)
      {
         System.out.printf("%nNo more records%n");
      } 
      catch (ClassNotFoundException classNotFoundException)
      {
         System.err.println("Invalid object type. Terminating.");
      } 
      catch (IOException ioException)
      {
         System.err.println("Error reading from file. Terminating.");
      } 
   } // end method readRecords

   // close file and terminate application
   public static void closeFile()
   {
      try
      {
         if (input != null)
            input.close();
      } 
      catch (IOException ioException)
      {
         System.err.println("Error closing file. Terminating.");
         System.exit(1);
      } 
   } 
} // end class ReadSequentialFile

测试结果：

2.

Enter account number, first name, last name and balance.
Enter end-of-file indicator to end input.
? 103 huang pd 158.99
? 106 jiang sc 998.88
?

3.

Account   First Name  Last Name      Balance
103       huang       pd              158.99
106       jiang       sc              998.88

No more records