Blog: Posts from November, 2012

Blog

Posts from November, 2012

Saturday, November 10, 2012Print Subscribe

Data integrity can be ensured on different tiers of a web application. Code On Time web apps take advantage of the business rules engine that allows creating JavaScript Business Rules (Client Tier), Code Business Rules (Application Tier), and SQL Business Rules (Data Tier).

About Business Rules

Business rules are abstracted from the presentation of data. Developers manipulate field values directly as if the field values are local variables. The client library and application framework pass collections of values to the business rules making unnecessary a complex task of inspecting user interface elements. A business rule can access “old” value, “new” value, and “current” value of any field. It is also known if a field is “read-only” or “modified”. Business rules are executed in response to actions that have “before”, “execute”, and “after” phase. Changes to the values of the fields may affect the data that ends up in the database. Calculated field values are presented to the user on the client device.

This approach to business rule implementation allows continues improvement to the user interface client library. It guarantees that business rules will remain unchanged even for the future supported client devices.

Selecting an Application Tier

The major challenge is to select an application tier for a business rule implementation.

The client tier is most commonly used to correct user spelling or for basic data integrity enforcement. For example, formatting of a phone number most definitely lends itself to a client side business rule. Client business rules allow avoiding a server-side round trip.

If a business rule requires a database lookup then the data tier works best in most situation. A script written in SQL dialect of the application database engine can select data from a table, call a stored procedure, and perform complex data manipulations.

Some business rules may require access to operating system resources, file system, or web services. Application tier business rules are written in C# or Visual Basic. The full power of Microsoft.NET is at disposal of a developer. “Code” business rules supersede SQL business rules at a cost of using special classes when a database access is required.

Hybrid Business Rules

If a server-side data is required for a client-side JavaScript business rule, then the business rule is a hybrid. This type of rules is difficult to implement.

The server-code implemented on the application or data tier cannot have a “conversation” with a user. Conditional execution with a user confirmation can be performed on the client only. The client business rule must have a way to request information from the server before confronting a user with requests for additional information.

RESTFul Application Server

Code On Time web applications may include application server components that enable interaction with clients supporting Representational State Transfer protocol know as REST. When enable, the application server components can respond to HTTP requests for information or commands to execute an action.

The responses to such HTTP request are encoded in XML or JSON. The latter is a great match to JavaScript Business Rules since a response is essentially a JavaScript object.

Example of a RESTful Business Rule

Consider entering of new products in the Northwind sample.

There is product with the name “Chai” with a different price. The existing product is supplied by another vendor.

There may be a business requirement to warn a user about a potential duplicate.

A business rule written in JavaScript may contact the app to verify if a matching product exists. The URL of a web request may look as follow:

http://demo.codeontime.com/northwind/appservices/Products?ProductName=Chai

http://demo.codeontime.com/northwind/appservices/Products?ProductName_Filter_Equals=Chai

Here is the response encoded in XML.

<?xml version="1.0" encoding="utf-8"?>
<Products totalRowCount="1" pageSize="100" pageIndex="0" rowCount="1">
  <items>
    <item ProductName="Chai" SupplierID="1" CategoryID="1" QuantityPerUnit="10 boxes x 20 bags" 
          UnitPrice="$18.00" UnitsInStock="39" UnitsOnOrder="0" ReorderLevel="10" 
          Discontinued="False" ProductID="1" 
          SupplierCompanyName="Exotic Liquids" CategoryCategoryName="Beverages" />
  </items>
</Products>

The business rule can display a warning to a user about a potential duplicate. If a user does not confirm creation of a duplicate product, then a new record is not created.

First, may sure to enable REST requests to the data controller products. Select the data controller in Project Explorer and change it as follows.

Property	Value
Representational State Transfer (REST) Configuration	Uri: . Users: *

This will ensure that only authenticated users can send requests to application server components.

Enter a new JavaScript business rule in Products data controller configured as follows:

Property	Value
Type	JavaScript
Command Name	Insert
Phase	Before

Enter this code in the Script property of the rule and click OK button.

var duplicateProduct = null;
$.ajax({
    url: '../appservices/Products?ProductName=' + [ProductName],
    cache: false,
    async: false,
    dataType: 'json',
    success: function (result) {
        if (result.Products.length > 0)
            duplicateProduct = result.Products[0];
    }
});
if (duplicateProduct)
    if (confirm('This product is a duplicate. Continue?') == false) {
        this.preventDefault();
        this.result.focus('ProductName',
            'Product with this name and price of {0} is supplied by "{1}".',
            duplicateProduct.UnitPrice, duplicateProduct.SupplierCompanyName);
    }

This is how the rule will be displayed in Project Explorer.

