EMF - The off beat path

Chetan Kumar K, RBEIjointly with Annamalai C, ANCiT

Chetan Kumar K | Annamalai C | Eclipse India Summit, Bangalore, 17th July 2009

In-memory dbase contentD-

Base

UI display

What is a model ???

That is a model!


What is model ???

Placeholder of data Can “get” and “set” data

Get data

Set dataGet dataData

In memory representation of data

Can be derived from a design


… and so on

Will you spend time writing each class ??

Map design and code (model)

PIM PSM

Or be smart and generate them ??

UML Java


PIM Generator Model

Code Generation Engine

Code generation templates

PSMPSM

Typical code-generation flow


EMF a code generator. EMF is one such code-generator Let’s you generate concrete classes based on a design

(UML)

Let’s look at an example…


PIM(ecore)

Generator Modelgenmodel

EMFCode Generation

Engine

Code generation Templates

(JET)

PSM(Java)

Code generation flow – EMF way


Tap along guys…

First look of EMF as a code-generator…


The complete Example UML


Properties of (E)Attribute

Property Meaning

Volatile No associated storage (value can be calculated)

Transient Attribute isn’t persisted

Changeable Value can be changed or not

Unsettable Find out if an attribute was touched

Default value Literal

Default value assigned when containing class is instantiated

EType Data type of attribute


M-V-C architecture thru EMF


…EMF first impressions. EMF generates code – will it steal my job!

EMF generates UI stuff – why pay a UI developer ?

Oh god! Something new – too much learning curve

Should I learn “Modeling” or write code now ?

Points 3, 4 courtesy Ed Merks

It will be great if these points are myths … wat say ?

EMF.Edit

Control how model elements are displayed, edited.


EMF.Edit – bird’s eye view.

Contains UI Providers for each Model Element.

Content Provider

Label Provider

Property Source

Item Provider

Generated implementation for different providers


EMF.Edit control flow – Content Providers

“+” clicked

Item provider code

eGet api calls

Generated api getter(s)


EMF.Edit control flow – Label Providers

Item provider code

eGet api callsGenerated

api getter(s)


EMF.Edit control flow – Property Source

Tree item selected

Item provider code

Individual feature’s property descriptor

built

Property descriptors


EMF.Edit providers – one for all, all for one Content, Label, Image, and Property source

providers all through one provider instance!!

Now that’s called … convenience.

EMF.Edit commands

Command based model editing support


EMF.Edit CommandsCommand based editing of model instances

Model object

Editing domainUI display

“Set” event as

Command Command stack

setXXX()

undoable


EMF.Edit – How do I create/use Commands ?

Model object

EMF Editing Domain

•Contains command stack

•Factories to create commands


EMF.Edit – commands, a deeper look

Command interface Existing Command implementations

Do you need to implement this interface ??


EMF.Edit – “Change… is here!”Should I have one command per operation ?

Can I “record” changes done to a model ?

Oooo yess!!

Works on change notofications given on each operation

ChangeRecorder recoreds these notifications from individual setters. Hence, bulk undo is possible

Can I perform many operations in one command ?


Should I always generate EMF.xxx code ?

Nope … can work with “Dynamic EMF” Ecore – instantiate model (load) – edit – persist … is possible

Responsible code: EMF Reflective API, EMF Reflective Item Providers


Model xml / xmi

loadsave

UI display

What after you edit ?? – can ya persist ?


EMF serialization

Model object

EMF Resource

EMF Resource Set

xml / xmi


Load and save flows

Model object

xml / xmi

loadsave

EMF Reosource

Typical code snippet:


EMF Serialization – behind the scenes

•EAnnotations stores mapping b/w XML and Ecore

•Any model element can have EAnnotations


Can I directly persist EMF Objects into dbase ?

Yes, u can – using EMF Teneo (http://www.eclipse.org/modeling/emf/?project=teneo)

Create HbDataSt

ore

Create Hibernate Session,

Transaction

Begin Transaction

Create EMF Model root

object, make it persistent

Create sub-tree under

persistent rootCommit Tx


Get all students aged > 5

Model Navigation and search

Isn’t there a better way than loops ?Can’t I “Query” an EMF model ??

The cool “Query way”


In the end… what is EMF ?

•Code generator based on a design (UML)

•Means of Java XML binding with Inbuilt persistence mechanism

•Command based model editing support, with generated item providers

•All in all, a base for applications based on MDA

EMF Transaction

Thread-safe editing of a single Model InstanceTransaction style editing of model instances


Model editing through multiple threads

Model object

Thread 1

Change name :

“Jimmy Bend”

Thread 2

Change name

“James Bond”

Model objectname: Harry Potter

name: ???


“A mind once stretched by a thought never regains its original dimensions”


References EMF newsgroups: http://www.eclipse.org/newsportal/thread.php?

group=eclipse.tools.emf

EMF book: Eclipse Modeling Framework by Ed Merks et.al

EMF Refcard on DZone: http://refcardz.dzone.com/refcardz/essential-emf

Articles on Dynamic EMF - IBM developerWorks (http://www.ibm.com/developerworks/library/os-eclipse-dynamicemf/)

- devX.com (http://www.devx.com/Java/Article/29093/0/page/1 )

Blogs: http://tweakeclipse.blogspot.com/ http://eclipseo.blogspot.com/ and many more!!

Technology

EMF - The off beat path