Java中对象集合的序列化

java的IO中提供了一个 ObjectOutputStream对象，其中的方法writeObject（）文档如下：

    /**
     * Write the specified object to the ObjectOutputStream.  The class of the
     * object, the signature of the class, and the values of the non-transient
     * and non-static fields of the class and all of its supertypes are
     * written.  Default serialization for a class can be overridden using the
     * writeObject and the readObject methods.  Objects referenced by this
     * object are written transitively so that a complete equivalent graph of
     * objects can be reconstructed by an ObjectInputStream.
     *
     * <p>Exceptions are thrown for problems with the OutputStream and for
     * classes that should not be serialized.  All exceptions are fatal to the
     * OutputStream, which is left in an indeterminate state, and it is up to
     * the caller to ignore or recover the stream state.
     *
     * @throws	InvalidClassException Something is wrong with a class used by
     *		serialization.
     * @throws	NotSerializableException Some object to be serialized does not
     *		implement the java.io.Serializable interface.
     * @throws	IOException Any exception thrown by the underlying
     * 		OutputStream.
     */
    public final void writeObject(Object obj) throws IOException {
    }

 简要的翻译就是“将指定的对象写到输出流”。其实这个方法的文档有些误导的意思，下面这个例子我们会发现，这个方法甚至可以直接序列化集合，如List，Array等。

例子引用自http://blog.csdn.net/hdAptechIvan/

 

首先建立2个对象，

package serialization;

import java.io.Serializable;

class Employee implements Serializable
{
    /**
	 * 
	 */
	private static final long serialVersionUID = -316102412618444933L;
	public Employee(String n, double s)
    {
        name = n;
        salary = s;
    }
    
    /**
     *加薪水
     */
    public void raiseSalary(double byPercent)
    {
        double raise = salary * byPercent / 100;
        salary += raise;
    }
    
    public String toString()
    {
        return getClass().getName()
            + "[name = "+ name
            + ",salary = "+ salary
            + "]";
    }
    
    private String name;
    private double salary;
}

 

 

package serialization;

class Manager extends Employee
{
    public Manager(String n, double s)
    {
        super(n, s);
        secretary = null;
    }
    
    /**
     *设置秘书
     */
    public void setSecretary(Employee s)
    {
        secretary = s;
    }
    
    public String toString()
    {
        return super.toString()
            + "[secretary = "+ secretary
            + "]";
    }
    
    //secretary代表秘书
    private Employee secretary; 
}

 然后直接序列化集合到文件，并通过读取文件，修改数据来验证序列化是成功的：

package serialization;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;

/**
 * 对象的序列化
 *
 */
public class Test 
{
    public static void main(String[] args) 
    {
        Employee harry = new Employee("Harry Hacker", 50000);
        Manager manager1 = new Manager("Tony Tester", 80000);
        manager1.setSecretary(harry);

        List<Employee> staff = new ArrayList<Employee>(2);
        staff.add(harry);
        staff.add(manager1);
    //数组也可以
//    Employee[] staff = new Employee[2];
//    
//    staff[0] = harry;
//    staff[1] = manager1;
        try
        {
            ObjectOutputStream out = new ObjectOutputStream(
                new FileOutputStream("employee.dat"));
            out.writeObject(staff); //!!!!!!这个方法可以写集合、数组
            out.close();
            
            ObjectInputStream in = new ObjectInputStream(
                new FileInputStream("employee.dat"));
            List<Employee> newStaff = (List<Employee>)in.readObject();
            in.close();
   
            /**
             *通过harry对象来加薪
             *将在secretary上反映出来
             */
            newStaff.get(0).raiseSalary(10);
            
            for (int i = 0; i < newStaff.size(); i++)
                System.out.println(newStaff.get(i));
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }



}