ObjectOutputStream和ObjectInputStream类的学习

ObjectOutputStream和ObjectInputStream类所读写的对象必须实现了Serializable的接口,对象中的transient和static类型的成员变量不会被读取和写入.
下面是UML图





下面是代码例子1

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ObjectputStreamTest {

	private static File getFile()
	{
		return new File(System.getProperty("user.dir")+"/student.txt");
	}
	/**
	 * 读取文档数据
	 * @return
	 */
	@SuppressWarnings("unchecked")
	private static List<Student> getStudents()
	{
		File file = getFile();
		List<Student> list = null;
		FileInputStream fis = null;
		ObjectInputStream ois = null;

		try {
			fis = new FileInputStream(file);
			if(fis.available()!=-1)
			{
				ois = new ObjectInputStream(fis);
				Object obj = ois.readObject();
				list = (ArrayList<Student>)obj;
			}else
			{
				list = new ArrayList<Student>();
			}

		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}catch (ClassNotFoundException e) {
			e.printStackTrace();
		}finally
		{
			try {
				fis.close();
				ois.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			fis = null;
			ois=null;
		}
		return list;
	}
	/**
	 * 更改数据
	 * @param list
	 */
	private static void setStudents(List<Student> list)
	{
		File file = getFile();
		FileOutputStream fos =null;
		ObjectOutputStream oos=null;
		
		try {
			fos = new FileOutputStream(file);
			oos = new ObjectOutputStream(fos);
			oos.writeObject(list);
			oos.flush();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}finally
		{
			try {
				fos.close();
				oos.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			fos=null;
			oos=null;
			
		}
		
	}
	/**
	 * 插入数据
	 * @param stu
	 */
	public static void insert(Student stu)
	{
		List<Student> list = getStudents();
		list.add(stu);
		setStudents(list);
	}
	/**
	 * 更新数据
	 * @param i
	 * @param stu
	 */
	public static void update(int i,Student stu)
	{
		List<Student> list = getStudents();
		list.remove(i);
		list.add(i,stu);
		setStudents(list);
	}
	/**
	 * 删除数据
	 * @param i
	 */
	public static void delete(int i)
	{
		List<Student> list = getStudents();
		list.remove(i);
		setStudents(list);
	}
	
	@SuppressWarnings("static-access")
	public static void print(List<Student> list)
	{
		for (Iterator<Student> iterator = list.iterator(); iterator.hasNext();) {
			Student student = (Student) iterator.next();
			System.out.print("id="+student.getId()+",name="+student.getName()+",count="+student.getCount()+",sex="+student.getSex()+",serialVersionUID="+student.getSerialVersionUID());
			System.out.println();
		}
	}
	public static void main(String[] args) {
		List<Student> list = new ArrayList<Student>();
		Student stu = new Student();
		stu.setName("chendingqiang");
		stu.setSex("男");
		list.add(stu);
		
		stu = new Student();
		stu.setName("limoumou");
		list.add(stu);
		
		ObjectputStreamTest.setStudents(list);
		list = ObjectputStreamTest.getStudents();
		print(list);
		System.out.println("==================================");
		//修改
		
		stu = new Student();
		stu.setName("陈顶强");
		ObjectputStreamTest.update(0, stu);
		list = ObjectputStreamTest.getStudents();
		print(list);
		
		//删除
		System.out.println("==================================");
		ObjectputStreamTest.delete(0);
		list = ObjectputStreamTest.getStudents();
		print(list);
		
		//插入
		System.out.println("==================================");
		stu = new Student();
		stu.setName("zhumoumou");
		ObjectputStreamTest.insert(stu);
		list = ObjectputStreamTest.getStudents();
		print(list);
	}
	
	
	

}
class Student implements Serializable
{
	private static final long serialVersionUID = 1L;

	private transient String sex;//瞬态不能序列化
	private int id;
	private String name;
	private static int count=1;

	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Student() {
		id=count;
		count++;
	}
	@Override
	public boolean equals(Object obj) {
		if(obj instanceof Student)
		{
			Student stu = (Student)obj;
			if(this.id == stu.id)
			{
				return true;
			}
		}
		return false;
	}
	public static int getCount() {
		return count;
	}
	public static void setCount(int count) {
		Student.count = count;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public static long getSerialVersionUID() {
		return serialVersionUID;
	}
	

}

当在继承的时候，超类如果不是可序列化，那么超类一定要有一个无参数的构造函数，以便允许初始化其字段。在此情况下，子类负责保存和恢复不可序列化的类的状态。不然会抛出这个异常java.io.InvalidClassException
下面会出现异常的版本

public class Shape {
	private int diameter;

	public int getDiameter() {
		return diameter;
	}

	public void setDiameter(int diameter) {
		this.diameter = diameter;
	}

	/**
	 * 不提供无参数构造函数
	 * @param diameter
	 */
	public Shape(int diameter) {
		this.diameter = diameter;
	}
	
}
import java.io.Serializable;

@SuppressWarnings("serial")
public class Circle extends Shape implements Serializable {

	private int r;
	public Circle(int diameter,int r) {
		super(diameter);
		this.r = r;
		
	}
	public int getR() {
		return r;
	}
	public void setR(int r) {
		this.r = r;
	}

}
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class ExtendObjecTest {
	public static void main(String[] args) {
		File file = new File(System.getProperty("user.dir")+"/student.txt");
		Circle c  = new Circle(12,32);
		FileOutputStream fos =null;
		ObjectOutputStream oos=null;
		try {
			fos = new FileOutputStream(file);
			oos = new ObjectOutputStream(fos);
			oos.writeObject(c);
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}finally
		{
			try {
				fos.close();
				oos.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			fos=null;
			oos=null;
		}
		
		FileInputStream fis = null;
		ObjectInputStream ois = null;
		
		try {
			fis = new FileInputStream(file);
			ois = new ObjectInputStream(fis);
			Circle result = (Circle)ois.readObject();
			System.out.println("diameter:"+result.getDiameter()+",r:"+result.getR());
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
}

提供无参数构造函数的版本

public class Shape {
	private int diameter;

	public int getDiameter() {
		return diameter;
	}

	public void setDiameter(int diameter) {
		this.diameter = diameter;
	}

	/**
	 * 提供无参数构造函数
	 * @param diameter
	 */
	public Shape() {
		
	}
	
}
@SuppressWarnings("serial")
public class Circle extends Shape implements Serializable {

	private int r;
	public Circle(int r) {
		this.r = r;
		
	}
	public int getR() {
		return r;
	}
	public void setR(int r) {
		this.r = r;
	}

}
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class ExtendObjecTest {
	public static void main(String[] args) {
		File file = new File(System.getProperty("user.dir")+"/student.txt");
		Circle c  = new Circle(32);
		c.setDiameter(23);
		FileOutputStream fos =null;
		ObjectOutputStream oos=null;
		try {
			fos = new FileOutputStream(file);
			oos = new ObjectOutputStream(fos);
			oos.writeObject(c);
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}finally
		{
			try {
				fos.close();
				oos.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			fos=null;
			oos=null;
		}
		
		FileInputStream fis = null;
		ObjectInputStream ois = null;
		
		try {
			fis = new FileInputStream(file);
			ois = new ObjectInputStream(fis);
			Circle result = (Circle)ois.readObject();
			System.out.println("diameter:"+result.getDiameter()+",r:"+result.getR());
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
}