``

• [](https://en.wikipedia.org/wiki/Java_remote_method_invocation)

****``

public class Person implements Serializable {
    private String name;
    private int age;

    public Person() {
        System.out.println("无参构造.");
    }

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
        System.out.println("有参构造.");
    }

    @Override
    public String toString() {
        return "Person{" +
        "name='" + name + '\'' +
        ", age=" + age +
        '}';
    }
}

``

public class SerializableTest {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        Person person = new Person("zhangsan", 24);
        
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("abc.txt"));
        oos.writeObject(person);
        oos.close();
    }
}

有参构造.

public class SerializableTest {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("abc.txt"));
        Person p = (Person) ois.readObject();
        System.out.println(p);
    }

Person{name='zhangsan', age=24}

****

// 没有实现序列化接口
public class Person{
    private String name;
    private int age;

    public Person() {
        System.out.println("无参构造.");
    }

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
        System.out.println("有参构造.");
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

// 实现了序列化接口
public class Teacher implements Serializable {
    private String name;
    private Person person;

    public Teacher(String name, Person person) {
        this.name = name;
        this.person = person;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Person getPerson() {
        return person;
    }

    public void setPerson(Person person) {
        this.person = person;
    }

    @Override
    public String toString() {
        return "Teacher{" +
                "name='" + name + '\'' +
                ", person=" + person +
                '}';
    }
}

public class SerializableTest {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        Person person = new Person("zhangsan", 24);
        Teacher t = new Teacher("lisi", person);
        
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("abc.txt"));
        oos.writeObject(t);
        oos.close();
    }
}

有参构造.
Exception in thread "main" java.io.NotSerializableException: other.Person
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
	at other.SerializableTest.main(SerializableTest.java:10)

// 检查一：代码省略
...

// 检查二：代码省略
...

// 检查三：
if (obj instanceof String) {
    writeString((String) obj, unshared);
} else if (cl.isArray()) {
    writeArray(obj, desc, unshared);
} else if (obj instanceof Enum) {
    writeEnum((Enum<?>) obj, desc, unshared);
} else if (obj instanceof Serializable) {
    writeOrdinaryObject(obj, desc, unshared);
} else {
    if (extendedDebugInfo) {
        throw new NotSerializableException(
            cl.getName() + "\n" + debugInfoStack.toString());
    } else {
        throw new NotSerializableException(cl.getName());
    }
}

import java.io.*;

public class ExPerson implements Externalizable {
    private String name;
    private int age;

    public ExPerson() {
        System.out.println("无参构造.");
    }

    public ExPerson(String name, int age) {
        this.name = name;
        this.age = age;
        System.out.println("有参构造.");
    }

    @Override
    public String toString() {
        return name + age;
    }

    @Override
    public void writeExternal(ObjectOutput out) throws IOException {
        System.out.println("writeExternal() method.");
        out.writeObject(name);
        out.writeInt(age);
    }

    @Override
    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
        System.out.println("readExternal() method.");
        name = (String) in.readObject();
        age = in.readInt();
    }

    public static void main(String[] args) throws IOException, ClassNotFoundException {
        ExPerson exPerson = new ExPerson("zhangsan", 25);
        System.out.println(exPerson);
        // 序列化
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("123.txt"));
        System.out.println("保存对象：");
        oos.writeObject(exPerson);
        oos.close();

        // 反序列化
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("123.txt"));
        System.out.println("接收对象：");
        exPerson = (ExPerson) ois.readObject();
        System.out.println(exPerson);
    }
}

有参构造.
zhangsan25
保存对象：
writeExternal() method.
接收对象：
无参构造.
readExternal() method.
zhangsan25

````

import java.io.*;

public class Person implements Serializable {
    private transient String name;
    private transient int age;
    private int height;

    public Person() {
        System.out.println("无参构造.");
    }

    public Person(String name, int age, int height) {
        this.name = name;
        this.age = age;
        this.height = height;
        System.out.println("有参构造.");
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", height=" + height +
                '}';
    }
}

有参构造.
Person{name='null', age=0, height=180}

````

<font style="color:rgb(199, 37, 78);background-color:rgb(240, 242, 245);">transient</font>

• ``****``

public class StaticSerializableTest implements Serializable {
    private static int age = 25;

    public static void main(String[] args) throws IOException, ClassNotFoundException {
        // 序列化
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("staticSerializable.txt"));
        oos.writeObject(new StaticSerializableTest());
        oos.close();

        // 修改静态变量的值
        StaticSerializableTest.age = 30;

        // 反序列化
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("staticSerializable.txt"));
        StaticSerializableTest ss = null;
        ss = (StaticSerializableTest) ois.readObject();

        System.out.println(ss.age);
    }
}

30

****

****``````

``

• ``
• ``
• ``
• ``

````

public class Singleton implements Serializable {
    private volatile static Singleton instance;

    private Singleton() {

    }

    public static Singleton getInstance() {
        if (instance == null) {
            synchronized (Singleton.class) {
                if (instance == null) {
                    instance = new Singleton();
                }
            }
        }
        return instance;
    }
}

public class SerializableDemo {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        // 序列化
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("456.txt"));
        oos.writeObject(Singleton.getInstance());
        oos.close();

        // 反序列化
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("456.txt"));
        Singleton newSingleton = (Singleton)ois.readObject();

        // 比较是否相等
        System.out.println(Singleton.getInstance() == newSingleton);
    }
}

``

Object obj;
try {
    obj = desc.isInstantiable() ? desc.newInstance() : null;
} catch (Exception ex) {
    throw (IOException) new InvalidClassException(desc.forClass().getName(), 
                                                "unable to create instance").initCause(ex);
}

````

****

if (obj != null &&
    handles.lookupException(passHandle) == null &&
    desc.hasReadResolveMethod())
{
    Object rep = desc.invokeReadResolve(obj);
    if (unshared && rep.getClass().isArray()) {
        rep = cloneArray(rep);
    }
    if (rep != obj) {
        // Filter the replacement object
        if (rep != null) {
            if (rep.getClass().isArray()) {
                filterCheck(rep.getClass(), Array.getLength(rep));
            } else {
                filterCheck(rep.getClass(), -1);
            }
        }
        handles.setObject(passHandle, obj = rep);
    }
}

public class Singleton implements Serializable {
    private volatile static Singleton instance;

    private Singleton() {

    }

    public static Singleton getInstance() {
        if (instance == null) {
            synchronized (Singleton.class) {
                if (instance == null) {
                    instance = new Singleton();
                }
            }
        }
        return instance;
    }

    // 添加 readResolve 方法
    public Object readResolve() {
        return instance;
    }
}