ARCH-11: Building your Presentation with Classes John Sadd Fellow and OpenEdge Evangelist Sasha...

ARCH-11: Building your Presentation with Classes

John SaddFellow and OpenEdge Evangelist

Sasha KraljevicPrincipal TSE

© 2007 Progress Software Corporation2 ARCH-11: Building your Presentation with Classes

Agenda

Presentation Layer in the OERA Requirements Design Patterns Implementing the Model Implementing the Presentation Implementing the View Integration with Common Infrastructure Summary


Provides a high-level blueprint Allows you to separate concerns Helps you not to complicate your life Facilitates agile design and development

Presentation Layer in OERA

OpenEdge® Reference Architecture


OpenEdge Reference Architecture

PresentationPresentation

Business ComponentsBusiness Components

Data AccessData Access

Data SourcesData Sources

Co

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Infrastru

cture

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Infrastru

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Enterprise ServicesEnterprise Services


OpenEdge Reference Architecture





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Infrastru

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Infrastru

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Enterprise ServicesEnterprise Services

Presentation controls the user interface and requests data and other services


Demo – What do we want to achieve?


Agenda

Presentation Layer in OERA Requirements Design Patterns Implementing the Model Implementing the Presentation Implementing the View Integration with Common Infrastructure Summary


1. Have a clearly defined interface to Business Components (BC) and Common Infrastructure (CI)

2. Be able to serve different UI client types

3. Allow reuse of common code shared by different UI client types

4. Lend itself to testing

Presentation Layer - Requirements

…must:


Able to locate required services in the BC & CI layers

Able to communicate with them Able to handle dependencies on application

state in a loosely coupled way

Requirement 1: The Presentation has a clearly defined interface to BC & CI layers

Components in the Presentation layer should be:


Should not be a single monolithic body of code

Should handle user actions in the same way regardless of the UI type

Should take into account the UI type and session state, for example:• HTTP/*ML is ‘stateless’

• Client/Server GUI may maintain state

Requirement 2: The Presentation can serve different UI client types

The Presentation layer:


Some code is responsible for handling information • This should be UI independent

Some code is responsible for responding to user actions• This will be UI type dependent

Some code is responsible for rendering the user interface• This will be UI type dependent

Requirement 3: The Presentation allows reuse of common code

In the Presentation layer :


User interfaces are complicated to test • User actions can be hard to capture

• Small changes to the UI disrupt saved tests

The Presentation architecture should facilitate automated testing

Requirement 4: The Presentation lends itself to testing


Agenda



A number of existing patterns can be used Choose one or more that match best to the

requirements To list some:

- MVC (Model View Controller)- MVP (Model View Presenter)

and their derivatives…

Design Patterns


Model-View-Controller versus Model-View-Presenter

ControllerController

ModelModel ViewView

PresenterPresenter

ModelModel ViewView

MVC – Model View Controller

MVP – Model View Presenter


Presenter versus Passive View

PresenterPresenter

ModelModel ViewView

MVP – Model View Presenter

PresenterPresenter

ModelModel ViewView

MVP – Passive View


Design Patterns – Composite pattern for Views

cd CompositeView

View

+ Add() : View+ GetChild() : Component+ Remove() : View+ Render()

Request

SimpleView

+ Render()

CompositeView

+ Add() : View+ GetChild() : Component+ Remove() : View+ Render()

forall g in children g.Render();

-children

1..*


Design Patterns – Composite pattern for Presenters

cd CompositePresenter

Presenter

+ Add() : Presenter+ GetChild() : Component+ Operation()+ Remove() : Presenter

SimplePresenter

+ Operation()

CompositePresenter

+ Add() : Presenter+ GetChild() : Component+ Operation()

forall g in children g.Operation();

+ Remove() : Presenter

-children

1..*


Example View


The View with the Presenter and Model

VIEW

PRESENTER

MODEL


Design Patterns – Back to the OERA

cd PresentationInOERA

Presentation Layer

Client Business Component

(Model)Presenter

View

CommonInfrastructure

Serv iceAdapter

1 1..*

1

1..*

1..*

1..*


Agenda



The Service Adapter and Service Interface





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Enterprise ServicesEnterprise ServicesClient session

