将对象列表序列化为java中的文件

Question

我有一个大约20,000个对象的列表,而这个对象又有一个非常庞大的层次结构.我需要将对象转储到一个文件中,以便我可以在以后的任何时候阅读它.现在我的问题是,我已经在Java上工作但在序列化方面没有那么多,我没有那么多知识如何做到这一点.

在这种情况下,据我所知,我需要使用序列化和序列化.谁能请帮忙.我也可以使用任何新的API或普通的Java序列化.

问候.

Answer 1

请看这个链接http://www.java2s.com/Code/Java/File-Input-Output/Objectserialization.htm 它是这样的:

Card3 card = new Card3(12, Card3.SPADES);
    System.out.println("Card to write is: " + card);

    try {
      FileOutputStream out = new FileOutputStream("card.out");
      ObjectOutputStream oos = new ObjectOutputStream(out);
      oos.writeObject(card);
      oos.flush();
    } catch (Exception e) {
      System.out.println("Problem serializing: " + e);
    }

    Card3 acard = null;

    try {
      FileInputStream in = new FileInputStream("card.out");
      ObjectInputStream ois = new ObjectInputStream(in);
      acard = (Card3) (ois.readObject());
    } catch (Exception e) {
      System.out.println("Problem serializing: " + e);
    }

    System.out.println("Card read is: " + acard);

不要忘记在要保存的所有类中实现Serializable接口,并将修饰符"transient"放在您不想保存的所有字段中.(例如私有瞬态列表缓存;)

Answer 2

您可以直接保存对象列表，而不是单独保存每个对象。我正在使用下面的代码来实现这一点。虽然我正在序列化克隆，但学习基础知识应该足够了。

public static List<EmpoyeeTO> deepCloneList( List<EmpoyeeTO> objectList) {
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(baos);
            oos.writeObject(objectList);
            oos.flush();
            ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
            ObjectInputStream ois = new ObjectInputStream(bais);
            return (List<EmpoyeeTO>) ois.readObject();
        }catch(EOFException eof){
            return objectList;
        } 
        catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

Answer 3

我给你一个样本

import java.io.Serializable;

public class Account implements Serializable {

    private int accountNo;
    private String custName;
    private int balance;

    /** Creates a new instance of Account    */
    public Account(int accNo, String name, int bal) {
        this.accountNo = accNo;
        this.custName = name;
        this.balance = bal;
    }

    @Override
    public String toString() {
        String str = "Account No:" + this.accountNo;
        str += "\nCustomer name:" + this.custName;
        str += "\nBalance:" + this.balance;
        return str;
    }
}

写入和读取对象

package me.dev;

import java.io.EOFException;
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.logging.Level;
import java.util.logging.Logger;

public class Main {

    public void writeObject(ArrayList<Object> listAccount) throws IOException {
        //Create FileOutputStream to write file
        FileOutputStream fos = new FileOutputStream("C:\\bank.datum");
        //Create ObjectOutputStream to write object
        ObjectOutputStream objOutputStream = new ObjectOutputStream(fos);
        //Write object to file
        for (Object obj : listAccount) {

            objOutputStream.writeObject(obj);
            objOutputStream.reset();
        }
        objOutputStream.close();
    }

    public ArrayList<Account> readObject() throws ClassNotFoundException, IOException {
        ArrayList<Account> listAccount = new ArrayList();
        //Create new FileInputStream object to read file
        FileInputStream fis = new FileInputStream("C:\\bank.datum");
        //Create new ObjectInputStream object to read object from file
        ObjectInputStream obj = new ObjectInputStream(fis);
        try {
            while (fis.available() != -1) {
                //Read object from file
                Account acc = (Account) obj.readObject();
                listAccount.add(acc);
            }
        } catch (EOFException ex) {
            //ex.printStackTrace();
        }
        return listAccount;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws ClassNotFoundException {
        try {
            // TODO code application logic here
            ArrayList<Object> listAcc = new ArrayList<Object>();
            listAcc.add(new Account(1, "John", 1000));
            listAcc.add(new Account(2, "Smith", 2000));
            listAcc.add(new Account(3, "Tom", 3000));
            Main main = new Main();
            main.writeObject(listAcc);
            ArrayList<Account> listAccount = main.readObject();
            System.out.println("listisze:" + listAccount.size());
            if (listAccount.size() > 0) {
                for (Account account : listAccount) {
                    System.out.println(((Account) account).toString());
                }
            }
        } catch (IOException ex) {
            Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}