1	Rapid Development Web Software System – Design and Conversion to .NET Jonathan D. Melvin Vision Implementers, Inc., jdm@vi-i.com LA CSharp, October 15, 2002 Based in part on a talk given at Caltech, April 16, 2001
2	Framework Vision Allow a system to be created and run simply by specifying: data structures work flow
3	Reality: Implementation of the vision to date Not yet possible to eliminate all programming, but… Programming of the user interface is greatly simplified by using the web browser Much of the user interface is specified via naming conventions in the data Most of the code is in a framework which accesses simple scripts to present the user interface (setup framework) and work flow screens (application framework)
4	Advantages of using the web browser to facilitate the user interface Screen layout is largely carried out by the browser (e.g., you can tell the browser “start table”, “start row”, “start cell”, <contents>, “end cell”, … instead of having to specify the detailed layout of the table) Secure internet communication (SSL) is included "for free" Any kind of client machine can be used (PC, Mac, Sun, …)
5	Advantages of using the web browser to facilitate the user interfac, continued Code changes can be instantly deployed at a single location for all users Users can work from anywhere; support personnel can fix problems from anywhere The system can communicate with email, fax, cell phones, etc. without special programming The system can incorporate address validation, geographical mapping, and other services available for free on the Internet
6	Advantages of using a framework More rapid system implementation Simpler system maintenance Consistent user interface
7	The setup framework A setup framework executes scripts which describe the database using descriptive names for types of data elements. The framework creates the tables in a SQL database. A sample script excerpt follows: . . . Create Table "Teacher_",+_ "Last_Name Name,"+_ "First_Name Name,"+_ "Middle_Name Name,"+_ "Street_Address1 Long,"+_ "City_ Long,"+_ "State__lookup_ 2char,"+_ "Zip_Code ID,"+_ . . .
8	The database tables created have standardized structure (to be described more later):
9	Application Framework An application framework executes a second script to run the application. A sample excerpts from such a script follow: Work flow v.DrillDown("Teachers","Teacher","Last_Name","Classes“) ... ELSEIF v.BeginFindForm("Teachers","Teacher","Last_Name,First_Name") THEN v.SearchField "First name includes:","TeacherFirst",25,"First_Name","CN" v.SearchField "Last name includes:","TeacherLast",25,"Last_Name","CN" v.SearchField "Address includes:","TeacherAddress",25,"Street_Address+City_","CN“ v.EndCommandForm "List teachers" ELSEIF v.DoDrillDown("Teachers","%FIRST_NAME% %LAST_NAME%","Teacher",_ TRUE,"Classes") THEN v.BeginDetailList v.ListSendAdded "Class","Classes Taught","No classes","Course_","Students" v.EndDetailList ELSEIF v.EditList("Class","Class","Class") THEN
10	Application framework, continued Views of the data ELSEIF v.ViewParameters("View.Teacher","Teacher_",_ "_ID,_ID AS Teacher_ID,Last_Name,First_Name,"+cCampuses+_ ",Street_Address,Home_Phone AS Phone_",_ "",_ v.Where(CampusYearTeacher(),IIF(cGroup="TEACHER","_ID="+_ cParameter,""),FALSE),_ "Last_Name,First_Name",_ "*",_ "","",_ nMaxTxtBoxWidth,nColumns) THEN v.SetupTabs("135","540","360“) v.AddTab("Name and Address","",1) v.AddTab("Campus 1-2","Campus1__lookup_",1) v.AddTab("Campus 3-4","Campus3__lookup_",1)
11	Work flow query screen
12	Work flow list screen
13	Edit work flow item screen
14	Application framework security and navigation Login with username and password Membership of each user in a user group which controls access to entire tables, to columns and rows within tables, as to parts of the work flow Consistent work flow navigation structured as follows: User picks a step in the work flow User views a list of work that is at that step User selects an items on that list and carries out work. Work can involve entering new data and/or changing the step in the work flow for the item.
