Accessing/Manipulating XML Data with Oracle XML DB - Employee Management System

Table of Contents

• Objective
• Overview
• User Notes with Screen Shots
• Required Software
• Extracting the Sample
• Database Setup
• Preparing and Running the Sample
• Using the Sample
• Description of Sample Files

The purpose of this sample application is to demonstrate the following:

1) Retrieval of XML data from an Oracle9i Release 2 (9.2) database using XMLType views through Oracle Data Provider for .NET (ODP.NET).

2) Usage of OracleXmlType class to retrieve native XML data from an XMLType view.

3) Insert/Update/Delete operations on XML data from an XMLType view using instead-of triggers from ODP.NET.

With Oracle9i Database Release 2 (9.2) and higher, Oracle supports XML natively in the database as its own data type. Oracle XML DB makes XML data retrieval and manipulation easier to use and higher performing than other database solutions.

ODP.NET 9.2.0.4 and higher integrates with XML DB by storing XML data natively in the database server ( XmlType) and in .NET (OracleXMLType) as its own native XML data type.  A native XML data type makes manipulating XML easier because it is optimized for use specifically with XML as opposed to data types that handle generic text, such as strings.

XML application performance can be improved through the use of XMLType views.  XMLType views convert relational data into XML stored within the view.  This provides a performance savings as applications do not need to convert from relational data to XML during run-time. Another advantage of XMLType views is that you can exploit the Oracle XML DB feature without migrating your base legacy data (relational model). Each row in the XMLType view corresponds to an XMLType instance. Refer to figure 1, to get a clear understanding on how XMLType view works:

Figure 1: Understanding the workings of an XMLType view

In figure 1, 'Emp' is a relational table available in the 'Scott' schema. To optimize the  Emp table for use with XML, an XMLType view 'Emp_View' is created. On querying the 'Emp_View', the data is retrieved in the form of XML. For insert/update/delete operations, ODP.NET calls the instead-of triggers created on Emp_View to modify data in the XMLType view.

This ODP.NET sample, an Employee Management System, is a windows application using C#. It uses the 'Scott' schema available with the Oracle database. Some of the features provided by this sample include:

• Querying data from emp_view
• Inserting a new employee into emp_view
• Updating/Deleting employee details in emp_view

On establishing a successful connection to an Oracle database, employee data from the 'Emp_View' (XmlType view) is retrieved and displayed as XML and in a data grid. Users can update/delete this XML in the XMLType view and the relational table in the database with ODP.NET. The user can also insert a new employee record using an XML document.

When this sample is run, the user should first enter the appropriate connection details and click on the 'Connect' button to connect to an Oracle database. After the database connection is established successfully, the list of employees from the Emp_view (XMLType view) is displayed in tabular (DataGrid) and XML format, as shown in Figure 2.

Figure 2: Screenshot after connection is established

To insert a new record into the 'Emp_View' XMLType view using an XML document, click on the 'Create New Record' button. A sample XML record appears in the textbox that can be modified to have the required data within the appropriate tags, as shown in Figure 3 . Please refer to the hints displayed in the 'Hints to Execute the Sample' text on the application screen for the instructions to perform the current operation.

Figure 3: Displays sample XML record for insertion

To save the new record click on the 'Insert' button. The new data will be reflected in the datagrid and the XML document.

To update a record, the user can select a record from the datagrid. Its corresponding XML appears in the textbox. The user can modify the XML record displayed in the text area, as shown in Figure 4. Refer to the 'Hints to Execute the Sample' text for more details. The user can click on the 'Update' button to update the data in the database. The updated data will be reflected in the datagrid and the XML document.

Figure 4: Displays selected record for update

To delete a record, the user can select a record from the datagrid and click the 'Delete' button. The changed data will be reflected in the datagrid and the XML document.

