Java Serializable Object to Byte Array

Let's say I have a serializable class AppMessage.

I would like to transmit it as byte[] over sockets to another machine where it is rebuilt from the bytes received.

How could I achieve this?

Prepare the byte array to send:

ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream out = null;
try {
  out = new ObjectOutputStream(bos);   
  out.writeObject(yourObject);
  out.flush();
  byte[] yourBytes = bos.toByteArray();
  ...
} finally {
  try {
    bos.close();
  } catch (IOException ex) {
    // ignore close exception
  }
}

Create an object from a byte array:

ByteArrayInputStream bis = new ByteArrayInputStream(yourBytes);
ObjectInput in = null;
try {
  in = new ObjectInputStream(bis);
  Object o = in.readObject(); 
  ...
} finally {
  try {
    if (in != null) {
      in.close();
    }
  } catch (IOException ex) {
    // ignore close exception
  }
}

The best way to do it is to use SerializationUtils from Apache Commons Lang.

To serialize:

byte[] data = SerializationUtils.serialize(yourObject);

To deserialize:

YourObject yourObject = SerializationUtils.deserialize(data)

---

As mentioned, this requires Commons Lang library. It can be imported using Gradle:

compile 'org.apache.commons:commons-lang3:3.5'

Maven:

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.5</version>
</dependency>

Jar file

And more ways mentioned here

Alternatively, the whole collection can be imported. Refer this link

If you use Java >= 7, you could improve the accepted solution using try with resources:

private byte[] convertToBytes(Object object) throws IOException {
    try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
         ObjectOutputStream out = new ObjectOutputStream(bos)) {
        out.writeObject(object);
        return bos.toByteArray();
    } 
}

And the other way around:

private Object convertFromBytes(byte[] bytes) throws IOException, ClassNotFoundException {
    try (ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
         ObjectInputStream in = new ObjectInputStream(bis)) {
        return in.readObject();
    } 
}

Can be done by SerializationUtils, by serialize & deserialize method by ApacheUtils to convert object to byte[] and vice-versa , as stated in @uris answer.

To convert an object to byte[] by serializing:

byte[] data = SerializationUtils.serialize(object);

To convert byte[] to object by deserializing::

Object object = (Object) SerializationUtils.deserialize(byte[] data)

Click on the link to Download org-apache-commons-lang.jar

Integrate .jar file by clicking:

FileName -> Open Medule Settings -> Select your module -> Dependencies -> Add Jar file and you are done.

Hope this helps.

I also recommend to use SerializationUtils tool. I want to make a ajust on a wrong comment by @Abilash. The SerializationUtils.serialize() method is not restricted to 1024 bytes, contrary to another answer here.

public static byte[] serialize(Object object) {
	if (object == null) {
		return null;
	}
	ByteArrayOutputStream baos = new ByteArrayOutputStream(1024);
	try {
		ObjectOutputStream oos = new ObjectOutputStream(baos);
		oos.writeObject(object);
		oos.flush();
	}
	catch (IOException ex) {
		throw new IllegalArgumentException("Failed to serialize object of type: " + object.getClass(), ex);
	}
	return baos.toByteArray();
}

At first sight， you may think that new ByteArrayOutputStream(1024) will only allow a fixed size. But if you take a close look at the ByteArrayOutputStream, you will figure out the the stream will grow if necessary:

> This class implements an output stream in which the data is > written into a byte array. The buffer automatically grows as data > is written to it. > The data can be retrieved using toByteArray() and > toString().

Another interesting method is from com.fasterxml.jackson.databind.ObjectMapper

byte[] data = new ObjectMapper().writeValueAsBytes(JAVA_OBJECT_HERE)

Maven Dependency

<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-databind</artifactId>
</dependency>

If you are using spring, there's a util class available in spring-core. You can simply do

import org.springframework.util.SerializationUtils;

byte[] bytes = SerializationUtils.serialize(anyObject);
Object object = SerializationUtils.deserialize(bytes);

> I would like to transmit it as byte[] over sockets to another machine

// When you connect
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
// When you want to send it
oos.writeObject(appMessage);

> where it is rebuilt from the bytes received.

// When you connect
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
// When you want to receive it
AppMessage appMessage = (AppMessage)ois.readObject();

Spring Framework org.springframework.util.SerializationUtils

byte[] data = SerializationUtils.serialize(obj);

In case you want a nice no dependencies copy-paste solution. Grab the code below.

Example

MyObject myObject = ...

byte[] bytes = SerializeUtils.serialize(myObject);
myObject = SerializeUtils.deserialize(bytes);

Source

import java.io.*;

public class SerializeUtils {

    public static byte[] serialize(Serializable value) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();

        try(ObjectOutputStream outputStream = new ObjectOutputStream(out)) {
            outputStream.writeObject(value);
        }

        return out.toByteArray();
    }

    public static <T extends Serializable> T deserialize(byte[] data) throws IOException, ClassNotFoundException {
        try(ByteArrayInputStream bis = new ByteArrayInputStream(data)) {
            //noinspection unchecked
            return (T) new ObjectInputStream(bis).readObject();
        }
    }
}

This is just an optimized code form of the accepted answer in case anyone wants to use this in production :

	public static void byteArrayOps() throws IOException, ClassNotFoundException{
	
	String str="123";
	 byte[] yourBytes = null;
	
	// Convert to byte[]
	
	try(ByteArrayOutputStream bos = new ByteArrayOutputStream();
			ObjectOutputStream out =  new ObjectOutputStream(bos);) {
	  
		
	  out.writeObject(str);
	  out.flush();
	  yourBytes = bos.toByteArray();
	  
	} finally {
	
	}
	
	// convert back to Object
	
	try(ByteArrayInputStream bis = new ByteArrayInputStream(yourBytes);
			ObjectInput in = new ObjectInputStream(bis);) {

	  Object o = in.readObject(); 
	  
	} finally {
	  
	}
	
	
	
	
}

code example with java 8+:

public class Person implements Serializable {

private String lastName;
private String firstName;

public Person() {
}

public Person(String firstName, String lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
}

public void setFirstName(String firstName) {
    this.firstName = firstName;
}

public String getFirstName() {
    return firstName;
}

public String getLastName() {
    return lastName;
}

public void setLastName(String lastName) {
    this.lastName = lastName;
}

@Override
public String toString() {
    return "firstName: " + firstName + ", lastName: " + lastName;
}
}


public interface PersonMarshaller {
default Person fromStream(InputStream inputStream) {
    try (ObjectInputStream objectInputStream = new ObjectInputStream(inputStream)) {
        Person person= (Person) objectInputStream.readObject();
        return person;
    } catch (IOException | ClassNotFoundException e) {
        System.err.println(e.getMessage());
        return null;
    }
}

default OutputStream toStream(Person person) {
    try (OutputStream outputStream = new ByteArrayOutputStream()) {
        ObjectOutput objectOutput = new ObjectOutputStream(outputStream);
        objectOutput.writeObject(person);
        objectOutput.flush();
        return outputStream;
    } catch (IOException e) {
        System.err.println(e.getMessage());
        return null;
    }

}

}