org.jhotdraw8.icollection.serialization.SetSerializationProxy Maven / Gradle / Ivy

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/*
 * @(#)SetSerializationProxy.java
 * Copyright © 2023 The authors and contributors of JHotDraw. MIT License.
 */

package org.jhotdraw8.icollection.serialization;


import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serial;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;

/**
 * A serialization proxy that serializes a set independently of its internal
 * structure.
 * 
 * Usage:
 * 
 * class MySet<E> implements Set<E>, Serializable {
 *   private final static long serialVersionUID = 0L;
 *
 *   private Object writeReplace() throws ObjectStreamException {
 *      return new SerializationProxy<>(this);
 *   }
 *
 *   static class SerializationProxy<E>
 *                  extends SetSerializationProxy<E> {
 *      private final static long serialVersionUID = 0L;
 *      SerializationProxy(Set<E> target) {
 *          super(target);
 *      }
 *     {@literal @Override}
 *      protected Object readResolve() {
 *          return new MySet<>(deserializedElements);
 *      }
 *   }
 * }
 * 
 * 
 * References:
 * 

 *     Java Object Serialization Specification: 2 - Object Output Classes,
 *     2.5 The writeReplace Method
 *     oracle.com
 *
 *     Java Object Serialization Specification: 3 - Object Input Classes,
 *     3.7 The readResolve Method
 *     oracle.com
 * 
 *
 * @param  the element type
 */
public abstract class SetSerializationProxy implements Serializable {
    @Serial
    private static final long serialVersionUID = 0L;
    private final transient Set serialized;
    protected transient List deserializedElements;

    protected SetSerializationProxy(Set serialized) {
        this.serialized = serialized;
    }

    @Serial
    private void writeObject(ObjectOutputStream s)
            throws IOException {
        s.writeInt(serialized.size());
        for (E e : serialized) {
            s.writeObject(e);
        }
    }

    @Serial
    private void readObject(ObjectInputStream s)
            throws IOException, ClassNotFoundException {
        int n = s.readInt();
        deserializedElements = new ArrayList<>(n);
        for (int i = 0; i < n; i++) {
            @SuppressWarnings("unchecked")
            E e = (E) s.readObject();
            deserializedElements.add(e);
        }
    }

    @Serial
    protected abstract Object readResolve();
}