【Java基础】序列化与反序列化深入分析
一、前言
复习Java基础知识点的序列化与反序列化过程,整理了如下学习笔记。
二、为什么需要序列化与反序列化
程序运行时,只要需要,对象可以一直存在,并且我们可以随时访问对象的一些状态信息,如果程序终止,那么对象是肯定不会存在的,但是有时候,我们需要再程序终止时保存对象的状态信息,之后程序再次运行时可以重新恢复到之前的状态,如,玩家玩游戏退出时,需要保存玩家的状态信息(如等级、装备等等),之后玩家再此登入时,必须要恢复这些状态信息。我们可以通过数据库手段来达到这个保存状态的目的,在Java中,我们有更简便的方法进行处理,那就是序列化与反序列化。序列化是一种对象持久化的手段,反序列化与序列化相反,其是通过序列化后的信息重新组装成对象。序列化与反序列化普遍应用在网络传输、RMI等场景中。
三、序列化概述
3.1 序列化类结构图
下面展示了与序列化相关的类的结构图
说明:虚线框的表示接口类型,实线框表示具体的类。
3.2 序列化关键字说明
与序列化相关的关键字如下
说明:
1. 关键字transient,用来修饰字段,表示此字段在默认序列化过程中不会被处理,但是可以采用另外的手段进行处理。
2. 关键字serialVersionUID,表示序列化版本号,当两个类的序列化ID一致时允许反序列化,默认可以采用编译器提供的值1L。
3.3 序列化方法说明
与序列化相关的方法如下
说明:writeObject与readObject方法分别在ObjectOutput接口与ObjectInput接口中声明,在ObjectOutputStream与ObjectInputStream中实现。
四、Serializable
4.1 Serializable定义
Serializable定义如下
public interface Serializable { }
说明:Serializable为一个接口,并且没有任何字段和方法,仅仅作为一个标识。
4.2 使用说明
当序列化对象时,只需要将对象标记为可序列化,即实现接口Serializable即可。下面的Person类实现了Serializable接口。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.Serializable; public class Person implements Serializable { /** * */ private static final long serialVersionUID = 1L; private String name; private String gender; private int age; private transient Person friend; public Person() { } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Person getFriend() { return friend; } public void setFriend(Person friend) { this.friend = friend; } @Override public String toString() { return "name = " + name + ", gender = " + gender + ", age = " + age + ", friend info is [" + friend + "]"; } }
Person类的friend字段设置为transient,表明不会被序列化,定义完Person类之后,我们即可以对Person类进行序列化与反序列化操作了,具体代码如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; public class SerializableDemo { public static void main(String[] args) throws Exception { Person leesf = new Person(); Person dyd = new Person(); leesf.setAge(24); leesf.setGender("man"); leesf.setName("leesf"); dyd.setAge(24); dyd.setGender("woman"); dyd.setName("dyd"); leesf.setFriend(dyd); dyd.setFriend(null); File file = new File("test"); ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file)); oos.writeObject(leesf); oos.flush(); oos.close(); System.out.println(leesf); ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file)); leesf = (Person) ois.readObject(); ois.close(); System.out.println(leesf); } }
运行结果如下
name = leesf, gender = man, age = 24, friend info is [name = dyd, gender = woman, age = 24, friend info is [null]] name = leesf, gender = man, age = 24, friend info is [null]
说明:由于friend字段标记为transient,则默认序列化操作时不会进行序列化,反序列化后其值为null。
4.3 问题说明
1. Person类不实现Serializable接口
若Person类不实现Serializable接口,进行序列化时,会发生什么,会出现如下异常。
Exception in thread "main" java.io.NotSerializableException:****
表示Person没有实现Serializable接口,具体原因如下
在调用writeObject方法后,会经过一系列的调用,具体的调用栈如下
说明:截取了writeObject0函数中的一段代码,可以看到会检查该对象是否是Serializable类型,不是,则会抛出异常。
2. 处理transient对象
当字段被transient修饰时,采用默认的序列化机制将不会对其进行处理,但是,如果要序列化transient字段时,如何做呢,可以在要进行序列化的类中添加writeObject和readObject方法,其方法签名如下
private void writeObject(ObjectOutputStream stream) throws IOException private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException
说明:注意,writeObject与readObject是采用private修饰符修饰的,说明,此方法只能在该类的其他方法中被调用,其他类中不能调用此方法,那么当调用ObjectOutputStream的writeObject方法时,如何调用到此方法来执行用户自定义处理逻辑的呢,答案是反射。利用反射可以在别的类中调用到此类中私有的方法,反射很强大。
利用这个方法,我们修改Person类如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; public class Person implements Serializable { /** * */ private static final long serialVersionUID = 1L; private String name; private String gender; private int age; private transient Person friend; public Person() { } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Person getFriend() { return friend; } public void setFriend(Person friend) { this.friend = friend; } @Override public String toString() { return "name = " + name + ", gender = " + gender + ", age = " + age + ", friend info is [" + friend + "]"; } private void writeObject(ObjectOutputStream stream) throws IOException { stream.defaultWriteObject(); stream.writeObject(friend); } private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { stream.defaultReadObject(); friend = (Person) stream.readObject(); } }
