Model–View Separation A subschema for ‘view’ classes (forms) enforces ModelSchema knows...

Model–View Separation

A subschema for ‘view’ classes (forms) enforces• ModelSchema knows nothing of the view• ViewSchema knows of the model through inheritance

Separate teams of developers can work in• Object model• User interface

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Add controls from palette

Set properties from dialog

Painter

eventssize and positionfont and color

commonspecific

labeltext boxbuttonstatus line

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Form Class

• Can have properties and methods (like a ‘model’ class)• Has references to controls and menu items on the form• Inherits from the Form and Window classes• Can be the superclass of other forms

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Event Method

• Automatically invoked when an event (in right pane) happens to a control or the <form> (in middle pane)

• Is a method of the form (So ‘self’ is the form)

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Lifecycle of a Form

create form;

load - paint - activate - gotFocus

form.show( );

self.unloadForm( );

queryUnload - unload53

Lifecycle of a Form

mnuCustomerAdd_click(menuItem : MenuItem input) updating;

vars

form : CustomerDetails;

begin

create form transient;

form.show();

end;

mnuCustomerAdd_click(menuItem : MenuItem input) updating;

vars

form : CustomerDetails;

begin


form.show();

end;

btnCancel_click(btn : Button input) updating;

begin

self.unloadForm();

delete self;

end;

btnCancel_click(btn : Button input) updating;

begin

self.unloadForm();

delete self;

end;

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Create a Customer (1)

An event method is executed whenthe Windows event occurs.

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A form captures information enteredby a user about a new customer

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A model class sets (and possibly)validates information about an instance

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MDI (Multiple Document Interface)

• A form that contains other forms is an ‘MDI frame’

• An MDI frame has the menu for the application

• A form inside an MDI frame is an ‘MDI child’

MDI Frame

MDI ChildMDI Child

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Adding a Menu

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Form load Event

• Occurs before a form is displayed• Can be used, for example, to put text into text boxes• In this example, sets MDI Frame for application

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Demonstration

Paint a form Add controls Set properties Size and align controls Test a form Code a button click event Add a menu Code a menu click event Build an MDI application

Your instructor will demonstrate how to

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• Add a BankingViewSchema

• Paint a CustomerDetails form

• Code a CustomerDetails::createCustomer method

• Code the click method for btnOK

• Code the click method for btnCancel

Challenge #9

name btnOK

caption OK

maxLength 25

name txtAddress

caption FirstNames:

caption Address:

caption LastName:

maxLength 25

name txtFirstNames

maxLength 15

name txtLastName

name btnCancel

caption Cancel

caption

name statusLine

caption Customer Details

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• Paint a MainMenu form

• Use the menu designer

• Code the click method for mnuCustomerAdd

• Code the load method for the form

• Run the form from Painter and add a customer

Challenge #10

name mnuCustomer

caption &Customer

name mnuCustomerAdd

caption &Add

caption Main Menu

mdiFrame True

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Application-Related Objects

Form Objecttransient copy of persistent object designed in Painter

process

global

aForm

transient

app

transient

Global Objectpersistent object that can validate application logon

Process Objectpersistent object represents thread of execution

Application Objecttransient instance of Application subclass

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aCustomer

Objects in an Application

transient

aForm

transient

aButton

aBank

transient

app process

aCustomer

aChequeAcct

transient

aTextBox

transient

aTextBoxaSavingsAcct

aChequeAcct

aCollectionaCollection

transient

aButton aSavingsAcct

global

two objects representing an application

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Application Type

• Four types– GUI– GUI, No forms– Non-GUI– Web-Enabled

• Specified on Define Application dialog67

Initialize and Finalize Methods

• Methods run at startup and closedown for each process• Methods in the Application class or sub class• Can use other names• Specified on Define Application dialog

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Root Object

• Persistent object (singleton) that represents the business• Has ‘complete’ collections of model objects• Accessed from the app object

transient

ApplicationSubclass (app)

myBank

initialize () updating;

begin

// set reference to root object

self.myBank := Bank.firstInstance();

end;

initialize () updating;

begin

// set reference to root object

self.myBank := Bank.firstInstance();

end;

