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Build a Simple VCL Application for HDFS データ
How to build a simple VCL Application to view HDFS データ in RAD Studio using the CData ODBC Driver for HDFS.
最終更新日：2023-06-12Embarcadero RAD Studio provides a development environment for Delphi and C++Builder applications. With the CData ODBC Driver for HDFS, you gain access to live HDFS データ within RAD Studio, abstracting the data into tables, views, and stored procedures that can be used to retrieve HDFS データ. This article will walk through connecting to HDFS and creating a simple VCL application with the Form Designer.
Create a Connection to HDFS データ
If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.
HDFS 接続プロパティの取得・設定方法
HDFS への認証には、次の接続プロパティを設定します。
- Host：HDFS インスタンスのホストに設定してください。
- Port: HDFS インスタンスのポートに設定してください。デフォルトのポートは"50070" です。
You can then follow the steps below to use the Data Explorer to create a FireDAC connection to HDFS データ.
- In a new VCL Forms application, expand the FireDAC node in the Data Explorer.
- Right-click the ODBC Data Source node in the Data Explorer.
- Click Add New Connection.
- Enter a name for the connection.
- In the FireDAC Connection Editor that appears, set the DataSource property to the name of the ODBC DSN for HDFS.
Create VCL Applications with Connectivity to HDFS データ
Follow the procedure below to start executing queries to HDFS データ from a simple VCL application that displays the results of a query in a grid.
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Drop a TFDConnection component onto the form and set the following properties:
- ConnectionDefName: Select the FireDAC connection to HDFS データ.
- Connected: Select True from the menu and, in the dialog that appears, enter your credentials.
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Drop a TFDQuery component onto the form and set the properties below:
- Connection: Set this property to the TFDConnection component, if this component is not already specified.
SQL: Click the button in the SQL property and enter a query. For example:
SELECT FileId, ChildrenNum FROM Files WHERE FileId = '119116'- Active: Set this property to true.
Drop a TDataSource component onto the form and set the following property:
- DataSet: In the menu for this property, select the name of the TFDQuery component.
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Drop a TDBGrid control onto the form and set the following property:
- DataSource: Select the name of the TDataSource.
- Drop a TFDGUIxWaitCursor onto the form — this is required to avoid a run-time error.
You now have an executable application that displays the results of the SQL Query set in the TFDQuery object.
Related Articles
Below you can find other articles for using the CData ODBC Driver with RAD Studio, Delphi, and C++ Builder.
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