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Create a Data Access Object for Parquet Data using JDBI


A brief overview of creating a SQL Object API for Parquet data in 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 Parquet integrates connectivity to live Parquet data in Java applications. By pairing these technologies, you gain simple, programmatic access to Parquet data. This article walks through building a basic Data Access Object (DAO) and the accompanying code to read Parquet data.

Create a DAO for the Parquet SampleTable_1 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 MySampleTable_1DAO { //request specific data from Parquet (String type is used for simplicity) @SqlQuery("SELECT Column1 FROM SampleTable_1 WHERE Column2 = :column2") String findColumn1ByColumn2(@Bind("column2") String column2); /* * close with no args is used to close the connection */ void close(); }

Open a Connection to Parquet

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

Connect to your local Parquet file(s) by setting the URI connection property to the location of the Parquet file.

Built-in Connection String Designer

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

java -jar cdata.jdbc.parquet.jar

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

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

jdbc:parquet:URI=C:/folder/table.parquet;

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:parquet:URI=C:/folder/table.parquet;"); MySampleTable_1DAO dao = dbi.open(MySampleTable_1DAO.class); //do stuff with the DAO dao.close();

Read Parquet Data

With the connection open to Parquet, simply call the previously defined method to retrieve data from the SampleTable_1 entity in Parquet.

//disply the result of our 'find' method String column1 = dao.findColumn1ByColumn2("SAMPLE_VALUE"); System.out.println(column1);

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