Serialization is the process of saving an object in a persistent form, e.g., on the harddisk as a bytestream. Deserialization is the process in the opposite direction, creating an object from a persistently saved data structure. In Java, an object can be serialized if it imports the java.io.Serializable interface.
Members of an object that are not supposed to be serialized, need to be prefixed with the keyword transient.
In the following you'll find some Java code snippets for serializing and deserializing a
J48 classifier. Of course, serialization is not limited to classifiers. Most schemes in Weka, like clusterers and filters, are also serializable.
Here we create a J48 classifier
cls, train it with a dataset
/some/where/data.arff, and save the built model to a file
// create J48 Classifier cls = new J48(); // train Instances inst = new Instances( new BufferedReader( new FileReader("/some/where/data.arff"))); inst.setClassIndex(inst.numAttributes() - 1); cls.buildClassifier(inst); // serialize model ObjectOutputStream oos = new ObjectOutputStream( new FileOutputStream("/some/where/j48.model")); oos.writeObject(cls); oos.flush(); oos.close();
If you use the
SerializationHelper class, then this shrinks to:
// serialize model weka.core.SerializationHelper.write("/some/where/j48.model", cls);
Here the previously saved model is deserialized as
cls and again available for classification.
// deserialize model ObjectInputStream ois = new ObjectInputStream( new FileInputStream("/some/where/j48.model")); Classifier cls = (Classifier) ois.readObject(); ois.close();
Or, with the
// deserialize model Classifier cls = (Classifier) weka.core.SerializationHelper.read("/some/where/j48.model");
Serialization in Weka
The Explorer serializes the classifier and the training header together. This makes it easy to test whether a dataset is compatible with the dataset the classifier was trained with. The commandline option -d
In order to read serialized models that contain the header information as well, you can use the
readAll method of the
weka.core.SerializationHelper. For serializing models with their datasets, use