Model Driven Engineering : Basic Concepts

Transcription

1 Model Driven Engineering : Basic Concepts Lesson 3 Model to Text Transformations : ACCELEO Guglielmo De Angelis CNR - IASI / ISTI guglielmo.deangelis@isti.cnr.it

2 model transformation MMM

3 model transformation MMM M2M

4 model transformation MMM M2M M2T

5 what is ACCELEO it is a framework supporting automatic model transformations programming language execution framework originally developed by Obeo, now in the Eclipse Modeling Framework ACCELEO has been designed following MDE principles enabling the automatic generation of text form a given metamodel (e.g. UML, MOF, EMF) available documentation : Acceleo 3 Web Site The Official Documentation The Offical Acceleo Wiki

6 about ACCELEO ACCELEO is a framework supporting the implementation, and the execution of MODEL 2 TEXT transformations

7 about ACCELEO Acceleo is a framework supporting the implementation, and the execution of MODEL 2 TEXT transformations Acceleo Transformator (i.e. the program) Acceleo Execution Engine

8 about templates 1 a template can be seen as a document which it is partially specified common structure for all the instances of the document empty fields containing istance-specific information examples of documents are : textual documents models source codes

9 about templates 2

10 about templates 3 Common Structure Generated Parts

11 definition the type of the elements which can be elaborated in each empty field of a template is referred context all the possible contexts (so all the admissible type of information) depend from the referred metamodel

12 context = title about templates 4 contesto = authors contesto =

13 definition the type of the elements which can be elaborated in each empty field of a template is referred context all the possible contexts (so all the admissible type of information) depend from the referred metamodel example : if we consider the metamodel of UML2, the example of context are: class, attribute, package, behavior, action

14 syntax 1 the empty fields represents the variable part of a template they are filled by script areas which can emit text, according to both the context they are executed, and the given input model any script area is marked by means of specific tags [<example_of_tag>]... [/<example_of_tag>] [<another_example_of_tag> /]

15 syntax 2 the acceleo programming language forseen also comment area : [comment... /] la direttiva module, definisce il modulo Acceleo che si sta implementando ed il tipo di linguaggio dei modelli in ingresso il metamodello può essere considerato la grammatica sulla quale sono basati i modelli oggetto della trasformazione [module <modulename>(<metamodeluri>)/]

16 refer in an ACCELEO program the UML 2.0 metamodel example URI: [module mygenerate(' /]

17 syntax template the statement template declares a trasformator and it defines the elements that will match [template public mygenerator(instance : mytype)] [/template] the declaration of a template can include: overriding properties pre-conditions :?(<condition>) post-treatments : post(<funzione/template>) inizialization : { <varname>:<type> = <val>; } mytype is the type of the parsed instance that matching will activate the script (Package, Class, Properties, ) templates can be called each-other please always think to templates as functions, and design them with modularity

18 syntax file the statement file declares on which file the emitted text will be redirected [template public mygenerator(instance : mytype)/] [file(filename, appendmode, charencoding)] [/file] [/template] filename is the file that will be created during the execution ( the ext. must be given) appendmode and charencoding are optional parameters

19 template && file example [template public mygenerator(uc : UseCase)] [file (uc.name.concat('.txt'), false)] These are all the instructions for the script generate. [/file] [/template]

20 template && file example [template public mygenerator(uc : UseCase)] [file (uc.name.concat('.txt'), false)] These are all the instructions for the script generate. [/file] [/template] the attributes of an element are accessed like in most of the objectoriented notations but, some conditional expression will use the syntaxt -> (see the following example on the IF statement) the reason is that such expression are not attributes, but functions in the OCL constraint language

21 context [template public generate(uc : UseCase)] * Explicit Name : [uc.name/] Implicit Name : [name/] [/template] the context is given by the element of the metamodel (i.e. a type) that is considered for that specifc portion of code the context subsumes the visibility of the functionalities and the properties that are accessible it is possible to refer properties both explicitely or implicetely

22 syntax for the for statement defines loops on the matching modelied elements usage: [for (<iterableexpr>) ] This text will be generated for each element [/for] [for (<iterationvar> : <iteratortype> <iterableexpr>)] This text will be generated for each element [/for] it defines an implicit context-switch

23 for example... for any use case in the input model generate a list (e.g. HTML list item tag) with the names of all the contained extension point [template public generate(uc : UseCase)] [file (uc.name.concat('.html'), false)] <ul> [for (uc.extensionpoint)] <li>[name/]</li> [/for] </ul> [/file] [/template]

