This article mainly concentrates on using XML as data storage (instead of using RDBMS). We will cover how to develop a Web application using ASP.NET by developing our own simple business logic, which gets directly mapped to XML data and XML schema files.
Designing a simple XML Wrapper:
The main advantage to designing an XML wrapper is to maintain common operations such as add, update and delete at a single point. We need to design this wrapper in such a way that it works with almost any type of XML file. If we think logically, the wrapper needs to know the following issues before it implements any operations:
- What XML document should it write to?
- What sort of XML Schema should it write on?
- Which tag behaves as the table name?
- What are the other tags, which behave as column names?
- What are the column values that need to be written?
Considering the above issues, it is obvious that we need to design some properties to hold that information. The following members would make a simple XML wrapper class to solve our requirements.
FilenameXMLSchema (m_FilenameXMLSchema)
FilenameXMLDocument (m_FilenameXMLDocument)
TableName (m_TableName)
ColumnNames (m_ColumnNames)
ColumnValues (m_ColumnValues)
Add
Update
Delete
"FilenameXMLSchema," "FilenameXMLDocument" and "TableName" are simple properties of the string type. "ColumnNames" and "ColumnValues" are the properties of string array (as they hold more than one value). The words given opposite them (in parentheses) are the private memory variables inside the class, which hold the property values.
"Add," "Update" and "Delete" are methods to provide appropriate operations. "Update" and "Delete" will have a parameter "Criteria" to provide a condition in the form of a string.
The entire class is available in the "supported download files" section with the filename CXMLWrapper.vb. The next section explains bit about the main methods in that class.
{mospagebreak title=Implementing DML operations within the XML wrapper}
Let's take a look at the code for the "add" method.
PublicSubadd()
DimdsAsNewDataSet
ds.ReadXmlSchema(m_FilenameXMLSchema)
ds.ReadXml(m_FilenameXMLDocument)
DimdtAsDataTable
dt = ds.Tables(m_TableName)
DimdrAsDataRow = dt.NewRow
DimcAsInteger
Forc = 0Tom_ColumnNames.Length - 1
DimFieldNameAsString= m_ColumnNames(c)
DimFieldValueAsString= m_ColumnValues(c)
dr(FieldName) = FieldValue
Next
dt.Rows.Add(dr)
ds.WriteXml(m_FilenameXMLDocument)
ds.Dispose()
EndSub
I hope the steps are very simple. Here ReadXMLSchema and ReadXML methods are used to read XML Schema Structure and XML document data, respectively. The datatable (dt) points to a particular table in the dataset (ds) identified by “m_TableName.” We add a new row (dr) to the datatable (dt), and we assign all the column values available in “m_ColumnValues” using a loop to that new row (dr). Finally, we add that row (dr) to the datatable (dt), and the dataset (ds) is written into the XML document (filename in “m_FilenameXMLDocument”) using “writeXML” method.
Now let's examine the code for the "update" method.
PublicSubupdate(ByValcriteriaAsString)
DimdsAsNewDataSet
ds.ReadXmlSchema(m_FilenameXMLSchema)
ds.ReadXml(m_FilenameXMLDocument)
DimdtAsDataTable
dt = ds.Tables(m_TableName)
DimdvAsDataView = dt.DefaultView
dv.RowFilter = criteria
DimdrvAsDataRowView
ForEachdrvIndv'go through all filtered rows
DimcAsInteger
'go through the columns to be updated for the particular row
Forc = 0Tom_ColumnNames.Length - 1
DimFieldNameAsString= m_ColumnNames(c)
DimFieldValueAsString= m_ColumnValues(c)
drv(FieldName) = FieldValue
Next
Next
'write to XML file if there exists any rows in filter
Ifdv.Count > 0Thends.WriteXml(m_FilenameXMLDocument)
ds.Dispose()
EndSub
Even here, the steps are somewhat similar. But here we are passing "criteria" as a parameter to this method. The primary requirement to update data is that rows need be filtered depending on criteria. So, the "defaultview" of "datatable" will be used to filter the rows, and its reference gets stored in the "dataview" object (dv). We assign "criteria" to the "RowFilter" property of "dv" (which filters the rows automatically). We then declare object "drv" of type "DataRowView," which will loop through all filtered rows. The columns get updated for every filtered row by using a nested loop. The final step is to write to the XML file if and only if there exists any rows in the filter.
