Java IO： 序列化-将对象写入文件

序列化 (serialization) 将对象的状态信息转换为可以存储或传输的形式的过程。在序列化期间，对象将其当前状态写入到临时或持久性存储区。以后，可以通过从存储区中读取或反序列化对象的状态，重新创建该对象。

Java object can write into a file for future access, this is called serialization. In order to do this, you have to implement the Serializableinterface, and use ObjectOutputStream to write the object into a file.

FileOutputStream fout = new FileOutputStream("c:\\user.ser");
ObjectOutputStream oos = new ObjectOutputStream(fout);
oos.writeObject(user);

Create an “User” object and implement Serializable interface. This object is going to write into a file.

package org.hello.io;

import java.io.Serializable;

public class User implements Serializable {


    private static final long serialVersionUID = 1L;
    long id;
    String username;
    String password;

    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    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;
    }

    @Override
    public String toString(){

        return new StringBuffer("ID: ")
        .append(this.id)
        .append(" Username: ")
        .append(this.username)
        .append(" Password: ")
        .append(this.password).toString();
    }
}

The method serializeUser() will write the “User” object and it’s variable value(18,"Harry","pass") into a file named “user.ser”, locate in c drive.

The method deserializeUser() will read a serialized file “c:\\user.ser” – created in this example, and convert it back to “User” object and print out the saved value.

完整实例如下：

package org.hello.io;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;
/*
 *
 * 序列化 (serialization) 将对象的状态信息转换为可以存储或传输的形式的过程。
 * 在序列化期间，对象将其当前状态写入到临时或持久性存储区。
 * 以后，可以通过从存储区中读取或反序列化对象的状态，重新创建该对象。
 */
public class Serializer {

    public static void main(String[] args){
        Serializer serializer = new Serializer();
        serializer.serializeUser(18,"Harry","pass");

        try {
            User user = serializer.deserializeUser();
            System.out.println(user);

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }


    }

    public void serializeUser(int id, String username, String password) {
        User user = new User();
        user.setId(id);
        user.setUsername(username);
        user.setPassword(password);

        try{
            FileOutputStream fout = new FileOutputStream("C:\\user.ser");
            ObjectOutputStream oos = new ObjectOutputStream(fout);
            oos.writeObject(user);
            oos.close();
            System.out.println("Done.");

        }catch(IOException e){
            e.printStackTrace();
        }
    }

    public User deserializeUser() throws ClassNotFoundException{
        User user = null;
        try{
            FileInputStream fin = new FileInputStream("C:\\user.ser");
            ObjectInputStream ois = new ObjectInputStream(fin);
            user = (User)ois.readObject();
            ois.close();
            return user;
        }catch(IOException e){
            e.printStackTrace();
            return null;
        }
    }
}