测试类的代码不做修改,运行结果如下
name = leesf, gender = man, age = 24, friend info is [name = dyd, gender = woman, age = 24, friend info is [null]] name = leesf, gender = man, age = 24, friend info is [name = dyd, gender = woman, age = 24, friend info is [null]]
说明:在实现自定义的逻辑时,在writeObject方法中可以调用defaultWriteObject()方法实现默认序列化(序列化非transient字段),可以单独处理transient关键字;在readObject方法中可以调用defaultReadObject()方法实现默认反序列化,可以单独处理transient关键字(需要赋值)。值得注意的是,writeObject方法中defaultWriteObject和处理transient关键字的逻辑必须与readObject中defaultReadObject和处理transient关键字的逻辑顺序一致,否则会抛出异常。
在调用writeObject方法后,会经过一系列的调用,具体的调用栈如下
说明:经过反射,最终会调用到在Person类中定义的writeObject方法。readObject方法的调用可以以此类比,不再累赘。
五、Externalizable
除了使用Serializable接口进行序列化以外,还可以使用Externalizable接口来进行序列化。
5.1 Externalizable定义
Externalizable的定义如下
public interface Externalizable extends java.io.Serializable { void writeExternal(ObjectOutput out) throws IOException; void readExternal(ObjectInput in) throws IOException, ClassNotFoundException; }
说明:Externalizable实现了Serializable接口,并且添加了两个方法writeExternal与readExternal,需要序列化的类需要实现Externalizable接口,并且重写接口中定义的两个方法。
5.2 使用说明
首先将序列化的类实现Externalizable接口并且重写writeExternal与readExternal方法,并在这两个方法中实现处理逻辑。我们定义Person类如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.Externalizable; import java.io.IOException; import java.io.ObjectInput; import java.io.ObjectOutput; public class Person implements Externalizable { /** * */ private static final long serialVersionUID = 1L; private String name; private String gender; private int age; private transient Person friend; public Person() { } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Person getFriend() { return friend; } public void setFriend(Person friend) { this.friend = friend; } @Override public String toString() { return "name = " + name + ", gender = " + gender + ", age = " + age + ", friend info is [" + friend + "]"; } @Override public void writeExternal(ObjectOutput out) throws IOException { out.writeUTF(name); out.writeUTF(gender); out.writeInt(age); out.writeObject(friend); } @Override public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException { name = in.readUTF(); gender = in.readUTF(); age = in.readInt(); friend = (Person) in.readObject(); } }
说明:Person类实现了Externalizable接口,重写了writeExternal与readExternal方法,并且实现了用户自定义序列化与反序列化逻辑。测试类代码不变,运行结果如下:
name = leesf, gender = man, age = 24, friend info is [name = dyd, gender = woman, age = 24, friend info is [null]] name = leesf, gender = man, age = 24, friend info is [name = dyd, gender = woman, age = 24, friend info is [null]]
说明:从结果可知,成功进行了序列化与反序列化过程。值得注意的是,我们必须要给Person类提供一个无参构造器,才能正确完成序列化与反序列化过程。否则会抛出如下异常
修改Person类如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.Externalizable; import java.io.IOException; import java.io.ObjectInput; import java.io.ObjectOutput; public class Person implements Externalizable { /** * */ private static final long serialVersionUID = 1L; private String name; private String gender; private int age; private transient Person friend; public Person(String name) { this.name = name; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Person getFriend() { return friend; } public void setFriend(Person friend) { this.friend = friend; } @Override public String toString() { return "name = " + name + ", gender = " + gender + ", age = " + age + ", friend info is [" + friend + "]"; } @Override public void writeExternal(ObjectOutput out) throws IOException { out.writeUTF(name); out.writeUTF(gender); out.writeInt(age); out.writeObject(friend); } @Override public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException { name = in.readUTF(); gender = in.readUTF(); age = in.readInt(); friend = (Person) in.readObject(); } }
说明:提供一个参数的构造函数,没有无参构造函数,修改测试类代码如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; public class SerializableDemo { public static void main(String[] args) throws Exception { Person leesf = new Person("leesf"); Person dyd = new Person("dyd"); leesf.setAge(24); leesf.setGender("man"); leesf.setName("leesf"); dyd.setAge(24); dyd.setGender("woman"); dyd.setName("dyd"); leesf.setFriend(dyd); dyd.setFriend(null); File file = new File("test"); ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file)); oos.writeObject(leesf); oos.flush(); oos.close(); System.out.println(leesf); ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file)); leesf = (Person) ois.readObject(); ois.close(); System.out.println(leesf); } }