24 for example another implementation : [template public generate(uc : UseCase)] [file (uc.name.concat('.html'), false)] <ul> [for ( e : ExtensionPoint uc.extensionpoint ) ] <li>[name/]</li> <li>[e.name/]</li> [/for] </ul> [/file] [/template]

25 syntax if the statement if enables conditional generations: [if (<condition>) ] [else] [/if] <statements> <statements> where condition is a boolean admissible operators are : =, <>, <, <=, >, >=, or, and, not operands: values, objects, call to scripts, call to services, links to metamodels

26 if example [template public generate(uc : UseCase)] [file (uc.name.concat('.html'), false)] [if (uc.extensionpoint >isempty())] <p>no Extension Points</p> [/fi] <ul> [for ( e : ExtensionPoint extensionpoint ) ] <li>[e.name/]</li> [/for] </ul> [/file] [/template]

27 syntax let ACCELEO in mostly declarative!!! Nevertheless...

28 the statement let stores the result of an expression within a local variable syntax let a local variable is accessible only within the scope of its declaration block a local variable CANNOT have modified its value after the initialization [let <varname>:<vartype>=<expression> ]... [/let]

29 ACCELEO services : advanced features the ACCELEO services are primitives which extend the minimal (default) language typically they implements functionalities which are difficult to be directly coded within a.mtl file two type of services: native services offered by the ACCELEO platform among the others services for the OCL support services developed by the user of the platform coded directly in Java basically, a service is a(ny) public method offered by a Java class the Java classes providing services must be imported within the templates integrated with the generator

30 ACCELEO services example the service indexof : it can be applied to a sting R ( i.e. the input ) it takes a string S as parameter it returns the position of the first occurrence of S in R its signature in a Java class would be : public int indexof (String R, String S) defining a service by means of a Java class: the first parameter of (public) method is the receiver of the service the receiver defines the type of the objects where that service can be applied the other parameters of the (public) method are the (ordered) parameters of the service the return type of the (public) method matches with the type returned by the service

31 ACCELEO services : how to how to define/import services in ACCELEO? this part is well explained in several tutorials: receipt I want see what happens under the hood : implement a Java class implement the public method offering the service ATTENTION!!: remember the convention about the receiver link the service in Java to an ACCELEO query [query public <query_name>(<receiver_formale> : <type> [, <par_formale> : <type>]) : <ret_type> = invoke('<percorso_alla_classe>','<segantura_metodo>', Sequence{<receiver_formale>[, <lista_par_formali>]}) /] import the query, if defined in some other template [import <template_da_importare> /]

32 ACCELEO services example 1 write an ACCELEO service which sets to capital the first caracther of a string

33 ACCELEO services example 1.1 public class MyService { } public String firstupper(string s){ if (s.length() > 0) s = Character.toUpperCase(s.charAt(0)) + s.substring(1); } return s;

34 ACCELEO services example 1.2 public class MyService { public String firstupper(string s){ if (s.length() > 0) s = Character.toUpperCase(s.charAt(0)) + s.substring(1); } } [query return s; public acceleofirstupper (rec : String) : String = invoke('myservice', 'firstupper(java.lang.string)', Sequence{'rec'}) /]

35 ACCELEO services example 2 write an ACCELEO service which counts the occurrences of a given char (as integer in ASCII) in an input string.

36 ACCELEO services example 2.1 public class MyService { public int count(string str, int asciicodecar){ } } int counter=0; char c = (char) asciicodecar; for (int i=0; i < str.length(); i++) if (str.charat(i) == c) counter++; return counter;

37 ACCELEO services example 2.2 public class MyService { public int count(string str, int asciicodecar){ } } [ query int counter=0; char c = (char) asciicodecar; for (int i=0; i < str.length(); i++) if (str.charat(i) == c) counter++; return counter; public acceleocount (rec:string,code:integer): Integer = invoke('myservice','count(java.lang.string,int)', Sequence{'rec','code'}) /]

38 basic biblio Marco Brambilla, Jordi Cabot, Manuel Wimmer : Model-Driven Software Engineering in Practice. Synthesis Lectures on Software Engineering, Morgan & Claypool Publishers (2012) J. Arlow, I. Neustadt: UML2 e Unified Process - analisi e progettazione Object-Oriented, 2a Ed., McgrawHill Acceleo The Official Documentation The Offical Acceleo Wiki Acceleo 3 Web Site