Create a Data Access Object for Kafka 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 Kafka integrates connectivity to live Kafka data in Java applications. By pairing these technologies, you gain simple, programmatic access to Kafka data. This article explains how to build a basic Data Access Object (DAO) and the accompanying code to read and write Kafka data.

Create a DAO for the Kafka 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 {
 //insert new data into Kafka
 @SqlUpdate("INSERT INTO SampleTable_1 (Column2, Column1) values (:column2, :column1)")
 void insert(@Bind("column2") String column2, @Bind("column1") String column1);

 //request specific data from Kafka (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 Kafka

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

Set BootstrapServers and the Topic properties to specify the address of your Apache Kafka server, as well as the topic you would like to interact with.

Authorization Mechanisms

• SASL Plain: The User and Password properties should be specified. AuthScheme should be set to 'Plain'.
• SASL SSL: The User and Password properties should be specified. AuthScheme should be set to 'Scram'. UseSSL should be set to true.
• SSL: The SSLCert and SSLCertPassword properties should be specified. UseSSL should be set to true.
• Kerberos: The User and Password properties should be specified. AuthScheme should be set to 'Kerberos'.

You may be required to trust the server certificate. In such cases, specify the TrustStorePath and the TrustStorePassword if necessary.

Built-in Connection String Designer

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

java -jar cdata.jdbc.apachekafka.jar

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

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

jdbc:apachekafka:User=admin;Password=pass;BootStrapServers=https://localhost:9091;Topic=MyTopic;

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:apachekafka:User=admin;Password=pass;BootStrapServers=https://localhost:9091;Topic=MyTopic;");
MySampleTable_1DAO dao = dbi.open(MySampleTable_1DAO.class);

//do stuff with the DAO

dao.close();

Read Kafka Data

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

//disply the result of our 'find' method
String column1 = dao.findColumn1ByColumn2("100");
System.out.println(column1);

Write Kafka Data

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

//add a new entry to the SampleTable_1 entity
dao.insert(newColumn2, newColumn1);

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