The procedure for "delete" is very similar to the "update" method, except that we put "drv.Delete()" within the nested loop.
{mospagebreak title=Adding a module (gModule) to store constants}
Everyone needs (in general) some project-wide constants (or values) to be stored and accessed throughout the project. It is recommended that theThe constants (or some frequently used utility methods) be embedded in a separate module.
In our case, the file names of XML Schema and XML Data need to be stored in some constant values. Even physical paths must be maintained. So, I decided to use a module (gModule) to maintain all these aspects. The following code helps for all of these matters.
ModulegModule
PublicHostRootPathAsString'gets initilized at InitPaths
PrivateXMLDATA_PATHAsString= "data/"
PublicEMPLOYEE_FILENAMEAsString= "XMLStoreData.xml"
PublicEMPLOYEESCHEMA_FILENAMEAsString= "XMLStoreSchema.xsd"
PublicSubInitPaths(ByReffrAsObject)
'this method should be executed in session_start event of global.asax
HostRootPath = fr.Request.ServerVariables("APPL_PHYSICAL_PATH")
EndSub
PublicFunctiongetXMLDATAPATH()AsString
ReturnHostRootPath & XMLDATA_PATH
EndFunction
EndModule
The matter is very straightforward. We need the physical path of XML files (even in a hosted environment) to store our data. And these small routines will simplify our lives.
{mospagebreak title=Designing a CEmployee class to work with the wrapper}
First of all, is this class necessary? The answer is yes, if we want to use the power of OOPS in our project. I considered designing using OOPS; this is the class for that.
To pass the entire data of an Employee as a simple object in between different objects, I implemented a structure to hold all of the Employee information as follows (inside this class):
PublicStructuretEmployee
PublicEmpNOAsString
PublicENameAsString
PublicDeptNoAsInteger
PublicSalAsInteger
EndStructure
Another "private" method for returning a concrete CXMLWrapper object, which will be used to directly access the physical XML family of files, is shown below.
PrivateFunctiongetXMLDBWrapper()AsCXMLWrapper
DimObjXMLAsNewCXMLWrapper
WithObjXML
.FilenameXMLSchema = gModule.getXMLDATAPATH & gModule.EMPLOYEESCHEMA_FILENAME
.FilenameXMLDocument = gModule.getXMLDATAPATH & gModule.EMPLOYEE_FILENAME
.TableName = "Employee"
EndWith
ReturnObjXML
EndFunction
Two more "get" methods for retrieving the information related to employee(s) are shown here:
PublicFunctiongetEmployeeList()AsDataTable
DimdsAsNewXMLStoreSchema
ds.ReadXml(gModule.getXMLDATAPATH() & EMPLOYEE_FILENAME)
DimdtAsDataTable = ds.Tables("Employee")
Returndt
EndFunction
PublicFunctiongetEmployee(ByValEmpNoAsString)AsDataRow
DimdtAsDataTable = getEmployeeList()
Dimdr()AsDataRow = dt.Select("EmpNo='" & EmpNo & "'")
Ifdr.Length = 0ThenReturnNothingElseReturndr(0)
EndFunction
Here is one more method for adding the employee details:
PublicFunctionaddEmployee(ByValEmployeeAstEmployee)
DimObjXMLAsCXMLWrapper = getXMLDBWrapper()
DimColumnValues()AsString
WithEmployee
ColumnValues =NewString() {.EmpNO, .EName, .DeptNo, .Sal}
EndWith
DimColumnNames()AsString
ColumnNames =NewString() {"EmpNO", "EName", "DeptNo", "Sal"}
WithObjXML
.ColumnValues = ColumnValues
.ColumnNames = ColumnNames
.add()
EndWith
EndFunction
"UpdateEmployee" and "DeleteEmployee" methods will be almost similar to that of "addEmployee," except that "criteria" is necessary.