• Visual C# .NET installed with Microsoft Visual Studio .NET 2002 or higher

• Connectivity to an Oracle9i Database Release 2 (9.2) or higher , running SQL*Net TCP/IP listener

• Oracle Data Provider for .NET (ODP.NET) 9.2.0.4 or higher

Unzip XmlViewSample.zip using Winzip or the command utility to a convenient directory referred to as <Extract_Dir>. Extraction of the zip file results in the creation of "XmlViewSample" directory.  Refer Description of Sample Files section for more details.     

1. This sample uses 'Scott' sample schema available with the Oracle databases. It uses 'Emp' and 'Dept' tables. In case you do not have the 'Scott' schema, you can alternatively connect to a different database user and create the required tables by running the demobld.sql script available at <Extract_Dir>\XmlViewSample\setup at SQL*plus prompt:

SQL> @<Extract_Dir>\XmlViewSample\setup\demobld.sql

<Extract_Dir> - is the directory where you have extracted the XmlViewSample.zip file.

2. To create the XMLType view and the instead-of triggers for data manipulation on the XMLType view, run the CreateView.sql script available under <Extract_dir>\XmlViewSample\setup at the SQL*prompt:

SQL> @<Extract_Dir>\XmlViewSample\setup\CreateView.sql

The following database objects will get created on successfully running of this script:

1. Ensure completion of the Database setup.

2. Open XmlViewSample.sln using Visual Studio .NET from the <Extract_Dir>\XmlViewSample\src folder. 

3. Ensure that the following .NET Component References have been added to XmlViewSample project: 
          System, 
          System.Data, 
          System.Drawing, 
          System.Windows.Forms, 
          System.XML,
          Oracle.DataAccess. 

To add the above .NET Components 
a)Go to Menu->View-> Solution Explorer. 
b)Right click on XmlViewSample project, choose 'Add Reference'. 
c)Choose the above .NET Components from the list displayed. 
d)Click 'Select', then OK. 
e) The chosen .NET component gets added to the project. 

5. Build and run the sample by pressing Ctrl+F5. Refer to Using the Sample section on how to use this sample.

1. When running this sample, enter the connection details. Provide the username and password for the schema that contains the Emp and Dept tables. Enter the host string as appropriate to your database setup.

2. After providing the connection details, click on the 'Connect' button. In case the connection could not be established successfully, the connection status is displayed as 'Not Connected' in red color. On successful connection, the connection status is displayed as 'Connected' in green color- the DataGrid and textArea are populated with data from the Emp_View and the UI controls are enabled.

3. To update a record, the user can navigate to the row in the datagrid, that he/she wishes to update. Its corresponding XML appears in the textbox. The user can modify the XML record. To change the value of deptno the user can check the value from the list of valid deptno. Do not modify the empno as it is a key column. Also, refer to the hints given on the screen. Click on the 'Update' button to update the data in the database. On successful update, a confirmation message is displayed. If any error occurs, the error message is displayed to the user.

4. To insert a new record, the user can click on the 'Create New Record' button. On clicking this button, the text area generates a new XML record that can be edited by the user. Do not modify 'empno' as it is a key column that is produced automatically by the application as a unique value. The user can view the list of valid 'deptno' from the list. Refer to the hints given on the page for more details. After editing the sample record, the user can click on the 'Insert' button to save the data in the database. On successful insertion of the record, a confirmation message is displayed. If any error occurs, the error message is displayed to the user.

5. To delete a record, the user can navigate to the row in the datagrid, which he/she wishes to delete. The corresponding XML of that row appears in the textbox. The user can click on the 'Delete' button. A confirmation dialog appears, with Yes/No option. On selecting 'Yes' the record(s) gets deleted and a confirmation message is displayed. On selecting 'No', no deletion happens.

6. If the user wants to change the database connection, then he/she can click on the 'Disconnect' button and connect to another database by providing the connection details.

7. To exit the application, click on the 'Exit' button.

Description of Sample Files

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Following is the directory structure of the XmlViewSample.zip :

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