Click Browse and navigate to Products page. Enter a new product with the name “Chai” and click OK to save the new record.

A standard browser confirmation will be displayed.

Click Cancel button to prevent creation of the product. The focus will be on Product Name field. The information about the duplicate product will be displayed next to the field.

The script makes a web request to the application server to locate a potential duplicate product. The request is executed synchronously making both user and web browser wait for its completion.

The scripts analyzes the response and displays a confirmation if there is a duplicate product. The supplier name and unit price of the existing product are displayed next to the product name field. A call to the method preventDefault will not allow the Insert action to proceed.

The screenshot displays a JSON response to a request for a product by name as presented in Visual Studio 2012.

Labels: Business Rules/Logic, Cloud, EASE, JavaScript, REST, Web Application Generator

Friday, November 9, 2012Print Subscribe

Advanced Membership Provider for MySQL

Requirements

An advanced membership and role provider requires three tables.

One table keeps track of user information. This information includes the UserName, Email, and a Comment. Additional columns allow for implementation of a password question and answer in order to recover a forgotten password. When users are created, they can not be approved by default. Additional information is captured about the most recent login, activity, and change of password. When a user inputs an incorrect password past the limit, the user will become locked out. The number of failed attempts and most recent failed attempt will be stored.

Two tables are required to keep track of roles and associations of users with roles.

These are the advanced membership and role provider tables with “identity” primary keys.

SQL:

create table Users (
    UserID int not null AUTO_INCREMENT primary key,
    UserName varchar(128) not null,
    Password varchar(128) not null,
    Email varchar(256),
    `Comment` text,
    PasswordQuestion varchar(256),
    PasswordAnswer varchar(128),
    IsApproved bit not null,
    LastActivityDate datetime not null,
    LastLoginDate datetime not null,
    LastPasswordChangedDate datetime not null,
    CreationDate datetime not null,
    IsLockedOut bit not null,
    LastLockedOutDate datetime not null,
    FailedPasswordAttemptCount int not null,
    FailedPasswordAttemptWindowStart datetime not null,
    FailedPasswordAnswerAttemptCount int not null,
    FailedPasswordAnswerAttemptWindowStart datetime not null
    );
    
create table Roles (
    RoleID int not null AUTO_INCREMENT primary key,
    RoleName varchar(128) not null
    );

create table UserRoles (
    UserID int not null,
    RoleID int not null,
    primary key (UserID, RoleID),
    foreign key (UserID) references Users(UserID),
    foreign key (RoleID) references Roles(RoleID)
    );

These are the advanced membership and role provider tables with “unique identifier” primary keys.

SQL:

create table Users (
    UserID varchar(36) not null primary key default '',
    UserName varchar(128) not null,
    Password varchar(128) not null,
    Email varchar(256),
    `Comment` text,
    PasswordQuestion varchar(256),
    PasswordAnswer varchar(128),
    IsApproved bit not null,
    LastActivityDate datetime not null,
    LastLoginDate datetime not null,
    LastPasswordChangedDate datetime not null,
    CreationDate datetime not null,
    IsLockedOut bit not null,
    LastLockedOutDate datetime not null,
    FailedPasswordAttemptCount int not null,
    FailedPasswordAttemptWindowStart datetime not null,
    FailedPasswordAnswerAttemptCount int not null,
    FailedPasswordAnswerAttemptWindowStart datetime not null
    );
    
create table Roles (
    RoleID varchar(36) not null primary key default '',
    RoleName varchar(128) not null
    );
    
create table UserRoles (
    UserID varchar(36) not null,
    RoleID varchar(36) not null,
    primary key (UserID, RoleID),
    foreign key (UserID) references Users(UserID),
    foreign key (RoleID) references Roles(RoleID)
    );
    
delimiter $$ 
create trigger userinsert
before insert on Users
for each row
begin
    set New.UserID = UUID();
end $$

create trigger roleinsert
before insert on Roles
for each row
begin
    set New.RoleID = UUID();
end $$

Configuration

Use one of the scripts above to create the membership and role provider tables in your database.

