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Esfand S

MVP with EventBus question - Google Web Toolkit | Google Groups - 0 views

groups.google.com/...8734517776c1c6f1

mvp uibinder gwt

shared by Esfand S on 26 Jun 10 - Cached
  • Yeah, the one problem with UiBinder and MVP is this pattern collision.... UiBinder says, "view are directly attached to views". MVP says, "view's are attached to presenters, if you want to chain views the presenters control this". Consequently, you can't get UiBinder to create your @UiFields (i.e. empty constructor) and you can't get Gin to @Inject them into the view either... because they are in the presenter. Unless of course you use @Named+Singleton bindings in Gin and then both presenter and view will be injected with the same object. This is the one bit of boilerplate we're still writing.
  • I looked into that, and (unless I'm wrong), I think that @UiField(provided=true) will cause the UiBinder to look in the .ui.xml file for argument to satisfy Foo. In my case I am trying to "inject" an EventBus into the widget, not a visual element.
Esfand S

overlook - Tech Blog - 2 views

www.over-look.com/...t-2-1-tutorial-1-mvp-the-model

gwt gwt21 mvp

shared by Esfand S on 09 Jul 10 - Cached
  • The main issue in MVC is that these three elements are tighly bound together: the controller has to register to both the model and the view (and unregister if either changes), and when a view serves multiple controllers or a controller uses multiple models, that becomes quickly a mess.
  • MVP approach is more message-oriented. All messages (events) are fired on a single EventBus that is shared by all Presenters. Each presenter listens to events of interest, and fires new events according to actions. So a change in the in the EmployeeModel may be fired with an EmployeeModelChangedEvent, instead of attaching a listener to the model object. And we can easily create new Presenters that receive that same event and react accordingly.
  • The magnitude of such a shift is great: the model is no more the center and source of events (which would require special care in attaching and detaching to a specific instance), but it more a passive container of data, which may be copied, proxied, transformed, cached, without the GWT appliction any special care.Since the model is more a container of data ment for communication, I've highlighted the fact that it needs to be Serializable.
  • ...11 more annotations...
  • It is now the time to introduce the Model in GWT 2.1. The direction taken in 2.0.x has been pushed one step further, so that the Model is, in fact, only a Data Transfer Obejct (DTO). A DTO is an object whose main purpose is to be transferred, usually from one Tier to another Tier of a layered architecture such as Browser/Server/Database.
  • Value Store, the package that defines the Model/DTO programming interface.
  • Valuestore is the management interface that performs CRUD (Create, Read, Update, Delete) operations on the Records, like Entity Manager in JPA and Persistence Manager in JDO.
  • The first interface to discuss is Record, the base interface to implement to define a DTO class. A Record holds data for a single instance of an entity. Let's suppose that in your server-side business model there's an entity called 'Employee' to represent a company employee list.  To use it on the client side, you would need to define an EmployeeRecord class to hold the values of one of your employees, e.g. the employee name, birth date, etc.
  • A Record is able to provide values using Property objects as keys. The properties are type-aware, so that the employee name is a Property<String>, the employee birth data a Property<Date>, and so on. The following table reports these elements in a single example:
  • The Record interface doesn't provide a generic reflection mechanism, so it's not possible to inspect a Record to know what kind of Properties it is made of. The current implementation RecordImpl, which delegates to JavaScriptObject implementation and provides JSON serialization, is actually holding a schema of the record properties in a RecordSchema object.
  • note the annotation @DataTransferObject, that GWT uses to map the record to the equivalent server-side class. By declaring the connection, GWT is capable of binding automatically the interface properties with the JPA-annotated properties, thus greatly reducing the amount of boilerplate mapping work to be performed.
  • Of course, when you add or modify a property in your real Model, appropriate changes must be applied to the equivalent Record. That's where the teamwork with Spring Roo comes handy: Spring Roo generates and keeps aligned a lot of these elements, and would reflect (overwrite) your EmployeeRecord java file every time you change your domain model definition.
  • As a general rule, you are encouraged to define specific interface methods to extract data from you Record, e.g. getName() to get the Employee name. Record exposes also method to retrieve a value given a property. For instance, in a Renderer of a CellTree, when you are given an EmployeeRecord you should access its data through public getter methods.
  • The model-agnostic way that GWT uses to access a value is the Record.get(Property<V>) method. There's also a way to get not the value itself, but a PropertyReference<V>, which is just the property of a specific record, e.g. the Property 'name' of Record 'r2' in the example table above. In a few words, a property reference is just a value, which is exactly how Value<V> is defined. That is most useful to perform late bindings during RPC calls when the data is not yet available.
  • The DeltaValueStore is also worth mentioning a few words: as your model is now decomposed in Records and Properties, it is also possible to transfer only the data you need to. Hence the retrieval requests can dowload only a few properties of the Records. Furthermore, 'Update' operations can transmit back only the user changes (delta) instead of whole objects, which may give a nice performance boost.
Esfand S

