Question

My Code-

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

public class ObjectStreamExample {

    /**
     * @param args
     */
    public static void main(String[] args) {

        Person person = new Person();
        person.setFirstName("Abhishek");
        person.setLastName("Choudhary");
        person.setAge(25);
        person.setHouseNum(256);
        ObjectOutputStream stream = null;
        try {
            stream = new ObjectOutputStream(new FileOutputStream(new File("Serialize.txt")));
            stream.writeUTF(person.toString());
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {

            e.printStackTrace();
        }finally{
            if(stream != null)
                try {
                    stream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
        }

        ObjectInputStream input = null;

        try {
            input = new ObjectInputStream(new FileInputStream(new File("Serialize.txt")));

            Person person2 = (Person) input.readObject();
            System.out.println(person2.getFirstName());
            System.out.println(person2.getLastName());
            System.out.println(person2.getAge());
            System.out.println(person2.getHouseNum());
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }finally{
            if(input != null)
                try {
                    input.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
        }


    }

}

and one Person bean file.

I am getting exception

java.io.OptionalDataException at
java.io.ObjectInputStream.readObject0(Unknown Source) at
java.io.ObjectInputStream.readObject(Unknown Source) at
com.practise.interview.nio.ObjectStreamExample.main(ObjectStreamExample.java:62)

This is getting raised because I think –

An attempt was made to read an object when the next element in the
stream is primitive data. In this case, the OptionalDataException’s
length field is set to the number of bytes of primitive data
immediately readable from the stream, and the eof field is set to
false.

But how to avoid it as I know I set a primitive value, so way to avoid.?

Answer 1

You are writing a String and try to read a Person. That’s not how serialization works. In the context of serialization, an UTF string is considered primitive data, because it does not contain object information (class name, attributes etc.), but only the string data.

Write out the person object itself, if you want to read a Person afterwards:

stream.writeObject(person);

Addendum: If writing a String would behave like with any other Object, you would get a ClassCastException instead, because the String could not be cast to Person. In any case, the mismatch between what you write and what you read is causing the error you got.