Create a Data Access Object for Google Data Catalog Data using JDBI

JDBI is a SQL convenience library for Java that exposes two different style APIs, a fluent style and a SQL object style. The CData JDBC Driver for Google Data Catalog integrates connectivity to live Google Data Catalog data in Java applications. By pairing these technologies, you gain simple, programmatic access to Google Data Catalog data. This article explains how to build a basic Data Access Object (DAO) and the accompanying code to read Google Data Catalog data.

Create a DAO for the Google Data Catalog Schemas Entity

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 MySchemasDAO {
 //request specific data from Google Data Catalog (String type is used for simplicity)
 @SqlQuery("SELECT DatasetName FROM Schemas WHERE ProjectId = :projectId")
 String findDatasetNameByProjectId(@Bind("projectId") String projectId);

 /*
 * close with no args is used to close the connection
 */
 void close();
}

Open a Connection to Google Data Catalog

Collect the necessary connection properties and construct the appropriate JDBC URL for connecting to Google Data Catalog.

Google Data Catalog uses the OAuth authentication standard. Authorize access to Google APIs on behalf on individual users or on behalf of users in a domain.

Before connecting, specify the following to identify the organization and project you would like to connect to:

• OrganizationId: The ID associated with the Google Cloud Platform organization resource you would like to connect to. Find this by navigating to the cloud console.

  Click the project selection drop-down, and select your organization from the list. Then, click More -> Settings. The organization ID is displayed on this page.

• ProjectId: The ID associated with the Google Cloud Platform project resource you would like to connect to.

  Find this by navigating to the cloud console dashboard and selecting your project from the Select from drop-down. The project ID will be present in the Project info card.

When you connect, the OAuth endpoint opens in your default browser. Log in and grant permissions to the application to completes the OAuth process. For more information, refer to the OAuth section in the Help documentation.

Built-in Connection String Designer

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

java -jar cdata.jdbc.googledatacatalog.jar

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

A connection string for Google Data Catalog will typically look like the following:

jdbc:googledatacatalog:ProjectId=YourProjectId;InitiateOAuth=GETANDREFRESH;

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:googledatacatalog:ProjectId=YourProjectId;InitiateOAuth=GETANDREFRESH;");
MySchemasDAO dao = dbi.open(MySchemasDAO.class);

//do stuff with the DAO

dao.close();

Read Google Data Catalog Data

With the connection open to Google Data Catalog, simply call the previously defined method to retrieve data from the Schemas entity in Google Data Catalog.

//disply the result of our 'find' method
String datasetName = dao.findDatasetNameByProjectId("bigquery-public-data");
System.out.println(datasetName);

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