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Model–View Separation

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. 49. Painter. Add controls from palette

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Model–View Separation

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  1. 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 49

  2. Painter • Add controls from palette • Set properties from dialog label text box button status line common specific font and color size and position events 50

  3. 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 51

  4. 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) 52

  5. Lifecycle of a Form create form; form.show( ); load - paint - activate - gotFocus self.unloadForm( ); queryUnload - unload 53

  6. Lifecycle of a Form mnuCustomerAdd_click(menuItem : MenuItem input) updating; vars form : CustomerDetails; begin create form transient; form.show(); end; btnCancel_click(btn : Button input) updating; begin self.unloadForm(); deleteself; end; 54

  7. Create a Customer (1) An event method is executed whenthe Windows event occurs. 55

  8. Create a Customer (2) A form captures information enteredby a user about a new customer 56

  9. Create a Customer (3) A model class sets (and possibly)validates information about an instance 58

  10. MDI (Multiple Document Interface) MDI Frame • 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 Child MDI Child 59

  11. Adding a Menu 60

  12. 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 61

  13. 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 62

  14. caption Customer Details caption LastName: caption FirstNames: caption name statusLine caption Address: name btnOK caption OK maxLength 15 name txtLastName name btnCancel maxLength 25 caption Cancel name txtAddress maxLength 25 name txtFirstNames Challenge #9 • Add a BankingViewSchema • Paint a CustomerDetails form • Code a CustomerDetails::createCustomer method • Code the click method for btnOK • Code the click method for btnCancel 63

  15. caption Main Menu name mnuCustomer mdiFrame True caption &Customer name mnuCustomerAdd caption &Add Challenge #10 • 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 64

  16. app process aForm global transient transient Application-Related Objects Form Objecttransient copy of persistent object designed in Painter Application Objecttransient instance of Application subclass Process Objectpersistent object represents thread of execution Global Objectpersistent object that can validate application logon 65

  17. aCustomer aCustomer aBank process global aCollection aCollection aSavingsAcct aSavingsAcct app aChequeAcct aChequeAcct transient aForm transient aButton aButton aTextBox aTextBox transient transient transient transient Objects in an Application • two objects representing an application 66

  18. Application Type • Four types • GUI • GUI, No forms • Non-GUI • Web-Enabled • Specified on Define Application dialog 67

  19. 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 68

  20. 3000.1 Bank Customer Collection allBankAccounts BankAccount Collection allCustomers // accessing collections app.myBank.allCustomers app.myBank.allBankAccounts Root Object • Persistent object (singleton) that represents the business • Has ‘complete’ collections of model objects • Accessed from the app object Application Subclass (app) myBank transient initialize () updating; begin // set reference to root object self.myBank := Bank.firstInstance(); end; 69

  21. Security Methods • Global class methods • getAndValidateUser • isUserValid • Application class property • userSecurityLevel • Form and Controls • securityLevelEnabled • securityLevelVisible 70

  22. Logon Validation getAndValidateUser(usercode : String output; password : String output): Boolean; vars form : Logon; accept : Boolean; begin create form transient; form.showModal(); accept := form.txtPassword.text.toLower() = 'secret'; ifnot accept then app.msgBox('Please enter your password again', 'Access Denied', MsgBox_OK_Only); endif; return accept; end; 71

  23. Shortcut • c:\jadecourse\bin\jade.exe path=c:\jadecourse\system app=BankingViewSchema schema=BankingViewSchema host=localhost port=6005 server=multiuser 72

  24. Demonstration • Define an application • Display a message box • Provide logon validation • Run application from development • Create an application shortcut Your instructor will demonstrate how to 73

  25. Challenge #11 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 74

  26. mdiChild Not MDI form caption Enter the password Challenge #12 • Paint a Logon form • Code the btnOK_click method • Code the getAndValidateUser method • Test the logon security name txtPassword passwordField True name btnOK caption OK default True 75

  27. Manage the Database Server Client Client Run the Application Distributed Processing 76

  28. JADE Application JADE Database JADE Database 77

  29. JADE Database JADE Database ‘specification’ objects classes methods forms reports ‘data’ objects branches accounts deposits withdrawals 78

