使用ObjectInputStream的readObject()方法如何判断读取到多个对象的结尾

Posted 2020-08-21 LiuYanYGZ

摘自http://blog.csdn.net/fjdingsd/article/details/46765803

使用ObjectInputStream的readObject()方法如何判断读取到多个对象的结尾

 

import java.io.EOFException;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;

import cn.com.mybolg.bean.Person;

/*
 * 若文件中有若干个Object对象，你用ObjectInputStream中的readObject()去读，何时判读到结尾？
 * 方法之一：（常用的方法）将若干个对象（数量不定）都装入一个容器中（如：ArrayList之类），
 * 然后将容器这一个对象写入就行了。读取时，只要读取一个对象（即容器对象）就行了。
 * 
 * 方法之二：（若不想用容器），则由于数量不定，正是用EOFException来判断结束。
 * 代码结构如下：(无论是readInt()读int，还是readObject()读对象) 
 * try{
 *  while(true) {
 *   Object o=ois.radObject(); 
 *   处理已读出的对象o; 
 *   }
 *  }
 *  catch(EOFException e){ 
 *  //已从流中读完。 
 *  } 
 *  finallly {
 * 流的关闭。 }
 */

public class ObjectInputStreamDemo {

    public static void main(String[] args) throws IOException, ClassNotFoundException {
        
        FileInputStream fis = new FileInputStream("F:\\\\person.object");
        ObjectInputStream osi = new ObjectInputStream(fis);
        
        try {
            while(true) {
                Person p = (Person) osi.readObject();
                System.out.println(p.getName()+":"+p.getAge());
            }
        }
        catch(EOFException e) {
            
        }
        finally {
            osi.close();
        }
    }

}

 

 以下是自己的试验：

往文件里存多个对象也没问题，调用writeObject()一直往里写即可，readObject()一次返回一个对象，再readObject()一次返回第二个对象，自动在每个对象后面做标记。并且同一个文件中可以依次存入不同类的对象。先存入一个Person对象，再存入一个Demo对象，再存个Haha对象都可以。按顺序读就行了。

package packa;

import java.io.*;

class ObjectInputOutputStream
{
    public static void main(String[] args)throws Exception
    {
        writeObj();
        readObj();
    }

    private static void writeObj()throws Exception
    {
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("person.object"));

        oos.writeObject(new Person("liu", 30, "kr"));
        oos.writeObject(new Person2("liu", "kr", "kr2"));
        oos.writeObject(new Person3(10, 30, 50));

        oos.close();
    }

    private static void readObj()throws Exception
    {
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("person.object"));
        System.out.println(ois.readObject());
        System.out.println(ois.readObject());
        System.out.println(ois.readObject());

        ois.close();
    }
}

 

package packa;

import java.io.*;

class Person implements Serializable
{
    public static final long serialVersionUID = 44L;

    String name;
    transient int age;
    static String country = "cn";

    Person(String name, int age, String country)
    {
        this.name = name;
        this.age = age;
        this.country = country;
    }

    public String toString()
    {
        return name + " " + age + " " + country;
    }

}
class Person2 implements Serializable
{
    public static final long serialVersionUID = 45L;

    String name;
    String country;
    String country2;

    Person2(String name, String country, String country2)
    {
        this.name = name;
        this.country = country;
        this.country2 = country2;
    }

    public String toString()
    {
        return name + " " + country + " " + country2;
    }

}
class Person3 implements Serializable
{
    public static final long serialVersionUID = 46L;

    int age;
    int age2;
    int age3;

    Person3(int age, int age2, int age3)
    {
        this.age = age;
        this.age2 = age2;
        this.age3 = age3;
    }

    public String toString()
    {
        return age + " " + age2 + " " + age3;
    }

}