Serialize and deserialize Java lambda functions and classes.

serialize-deserialize-lambda-and-class.java

package com.example;

import java.io.*;
import java.util.function.Function;

/**
 * Serialize and deserialize lambda functions and classes.
 */
public class Main {
  public static void main(String[] args) throws Exception {
    serializeAndDeserializeFunction();
    serializeAndDeserializeClass();
  }

  private static void serializeAndDeserializeClass() throws Exception {
    String path = "./serialized-class";
    serialize(MyImpl.class, path);
    System.out.println("Serialized class to " + path);

    // Pretending we don't know the exact class of the serialized bits,
    // create an instance from the class and use it through the interface.
    Class<?> myImplClass = (Class<?>) deserialize(path);
    System.out.println("Deserialized class from " + path);
    MyInterface instance = (MyInterface) myImplClass.newInstance();
    instance.hello("Java");
  }

  private static void serializeAndDeserializeFunction() throws Exception {
    Function<Integer, String> fn = (Function<Integer, String> & Serializable) (n) -> "Hello " + n;
    System.out.println("Run original function: " + fn.apply(10));

    String path = "./serialized-fn";

    serialize((Serializable) fn, path);
    System.out.println("Serialized function to " + path);

    Function<Integer, String> deserializedFn = (Function<Integer, String>) deserialize(path);
    System.out.println("Deserialized function from " + path);
    System.out.println("Run deserialized function: " + deserializedFn.apply(11));
  }

  private static void serialize(Serializable obj, String outputPath) throws IOException {
    File outputFile = new File(outputPath);
    if (!outputFile.exists()) {
      outputFile.createNewFile();
    }
    try (ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream(outputFile))) {
      outputStream.writeObject(obj);
    }
  }

  private static Object deserialize(String inputPath) throws IOException, ClassNotFoundException {
    File inputFile = new File(inputPath);
    try (ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream(inputFile))) {
      return inputStream.readObject();
    }
  }
}

interface MyInterface {
  void hello(String name);
}

class MyImpl implements MyInterface {
  public void hello(String name) {
    System.out.println("Hello " + name);
  }
}