AppServer session

Service AdapterService Adapter

Service InterfaceService Interface

Service Adapter sits outside the Model• Connects the Presentation to Service Interface

Service Interface sits “above” the Business Components• Routes each request to the right Business Component


Support for a Business Component Type

The Model

The role of the Model in the Architecture

Service AdapterClient Business Component

Data Instance


Data Instance

Service AdapterClient Business Component

Data Instance


Data Instance

Service Interface Business Component


Implementing the Model with classes

The Model holds data on behalf of the View There is a Client Business Component (CBC)

type for each Business Component type• Presentation layer Customer CBC type maps

to a Customer Business Entity

There is one instance of a CBC for each View element that requests distinct data of the type


Data instances

Data is not held persistently in the Business Components on the server

A Data Instance can represent a simple object (a row), a complex object (a DataSet or other form), a set of rows

A Data Instance can be held by a Client Business Component and bound to by the View

A Data Instance in the Model can be held as long as the data is needed

A Data Instance can be shared by multiple Views



Business ComponentBusiness Component



Enterprise ServicesEnterprise ServicesCBC

SalesRep

SalesRep

View1SalesReps

View2

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Example: a data instance for SalesReps

Presenter

All SalesRepsSvc Adapter

SalesRep

SalesRep BE

All SalesReps

SalesRep DAO

BIND


Data Instances on server and client

On the server:• A single Business Component can be

refreshed and reused for all requests• The same Business Components can be used

to supply data to Enterprise Services On the client:

• A single Service Adapter can be used for all instances of a type in a session

• Distinct Views can have distinct CBC instances

• A single CBC instance can be reused to supply different data to a given View


Order BE


Business ComponentBusiness Component



Enterprise ServicesEnterprise Services Order

Order OrderLine

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Infrastru

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CBCOrder

View1Order

View2OrderPresenter

Order 1Svc Adapter

Orders

Order 1

CBC

Order 3

Order 3Order 5

Order 5 Order 5

Example: Sharing and reusing data instances

Order DAO


Service Adapters Common InfrastructureThe Model

Client-side code hierarchies

componentbase.cls

clientcomponent.cls

beCustomer.cls

serviceadapter.cls

saCustomer.cls servicemanager.cls

manager.cls

factory.p

INHERITS

INVOKES


Looking at class-based ABL code:clientcomponent super class

CLASS inherits behavior from a base class PUBLIC property protects setting the value PROTECTED VARIABLE protects access to the value

• Also defined as a specific class type

CLASS pres.clientcomponent INHERITS base.componentbase:

/* Handle for the default query on the top-level DataSet buffer */DEFINE PUBLIC PROPERTY hTopRelQuery AS HANDLE NO-UNDO GET. PROTECTED SET.

DEFINE PROTECTED VARIABLE AdapterRef AS pres.serviceadapter NO-UNDO.

END CLASS.


Client Business Component subclass

CLASS inherits behavior from the super class CONSTRUCTOR executed on creation PROTECTED variable can be set from this subclass

PROPERTY hTopRelQuery accessed just like a variable

CLASS samples.pres.beCustomer INHERITS pres.clientcomponent:

{samples/dsCustomer.i} CONSTRUCTOR beCustomer(): AdapterRef = CAST (servicemgr:startService ("samples.pres.saCustomer“, "sa"), samples.pres.saCustomer). CREATE QUERY hTopRelQuery. hTopRelQuery:ADD-BUFFER(DATASET dsCustomer:GET-BUFFER-HANDLE(1)). hTopRelQuery:QUERY-PREPARE ("FOR EACH " + DATASET dsCustomer:GET-BUFFER-HANDLE(1):NAME). END CONSTRUCTOR.



Methods in the Client Business Component

Method is PUBLIC to allow access from Presenter• VOID return type

fetchData reference in AdapterRef verified by compiler

METHOD PUBLIC VOID fetchWhere (INPUT-OUTPUT DATASET-HANDLE phDSContext): DEFINE VARIABLE iBuffer AS INTEGER NO-UNDO. DEFINE VARIABLE hDataSet AS HANDLE NO-UNDO.