One v.s N EventBus - Google Web Toolkit | Google Groups - 2 views

groups.google.com/...1b79e96bed1f02b2

gwt mvp

shared by Esfand S on 02 Aug 10 - Cached
  • My application has several modules, and in each module, it may have different layout. Hence I have multiple level of Activity and in each module, I have an ActivityManager and ActivityMapper to create an appropriate Activity according to the Place or return null if not interested.  All the ActivityManagers are attached to a global Event bus.
Marco Antonio Almeida

GWT MVP Development with Activities and Places - Google Web Toolkit - Google Code - 2 views

code.google.com/...ideMvpActivitiesAndPlaces.html

gwt mvp development activities places

shared by Marco Antonio Almeida on 30 Oct 10 - No Cached
  • An activity in GWT 2.1 is analogous to a presenter in MVP terminology. It contains no Widgets or UI code. Activities are started and stopped by an ActivityManager associated with a container Widget. A powerful new feature in GWT 2.1 is that an Activity can automatically display a warning confirmation when the Activity is about to be stopped (such as when the user navigates to a new Place). In addition, the ActivityManager warns the user before the window is about to be closed.
  • A place in GWT 2.1 is a Java object representing a particular state of the UI. A Place can be converted to and from a URL history token (see GWT's History object) by defining a PlaceTokenizer for each Place, and the PlaceHistoryHandler automatically updates the browser URL corresponding to each Place in your app.
  • A key concept of MVP development is that a view is defined by an interface.
  • ...23 more annotations...
  • It is useful for views to extend IsWidget if they do in fact provide a Widget.
  • more complicated view that additionally defines an interface for its corresponding presenter (activity)
  • The Presenter interface and setPresenter method allow for bi-directional communication between view and presenter,
  •   @UiHandler("goodbyeLink")        void onClickGoodbye(ClickEvent e) {                presenter.goTo(new GoodbyePlace(name));        }
  • Because Widget creation involves DOM operations, views are relatively expensive to create. It is therefore good practice to make them reusable, and a relatively easy way to do this is via a view factory, which might be part of a larger ClientFactory.
  • Note the use of @UiHandler that delegates to the presenter
  • Another advantage of using a ClientFactory is that you can use it with GWT deferred binding to use different implementation classes based on user.agent or other properties. For example, you might use a MobileClientFactory to provide different view implementations than the default DesktopClientFactory.
  • ClientFactory A ClientFactory is not strictly required in GWT 2.1; however, it is helpful to use a factory or dependency injection framework like GIN to obtain references to objects needed throughout your application like the event bus.
  • Specify the implementation class in .gwt.xml:     <!-- Use ClientFactoryImpl by default -->    <replace-with class="com.hellomvp.client.ClientFactoryImpl">    <when-type-is class="com.hellomvp.client.ClientFactory"/>    </replace-with> You can use <when-property-is> to specify different implementations based on user.agent, locale, or other properties you define.
  • Activities Activity classes implement com.google.gwt.app.place.Activity. For convenience, you can extend AbstractActivity, which provides default (null) implementations of all required methods.
  • The first thing to notice is that HelloActivity makes reference to HelloView. This is a view interface, not an implementation.
  • The HelloActivity constructor takes two arguments: a HelloPlace and the ClientFactory
  • In GWT 2.1, activities are designed to be disposable, whereas views, which are more expensive to create due to the DOM calls required, should be reusable. In keeping with this idea, ClientFactory is used by HelloActivity to obtain a reference to the HelloView as well as the EventBus and PlaceController.
  • Finally, the goTo() method invokes the PlaceController to navigate to a new Place. PlaceController in turn notifies the ActivityManager to stop the current Activity, find and start the Activity associated with the new Place, and update the URL in PlaceHistoryHandler.
  • The non-null mayStop() method provides a warning that will be shown to the user when the Activity is about to be stopped due to window closing or navigation to another Place. If it returns null, no such warning will be shown.
  • In order to be accessible via a URL, an Activity needs a corresponding Place. A Place extends com.google.gwt.app.place.Place and must have an associated PlaceTokenizer which knows how to serialize the Place's state to a URL token.
  • It is convenient (though not required) to declare the PlaceTokenizer as a static class inside the corresponding Place. However, you need not have a PlaceTokenizer for each Place. Many Places in your app might not save any state to the URL, so they could just extend a BasicPlace which declares a PlaceTokenizer that returns a null token.
  • For even more control, you can instead implement PlaceHistoryMapperWithFactory and provide a TokenizerFactory that, in turn, provides individual PlaceTokenizers.
  • For more control of the PlaceHistoryMapper, you can use the @Prefix annotation on a PlaceTokenizer to change the first part of the URL associated with the Place
  • PlaceHistoryMapper PlaceHistoryMapper declares all the Places available in your app. You create an interface that extends PlaceHistoryMapper and uses the annotation @WithTokenizers to list each of your tokenizer classes.
  • ActivityMapper Finally, your app's ActivityMapper maps each Place to its corresponding Activity. It must implement ActivityMapper, and will likely have lots of code like "if (place instanceof SomePlace) return new SomeActivity(place)".
  • How it all works The ActivityManager keeps track of all Activities running within the context of one container widget. It listens for PlaceChangeRequestEvents and notifies the current activity when a new Place has been requested.
  • To navigate to a new Place in your application, call the goTo() method on your PlaceController.
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