如何使用缓冲区读取和写入Java对象

Question

I need to write and read objects to file. How i can do it with use of buffer? When i use it like that it's only write the last object to the file.

        OutputStream file = new FileOutputStream(DRB );
        OutputStream buffer = new BufferedOutputStream( file );
        ObjectOutput out = new ObjectOutputStream( buffer );

        try{
            out.writeObject(e1);
          }
          finally
          {
            buffer.flush();
            out.close();
          }

Answer 1

To append to an ObjectOutputStream there is only two options as I see it

• read all the data into a list, add the item and write all the objects. An ObjectStream is a single continous stream. It is not like text where you can keep adding to the end.
• use your own format to write multiple independent stream to the same file. You can write to a ByteArrayOutputStream, and use this to write the length of the stream before writing the contents. This way you can read the individual stream back in. I would only do this if you are confident in processing binary files.

Answer 2

The object you used e1 must be serialized class.

That's the only criteria.

Answer 3

You can have List of objects you want to write. Then, you can write this list.

Answer 4

Please see the code give below. Hope this will solve your problem:

package com.shineed.io;

import java.io.FileInputStream;

import java.io.ObjectInputStream;

import java.io.Serializable;

public class Deserializer{

   public static void main (String args[]) {

       Deserializer deserializer = new Deserializer();

       Customer customer = deserializer.deserialzeCustomer();

       System.out.println(customer);
   }

   public Customer deserialzeCustomer(){

       Customer customer;

       try{

           FileInputStream fin = new FileInputStream("c:\\customer.txt");
           ObjectInputStream ois = new ObjectInputStream(fin);
           customer = (Customer) ois.readObject();
           ois.close();

           return customer;

       }catch(Exception e){
           e.printStackTrace();
           return null;
       } 
   } 
}

Also see the Customer class given below:

package com.shineed.io;

import java.io.Serializable;

public class Customer implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    private String name;
    private String adress;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getAdress() {
        return adress;
    }
    public void setAdress(String adress) {
        this.adress = adress;
    }

}