运行结果如下
name = leesf, gender = man, age = 24, friend info is [name = dyd, gender = woman, age = 24, friend info is [null]] Exception in thread "main" java.io.InvalidClassException: com.hust.grid.leesf.serializable.Person; no valid constructor at java.io.ObjectStreamClass$ExceptionInfo.newInvalidClassException(ObjectStreamClass.java:150) at java.io.ObjectStreamClass.checkDeserialize(ObjectStreamClass.java:768) at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1775) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351) at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371) at com.hust.grid.leesf.serializable.SerializableDemo.main(SerializableDemo.java:32)
说明:在反序列化的过程抛出了异常,可以看出是Person类没有合法的构造器,合法的构造器就是指无参构造器。当提供了无参构造器之后,就可以正确运行。
5.3 问题说明
1. Externalizable,writeObject与readObject方法
如果Person类实现了Externalizable接口,并且在Person类中添加了writeObject与readObject方法,那么在进行序列化与反序列化时,是以哪种方法为准呢,修改Person类如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.Externalizable; import java.io.IOException; import java.io.ObjectInput; import java.io.ObjectInputStream; import java.io.ObjectOutput; import java.io.ObjectOutputStream; public class Person implements Externalizable { /** * */ private static final long serialVersionUID = 1L; private String name; private String gender; private int age; private transient Person friend; public Person() { } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Person getFriend() { return friend; } public void setFriend(Person friend) { this.friend = friend; } @Override public String toString() { return "name = " + name + ", gender = " + gender + ", age = " + age + ", friend info is [" + friend + "]"; } @Override public void writeExternal(ObjectOutput out) throws IOException { System.out.println("use writeExternal method"); out.writeUTF(name); out.writeUTF(gender); out.writeInt(age); out.writeObject(friend); } @Override public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException { System.out.println("use readExternal method"); name = in.readUTF(); gender = in.readUTF(); age = in.readInt(); friend = (Person) in.readObject(); } private void writeObject(ObjectOutputStream stream) throws IOException { System.out.println("use writeObject method"); stream.defaultWriteObject(); stream.writeObject(friend); } private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { System.out.println("use readObject method"); stream.defaultReadObject(); friend = (Person) stream.readObject(); } }
说明:在方法中添加了打印语句,这样就可以轻易判别采用的何种方式。测试类代码如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; public class SerializableDemo { public static void main(String[] args) throws Exception { Person leesf = new Person(); Person dyd = new Person(); leesf.setAge(24); leesf.setGender("man"); leesf.setName("leesf"); dyd.setAge(24); dyd.setGender("woman"); dyd.setName("dyd"); leesf.setFriend(dyd); dyd.setFriend(null); File file = new File("test"); ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file)); oos.writeObject(leesf); oos.flush(); oos.close(); System.out.println(leesf); ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file)); leesf = (Person) ois.readObject(); ois.close(); System.out.println(leesf); } }
运行结果
use writeExternal method use writeExternal method name = leesf, gender = man, age = 24, friend info is [name = dyd, gender = woman, age = 24, friend info is [null]] use readExternal method use readExternal method name = leesf, gender = man, age = 24, friend info is [name = dyd, gender = woman, age = 24, friend info is [null]]
说明:从结果可以看出,是以Externalizable接口中定义的两个方法进行序列化与反序列化的,这时,读者可能又会有另外一个疑问,那就是为什么会打印两次呢?答案是因为该方法被调用了两次,因为Person类有一个Person域,会导致调用两次。
2. 处理transient字段
可以在writeExternal与readExternal方法中实现自定义逻辑,对transient字段进行序列化与反序列化。
六、序列化问题
6.1 采用默认序列化机制,类的静态字段会被序列化吗?