3000.1

Bank

allCustomers

// accessing collections

app.myBank.allCustomers

app.myBank.allBankAccounts

// accessing collections

app.myBank.allCustomers

app.myBank.allBankAccounts

CustomerCollection

BankAccountCollection

allBankAccounts

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Security Methods

• Global class methods– getAndValidateUser– isUserValid

• Application class property– userSecurityLevel

• Form and Controls– securityLevelEnabled– securityLevelVisible

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Logon Validation

getAndValidateUser(usercode : String output; password : String output): Boolean;

vars

form : Logon;

accept : Boolean;

begin


form.showModal();

accept := form.txtPassword.text.toLower() = 'secret';

if not accept then

app.msgBox('Please enter your password again',

'Access Denied',

MsgBox_OK_Only);

endif;

return accept;

end;

getAndValidateUser(usercode : String output; password : String output): Boolean;

vars

form : Logon;

accept : Boolean;

begin


form.showModal();

accept := form.txtPassword.text.toLower() = 'secret';

if not accept then

app.msgBox('Please enter your password again',

'Access Denied',

MsgBox_OK_Only);

endif;

return accept;

end;

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Shortcut

c:\jadecourse\bin\jade.exe path=c:\jadecourse\system

app=BankingViewSchema

schema=BankingViewSchema

host=localhost

port=6005

server=multiuser

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Demonstration

Define an application Display a message box Provide logon validation Run application from development Create an application shortcut


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In the BankingModelSchema

• Add a Bank class (no properties or methods yet)

• Code and execute a JadeScript::createBank method

• Add a myBank reference to BankingModelSchema

• Code a BankingModelSchema::initialize method

In the BankingViewSchema

• Modify the definition of the application to startwith MainMenu and run initialize

On the desktop

• Create a shortcut to run the application

Challenge #11

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• Paint a Logon form

• Code the btnOK_click method

• Code the getAndValidateUser method

• Test the logon security

Challenge #12

name btnOK

caption OK

caption Enter the passwordname txtPassword

passwordField True

mdiChild Not MDI form

default True

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Distributed Processing

Server

Run the Application

Manage the Database

ClientClient

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JADE Database

JADE DatabaseJADE Application

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JADE Database

‘data’ objects

branches

accounts

deposits

withdrawals

‘specification’ objects

classes

methods

forms

reports

JADE Database

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JADE Database

Persistent Cache automatic storage

automatic retrieval

JADE Database

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Architecture

Database Server

Internet Server(Microsoft IIS)

Fat Client(Web-Enabled Application)

HTML Client(Browser)

HTML Client(Browser)

