Serialize objects in java
Serialization is the process of converting an object into a sequence of bits, so that it can be persisted on a storage medium such as a file or a memory buffer. This guide shows how to make a java class serializable and how to serialize/deserialize java objects and save/load them into files.
Our example class:
class Person {
private String firstName;
private String lastName;

public Person(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
}
The only change we need is implementing the Serializable interface. This is an empty, tagging interface, no need to implement any additional methods:
import java.io.Serializable;

class Person implements Serializable {
private String firstName;
private String lastName;

public Person(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
}
ObjectSerializer is an example class, shows how to perform object serialization in Java. The ObjectSerializer serializes or deserializes a serializable java object and write / read it to a file.
import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.io.IOException;
import java.io.FileInputStream;
import java.io.ObjectInputStream;

class ObjectSerializer {
public void serializeObject(String fileName, Object obj) {
ObjectOutputStream out = null;
try {
FileOutputStream fos = new FileOutputStream(fileName);
out = new ObjectOutputStream(fos);
out.writeObject(obj);
out.close();
} catch (IOException ex) {
throw new RuntimeException("Serialization failed", ex);
} finally {
try {
if(out != null) out.close();
} catch(Exception e) {
// do nothing
}
}

}

public Object deSerializeObject(String fileName) {
Object obj;
ObjectInputStream in = null;
try {
FileInputStream fis = new FileInputStream(fileName);
in = new ObjectInputStream(fis);
obj = in.readObject();
return obj;
}
catch (Exception e) {
throw new RuntimeException("De-serialization failed", e);
} finally {
try {
if(in != null)
in.close();
} catch(Exception e) {
// do nothing
}
}
}
}
Using the ObjectSerializer:
public class Test {
public static void main(String[] args) {
// writing to a file
Person person = new Person("John", "Doe");
ObjectSerializer serializer = new ObjectSerializer();
serializer.serializeObject("person.dat", person);

// reading from a file
Person personFromFile = (Person) serializer.deSerializeObject("person.dat");
}
}