How To Serialize a Lambda In Java

Serializing a Lambda in Java

Lambdas are an important part of modern Java programming. They provide an intuitive way to define and work with anonymous classes, allowing for concise and expressive code. But, like all objects, lambdas must be properly serialized if they are to be handled and shared between different applications. Thankfully, with a few simple steps, this process can be straightforward and efficient.

What is Serialization?

Serialization is the process of converting an object into a series of bytes, which can then be transmitted across a network or stored on disk. This process allows an object to be reconstructed later, making it an essential part of data persistence. It is also required in order to share an object between different applications.

Serializing Lamdas

In order to serialize a lambda in Java, we must first capture the object in a wrapper class. This wrapper class should have a method that can return the lambda as a Serializable object. It should also implement methods for setting and getting the lambda object.

Example

For example, let's say we have a lambda defined as follows:

Runnable run = () -> System.out.println("Hello World");

We can create a wrapper class to capture this lambda, like so:

public class MyRunnable implements Serializable {
  private static final long serialVersionUID = 1L;
  private transient Runnable runnable;

  public void setRunnable(Runnable runnable) {
    this.runnable = runnable;
  }

  public Runnable getRunnable() {
    return runnable;
  }

  private void writeObject(ObjectOutputStream out) throws IOException {
    out.defaultWriteObject();
    out.writeObject(runnable);
  }

  private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
    in.defaultReadObject();
    runnable = (Runnable)in.readObject();
  }
}

With this wrapper class in place, we can now serialize the lambda. To do this, we simply create an instance of MyRunnable and set the Runnable to our lambda, then serialize the instance. The resulting byte stream can then be sent over a network, stored on disk, etc. and can be deserialized at a later point in time.

In this way, we can easily serialize and share lambdas between different applications, making them much more useful in modern programming.