Class wwBusinessObject - West Wind Web Connection

Class wwBusinessObject

wwBusinessObject provides a base business object for CRUD (Created, Read, Update, Delete) services. This class is a single level business object class that implements both the business and data tier in a single object to provide ease of use and maximum performance. This class is a thin wrapper over the underlying data access layer using either direct FoxPro DAL commands or SQL Passthrough for SQL backends.

It provides the following features:

Easy CRUD - Automated Base Data Access

The base object provides core CRUD functionality through its base class methods. Native query based data access is also supported through native FoxPro or SQL syntax, using the class methods which can route to the appropriate server backend.

loCustBus = CREATEOBJECT("cCustomer")
loCustBus.New() 
? loCustBus.oData.LastName
loCustBus.oData.LastName = "Strahl Jr."
? loCustBus.Save()

*** save the new PK
pnPk = loCustBus.oData.Pk
? pnPk

* New instance to demonstrate
loCustBus = CREATEOBJECT("cCustomer")

? loCustBus.Load(pnPk)   && reload the record
? loCustBus.oData.LastName
loCustBus.oData.LastName = "Strahl"
loCustBus.Save()

loCustBus.Query("where pk = ?pnPk")  && load data
BROWSE

loCustBus.Delete(pnPk)

FoxPro and SQL Backend Data Access

Fox or SQL Server are natively supported. SQL Server is supported with SQL Passthrough commands.The object also supports remote data access over the Web against a SQL Server backend (with some limitations a Fox backend can be used as well). It accomplishes this through CRUD helper methods that can handle many load/save/list operations without SQL code, and string based SQL commands for SQL query execution that can run on multiple data platforms.

The commands in the previous section all would work against SQL Server for example.

Internal Data Record Representation in .oData

Single record CRUD operation operate with an internal .oData member that receives database record data during Load() or New() operations.

The .oData member hold record data (record level operations) as a class and is completely disconnected from the database while loaded in memory - free to make changes as needed. Save() can then be used to write the changes into the database.

Query Handling via String based SQL Commands

Queries are run a string based SQL commands that are executed and returned as cursors by default. Errors are captured and return an error code and you can easily query the result count. There also options to return query results directly as JSON, XML, HTML and a few other formats.

Queries typically are run as strings using the Execute() method, but if you implement custom business objects with your own business class methods you can also use raw FoxPro commands to return result data.

Support for Validation

wwBusinessObject also includes a Validate() method and an OnValidate() handler method that business objects can implement to consistently validate business rules for field data and business rule validations.

Web Focused but works for Desktop as well

This object framework is uniquely geared towards offline operation which is ideal for Web operations and passing data around the Web. In Web applications the object's .oData member is useful for holding Model data for databinding into HTML templates (ie. <%= loCustomer.oData.FirstName %> or binding to these values) and reading data back in bulk using Request.FormVarsToObject().

The disconnected data model also makes it uniquely qualified for object aggregation by combining multiple objects into an object hierarchy. For example, an oInvoice object can contain oInvoice.oCustomer and oInvoice.oLineItems which are accessible through the single oInvoice object reference. Because of the self-contained nature of objects, it's easy to persist data to and from XML and pass them around the Web as well as making it very easy to use the business objects in HTML templates where data is bound to the object properties (<%= oInvoice.oCustomer.oData.LastName %>). Web Connection's object centric approach also allows you to pull in data back into the object from forms using Request.FormVarsToObject() resulting in very little code written to transfer data to and from HTML pages.

Easy to get started with

Because the framework consists only of a minimal set of methods on this object it's easy to get started with it. Because of the single level implementation the framework is also very efficient. In addition a Wizard is provided to help you create business objects by mapping to tables.

Required Dependencies

wwUtils.prg
wwApi.prg
wwCollections.prg

Optional Dependencis

wwSQL.prg (only if you use nDataMode = 2)
wwHttpSql.prg (only if you use nDataMode = 4)
wwXmlState.prg (only if you use Get/SetProperty methods)

