Introduction
One of the biggest issues a developer faces when developing a large application, is maintaining design standards and methods. Design documents, coding standards, and code review were the only tools a developer had to work with in the golden days of coding. With the birth of code generators such as CodeSmith, development teams are now armed with a powerful tool to expedite the development process and maintain a standard throughout the application. When developing applications, templates can save you a lot of time by using common design patterns for generating different business objects. By definition, templates are repeatable patterns, which can be derived from any design methods. The benefit of using templates in code generation is the ability to enforce design methods and standards while saving development costs for any application. This article will present a basic design pattern and the templates to generate code for the design pattern.
Business Object Design Pattern
Business objects contain properties that reflect data; you will find objects named invoice, invoice detail, etc. Commonly, they include embedded relationships -- for example, an invoice object may have a property that retrieves the details for that invoice instance.
Based on this simple observation, we can develop a design standard for our business objects:
- Business Objects Contain Properties
- Business Objects Require Collections
- Business Objects Require Access Data
Business Object:
The Business Object Class Template (ClassGenerator.cst) is used to create a business object�s properties and methods. A standard set of methods for accessing the object's data will be generated for each object defined in an XML document. The following methods will be created for each business object defined:
Public Static Methods
CreateNewObject: Creates a new Object.
DeleteObject: Deletes an Object.
Public Instance Constructors
Object - Overloaded. Initializes a new instance of the Object class.
Public Instance Methods
Copy: Copies an Object.
Delete: Deletes an Object.
Fetch: Fetches an Object.
Save: Saves an Object.
Update: Updates an Object.
Business Object Collection:
The Business Object Collections Template (CollectionGenerator.cst) is used to create a collection class for each business object. The collection object uses the 'CollectionBase' as the base class. The following methods will be created for each business object defined:
Public Instance Constructors
ObjectCollection: Constructor initializes a new instance of the ObjectCollection class.
Public Instance Properties
Count: Gets the number of elements contained in the CollectionBase instance.
Item: Gets or sets the value associated with the specified key.
Public Instance Methods
Add: Adds an item to the Object Collection.
Contains: Determines whether the Object Collection contains a specific Object.
IndexOf: Determines the index of a specific item in the Object Collection.
Insert: Inserts an item to the Object Collection at the specified position.
Remove: Removes the first occurrence of Object in the Object Collection.
Protected Instance Methods
OnInsert: Validates before inserting a new Object into the Object Collection.
OnRemove: Validates before removing a new Object from the Object Collection.
OnSet: Validates before setting an Object in the Object Collection.
OnValidate: Performs additional custom processes when validating an Object.
Business Object Data:
The Business Object Data Class Template (DataClassGenerator.cst) is used to define the data access layer for each business object. The following methods will be created for each business object defined:
Public Instance Constructors
ObjectData: Constructor initializes a new instance of the ObjectData class.
Public Instance Methods
CreateNewObject: Creates a new Object in the database.
DeleteObject: Deletes an Object from the database.
FetchObject: Gets a single Object from the database.
UpdateObject: Updates an Object in the database.
Base Object Classes:
The Business Object Base Class Template (BaseObjectClass.cst) is used to create the base class for each business object. The following are the properties used for each business object:
Public Instance Properties
Id: ID of Business Object.
Name: Name of Business Logic Object.
Internal
GenerateObjectId: Generates an ID for the given object.
Base Object Data Class
The Business Object Base Data Class Template (BaseDataClass.cst) is used to create the base class for each business object. The following are the properties used for each business object:
Public Instance Constructors
BaseDataClass: Constructor initializes a new instance of the BaseDataClass class.
Public Instance Properties
ConnectionString: Gets Connection String configuration from a config file.
Public Instance Methods
AddParamToSQLCmd: Adds a parameter to a SqlCommand.
ExecuteCollectionReader: Returns an object collection from a SQL Data Reader.
ExecuteObjectReader: Returns an object from a SQL Data Reader.
ExecuteReaderCmd: Generates Object Collection from SQL Data Reader.
ExecuteScalarCmd: Executes a query.
SetCommandType: Sets the CommandText property to the name of the stored procedure.
Data Layer Generator:
The Data Layer Template (DataGenerator.cst) is used to create the required database objects needed to support the business objects.
Procedures
Object_Create: Creates a new Object in the database.
Object_Delete: Deletes an Object from the database.
Object_Fetch: Gets a single Object from the database.
Object_Update: Updates an Object in the database.
Using the Generator
Based on a definition provided by an XML Document, the generator will produce code for your business object, business object collection, business object data access, business object tables, and stored procedures.
Business Objects Attributes
|
attribute |
maps to |
remarks |
|
class
|
table |
name will represent the table name |
|
property
|
column |
name will represent the column name |
Class Attributes
|
attribute |
remarks |
|
name
|
represents the table name |
Property Attributes
|
attribute |
remarks |
|
name
|
represents the column name |
|
type
|
represents a system type or a business object collection |
|
maxSize
|
|
Supported Types
|
C# Type |
Maps to SQL type |
|
string
|
nvarchar
|
|
int
|
int
|
|
DateTime
|
smalldatetime
|
|
bool
|
bit
|
|
decimal
|
money
|
Defining the Business Objects:
Let's create a simple Invoice Business Object. The invoice object will contain a customer name, invoice date, invoice paid status, and line items. The following XML document defines the objects:
="1.0" ="utf-8"
<BusinessObjects xmlns="http://www.austinconnergroup.com">
<class name="Invoice">
<properties>
<property name="Id" type="String" maxSize="36" />
<property name="Customer" type="String" maxSize="96" />
<property name="InvoiceDate" type="DateTime" maxSize="" />
<property name="InvoicePaid" type="bool" maxSize="" />
<property name="InvoiceDetails" type="InvoiceDetailCollection" maxSize="" />
</properties>
</class>
<class name="InvoiceDetail">
<properties>
<property name="Id" type="String" maxSize="36" />
<property name="InvoiceId" type="String" maxSize="36" />
<property name="LineItem" type="Int" maxSize="" />
<property name="ItemDescription" type="String" maxSize="96" />
<property name="ItemCostPerUnit" type="Single" maxSize="" />
<property name="ItemQuanity" type="Int" maxSize="" />
<property name="ItemUnit" type="String" maxSize="8" />
</properties>
</class>
</BusinessObjects>
In our definition document, we define two objects, Invoice and InvoiceDetail. You will notice that the Invoice object contains a property InvoiceDetails which is of the type InvoiceDetailCollection. This defines a relationship between InvoiceDetail and Invoice, and will produce the required methods and SQL statements for this relationship.
Running the Generator
Once we have our model, we are ready to generate our code. BuildTemplate.cst is the main entry point for generating the code for all the business objects, and has the following properties:
XmlFile - XML Document that the classes will be generated from.
OutputDirectory - The base directory for code output.
GenerateBaseClasses - Set true to generate base classes.
RootNamespace - The root namespace generated classes will be a member of.
ObjectNamespace - The object namespace generated classes will be a member of.
BusinessLogicNamespace - The business object namespace generated classes will be a member of.
DataAccessNamespace - The data object namespace generated classes will be a member of.
DeveloperName - Developer's name.
CompanyName - Company name.
Points of Interest
The article here presents the prototype that I developed for proof of concept. After writing the generator and supporting templates, I was so amazed at the results, I immediately wrote the templates for our team and deployed them into our production environment. One of the biggest benefits was not the cost savings in time, but the fact that all the generated code was self documenting. This fact alone was worth the efforts in creating these templates. The biggest battle I faced everyday was the lack of documented code, now it's a snap.
History
- 11/23/2004 - Initial article.
