java序列化问题：

Serializable

Student.java

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.io.Serializable;


 /* Title:学生类 Description:实现序列化接口的学生类 Copyright: copyright2018
 * Filename:
 * Student.java
 * 
 * @author He Li Ming
 */ @version 1.0

public class Student implements Serializable {
    /**
 * 坑1.类里一定要serialVersionUID否则旧数据会反序列化失败
 * 坑2.一旦序列化保存到磁盘操作后，就不要修改类名了，否则旧数据会反序列化失败
 * 记住：对象的序列化是基于字节的，不能使用Reader和Writer等基于字符的层次结构
 * 尽量把对象转换成json保存更稳妥。
 */
private static final long serialVersionUID = 5175151654234923238L;
private String name;
private transient char sex;//属性上加入transient可以在实现了Serializable接口的类中隐藏属性
private int year;
private double gpa;

public Student() {

}

public Student(String name, char sex, int year, double gpa) {
    this.name = name;
    this.sex = sex;
    this.year = year;
    this.gpa = gpa;
}

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

public void setSex(char sex) {
    this.sex = sex;
}

public void setYear(int year) {
    this.year = year;
}

public void setGpa(double gpa) {
    this.gpa = gpa;
}

public String getName() {
    return this.name;
}

public char getSex() {
    return this.sex;
}

public int getYear() {
    return this.year;
}

public double getGpa() {
    return this.gpa;
}
}

UseStudent.java

import java.io.*;

/**
 *Title:应用学生类
 *Description:实现学生类实例的序列化与反序列化
 *Copyright: copyright(c) 2012
 *Filename: UseStudent.java
 *@author He LiMing
 *@version 1.0
 */

public class UseStudent
{
 public static void main(String[] args)
 {
  Student st = new Student("Tom",'M',20,3.6);
  File file = new File("e:\\20171204.txt");
  try
  {
   file.createNewFile();
  }
  catch(IOException e)
  {
   e.printStackTrace();
  }
  try
  {
   //Student对象序列化过程
   FileOutputStream fos = new FileOutputStream(file);
   ObjectOutputStream oos = new ObjectOutputStream(fos);
   oos.writeObject(st);
   oos.flush();
   oos.close();
   fos.close();

   //Student对象反序列化过程
   FileInputStream fis = new FileInputStream(file);
   ObjectInputStream ois = new ObjectInputStream(fis);
   Student st1 = (Student) ois.readObject();
   System.out.println("name = " + st1.getName());
   System.out.println("sex = " + st1.getSex());
   System.out.println("year = " + st1.getYear());
   System.out.println("gpa = " + st1.getGpa());
   ois.close();
   fis.close();
  }
  catch(ClassNotFoundException e)
  {
   e.printStackTrace();
  }
  catch (IOException e)
  {
   e.printStackTrace();
  }             
 }
}

//控制台
name = Tom
sex = 
year = 20
gpa = 3.6

2.Externalizable

ExternalizableTest.java

import java.io.Externalizable;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;

/**
 *Title:应用工资类
 *Description:实现工资类实例的序列化与反序列化
 *Copyright: copyright(c) 2012
 *Filename: ExternalizableTest.java
 *@author He LiMing
 *@version 1.0
 */

public class ExternalizableTest implements Externalizable {

private transient String content ;
private transient String username ;
private transient String password  ;
private transient String money  ;
@Override
public void writeExternal(ObjectOutput out) throws IOException {
    out.writeObject(content);
    out.writeObject(username);//如果我们不将content和username的值写入的话，那么在反序列化的时候，就不会得到这些值。
}

@Override
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
    content = (String) in.readObject();//在反序列化时，需要初始化content和username，否则只是调用默认构造函数，得不到content和username的值
    username = (String) in.readObject();
}
public static void main(String[] args) {

ExternalizableTest externalizableTest = new ExternalizableTest("我会被序列化，不管我是不是transient修饰的哈！","我也会被序列化admin！","123456！","500万！");

try {
    ObjectOutput out = new ObjectOutputStream(new FileOutputStream(new File(
            "test")));
    out.writeObject(externalizableTest);

    ObjectInput in = new ObjectInputStream(new FileInputStream(new File(
            "test")));
    try {
        externalizableTest = (ExternalizableTest) in.readObject();
         System.out.println(externalizableTest.content);
         System.out.println(externalizableTest.username);
         System.out.println(externalizableTest.password);
         System.out.println(externalizableTest.money);
         out.close();
         in.close();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

System.exit(0);//解决控制台报错
}

public ExternalizableTest(String content, String username, String password, String money) {
    super();
    this.content = content;
    this.username = username;
    this.password = password;
    this.money = money;
}

public ExternalizableTest() {
    super();
}

public String getContent() {
    return content;
}

public void setContent(String content) {
    this.content = content;
}

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}

public String getMoney() {
    return money;
}

public void setMoney(String money) {
    this.money = money;
}


}

//控制台
我会被序列化，不管我是不是transient修饰的哈！
我也会被序列化admin！
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java序列化问题

java序列化问题：

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