Events

Events and Handlers in Piriti

Events

When POJOs are (de)serialized by Piriti you can register event handlers to get notified

• after a POJO was read from JSON / XML
• after a POJO is written to JSON / XML

The events, handlers and relevant interfaces are all based on the event handlers used by GWT. See [http://code.google.com/webtoolkit/doc/latest/DevGuideUiHandlers.html] for details.

Reading POJOs from JSON / XML

JsonReader<T> and XmlReader<T> both extend the interface HasModelReadHandler<T> which offers the method addModelReadHandler(ModelReadHandler<T>).

Writing POJOs as JSON / XML

JsonWriter<T> and XmlWriter<T> both extend the interface HasModelWriteHandler<T> which offers the method addModelWriteHandler(ModelWriteHandler<T>).

Example

In this simple example every mapped person is logged by the event handler LogHandler<Person>: public class Person { public interface PersonJsonWriter extends JsonWriter {} public static final PersonJsonWriter JSON_WRITER = GWT.create(PersonJsonWriter.class);

    public interface PersonJsonReader extends JsonReader<Person> {}
    public static final PersonJsonReader JSON_READER = GWT.create(PersonJsonReader.class);

    public interface PersonXmlReader extends XmlReader<Person> {}
    public static final PersonXmlReader XML_READER = GWT.create(PersonXmlReader.class);

    public interface PersonXmlWriter extends XmlWriter<Person> {}
    public static final PersonXmlWriter XML_WRITER = GWT.create(PersonXmlWriter.class);

    String firstname;
    String surname;
}

public class LogHandler<C> implements ModelReadHandler<Person, C>, ModelWriteHandler<Person>
{
    @Override
    public void onModelRead(ModelReadEvent<Person> event)
    {
        logger.info("Read person " + event.getModel() + " from " + event.getContext());
    }

    @Override
    public void onModelWrite(ModelWriteEvent<Person> event)
    {
        logger.info("Wrote person " + event.getModel() + " to " + event.getRepresentation());
    }
}

public class Main implements EntryPoint
{
    public void onModuleLoad()
    {
        LogHandler handler = new LogHandler();
        Person.JSON_READER.addModelReadHandler(handler); 
        Person.JSON_WRITER.addModelWriteHandler(handler); 
        Person.XML_READER.addModelReadHandler(handler); 
        Person.XML_WRITER.addModelWriteHandler(handler); 

        // start reading / writing persons
        ...
    }
} 

As you can see the read event carries information about the model and the context. The context is a JSONValue for JSON and a node in case of XML. The write event holds the model written and its representation as string.