Question

I want to serialize a class using ByteArrayOutputStream of java:

public void serializ(UniqueTag m) throws IOException {
        ByteArrayOutputStream byteOutput = new ByteArrayOutputStream();
        ObjectOutputStream stream = new ObjectOutputStream(byteOutput);
            stream.writeObject(m);

        stream.flush();
        stream.close();
        byteOutput.flush();
        byteOutput.close();    
    }

A class want to serialize :

import java.io.Serializable;

public class UniqueTag implements Comparable<UniqueTag>, Serializable {
    public final static UniqueTag MIN = new UniqueTag(Integer.MIN_VALUE,
            Integer.MIN_VALUE);
    public final static UniqueTag MAX = new UniqueTag(Integer.MAX_VALUE,
            Integer.MAX_VALUE);

    private final int replicaId;
    private final int counter;

    public static UniqueTagGenerator createGenerator() {
        return new UniqueTagGenerator() {
            int currentStamp;

            @Override
            public UniqueTag nextTag(final int replicaId) {
                return new UniqueTag(replicaId, currentStamp++);
            }
        };
    }

    public UniqueTag(final int replicaId, final int counter) {
        this.replicaId = replicaId;
        this.counter = counter;
    }

    public int getReplicaId() {
        return replicaId;
    }

    public int getCounter() {
        return counter;
    }

    @Override
    public int compareTo(UniqueTag o) {
        if (replicaId != o.replicaId) {
            return replicaId - o.replicaId;
        }
        return counter - o.counter;
    }

    public UniqueTag clone() {
        return new UniqueTag(replicaId, counter);
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof UniqueTag))
            return false;
        final UniqueTag other = (UniqueTag) obj;
        return counter == other.counter && replicaId == other.replicaId;
    }

    @Override
    public String toString() {
        return "(" + replicaId + "," + counter + ")";
    }
}

I have this error :

Exception in thread "main" java.io.NotSerializableException: jbenchmarker.treedoc.UniqueTag$1
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1164)
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1518)
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1483)
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158)
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1518)
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1483)
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:330)

Please where is a problem ? i serialize a class but it displays to me an error ! 🙁

Answer 1

It’s complaining that an anonymous inner class is causing the problem, and you only have one anonymous inner class, so I believe that you can solve the problem by making UniqueTagGenerator implement Serializable.

I’m not entirely certain why this exception is being thrown, as an instance of UniqueTag should not hold any reference to the generator that created it. I suspect there’s some needless chasing of class references going on (or you aren’t showing the exact code).

Another way to fix it — better, IMO — is to separate out the tag generator implementation from UniqueTag. Either create a separate class, or add the factory method to UniqueTagGenerator.