Start Code On Time web application generator, select the project name on the start page, and choose Settings. Select Authentication and Membership.

Select “Enable custom membership and role providers” option and enter the following configuration settings.

table Users = Users
column [int|uiid] UserID = UserID
column [text] UserName = UserName
column [text] Password = Password
column [text] Email = Email
column [text] Comment = Comment
column [text] PasswordQuestion = PasswordQuestion
column [text] PasswordAnswer = PasswordAnswer
column [bool] IsApproved = IsApproved
column [date] LastActivityDate = LastActivityDate
column [date] LastLoginDate = LastLoginDate
column [date] LastPasswordChangedDate = LastPasswordChangedDate
column [date] CreationDate = CreationDate
column [bool] IsLockedOut = IsLockedOut
column [date] LastLockedOutDate = LastLockedOutDate
column [int] FailedPasswordAttemptCount = FailedPasswordAttemptCount
column [date] FailedPasswordAttemptWindowStart = FailedPasswordAttemptWindowStart
column [int] FailedPasswordAnswerAttemptCount = FailedPasswordAnswerAttemptCount
column [date] FailedPasswordAnswerAttemptWindowStart = FailedPasswordAnswerAttemptWindowStart

table Roles = Roles
column [int|uiid] RoleID = RoleID
column [text] RoleName = RoleName

table UserRoles = UserRoles
column [int|uiid] UserID = UserID
column [int|uiid] RoleID = RoleID

The configuration will guide the code generator in mapping the logical tables Users, Roles, and UserRoles to the physical tables in the database.

Generate the project to create the custom membership and role provider.

Labels: Application Factory, ASP.NET Membership, Designer, MySQL, Security, Tutorials, Web Application Generator

Friday, November 9, 2012Print Subscribe

Basic Membership Provider for MySQL

Requirements

A basic membership provider requires a dedicated table to keep track of user names, passwords, and emails.

A role provider will require two tables to keep track of roles and associations of users with roles.

These are the basic membership and role provider tables with “identity” primary keys.

SQL:

create table Users (
    UserID int not null AUTO_INCREMENT primary key,
    UserName varchar(128) not null,
    Password varchar(128) not null,
    Email varchar(256)
    );
    
create table Roles (
    RoleID int not null AUTO_INCREMENT primary key,
    RoleName varchar(128) not null
    );
    
create table UserRoles (
    UserID int not null,
    RoleID int not null,
    primary key (UserID, RoleID),
    foreign key (UserID) references Users(UserID),
    foreign key (RoleID) references Roles(RoleID)
    );

These are the basic membership and role provider tables with “unique identifier” primary keys.

SQL:

create table Users (
    UserID varchar(36) not null primary key default '',
    UserName varchar(128) not null,
    Password varchar(128) not null,
    Email varchar(256)
    );
    
create table Roles (
    RoleID varchar(36) not null primary key default '',
    RoleName varchar(128) not null
    );

create table UserRoles (
    UserID varchar(36) not null,
    RoleID varchar(36) not null,
    primary key (UserID, RoleID),
    foreign key (UserID) references Users(UserID),
    foreign key (RoleID) references Roles(RoleID)
    );
    
delimiter $$ 
create trigger userinsert
before insert on Users
for each row
begin
    set New.UserID = UUID();
end $$

create trigger roleinsert
before insert on Roles
for each row
begin
    set New.RoleID = UUID();
end $$

Configuration

Use one of the scripts above to create the tables in your database.

Start Code On Time web application generator, select the project name on the start page, and choose Settings. Select Authentication and Membership.

Select “Enable custom membership and role providers” option and enter the following configuration settings.

table Users = Users
column [int|uiid] UserID = UserID
column [text] UserName = UserName
column [text] Password = Password
column [text] Email = Email

table Roles = Roles
column [int|uiid] RoleID = RoleID
column [text] RoleName = RoleName

table UserRoles = UserRoles
column [int|uiid] UserID = UserID
column [int|uiid] RoleID = RoleID

The configuration will guide the code generator in mapping the logical tables Users, Roles, and UserRoles to the physical tables in the database.

Generate the project to create the custom membership and role provider.

Labels: Application Factory, MySQL, Security, Tutorials, Web Application Generator