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Create a Data Access Object for Impala Data using JDBI


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

Create a DAO for the Impala Customers 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 MyCustomersDAO { //insert new data into Impala @SqlUpdate("INSERT INTO Customers (Country, CompanyName) values (:country, :companyName)") void insert(@Bind("country") String country, @Bind("companyName") String companyName); //request specific data from Impala (String type is used for simplicity) @SqlQuery("SELECT CompanyName FROM Customers WHERE Country = :country") String findCompanyNameByCountry(@Bind("country") String country); /* * close with no args is used to close the connection */ void close(); }

Open a Connection to Impala

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

In order to connect to Apache Impala, set the Server, Port, and ProtocolVersion. You may optionally specify a default Database. To connect using alternative methods, such as NOSASL, LDAP, or Kerberos, refer to the online Help documentation.

Built-in Connection String Designer

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

java -jar cdata.jdbc.apacheimpala.jar

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

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

jdbc:apacheimpala:Server=127.0.0.1;Port=21050;

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:apacheimpala:Server=127.0.0.1;Port=21050;"); MyCustomersDAO dao = dbi.open(MyCustomersDAO.class); //do stuff with the DAO dao.close();

Read Impala Data

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

//disply the result of our 'find' method String companyName = dao.findCompanyNameByCountry("US"); System.out.println(companyName);

Write Impala Data

It is also simple to write data to Impala, using the previously defined method.

//add a new entry to the Customers entity dao.insert(newCountry, newCompanyName);

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

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