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Create a Data Access Object for Cassandra Data using JDBI


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

Create a DAO for the Cassandra Customer 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 MyCustomerDAO { //insert new data into Cassandra @SqlUpdate("INSERT INTO Customer (FirstName, TotalDue) values (:firstName, :totalDue)") void insert(@Bind("firstName") String firstName, @Bind("totalDue") String totalDue); //request specific data from Cassandra (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(); }

Open a Connection to Cassandra

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

Set the Server, Port, and Database connection properties to connect to Cassandra. Additionally, to use internal authentication set the User and Password connection properties.

Built-in Connection String Designer

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

java -jar cdata.jdbc.cassandra.jar

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

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

jdbc:cassandra:Database=MyCassandraDB;Port=7000;Server=127.0.0.1;

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:cassandra:Database=MyCassandraDB;Port=7000;Server=127.0.0.1;"); MyCustomerDAO dao = dbi.open(MyCustomerDAO.class); //do stuff with the DAO dao.close();

Read Cassandra Data

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

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

Write Cassandra Data

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

//add a new entry to the Customer entity dao.insert(newFirstName, newTotalDue);

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

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