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