{mospagebreak title=Preparing a "strict" structure to work with XML wrapper using VS.NET}
Now we will start by creating a "proper" sequence to work with ASP.NET and XML using Visual Studio.NET 2003 Enterprise Architect as our main Objective. Working with Visual C#.NET is also quite similar to the steps we discuss here (except for the syntactical differences in programming statements).
Using Visual Studio.NET, proceed with the following steps:
Go to File >> New Project.
Select Project type "Visual Basic" (select Visual C# if you work with C#) from the left panel. Next, select "ASP.NET Web Application" from the right panel and name the Web application "Sample."
Right click on project name "Sample" (using "Solution Explorer") and add a new folder named Data.
Right click again on project name "Sample" and select Add->Add new item. Select "Dataset" and name it XMLStoreSchema.xsd. You will be presented with a layout where you can create your own XML schema.
Select the
Element tool from
toolbox and drag it on to the layout. Make the modifications to the newly created object as shown in the following figure (Fig 1).
Make sure that "generate dataset" is checked "on" in the "schema" menu (as shown in Fig 2) and save the solution. This "generate dataset" option internally creates a new dataset class inherited from pre-defined dataset class, which gets mapped to the current XML Schema design.
Right click again on project name "Sample" and select Add->Add new item. Select "XML file" and name it XMLStoreData.xml to the existing project.
Click on the Data tab; provide data accordingly (shown in Figure 3) and save the solution again.
Right click again on project name "Sample" and select Add->Add new item. Select "Class" and name it CXMLWrapper.vb. This wrapper contains the Add, Update and Delete methods to operate with any XML file. Copy and paste code (from CXMLWrapper.vb) from the "supported download files" section of this article.
Right click again on project name "Sample" and select Add->Add new item. Select "Class" and name it CEmployee.vb. This class contains AddEmployee, UpdateEmployee, DeleteEmployee and methods to operate with any CXMLWrapper object. Copy and paste code (from CEmployee.vb) from "supported download files" section of the article.
Right click again on project name "Sample" and select Add->Add new item. Select "Module" and name it gModule.vb. This contains "public" constants used throughout the project. Copy and paste code (from gModule.vb) from the "supported download files" section of this article.
{mospagebreak title=Designing the Web page}
Up to this point we completed the main business logic we need to work with XML. Now we must design a Web page which accesses the XML data file though our business logic.
Let us start by designing a Web form which will be similar to Figure 4. As you can see from the figure, I heavily use the "DIVs" running at server side. Of course you can also replace them with Panel controls. The Web form can be downloaded from the "supported files" section.
To add a new employee to the XML store, the following code would do the task very easily:
DimtAsCEmployee.tEmployee
Witht
.EmpNO =Me.txtEmpNo.Text
.EName =Me.txtEName.Text
.DeptNo =Me.txtDeptNo.Text
.Sal =Me.txtSal.Text
EndWith
DimobjAsNewCEmployee
obj.addEmployee(t)
Similarly, for the update, the code would be as follows:
DimtAsCEmployee.tEmployee
Witht
.EmpNO =Me.txtEmpNo.Text
.EName =Me.txtEName.Text
.DeptNo =Me.txtDeptNo.Text
.Sal =Me.txtSal.Text
EndWith
DimobjAsNewCEmployee
obj.updateEmployee (t)
For the delete operation, the code is further simple than the above:
DimobjAsNewCEmployee
obj.deleteEmployee (Empno)
The rest of the code is just the UI logic, which is quite common among almost any type of ASP.NET application.
NOTE: Make sure you provide the write access privileges to the folder “data” within your project. Otherwise you may experience the “Access Denied” error. You should also remember that XML is case sensitive. So, I ask that you follow the same case or convention that you have designed in your XML Schema.
Remarks: The entire source code of this article exists in the form of a downloadable zip (including the figures). I developed this small project using just Microsoft Visual Studio.NET 2003 Enterprise Architect.