采用默认序列化机制进行序列化时,类的静态字段会被序列化吗,此时类的静态字段不会被序列化,当然,我们可以采用自定义序列化逻辑对静态变量进行序列化。
6.2 父类序列化问题
采用默认序列化机制序列化子类时,其父类的字段会被序列化吗?可以分为如下情形
1. 父类没有实现Serializable接口,没有提供默认构造函数
这时,反序列化会出错,提示没有提供正确的构造函数。修改Person类,代码如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.Serializable; class Human { private int number; public Human(int number) { this.number = number; } public int getNumber() { return number; } public void setNumber(int number) { this.number = number; } public String toString() { return "number = " + number; } } public class Person extends Human implements Serializable { /** * */ private static final long serialVersionUID = 1L; private String name; private String gender; private int age; private transient Person friend; public Person(int number, String name) { super(number); this.name = name; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Person getFriend() { return friend; } public void setFriend(Person friend) { this.friend = friend; } @Override public String toString() { return super.toString() + ", name = " + name + ", gender = " + gender + ", age = " + age + ", friend info is [" + friend + "]"; } }
测试类的的代码如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; public class SerializableDemo { public static void main(String[] args) throws Exception { Person leesf = new Person(1, "leesf"); Person dyd = new Person(2, "dyd"); leesf.setAge(24); leesf.setGender("man"); leesf.setName("leesf"); dyd.setAge(24); dyd.setGender("woman"); dyd.setName("dyd"); leesf.setFriend(dyd); dyd.setFriend(null); File file = new File("test"); ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file)); oos.writeObject(leesf); oos.flush(); oos.close(); System.out.println(leesf); ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file)); leesf = (Person) ois.readObject(); ois.close(); System.out.println(leesf); } }
运行结果
number = 1, name = leesf, gender = man, age = 24, friend info is [number = 2, name = dyd, gender = woman, age = 24, friend info is [null]] Exception in thread "main" java.io.InvalidClassException: com.hust.grid.leesf.serializable.Person; no valid constructor at java.io.ObjectStreamClass$ExceptionInfo.newInvalidClassException(ObjectStreamClass.java:150) at java.io.ObjectStreamClass.checkDeserialize(ObjectStreamClass.java:768) at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1775) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351) at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371) at com.hust.grid.leesf.serializable.SerializableDemo.main(SerializableDemo.java:32)
说明:可以看出是没有提供合法的构造函数。
2. 父类没有实现Serializable接口,提供默认构造函数
第一步中出现了错误,此时,我们修改Person类,代码如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.Serializable; class Human { private int number; public Human() { } public Human(int number) { this.number = number; } public int getNumber() { return number; } public void setNumber(int number) { this.number = number; } public String toString() { return "number = " + number; } } public class Person extends Human implements Serializable { /** * */ private static final long serialVersionUID = 1L; private String name; private String gender; private int age; private transient Person friend; public Person() { super(); } public Person(int number, String name) { super(number); this.name = name; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Person getFriend() { return friend; } public void setFriend(Person friend) { this.friend = friend; } @Override public String toString() { return super.toString() + ", name = " + name + ", gender = " + gender + ", age = " + age + ", friend info is [" + friend + "]"; } }
说明:给Human类提供了无参构造函数。测试类代码不变,运行结果如下
number = 1, name = leesf, gender = man, age = 24, friend info is [number = 2, name = dyd, gender = woman, age = 24, friend info is [null]] number = 0, name = leesf, gender = man, age = 24, friend info is [null]
说明:此时,我们可以看到,可以进行反序列化了,但是父类的number字段被赋值为int的默认值0,Person类的transient字段没有被序列化。
3. 父类实现Serializable接口