15	Application framework input/output Text, and numerical, date, and choice input Rapid data entry of multiple values for a set of data records (spreadsheet style input) Entry and deletion of records corresponding to entries in a standard list (e.g., inventory values for a list of items for a particular month) Formatted reports and forms Import and export data from other systems
16	Application framework database features: Background (1/4) Data in a “database” is organized into “tables” (rows and columns). Each row is called a “record”. Each column value in a row is called a “field”. A field value can be A number Text (of limited and of unlimited size) Graphics or other external data A date A pointer to a record in another table ("foreign key")
17	Database background (2/4) A database is “normalized” if information is never stored in two places. E.g., a normalized student database stores the student name once in a student table, not in each grade record. The data has “referential integrity” if all foreign keys point to valid records.
18	Database background (3/4) "SQL", or “Structured Query Language”, is a syntax for specifying in an almost English manner what is to be done to data. Examples: SELECT * FROM Student WHERE LEFT(Last_Name,1)=’M’ UPDATE Grade SET Grade.Final=’A’ FROM Grade LEFT JOIN STUDENT ON Grade.Student_ID=Student.ID WHERE Student.Major=’Physics’
19	Database background (4/4) “Tracking fields” are extra fields which record who created and who modified the record and when, version number for the record, and/or other such information relating to the use of the database (as opposed to the data in the database)
20	Application framework database features Supports normalized databases, enforces referential integrity, and incorporates tracking fields Uses SQL to standardize interaction with the database and to concisely specify data views (and through them control appearance of data on the screen)
21	Application framework Software Structure Framework implements user interface and data access structures Concise scripts (code) implement specifics of the design Data structure Work flow Queries, overview columns, and fields on detailed single record edit/view screens
22	Initial Implementation Active Server Page script language (VBScript) on Microsoft IIS Servers ODBC access to SQL databases, usually in SQLServer, but can also use FoxPro, Access, Excel, etc. All systems are implemented in a single ASP page; session (persistent state) variables are used to track where one is in the work flow (what part of the page will be executed next)
23	Second Implementation Conversion of the framework to a single VB class The application-specific script instantiates the framework and application objects and calls a method which creates the page
24	Current Implementation The framework is preserved All the code has been converted to .NET (VB.NET) The code is compiled into DLLs A single line aspx (ASP.NET) file instantiates the application object which creates the web page based on the session (state) and form (user input) values The code is object oriented, with a specific application object, a generic application object, an application template superclass, and the framework class
25	Converting the ASP code to ASP.NET Used a combination of manual and automatic tools used to convert 30,000 lines of code in a few weeks Made some VBScript syntax manual code changes Public variables were converted to properties of objects StringBuilder object was used to rapidly assemble the web page
26	Required VBScript to ASP.NET Syntax Changes All continued code lines must end in <space>_ (an space must precede the underscore) All procedures must be called as if functions: xyx(a,b,c) (not xyz a b c). All variables must be declared before use Preferred: All variables, parameters, and functions should be typed (e.g., DIM I AS Integer). This causes the code to execute much faster. Instead of declaring public variables that are global to all the code, make variables public properties of objects that are instantiated and call them as such, e.g., nDefaultIncrement becomes v.nDefaultIncrement. Added after evaluations of fields oRS(“…<field name>…”) the explicit property specification .Value., e.g.: oRS(“ID”).Value (not oRS(“ID”)) Recast the code into vb code modules as described on next slides