Application ServerFat Client Fat Client

Thin Client Thin Client

Runtime Systems OnlyDevelopment and Runtime Systems

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Node

Persistent Cache Transient Cache

TransientDatabase

Background Process

Process

Process

Node

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Server Node

Server Node

TransientDatabase

PersistentDatabase

Background Process

Server Application Process

Server Method Process


Remote Transient Cache

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Client Node

Client Node

TransientDatabase

Background Process

Development Process

Client Application Process

Painter Process

Debugger Process

Read-OnlySchema

User Interface


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AppServer Node

AppServer Node

Background Process

AppServer Application Process

Thin Client Process

Thin Client Process

Thin Client Process

TransientDatabase

Read-OnlySchema Thin Client

User Interface

CachedForms


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Object Editions

Server Node

Persistent Database

edition=4

Node

Persistent Cache

edition=5

Node

Persistent Cache

edition=4

Node

Persistent Cache

edition=2

modified but not committed latest edition obsolete

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Cache Synchronisation

Obtaining edition information

cust.edition(); // returns edition of customer in cache

cust.latestEdition(); // returns edition of customer on server

cust.edition(); // returns edition of customer in cache

cust.latestEdition(); // returns edition of customer on server

self.exclusiveLock(cust); // any lock ensures latest edition

if previousCustomerEdition <> cust.edition() then

// compare a previous edition number

self.exclusiveLock(cust); // any lock ensures latest edition

if previousCustomerEdition <> cust.edition() then

// compare a previous edition number

cust.resynch(); // customer resynchs itself

self.resynchObject(cust); // 'self' resynchs the customer

Customer.resynchInstances(); // resynchs all Customer instances

cust.resynch(); // customer resynchs itself

self.resynchObject(cust); // 'self' resynchs the customer

Customer.resynchInstances(); // resynchs all Customer instances

Locking to obtain the latest edition then checking editions

Resynching to obtain the latest edition

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Demonstration

Run the JADE monitor program Run a JADE application server Run a JADE thin client Extract your schema Run the JADE loader program


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• Run the JADE monitor program

• Monitor ‘Users’ – processes and nodes

• Run your application from a shortcut

• Run a JADE application server

• Run JADE development in thin client

• Run a second development thin client

• Identify processes and nodes

Challenge #13

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Challenge #14

Run the default application in the Architecture schema89

Challenge #15

• Extract your schemas

• Remove your schemas

• Run the JADE loader program

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Lock Diagrams

“The process . . . . . . . . . . has a lock on . . . . . . . . the object”

Who owns the lock?

object1.exclusiveLock (object2);object1.exclusiveLock (object2);

self.exclusiveLock (object2);self.exclusiveLock (object2);

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Lock Combinations

shared

shared

shared

shared

process A process B

process Cprocess D

Shared

shared

shared

reserve

shared

process A

process D

process B

process C

Reserve

exclusive

process AExclusive

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Lock Durations

• Session– released when process ceases

• Transaction– released when abortTransaction or commitTransaction

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Latest Edition

edition=2

Persistent CacheDatabase Server

edition=3

edition=3

successful lock edition check cache updated

resynchObject(object); // object marked as obsolete

write object.name; // edition checked so

// latest object now in cache

resynchObject(object); // object marked as obsolete

write object.name; // edition checked so

// latest object now in cache

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Transactions

session

process start

beginLoad

(beginLock)

endLoad

(endLock)

read

transaction

beginTransaction

update

transaction

process end

commitTransaction

(abortTransaction)

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Read Transactions

• Locks not required but must guarantee correct result. Has logical start and end.

• beginLock/endLock or beginLoad/endLoadbeginLock;

trial := trial + account.balance; // balance is a property, account is locked

endLock; // account is unlocked

beginLock;

trial := trial + account.balance; // balance is a property, account is locked


beginLock;

trial := trial + account.getBalance(); // getbalance is a method, account is locked


beginLock;

trial := trial + account.getBalance(); // getbalance is a method, account is locked


beginLoad;

sharedLock(account); // account is locked

trial := trial + account.getBalance();

endLoad; // account is unlocked

beginLoad;

sharedLock(account); // account is locked

trial := trial + account.getBalance();

endLoad; // account is unlocked96

Updating Transactions

edition=4


edition=3

edition=4

successful transaction database updated

edition=4


edition=3

failed transaction ‘dirty’ object discarded

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Locking an Object

lock (object, type, duration, timeout);

sharedLock (object);lock (object, Share_Lock, Transaction_Duration, LockTimeout_Server_Defined);

reserveLock(object);lock(object, Reserve_Lock, Transaction_Duration, LockTimeout_Server_Defined);

exclusiveLock(object);lock(object, Exclusive_Lock,Transaction_Duration, LockTimeout_Server_Defined);

tryLock (object, type, duration, timeout);

lock (object, type, duration, timeout);

sharedLock (object);lock (object, Share_Lock, Transaction_Duration, LockTimeout_Server_Defined);

reserveLock(object);lock(object, Reserve_Lock, Transaction_Duration, LockTimeout_Server_Defined);

exclusiveLock(object);lock(object, Exclusive_Lock,Transaction_Duration, LockTimeout_Server_Defined);

tryLock (object, type, duration, timeout);