  30. JADE Database JADE Database Persistent Cache automatic storage automatic retrieval 79

  31. Database Server Application Server Fat Client Fat Client Fat Client (Web-Enabled Application) Internet Server (Microsoft IIS) HTML Client (Browser) Thin Client Thin Client HTML Client (Browser) Development and Runtime Systems Runtime Systems Only Architecture 80

  32. Persistent Cache Transient Cache TransientDatabase Node Node Background Process Process Process 81

  33. Transient Cache Remote Transient Cache TransientDatabase PersistentDatabase Server Node Server Node Persistent Cache Background Process Server Application Process Server Method Process 82

  34. Persistent Cache Transient Cache Background Process Development Process Client Application Process Debugger Process Painter Process User Interface TransientDatabase Read-OnlySchema Client Node Client Node 83

  35. Persistent Cache Transient Cache Background Process AppServer Application Process Thin Client Process Thin Client Process Thin Client Thin Client Process User Interface CachedForms AppServer Node AppServer Node Read-OnlySchema TransientDatabase 84

  36. Server Node Persistent Database edition=4 Node Node Node Persistent Cache Persistent Cache Persistent Cache edition=5 edition=2 edition=4 Object Editions modified but not committed latest edition obsolete 85

  37. Cache Synchronisation cust.edition(); // returns edition of customer in cache cust.latestEdition(); // returns edition of customer on server Obtaining edition information Locking to obtain the latest edition then checking editions self.exclusiveLock(cust); // any lock ensures latest edition if previousCustomerEdition <> cust.edition() then // compare a previous edition number Resynching to obtain the latest edition cust.resynch(); // customer resynchs itself self.resynchObject(cust); // 'self' resynchs the customer Customer.resynchInstances(); // resynchs all Customer instances 86

  38. Demonstration • Run the JADE monitor program • Run a JADE application server • Run a JADE thin client • Extract your schema • Run the JADE loader program Your instructor will demonstrate how to 87

  39. Challenge #13 • 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 88

  40. Challenge #14 Run the default application in the Architecture schema 89

  41. Challenge #15 • Extract your schemas • Remove your schemas • Run the JADE loader program 90

  42. “The process . . . . . . . . . . has a lock on . . . . . . . . the object” Lock Diagrams Who owns the lock? object1.exclusiveLock (object2); self.exclusiveLock (object2); 91

  43. Lock Combinations exclusive Exclusive process A shared shared process A process B Shared shared shared process D process C reserve shared process A process B Reserve shared shared process D process C 92

  44. Lock Durations • Session • released when process ceases • Transaction • released when abortTransaction or commitTransaction 93

  45. Database Server Persistent Cache successful lock edition check cache updated edition=3 edition=2 edition=3 Latest Edition resynchObject(object); // object marked as obsolete write object.name; // edition checked so // latest object now in cache 94

  46. process start process end beginTransaction beginLoad (beginLock) endLoad (endLock) commitTransaction (abortTransaction) read transaction update transaction session Transactions 95

  47. Read Transactions • Locks not required but must guarantee correct result. Has logical start and end. • beginLock/endLock or beginLoad/endLoad beginLock; trial := trial + account.balance; // balance is a property, account is locked endLock; // account is unlocked beginLock; trial := trial + account.getBalance(); // getbalance is a method, account is locked endLock; // account is unlocked beginLoad; sharedLock(account); // account is locked trial := trial + account.getBalance(); endLoad; // account is unlocked 96

  48. Database Server  Persistent Cache failed transaction ‘dirty’ object discarded edition=4 edition=3 Database Server Persistent Cache successful transaction database updated edition=4 edition=3 edition=4 Updating Transactions 97

  49. 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); 98

  50. Lock Queue ServerTimeout=10000 (10 sec) LockQueueCheckInterval=1000 (1 sec) Lock Queue If lock cannot be obtained immediately If lock has not been obtained Lock Exception 99

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