I leave it to the programmers for further enhancements. Any doubts, comments, suggestions, bugs, errors or feedback are welcome at jag_chat@yahoo.com.
| DISCLAIMER: The content provided in this article is not warranted or guaranteed by Developer Shed, Inc. The content provided is intended for entertainment and/or educational purposes in order to introduce to the reader key ideas, concepts, and/or product reviews. As such it is incumbent upon the reader to employ real-world tactics for security and implementation of best practices. We are not liable for any negative consequences that may result from implementing any information covered in our articles or tutorials. If this is a hardware review, it is not recommended to open and/or modify your hardware. |
More ASP.NET Articles
More By Jagadish Chaterjee
 developerWorks - FREE Tools!
|
This whitepaper presents the benefits of successfully introducing static analysis into your organization using IBM Rational Software Analyzer. Additionally, it identifies some common pitfalls that can hinder the effective use of static analysis tooling as well as presents 10 simple strategies designed to help you quickly realize the value of static analysis using Rational Software Analyzer.
FREE! Go There Now!
|
|
|
|
Join us for this on demand webcast to learn about developing complex systems more quickly and efficiently. We'll cover market drivers for developing, governing and reusing systems software assets and how you can develop system software assets with Rational Asset Manager.
FREE! Go There Now!
|
|
|
|
Secure your Web applications with IBM Rational AppScan Standard Edition V7.7, previously known as Watchfire AppScan. This Web application security testing tool automates vulnerability assessments and scans and tests for common Web application vulnerabilities. Visit IBM developerWorks to download a free trial of IBM Rational AppScan Standard Edition V7.7.
FREE! Go There Now!
|
|
|
|
Asset Reuse is a key strategy for companies looking to create innovative solutions to solve complex software development problems. Searching for, identifying, updating, using and deploying software assets can be a difficult challenge. Listen to this webcast, to learn about strategies and tools that you can leverage for a successful project, including Rational Asset Manager, Rational Software Architect and WebSphere Service Registry and Repository.
FREE! Go There Now!
|
|
|
|
Join this Rational Talks to You teleconference on December 6 at 1:00 pm ET to participate in an agile application development discussion and get your questions answered on using IBM Rational Method Composer in a distributed environment.Get your questions answered!
FREE! Go There Now!
|
|
|
|
Try the latest version of IBM Rational Manual Tester V7.0.1 by downloading a free trial from IBM developerWorks. This manual test authoring and execution tool promotes test step reuse to reduce the impact of software change on testers and business analysts and addresses the needs of teams performing at least a portion of their testing manually.
FREE! Go There Now!
|
|
|
|
Visit IBM developerWorks to try the IBM SOA Sandbox for people. The SOA Sandbox for people provides a trial environment with the necessary tooling and components required to enable consistent human and process interaction and collaboration, showing how you can improve user experience and business productivity.
FREE! Go There Now!
|
|
|
|
Join the IBM Watchfire team for an informative discussion on techniques and best practices to proactively manage Web application security and how to effectively build application security testing into the software development lifecycle (SDLC). In this Software Delivery Platform webcast you will learn: How to better understand potential web application security vulnerabilities, best practices and how to effectively integrate application security testing into the software development lifecycle, the importance of detecting and removing software vulnerabilities during application development.
FREE! Go There Now!
|
|
|
|
The discipline of assembling and delivering software is maturing beyond standard developer-centric compile/test software builds. The end-to-end software development lifecycle is emerging as the new focus moves “Beyond the Build.” Join this on demand webcast to learn about methods for streamlining software delivery and key capabilities of the IBM Rational Build Forge framework for automating build and release management in environments of any size.
FREE! Go There Now!
|
|
|
|
Join this webcast to learn how IBM Rational's Functional Testing solution enables you to implement automation your way, at your pace, with your existing staff. In this webcast, you’ll learn how you can eliminate redundancy of manual test scripts, reduce errors, and increase test coverage through test automation. After this presentation you will understand how IBM Rational Functional Testing solution can streamline your manual testing and make test automation easily attainable.
FREE! Go There Now!
|
|
|
|
All FREE IBM® developerWorks Tools!
|
/ 37 
