Persistance support, XML serialization/deserialization

In most applications, persistency is generally required to guarantee the recovery and communication of structured data along time and applications.

While PAMELA framework is agnostic from a serialization format, today only XML serialization is provided, but other serialization formats are beeing considered, such as JSON.

Support for XML serialization in PAMELA requires that underlying model is annotated using those two annotations @XMLElement and @XMLAttribute.

• @XMLElement : This annotation should be defined either on a ModelEntity or on a ModelProperty (in this case with an eventual contextual prefix to avoid ambiguities between properties addressing this type).
• @XMLAttribute: This annotation should be defined on a ModelProperty

Serialization scheme relies on a String serializer/deserializer for common types, and allows alternatives types custom serializer/deserializer, which should be defined as add-ons.

The encoding of the object graph structure (and not only trees, as reflected by XML structure) relies on references (use of idref attributes). The serialization strategy is highly configurable, and allows a persistent-stable structure using a primary feature defined on some ModelProperties (referenced object will be preferably extensively serialized as this location).

Serialization and deserialization processes are provided with extension points (serialization/deserialization initializers/deserializers), where the developer may inject some specific code.

Excerpt of code showing XML serialization directives, and exposing deserialization extension points.

@ModelEntity
@ImplementationClass(Node.NodeImpl.class)
@XMLElement
public interface Node extends AccessibleProxyObject {

    public static final String NAME = "name";
    public static final String PARENT_NODE = "parent";
    public static final String NODES = "nodes";

    @Getter(value = NAME, defaultValue = "???")
    @XMLAttribute(xmlTag = NAME)
    public String getName();

    @Setter(NAME)
    public void setName(String name);

    @Getter(value = PARENT_NODE, inverse = NODES)
    public Node getParentNode();

    @Setter(PARENT_NODE)
    public void setParentNode(Node aNode);

    @Getter(value = NODES, cardinality = Cardinality.LIST, inverse = PARENT_NODE)
    @XMLElement(primary = true)
    @Embedded
    public List<Node> getNodes();

    @Setter(NODES)
    public void setNodes(List<Node> nodes);

    @Adder(NODES)
    public void addToNodes(Node node);

    @Remover(NODES)
    public void removeFromNodes(Node node);

    @DeserializationInitializer
    public void initializeDeserialization();

    @DeserializationFinalizer
    public void finalizeDeserialization();

    public static abstract class NodeImpl implements Node {

        public static String DESERIALIZATION_TRACE = "";

        private boolean isDeserializing = false;

        @Override
        public void initializeDeserialization() {
            System.out.println("Init deserialization for Node " + getName());
            isDeserializing = true;
        }

        @Override
        public void setName(String name) {
            if (isDeserializing) {
                DESERIALIZATION_TRACE += " BEGIN:" + name;
            }
            performSuperSetter(NAME, name);
        }

        @Override
        public void finalizeDeserialization() {
            isDeserializing = false;
            DESERIALIZATION_TRACE += " END:" + getName();
            System.out.println("Finalize deserialization for Node " + getName());
        }
    }

}
```java