父类可序列化子类可序列化否乎？

关于这个问题，写了个简单的代码测试了下：
可序列化的类Father

package com.taobao.test;

import java.io.Serializable;

/**
 * @author tina.wyn
 *
 */
public class Father implements Serializable {
	
	private static final long serialVersionUID = 1L;

	private Integer fatherage;
	
	private String str;
	
	public Father() {
		fatherage = 50;
		str = "I am father";
	}

	public Integer getNumber() {
		return fatherage;
	}

	public void setNumber(Integer number) {
		this.fatherage = number;
	}

	public String getStr() {
		return str;
	}

	public void setStr(String str) {
		this.str = str;
	}
}

不可序列化的类Mother

package com.taobao.test;

public class Mother {

	private Integer matherage;

	private String str;
	
	public Mother(){
		matherage = 30;
		str = "I am mother";
	}

	public Integer getMatherage() {
		return matherage;
	}

	public void setMatherage(Integer matherage) {
		this.matherage = matherage;
	}

	public String getStr() {
		return str;
	}

	public void setStr(String str) {
		this.str = str;
	}
	

}

子类Son继承了父类Father

package com.taobao.test;

/**
 * @author tina.wyn
 *
 */
public class Son extends Father {
	private static final long serialVersionUID = 1L;

	
	private int age;
	
	private transient String unserialize;
	
	public Son() {
                age = 10;
		unserialize = "hi";
	}
	

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}


	public String getUnserialize() {
		return unserialize;
	}


	public void setUnserialize(String unserialize) {
		this.unserialize = unserialize;
	}

	
}

package com.taobao.test;

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;

/**
 * @author tina.wyn
 *
 */
public class TestSerialize {

	public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
		
		Son s = new Son();
		ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("hello")));
		objectOutputStream.writeObject(s);
		
		ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream(new File("hello")));
		Son sn = (Son) objectInputStream.readObject();
		
		System.out.println(sn.getAge());
		System.out.println(sn.getNumber());
		System.out.println(sn.getStr());
		System.out.println(sn.getUnserialize());
           }
}

运行结果

10
50
I am father
null

由此证明父类可序列化子类也可序列化，而sn.getUnserialize()为null是因为子类里将它定义为了transient 类型的，所以子类的属性可否序列化取决于如何定义。
现在我们在子类里加入Mother类的引用

package com.taobao.test;

/**
 * @author tina.wyn
 *
 */
public class Son extends Father {
	private static final long serialVersionUID = 1L;

	
	private int age;
	
	private transient String unserialize;
        Mother mother;
	
	public Son() {
		mother = new Mother();
		age = 10;
		unserialize = "hi";
	}
	

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}


	public String getUnserialize() {
		return unserialize;
	}


	public void setUnserialize(String unserialize) {
		this.unserialize = unserialize;
	}


	public Mother getMother() {
		return mother;
	}


	public void setMother(Mother mother) {
		this.mother = mother;
	}

	
}

运行结果：
    

  Exception in thread "main" java.io.NotSerializableException: com.taobao.test.Mother
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1164)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1518)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1483)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:330)
	at com.taobao.test.TestSerialize.main(TestSerialize.java:21)

吼吼，出错鸟~Mother类不支持序列化哈~~~