AdapterRef:fetchData(OUTPUT DATASET dsCustomer, INPUT-OUTPUT DATASET-HANDLE phDSContext). hDataSet = DATASET dsCustomer:HANDLE. DO iBuffer = 1 TO hDataSet:NUM-BUFFERS: hDataSet:GET-BUFFER-HANDLE(iBuffer): TABLE-HANDLE:TRACKING-CHANGES = YES. END.END METHOD.



Agenda



CLASS presCustomerMaintenance INHERITS base.presenter:&Scoped-define REFERENCE-ONLY REFERENCE-ONLY{samples/dsCustomer.i {&REFERENCE-ONLY}}/* DEFINE DATASET dsCustomer REFERENCE-ONLY FOR eeCustomer . */

DEFINE VARIABLE clsCbcCustomer AS samples.cbcCustomerMaintenance NO-UNDO GET. PRIVATE SET.

DEFINE PRIVATE VARIABLE hViewer AS HANDLE NO-UNDO.…END CLASS.

Looking at class-based ABL code:presenter class

CLASS inherits behavior from a base presenter class PRIVATE setter protects setting the value PRIVATE VARIABLE protects access to the value

• Also defined as a specific class type where the view is realized using class type


CLASS presCustomerMaintenance INHERITS base.presenter:…CONSTRUCTOR PUBLIC presCustomerMaintenance ( ): SUPER (). clsCbcCustomer = NEW samples.cbcCustomerMaintenance().

IF SESSION:CLIENT-TYPE = "4GLCLIENT" OR SESSION:CLIENT-TYPE = "WEBCLIENT" THEN DO: RUN CustomerMaintenance.w PERSISTENT SET hViewer. RUN setPresenter IN hViewer (INPUT THIS-OBJECT ) NO-ERROR. RUN populateData IN hViewer NO-ERROR. RUN enable_UI IN hViewer NO-ERROR. WAIT-FOR CLOSE OF hViewer.END.

Looking at class-based ABL code:presenter constructor

SUPER() calls constructor in a base presenter class Instantiate the Client Business Component RUN the view, pass the reference to the presenter object, populate

data and enable the UI• The View can be realized as the specific class type instead of the

ABL persistent procedure


Agenda



The View:

/* ***********Included Temp-Table & Buffer definitions ******** */{samples/eCustomer.i} /*Temp-table defined as REFERENCE-ONLY */

/* Local Variable Definitions ---*/

DEFINE DATASET dsCustomer REFERENCE-ONLY FOR eeCustomer .DEFINE VARIABLE clsPresenter AS presCustomerMaintenance NO-UNDO .. . .

ON CHOOSE OF BtnDone IN FRAME DEFAULT-FRAME /* Done */DO: clsPresenter:exitObject() .END.

PROCEDURE populateData :

clsPresenter:fetchData(OUTPUT TABLE eeCustomer BY-REFERENCE ).

END PROCEDURE.

PROCEDURE setPresenter :

DEFINE INPUT PARAMETER clsObj AS presCustomerMaintenance .

clsPresenter = clsObj .

END PROCEDURE.


Agenda



Integration with Common Infrastructure

Presenter class & procedures – Service Adapter to CI

CLASS service.ServiceMgr INHERITS Base IMPLEMENTS IComponentFactory,IComponentRegistry USE-WIDGET-POOL :…END CLASS.

Remember inheritance?

presCustomerMaintenance inherits base.presenter Base.presenter inherits ‘base’ class ‘base’ class defines class variable ‘clsServiceMgr’

• Using Service Manager class methods, we now have access to all other services in CI !!!


Agenda



Demo – What have we achieved?


In Summary

Separate concerns! Use proven design patterns! Follow OERA best practices!


Relevant Exchange Sessions:

ARCH-1: Application Architecture Made Simple ARCH-2: OERA Latest Thinking! ARCH-7: A Class-based Implementation of the

OERA ARCH-12: Leveraging Design Patterns in ABL

Applications

For More Information, go to…

PSDN:www.psdn.com/library/kbcategory.jspa?categoryID=289

OpenEdge Principles: Implementing the OpenEdge Reference Architecture


Questions?


Thank you foryour time


Date post:	14-Dec-2015
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