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????Object Stream??Java??????????????Java????????????????????????????????????????????????

1. ??????

?????????ObjectInputStream?ObjectOutputStream??????????????????????????????Java???????????????????????????

????????

??????????????????Java??????????????????ObjectOutputStream??????????????ObjectInputStream??????????????????????????????????Serializable???????????NoSerializableException???

????

• ?????ObjectOutputStream?ObjectInputStream???????????????????????????????
• transient?????transient?????????????????????????????????int?0?Object?null??

2. ???????

???????????????????Serializable???????????????????????????????????

??????

• ??????????????????????Java???????????
• ???????????????????????????????????????
• ???????????????????????????????????

????????

??????????????????

3. ??????

??????

???????????????????

import java.io.*;
import java.io.Serializable;
public class TestObjectStream {
    public static void main(String[] args) throws IOException {
        // ?????
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("data.obj"));
        String data = "Hello, World!";
        oos.writeObject(data);
        oos.flush();
        oos.close();
        // ??????
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("data.obj"));
        Object obj = ois.readObject();
        System.out.println((String) obj); // ?? "Hello, World!"
        ois.close();
    }
}

???????ObjectOutputStream????"Hello, World!"??????????ObjectInputStream?????????????????

????????

???????????????????????????????????Serializable????????

public class Person implements Serializable {
    private static final long serialVersionUID = 123456789012345678L;
    private String name;
    private int age;
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Person{" + "name=" + name + ", age=" + age + '}';
    }
}

????????????????????????Address??????????Serializable???

4. ???????

?????????

???A??B??serialVersionUID?????????????InvalidClassException??????

• A????serialVersionUID?7246350247175365830L
• B????serialVersionUID?7346350247175365830L

??????JVM?????serialVersionUID??????????????

????????

??A??????????B????????????????????????????

• A???????

  public class Person implements Serializable {
      private static final long serialVersionUID = 7346350247175365830L;
      private String name;
      private int age;
      private int sex;
  }

• B???????

  public class Person implements Serializable {
      private static final long serialVersionUID = 7346350247175365830L;
      private String name;
      private int age;
  }

??????????

Person{name=???????, age=123}

???sex???????

?????????

??B????serialVersionUID??????????????????????????????

• A???????

  public class Person implements Serializable {
      private static final long serialVersionUID = 7346350247175365830L;
      private String name;
      private int age;
  }

• B???????

  public class Person implements Serializable {
      private static final long serialVersionUID = 7346350247175365830L;
      private String name;
      private int age;
      private int sex;
  }

??????????

Person{name=???????, age=123, sex=0}

???sex?????????????????0?

5. ???transient?????

????

???????ObjectOutputStream?ObjectInputStream????????????

public class TestStatic implements Serializable {
    private static final long serialVersionUID = -4662715330378065625L;
    public static int ver = 123;
    public transient String aa;
    public static void main(String[] args) throws IOException {
        TestStatic test = new TestStatic();
        test.setAa("dfadfasdf");
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("test.obj"));
        oos.writeObject(test);
        oos.flush();
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.obj"));
        Object obj = ois.readObject();
        if (obj instanceof TestStatic) {
            TestStatic test = (TestStatic) obj;
            System.out.println(test.getVer()); // ?? 123
            System.out.println(test.getAa()); // ?? "dfadfasdf"
        }
    }
    public int getVer() {
        return ver;
    }
    public void setVer(int ver) {
        TestStatic.ver = ver;
    }
    public String getAa() {
        return aa;
    }
    public void setAa(String aa) {
        this.aa = aa;
    }
    @Override
    public String toString() {
        return "TestStatic{" + "ver=" + ver + ", aa='" + aa + '\'' + '}';
    }
}

??????ver????123??aa???null???transient?????????

transient??

transient???????????????????????????

public class TestTransient implements Serializable {
    private static final long serialVersionUID = -4662715330378065625L;
    public transient String aa;
    public static void main(String[] args) throws IOException {
        TestTransient test = new TestTransient();
        test.setAa("dfadfasdf");
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("test.obj"));
        oos.writeObject(test);
        oos.flush();
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.obj"));
        Object obj = ois.readObject();
        if (obj instanceof TestTransient) {
            TestTransient test = (TestTransient) obj;
            System.out.println(test.getAa()); // ?? null
        }
    }
    public String getAa() {
        return aa;
    }
    public void setAa(String aa) {
        this.aa = aa;
    }
    @Override
    public String toString() {
        return "TestTransient{" + "aa='" + aa + '\'' + '}';
    }
}

??????aa???null???????transient???

6. ??

????Java??????????????????????????????ObjectInputStream?ObjectOutputStream??????????Java???????????????????????????????????????serialVersionUID????????static?transient??????????????????????