I am trying to serialize and deserialize objects of a custom class (say, SomeClass, having a default no-args constructor) to a byte[] array, using Kryo 2.19 and the default serializer (FieldSerializer).
Serialization seems to work OK, but I get various exceptions in deserialization, depending on the actual implementation of SomeClass.
The code looks something like this:
SomeClass object = getObject(); // Create and populate a new object of SomeClass
Kryo kryo = new Kryo();
FieldSerializer<?> serializer = new FieldSerializer<SomeClass>(kryo, SomeClass.class);
kryo.register(SomeClass.class, serializer);
ByteArrayOutputStream stream = new ByteArrayOutputStream();
Output output = new Output(stream);
kryo.writeObject(output, object);
output.close(); // Also calls output.flush()
byte[] buffer = stream.toByteArray(); // Serialization done, get bytes
// Deserialize the serialized object.
object = kryo.readObject(new Input(new ByteArrayInputStream(buffer)), SomeClass.class);
An example of the exceptions I am getting is:
Exception in thread "main" java.lang.IncompatibleClassChangeError: Found interface org.objectweb.asm.MethodVisitor, but class was expected
at com.esotericsoftware.reflectasm.ConstructorAccess.insertConstructor(ConstructorAccess.java:89)
at com.esotericsoftware.reflectasm.ConstructorAccess.get(ConstructorAccess.java:70)
at com.esotericsoftware.kryo.Kryo.newInstantiator(Kryo.java:1009)
at com.esotericsoftware.kryo.Kryo.newInstance(Kryo.java:1059)
at com.esotericsoftware.kryo.serializers.FieldSerializer.create(FieldSerializer.java:228)
at com.esotericsoftware.kryo.serializers.FieldSerializer.read(FieldSerializer.java:217)
at com.esotericsoftware.kryo.Kryo.readObject(Kryo.java:629)
It seems that parameterized types are problematic to deserialize. To test this assumption , here is a parameterized implementation of SomeClass and getObject():
class SomeClass<T extends Serializable>
{
private final T[] elements;
private final int first;
private final int second;
private SomeClass()
{
this.elements = null;
this.first = 0;
this.second = 0;
}
private SomeClass(T[] elements, int first, int second)
{
this.elements = elements;
this.first = first;
this.second = second;
}
}
SomeClass<?> getObject()
{
String[] elements = new String[] {"This is a test", "one"};
return new SomeClass<String>(elements, 1, 2);
}
This serializes fine, but deserialization throws the following exception (observe how the first letter of the string is not reported in the exception cause):
Exception in thread "main" com.esotericsoftware.kryo.KryoException: Unable to find class: his is a test
Serialization trace:
elements (net.cetas.parserserver.data.report.SourceDataReporter$SomeClass)
at com.esotericsoftware.kryo.util.DefaultClassResolver.readName(DefaultClassResolver.java:132)
at com.esotericsoftware.kryo.util.DefaultClassResolver.readClass(DefaultClassResolver.java:109)
at com.esotericsoftware.kryo.Kryo.readClass(Kryo.java:613)
at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:724)
at com.esotericsoftware.kryo.serializers.DefaultArraySerializers$ObjectArraySerializer.read(DefaultArraySerializers.java:338)
at com.esotericsoftware.kryo.serializers.DefaultArraySerializers$ObjectArraySerializer.read(DefaultArraySerializers.java:293)
at com.esotericsoftware.kryo.Kryo.readObjectOrNull(Kryo.java:702)
at com.esotericsoftware.kryo.serializers.FieldSerializer$ObjectField.read(FieldSerializer.java:521)
at com.esotericsoftware.kryo.serializers.FieldSerializer.read(FieldSerializer.java:221)
at com.esotericsoftware.kryo.Kryo.readObject(Kryo.java:629)
If the above class is implemented without parameterization (i.e., the elements array declared as a String[]), deserialization works as expected.
Any ideas?