Custom
wwBusinessObject

Class Members

Member		Description
	AddValidationError	Adds a validation error to the oValidationErrors collection. Pass an error string and optional object name. o.AddValidationError(lcMessage,lcObjectName)
	Backup	Takes the full content of the table and backs it up into the specified directory. o.Backup(lcPath,llCreatePath)
	Close	Closes the currently open master table or releases the SQL connection. o.close()
	ConvertData	Converts data from a cursor or the current object into the requested result mode. o.ConvertData(lnResultMode, lcDocRoot, lcTable, lcRow)
	CreateChildObject	Creates a child object instance that inherits the properties from the current object appropriate from the current object instance. o.createchildobject(lcClass)
	CreateNewId	Creates a new Primary Key ID number for the table using an ID table. o.createnewid()
	CreateTable	Create the primary table for this object. This method should always be subclassed and implemented by the developer. o.createtable(lcFileName)
	Delete	Deletes the specified record from the underlying table. If no PK is passed the current PK of the loaded object is used. o.delete(lnPk)
	Execute	Executes a fully qualified raw SQL statement against the database depending on the `nDataMode`. Can be used for any backend data command using either VFP syntax or SQLExec() style SQL commands and is meant to return a result set. o.Execute(lcSQL, lcCursor)
	ExecuteNonQuery	Executes a fully qualified raw SQL statement through the class that doesn't return a cursor. Can be used for backend commands like `INSERT`, `Update` or stored procedure calls etc. o.ExecuteNonQuery(lcSQL)
	Find	Return `.T.` or `.F.` if a SQL search expression (a `WHERE` clause essentially) can be found. o.find(lcFilter, llNoDataMember)
	GetBlankRecord	Retrieves an empty record and creates an empty oData member. Note no defaults are set. o.getblankrecord()
	GetProperty	Retrieves a property out of the XML field. Properties can be written with SetProperty. o.getproperty(lcProperty)
	ImportData	Imports data using the same o.importdata(lnMode,lcData,lcAlias)
	Load	Loads the `.oData` member with a record accessed by PK. This method or a specialized version of it should be used to load with record level objects and return them to the caller. o.Load(lnpk)
	LoadBase	A low level version of the Load() method that can be customized with a custom filter expression and a custom field list to load individual records into the oData member. o.LoadBase(lcFilter,lcFieldList)
	New	Creates a new oData member. Creates a PK value and sets any defaults coded in the New method. o.new(llNoNewPk)
	Open	Opens the data source or remote connection. For ODBC commands the oSQL member holds the SQL connection. o.open(lcFile, lcAlias, llForceReconnect)
	Query	High level query method that queries the underlying data store using `SELECT` statements. You can use partial SQL syntax (without using `INTO`) to retrieve query results that can be run on different SQL back ends. o.Query(lcSelect, lcCursor, lnResultmode)
	Reindex	Used to PACK and Reindex the data files. o.Reindex(llSaveIndexString)
	Save	Saves the current data member in the `.oData` property to the underlying table. o.save()
	SetError	Sets the error flag and error message properties. o.SetError(lcErrorMsg, lnError)
	SetProperty	Sets a property value in the XML field. Note: for performance reasons no checks are performed if the XML field exists. o.SetProperty(lcProperty, lvValue)
	SetSqlObject	Assigns existing SQL object to the oSQL object or creates one if a connection string is passed. Handles updating data mode and other admin tasks. o.setsqlobject(loSQL)
	StatusMessage	Displays status information. Use this method to have the business object communicate with whatever output mechanism required. Default is a WAIT WINDOW... o.StatusMessage(lcMessage)
	UpdateStructure	Update the structure of the file based on the CreateTable method's structure. o.updatestructure()
	Validate	Virtual method that can be used to hook up validation logic for your business objects. Validation typically gets called before saving an entity. o.validate()
	calias	The Alias of the master file.
	cconnectstring	SQL ConnectString if DataMode=2
	cdatapath	Location of the data
	cerrormsg	Any error messages that occurred.
	cfilename	Filename of the master file of this business object.
	cidtable	Table used to generate new PK Ids.
	cpkfield	The field used as the primary key in the table. This field must be an integer or numeric field.
	cresultxml	Methods returning XML will return the XML in this property.
	cServerUrl	A URL on the server that's running the wwHTTPSQLServer component to process client requests.
	cSkipFieldsForUpdates	Property that holds fields that are skipped for Insert and Update statements built on the fly. Fields are specified as a comma delimited list.
	csql	SQL String for a query
	csqlcursor	Requests that return a Fox cursor will use this name for the cursor name.
	lCompareUpdates	Will send updates by only updating fields that have changed.
	lerror	Error flag for the previous operation. Note this property must be managed by the developer for custom methods.
	lThrowOnError	If .T. causes errors to be thrown rather than captured and return in the error info of the various invoke/get/set methods.
	lValidateOnSave	Determines whether Save() automatically calls Validate().
	ndatamode	Data access mode for the business object. 0 - Fox Data native, 2 - ODBC (SQL Server)
	nresultmode	Determines how data requests are returned for `Query` or `ConvertData()` calls. Results are always returned in the `vResult` property.
	nupdatemode	Determines whether the data member is in edit or new mode.
	oData	Data member that receives all of the field names as property values.
	oHTTPSQL	An instance member for an wwHTTPSQL class that handles data access over the Web when nDataMode is set to 4.
	oSql	An instance of a wwSQL object that handles data connection if nDatamode = 2. All SQL commands run through this object for remote data.
	oValidationErrors	A collection of Validation Errors that let you indicate errors that occured during calls to the Validate() method or otherwise.
	vResult	Variable result property. Used at this point only for ADO recordsets returned as a result from queries.

Requirements

Assembly: wwBusinessObject.prg