27	Structure of the .NET class code modules: (1) Specific application Imports Microsoft.VisualBasic Imports System Namespace VI Public Class demo Inherits System.Web.UI.Page Sub Main(ByVal sender As System.Object, ByVal e As System.EventArgs) _ Handles MyBase.Load ' execute on page load (.NET event) Dim a As VI.ads a = new VI.ads ' instantiate application object a.cOrganization = "demo" a.cSchoolName = "Demo" a.cLogo = "<img SRC='images/vischoollogo.jpg' align=top>" a.cLoggedInLogo = _ "<img SRC='images/vischoollogo.jpg' height=75 align=top>" a.cConnectString = "DRIVER={SQL Server};SERVER="+ _ "(local);DATABASE=ads_demo;UID=ads;Password=ads1ads2;" a.cOrganizationName = "VI Demo School" a.cLoggedInOrganizationName = "VI School" a.cTranscriptHeader = "Demo School" a.cLetterHeader = "Demo School" a.WebResponse = Response ' pass web environment objects a.WebSession = Session a.WebServer = Server a.WebRequest = Request a.Main() ' call method to create web page End Sub End Class End Namespace
28	Code modules: (2) Generic application Imports Microsoft.VisualBasic Imports System Namespace VI Public Class ads Inherits VI.App_Template Public cOrganization As String ... ' public properties Private ... ' private properties Sub Main() ' main method builds web page Dim cCurrentEndDate As String ' overload App_Template methods as needed Overloads Sub GetViewData(ByVal cViewSelected As String) v.cViewName = cViewSelected … If v.ViewParameters("View.Student", "Student_", ... ElseIf v.ViewParameters("View.Student.Schedule", ... End Sub ... End Class End Namespace
29	Code modules: (3) Application template Public Class App_Template ' all framework control methods Inherits System.Web.UI.Page Public v As VisionFW Public WebResponse As System.Web.HttpResponse Public WebSession As System.Web.SessionState.HttpSessionState Public WebServer As System.Web.HttpServerUtility Public WebRequest As System.Web.HttpRequest ... Overridable Sub GetViewData(ByVal cViewSelected As String) ... Overridable Function GetUserData() As Boolean ... Overridable Sub InitializeNext(ByVal cViewName As String) ... Overridable Sub ValidateData(ByVal cViewName As String) ... Overridable Function DefaultValue(ByVal cViewName As String, ByVal cField As String) As String ... Overridable Function WhenRecordDeleted(ByVal cView As String, ByVal cIDList As String) As String ... Overridable Sub AfterRecordSaved(ByVal cViewName As String) ... Overridable Sub TopOfPage() ... Overridable Sub CreatePage(ByVal cView As String) ... Overridable Function EnableAdd(ByVal cView As String) As String ... Overridable Function Preprocess(ByVal cCommandString As String) As String ... Overridable Sub SetupRecordDisplay(ByVal cViewName As String) ... Overridable Sub SetupRecordDisplay2(ByVal cViewName As String) ... Overridable Function BeforeRecordSaved(ByVal cViewName As String) As String ... Overridable Function ValidateKey(ByVal cValue As String) As Boolean ... Overridable Function NewKey(ByVal cViewName As String) ... End Class End Namespace
30	Code modules: (4) Framework Imports Microsoft.VisualBasic Imports System Namespace VI Public Class VisionFW Inherits System.Web.UI.Page public ... ' public properties private ... ' private properties Sub Initialize() ' the methods ... End Class
31	Final steps for conversion to .NET Run FoxPro program vb2net which: Makes sure there is a space before each “_” continuation character Adds type declaration at end of each DIM statement Creates DIM statements for any variable the first time it is used Uses the first character of the variable name to determine the type: c=String, b=Boolean, n=Integer, d=Date Removes “SET ” at the beginning of an object value assignment Replaces various framework public variables XXX with v.XXX (v is the instance of the framework object that is created by all applications) Drop code into a Visual Studio project code-behind file and incrementally edit until Visual Studio shows no more errors (Visual Studio will also format with standard capitalization and indentation)
32	Final steps, continued Cut the code back out of the Visual Studio application and place into the specific application, general application, and framework .vb files Create a one line ASP.NET page to start the application: <%@ Page Language="vb" aspcompat=true Inherits="VI.Demo" %> (aspcompat allows use of recordsets in addition to datasets) Create .bat files to build the application DLLs: vbapp demo /r:./bin/ads.dll vbapp ads vbdll vfw where vbapp.bat contains vbc %1.vb /t:library /utf8output /r:system.dll /r:system.web.dll /r:./bin/vfw.dll /out:bin\%1.dll and vbdll.bat contains vbc %1.vb /t:library /utf8output /r:system.dll /r:system.web.dll /out:bin\%1.dll /debug:full Deploy .aspx page into web directory and .dll files into a bin subdirectory of that directory
33	Enable the application Make sure that the IIS properties of the application directory have an application created à And of course the server must have the .NET Framework loaded
34	Examples of Framework Applications An remote environmental monitoring system Gas station monitoring (old ASP system) Restaurant monitoring An academic data system