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Lock Queue

Lock

Exception

ServerTimeout=10000 (10 sec)

LockQueueCheckInterval=1000 (1 sec)

Lock Queue

If lock has not been obtained

If lock cannot be obtained

immediately

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Monitoring Locks

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Changing a Lock

• Duration• Type

Lock could attempt to change

Guidelines Duration upgrade Duration downgrade Type upgrade

(if object is locked with a session lock, a transaction duration upgrade inside a transaction is reversed when the transaction ends)

Type downgrade outside a transaction Type downgrade in a transaction

(if object is locked with a session lock, a session duration downgrade inside a transaction is delayed until the transaction ends)

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Collections and Locking

while i < collection.size() do // collection is locked

if collection.includes(object) then // collection is locked

while i < collection.size() do // collection is locked

if collection.includes(object) then // collection is locked

foreach object in collection do // collection is locked

. . .

endforeach; // collection is unlocked

iter := collection.createIterator();

while iter.next(object) do // collection is not locked

. . .

endwhile;


. . .

endforeach; // collection is unlocked

iter := collection.createIterator();

while iter.next(object) do // collection is not locked

. . .

endwhile;


beginTransaction;

object.update();

commitTransaction; // all locks released so collection is unlocked

endforeach;


beginTransaction;

object.update();

commitTransaction; // all locks released so collection is unlocked

endforeach;102

Lock Exceptions

“The process . . . . . . . . tries but cannot lock . . . . . . the object”

process A process B

process A

process B

process C103

Lock Exception Object

LockException

lockDurationlockTimeoutlockTyperetryCounttargetLockedBy

lockTargetretryLock

initialize() updating;

begin

on LockException do app.globalLockException (exception) global;

end;

initialize() updating;

begin

on LockException do app.globalLockException (exception) global;

end;

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Deadlocks

process A process B

shared

process Bprocess A

shared

exclusive

exclusive

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Deadlocks Many Processes

process A process B

process D process C

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Dirty Reads

Client or AppServer Node

Persistent Cacheedition=4

cache overflow partial commit ‘dirty’ object

Client or AppServer Node

Persistent Cache

Server Node

Transaction Log File Persistent Database

edition=3

edition=4

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Node


TransientDatabase

Background Process

Process

Process

Node

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getLockStatus (object, lockType, lockDuration, lockedBy);

isLockedByMe (obj);

create lockArray transient;

system.getLocks (lockArray, max);

getLockStatus (object, lockType, lockDuration, lockedBy);

isLockedByMe (obj);

create lockArray transient;

system.getLocks (lockArray, max);

Information on Locks

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Shared Transient Objects

beginTransaction;

create object persistent; // persistent

commitTransaction;

create object transient; // process transient

beginTransientTransaction;

create object sharedTransient; // shared transient

commitTransientTransaction;

beginTransaction;

create object persistent; // persistent

commitTransaction;

create object transient; // process transient

beginTransientTransaction;

create object sharedTransient; // shared transient

commitTransientTransaction;

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Demonstration

Lock and unlock an object Create a lock exception Carry out a read transaction Carry out an update transaction Monitor locks Monitor queued locks Execute code and observe locking Create transient and shared transient objects Cause a deadlock exception


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Run the default application in the TransactionAndLocking schema

Challenge #16

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Code a CustomerDetails::isInputOK method

Challenge #17

• Return true if all text boxes contain textand false otherwise

• If a text box is empty – display a message on the statusLine – set the focus to the text box

Code a CustomerDetails::clearTextBoxes method

Modify the btnOK_click method

• Call isInputOK and return if input is not OK• If input is okay

– create the customer as before – clear text boxes – display a message on the statusLine – set focus to txtLastName

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Model–View Separation A subschema for ‘view’ classes (forms) enforces ModelSchema knows...

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Transcript of Model–View Separation A subschema for ‘view’ classes (forms) enforces ModelSchema knows...