1. Aranea – Java Web Framework Construction and Integration Kit
Aranea -- Web Framework Construction and Integration Kit
Aranea – Java Web Framework Construction and Integration Kit
Oleg Mürk
Chalmers University of Technology,
Sweden
Jevgeni Kabanov
University of Tartu, Webmedia, Ltd.,
Estonia

2. Outline Introduction Hello World! In Aranea Framework construction
Framework integration
Further work
Voore 2006

3. Aranea -- Web Framework Construction and Integration Kit
Motivation
At the moment web applications are barely reusable!
Existing code cannot be reused for similar requirements without inserting if-then-else-s everywhere
Legacy migration is very hard!
Integrating applications built on different platforms is hard and often visible to user
Object-Oriented Design to the rescue!
OOD is all about structuring your application to make it more manageable and encapsulated.
Voore 2006

4. Aranea -- Web Framework Construction and Integration Kit
Web is
Procedural (Client calls server)
Synchronized (One window – one request)
Decomposable into pages
Client is mostly stateless (Current state with result, cookies)
In general web is based around a concept of a page, which is combining data, behavior and presentation
Note the choice of words – procedural, not functional!
Voore 2006

5. Aranea -- Web Framework Construction and Integration Kit
GUI applications are
Often stateful
Mostly synchronized (one window – one thread)
Decomposable into components
Comfortable to represent using OO concepts
Model-View-Controller pattern suggest to keep data, presentation and behavior separately
Voore 2006

6. Enter MVC Web Frameworks
Aranea -- Web Framework Construction and Integration Kit
Enter MVC Web Frameworks
Request-based: Struts, Spring MVC
Page-based: JSF, Wicket, Tapestry
Continuation/flow-based: RIFE, Spring WebFlow
AJAX-based: Echo2, GWT …
OO-based: Wicket, Aranea
Voore 2006

7. Aranea -- Web Framework Construction and Integration Kit
A Sea of Frameworks
Do we really need all those approaches?
They play out well for different requirements
Can we combine them?
We’ll try to do just that 
We’ll also hint how to make the existing frameworks work together…
Voore 2006

8. Aranea -- Web Framework Construction and Integration Kit
Introducing Aranea
An Open-Source project available at
A component object model styled after a variant of Hierarchical MVC pattern
Reusable components, which can be assembled into an MVC framework
Note that we are only examining the Controller part of MVC!
Voore 2006

9. Aranea -- Web Framework Construction and Integration Kit
Hello World!
NameWidget
name.jsp
Reads the name from requests and passes it to HelloWidget
HelloWidget
hello.jsp
Renders the “Hello ${name}!” greeting, where name is given by the caller.
Note that we need two widgets only for demonstration purposes
Voore 2006

10. Aranea -- Web Framework Construction and Integration Kit
NameWidget
public class NameWidget extends BaseUIWidget {
//Called on “hello” event
public void handleEventHello() {
String name = //reads “name” from request parameters
(String) getInputData().getGlobalData().get("name");
getFlowCtx().replace(new HelloWidget(name), null); }
name.jsp:
The important part is on line 2, where we both create the new object by hand and navigate (or rather switch) to it using Java API.
<ui:systemForm method="GET">
Insert your name: <input type=“text“ name="name"/><br/><br/>
<ui:eventButton labelId="#Say hello" eventId="hello"/>
</ui:systemForm>
Voore 2006

11. Aranea -- Web Framework Construction and Integration Kit
HelloWidget
public class HelloWidget extends BaseUIWidget {
private String name; //Widget state is in its fields
public HelloWidget(String name) {
this.name = name; //We could pass any Java object here }
public String getName() {
return this.name;
hello.jsp:
 Hello <c:out value="${widget.name}"/>!
Voore 2006

12. Hello World! reexamined
Aranea -- Web Framework Construction and Integration Kit
Hello World! reexamined
NameWidget
name.jsp
handleEventHello()
getFlowCtx().replace(new HelloWidget(name));
HelloWidget
hello.jsp
Note that we can pass any Java object to the widget constructor,
enabling e.g. polymorphism
Voore 2006

13. Framework construction
Aranea -- Web Framework Construction and Integration Kit
Framework construction
Components are assembled in a chain
Only 3 component kinds (components, services & widgets)
Some components may contain more than one child
Servlet: only dispatches the HTTP call to adaptor
Voore 2006

14. Aranea -- Web Framework Construction and Integration Kit
Component
interface Component {
void init(Environment env);
void destroy(); }
Voore 2006

15. Aranea -- Web Framework Construction and Integration Kit
Service
Services correspond to the procedural unsynchronized HTTP model
Unlike servlets no binding or configuration specified
interface Service extends Component {
void action(
Path path, //Routing destination for Composite case
InputData input, //Request abstraction
OutputData output); //Response abstraction }
Services are similar to servlets, but unlike those they is no convention on how they are configured, associated or used.
Voore 2006

