java - 如何序列化 lambda？

Question

如何优雅地序列化 lambda？

例如，下面的代码会抛出 NotSerializedException。如何在不创建 SerializedRunnable“虚拟”接口(interface)的情况下修复它？

public static void main(String[] args) throws Exception {
    File file = Files.createTempFile("lambda", "ser").toFile();
    try (ObjectOutput oo = new ObjectOutputStream(new FileOutputStream(file))) {
        Runnable r = () -> System.out.println("Can I be serialized?");
        oo.writeObject(r);
    }

    try (ObjectInput oi = new ObjectInputStream(new FileInputStream(file))) {
        Runnable  r = (Runnable) oi.readObject();
        r.run();
    }
}

Answer 1

Java 8 引入了 cast an object to an intersection of types by adding multiple bounds 的可能性。在序列化的情况下，可以这样写:

Runnable r = (Runnable & Serializable)() -> System.out.println("Serializable!");

并且 lambda 自动变得可序列化。