How to convert an object to byte array in java?

Step 1: Make the class serializable by implementing Serializable interface.

public class User implements Serializable {
    .......
    .......
}

 

Step 2: Write the Serializable object to ObjectOutputStream, make sure that ObjectOutputStream is internally using ByteArrayOutputStream.

ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
objectOutputStream.writeObject(serializable);
objectOutputStream.flush();

 

Step 3: Get the byte array from ByteArrayOutputStream.

byte[] byteArr = byteArrayOutputStream.toByteArray();

 

Find the below working application.

 

User.java

 

package com.sample.app.dto;

import java.io.Serializable;

public class User implements Serializable {

    private static final long serialVersionUID = 198623L;

    private int id;

    private String name;

    public User(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + "]";
    }

}

 

SerializationDemo.java

package com.sample.app;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

import com.sample.app.dto.User;

public class SerializationDemo {

    public static byte[] serialize(Serializable serializable) {

        try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
                ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream)) {
            objectOutputStream.writeObject(serializable);
            objectOutputStream.flush();
            return byteArrayOutputStream.toByteArray();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }

    }

    public static Object deserialize(byte[] byteArray) {
        try (ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(byteArray);
                ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream)) {
            return objectInputStream.readObject();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }

    }

    public static void main(String[] args) {

        byte[] byteArr = serialize(new User(1, "Krishna"));
        User user = (User) deserialize(byteArr);

        System.out.println("Byte array representaion of user object :");
        for (byte b : byteArr) {
            System.out.print(b + " ");
        }

        System.out.println("\n\nDeserialized version of user object from byte array : ");
        System.out.println("user : " + user);
    }

}

 

Output

Byte array representaion of user object :
-84 -19 0 5 115 114 0 23 99 111 109 46 115 97 109 112 108 101 46 97 112 112 46 100 116 111 46 85 115 101 114 0 0 0 0 0 3 7 -33 2 0 2 73 0 2 105 100 76 0 4 110 97 109 101 116 0 18 76 106 97 118 97 47 108 97 110 103 47 83 116 114 105 110 103 59 120 112 0 0 0 1 116 0 7 75 114 105 115 104 110 97 

Deserialized version of user object from byte array : 
user : User [id=1, name=Krishna]

 

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