16. SynchronizingFilterService
Aranea -- Web Framework Construction and Integration Kit
SynchronizingFilterService
Synchronizes the underlying calls
In reality childService is handled by the base class (BaseFilterService)
public class SynchronizingFilterService extends BaseService {
protected Service childService;
public void setChildService(Service childService) {
this.childService = childService; }
synchronized void action(
Path path, InputData input, OutputData output) {
childService.action(path, input, output);
E.g. user clicks a button, the processing takes some time and user stops and refreshes the browser getting an inconsistent state.
Voore 2006

17. Aranea -- Web Framework Construction and Integration Kit
Environment
Environment allows parents to let children access their features
interface Environment {
Object getEntry(Object key); }
Usage example:
L10nContext locCtx = (L10nContext)
getEnvironment().getEntry(L10nContext.class);
String message = locCtx.localize("message.key");
Voore 2006

18. LocalizationFilterService
Aranea -- Web Framework Construction and Integration Kit
LocalizationFilterService
Provides localization features
public class LocalizationFilterService
extends BaseFilterService implements L10nContext {
public void init(Environment env) {
childService.init(
new StandardEnvironment(env, L10nContext.class, this); }
public String localize(String key) {
//Look up a ResourceBundle and return the message
Voore 2006

19. SessionRouterService
Aranea -- Web Framework Construction and Integration Kit
SessionRouterService
Routes the action() to a service associated with the HTTP session
Creates new services using a service factory (assigned via setter)
public class SessionRouterService extends BaseService {
void action(Path p, InputData input, OutputData output) {
HttpSession sess = … //Lookup logic
if (sess.get(SERVICE_KEY) == null)
createService(sess); //Build service using factory
((Service) sess.get(SERVICE_KEY)).action(p, input, output); }
Voore 2006

20. Aranea -- Web Framework Construction and Integration Kit
Half of a framework
Service adaptor: creates Input- & OutputData
Session router: saves service chain under itself in session
Synchronizing filter: protects session state from concurrent modification
HTTP filter: sets headers
Voore 2006

21. Aranea -- Web Framework Construction and Integration Kit
Widget
Widget corresponds to a stateful synchronized GUI component
Most applications are built from widgets
interface Widget extends Service {
//Calls must be made in the same order:
void update(InputData data); //Sent to all widgets
void event(Path path, InputData input); //Routed to one widget
void process(); //Preparing to render
void render(OutputData output); //May be called several times }
We split the one action() calls in the update()/event()/process()/render() call chain. We also allow render() to be called outside the cycle to allow for re-rendering on refresh or back-button & such.
Voore 2006

22. Flows
Flows are pages which preserve nested state and can return values
Voore 2006

23. Aranea -- Web Framework Construction and Integration Kit
Flows examined
Flow container is a widget that contains a stack of widgets representing flows
Being a usual widget flow container can be used at an arbitrary place in framework or application
public interface FlowContext {
void start(Widget flow, Handler handler);
void replace(Widget flow)
void finish(Object result);
void cancel(); }
Voore 2006

24. Aranea -- Web Framework Construction and Integration Kit
And the final touch
Widget adapter: calls update(), event(), process() and render() for each action() call
Widget container: creates Path for event routing
Flow container: provides FlowContext and a widget stack
Voore 2006

25. Other configurations
We can assemble a system to bind stateless services to URLs like Struts actions
We can also assemble a system that will bind stateful widgets to URLs like Wicket pages
In fact it is easy to simulate all of the mentioned approaches
Voore 2006

26. Aranea -- Web Framework Construction and Integration Kit
Our goal is to use Aranea component model to structure our application
And then use it as glue to integrate with all other web frameworks
In fact Aranea was specially designed with integration in mind
But before 1.0 release we had to put our energy elsewhere
Well, rather well thought through goals :)
Voore 2006

27. Integration Picture
Voore 2006

28. Aranea -- Web Framework Construction and Integration Kit
Summary
A HMVC component model
A modular web framework supporting all common GUI approaches
A platform for web framework development and research
An Object-Oriented web framework with support for first-class flows
A web framework integration platform
Voore 2006

29. Aranea -- Web Framework Construction and Integration Kit
Further work
Remote integration: a service protocol with Environment over Web Services
Weaver: templating framework compatible with JSP tags, Wicket markup, JSF components, Facelets, …
Blocking continuation support
Integration with Wicket, JSF, Struts, Spring MVC & WebFlow, Echo2, GWT …
Aranea for rich client (Eclipse RCP)
Voore 2006

30. Thank you! Questions?
Voore 2006