当父类实现Serializable接口时,修改Person类代码如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.Serializable; class Human implements Serializable { /** * */ private static final long serialVersionUID = 1L; private int number; public Human() { } public Human(int number) { this.number = number; } public int getNumber() { return number; } public void setNumber(int number) { this.number = number; } public String toString() { return "number = " + number; } } public class Person extends Human implements Serializable { /** * */ private static final long serialVersionUID = 1L; private String name; private String gender; private int age; private transient Person friend; public Person() { super(); } public Person(int number, String name) { super(number); this.name = name; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Person getFriend() { return friend; } public void setFriend(Person friend) { this.friend = friend; } @Override public String toString() { return super.toString() + ", name = " + name + ", gender = " + gender + ", age = " + age + ", friend info is [" + friend + "]"; } }
测试类的代码不变,运行结果如下
number = 1, name = leesf, gender = man, age = 24, friend info is [number = 2, name = dyd, gender = woman, age = 24, friend info is [null]] number = 1, name = leesf, gender = man, age = 24, friend info is [null]
说明:从结果可知,已经可以进行正确的序列化与反序列化了,子类的transient字段没有被序列化。
6.3 共享对象序列化问题
当序列化的两个对象都包含另外一个对象的引用时,在反序列化时,另外一个对象只会出现一次吗?修改Person类代码如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.Serializable; public class Person implements Serializable { /** * */ private static final long serialVersionUID = 1L; private String name; private String gender; private int age; private transient Person friend; public Person() { } public Person(String name) { this.name = name; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Person getFriend() { return friend; } public void setFriend(Person friend) { this.friend = friend; } }
测试类代码如下
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.hust.grid.leesf.serializable; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.util.ArrayList; import java.util.List; public class SerializableDemo { @SuppressWarnings("unchecked") public static void main(String[] args) throws Exception { Person leesf = new Person("leesf"); Person dyd = new Person("dyd"); Person lr = new Person("lr"); leesf.setAge(24); leesf.setGender("man"); dyd.setAge(24); dyd.setGender("woman"); lr.setAge(25); lr.setGender("man"); leesf.setFriend(dyd); lr.setFriend(dyd); dyd.setFriend(null); List<Person> persons = new ArrayList<Person>(); persons.add(leesf); persons.add(dyd); persons.add(lr); ByteArrayOutputStream bos1 = new ByteArrayOutputStream(); ByteArrayOutputStream bos2 = new ByteArrayOutputStream(); ObjectOutputStream oos1 = new ObjectOutputStream(bos1); oos1.writeObject(persons); oos1.writeObject(persons); ObjectOutputStream oos2 = new ObjectOutputStream(bos2); oos2.writeObject(persons); ByteArrayInputStream bis1 = new ByteArrayInputStream(bos1.toByteArray()); ByteArrayInputStream bis2 = new ByteArrayInputStream(bos2.toByteArray()); ObjectInputStream ois1 = new ObjectInputStream(bis1); ObjectInputStream ois2 = new ObjectInputStream(bis2); List<Person> persons1 = (List<Person>) ois1.readObject(); List<Person> persons2 = (List<Person>) ois1.readObject(); List<Person> persons3 = (List<Person>) ois2.readObject(); System.out.println(persons1); System.out.println(persons2); System.out.println(persons3); } }
运行结果如下
[com.hust.grid.leesf.serializable.Person@7f31245a, com.hust.grid.leesf.serializable.Person@6d6f6e28, com.hust.grid.leesf.serializable.Person@135fbaa4]
[com.hust.grid.leesf.serializable.Person@7f31245a, com.hust.grid.leesf.serializable.Person@6d6f6e28, com.hust.grid.leesf.serializable.Person@135fbaa4]
[com.hust.grid.leesf.serializable.Person@45ee12a7, com.hust.grid.leesf.serializable.Person@330bedb4, com.hust.grid.leesf.serializable.Person@2503dbd3]
说明:从结果可知,oos1执行的writeObject是向同一个内存空间写了两次,从结果可看出,两次写入的对象的地址空间都是一样的,即进行了浅拷贝。而oos2执行的writeObject是向另外一个内存空间写了一次,从结果可看出,因为对象的地址不同于之前的对象地址,即采用了深拷贝。
七、总结
写到这里,关于Java中的序列化与反序列化机制就已经分析完了,经过此次分析,对序列化机制的认识更加深刻。学习一个知识点,就要认认真真,踏踏实实的弄懂一个知识点,写博客就是一个特别好的方式。谢谢各位园友的观看~
参考链接
http://blog.csdn.net/jiangwei0910410003/article/details/18989711/
http://www.hollischuang.com/archives/1140
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作者:leesf 掌控之中,才会成功;掌控之外,注定失败。
出处:http://www.cnblogs.com/leesf456/
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