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JDBI からCSV Data のデータアクセスオブジェクトを作成

JDBI でCSV data 用のSQL オブジェクトAPIを作成する方法を概説します。

JDBI は、Fluent スタイルとSQL オブジェクトスタイルという2つの異なるスタイルAPI を公開する、Java 用のSQL コンビニエンスライブラリです。CData JDBC Driver for CSV は、Java アプリケーションとリアルタイムCSV data のデータ連携を実現します。これらの技術を組み合わせることによって、CSV data へのシンプルなコードアクセスが可能になります。ここでは、基本的なDAO(Data Access Object )とそれに付随するCSV data の読み書きのためのコードの作成について説明します。

CSV Customer Entity のDAO を作成

The interface below declares the desired behavior for the SQL object to create a single method for each SQL statement to be implemented.

public interface MyCustomerDAO { //request specific data from CSV (String type is used for simplicity) @SqlQuery("SELECT TotalDue FROM Customer WHERE FirstName = :firstName") String findTotalDueByFirstName(@Bind("firstName") String firstName); /* * close with no args is used to close the connection */ void close(); }

CSV への接続を開く

Collect the necessary connection properties and construct the appropriate JDBC URL for connecting to CSV.

The DataSource property must be set to a valid local folder name.

Also, specify the IncludeFiles property to work with text files having extensions that differ from .csv, .tab, or .txt. Specify multiple file extensions in a comma-separated list. You can also set Extended Properties compatible with the Microsoft Jet OLE DB 4.0 driver. Alternatively, you can provide the format of text files in a Schema.ini file.

Set UseRowNumbers to true if you are deleting or updating in CSV. This will create a new column with the name RowNumber which will be used as key for that table.

ビルトイン接続文字列デザイナー

For assistance in constructing the JDBC URL, use the connection string designer built into the CSV JDBC Driver.Either double-click the JAR file or execute the jar file from the command-line.

java -jar cdata.jdbc.csv.jar

Fill in the connection properties and copy the connection string to the clipboard.

A connection string for CSV will typically look like the following:

jdbc:csv:DataSource=MyCSVFilesFolder;

Use the configured JDBC URL to obtain an instance of the DAO interface.The particular method shown below will open a handle bound to the instance, so the instance needs to be closed explicitly to release the handle and the bound JDBC connection.

DBI dbi = new DBI("jdbc:csv:DataSource=MyCSVFilesFolder;"); MyCustomerDAO dao = dbi.open(MyCustomerDAO.class); //do stuff with the DAO dao.close();

CSV Data について

With the connection open to CSV, simply call the previously defined method to retrieve data from the Customer entity in CSV.

//disply the result of our 'find' method String totalDue = dao.findTotalDueByFirstName("Bob"); System.out.println(totalDue);

Since the JDBI library is able to work with JDBC connections, you can easily produce a SQL Object API for CSV by integrating with the CData JDBC Driver for CSV.Download a free trial and work with live CSV data in custom Java applications today.

 
 
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