Generate Java data classes from Avro schemas

Generate Java data classes from Avro schema files (.avsc) to use with Apache Kafka® producers and consumers. Use the avro-tools JAR to create Java classes that match your schema structure.

Prerequisites

• An active Aiven for Apache Kafka® service

• Karapace Schema Registry enabled

• Java (JDK 8 or later)

• Apache Maven installed to manage dependencies

• avro-tools JAR file downloaded (such as avro-tools-1.12.0.jar)

• An Avro schema file with a .avsc extension

  note

  You can also use .json files if they contain a valid Avro schema. Do not use .avro files. They include both schema and data and are not compatible with avro-tools.

Generate the Java classes

Run the following command to generate Java classes from your Avro schema:

note

Use the latest version of avro-tools if available. You can check for newer releases at https://avro.apache.org/releases.html.

java -jar avro-tools-1.12.0.jar compile schema src/main/resources/user-value.avsc src/main/java/

• Replace user-value.avsc with your schema file.
• Replace src/main/java/ with your preferred output directory.

The generated class is named based on the name field in your schema, and it is placed in a subdirectory matching the namespace.

Example schema

{
  "type": "record",
  "name": "User",
  "namespace": "io.aiven.example",
  "fields": [
    { "name": "id", "type": "int" },
    { "name": "email", "type": "string" }
  ]
}

This schema produces the following file:

src/main/java/io/aiven/example/User.java

Add Maven dependencies

Add these dependencies to your pom.xml to compile and use the generated classes for Avro serialization and deserialization in Kafka producers and consumers.

<dependencies>
  <!-- Apache Kafka client dependency -->
  <dependency>
    <groupId>org.apache.kafka</groupId>
    <artifactId>kafka-clients</artifactId>
    <version>3.8.1</version>
  </dependency>

  <!-- Confluent dependencies for Avro serialization and Schema Registry -->
  <dependency>
    <groupId>io.confluent</groupId>
    <artifactId>kafka-avro-serializer</artifactId>
    <version>8.0.0</version>
  </dependency>
  <dependency>
    <groupId>io.confluent</groupId>
    <artifactId>kafka-schema-registry-client</artifactId>
    <version>8.0.0</version>
  </dependency>
  <dependency>
    <groupId>io.confluent</groupId>
    <artifactId>kafka-schema-serializer</artifactId>
    <version>8.0.0</version>
  </dependency>

  <!-- Apache Avro dependency -->
  <dependency>
    <groupId>org.apache.avro</groupId>
    <artifactId>avro</artifactId>
    <version>1.12.0</version>
  </dependency>
</dependencies>

note

Ensure that the versions of Avro, Kafka, and Confluent dependencies are compatible with each other and with your Kafka setup.

Optional dependencies

You can use additional libraries depending on your schema or Avro usage:

<!-- Jackson support for Java 8 types (used with generated POJOs) -->
<dependency>
  <groupId>com.fasterxml.jackson.datatype</groupId>
  <artifactId>jackson-datatype-jdk8</artifactId>
  <version>2.19.2</version>
</dependency>

<!-- Guava support (used in some Avro-related tooling) -->
<dependency>
  <groupId>com.google.guava</groupId>
  <artifactId>guava</artifactId>
  <version>33.4.8-jre</version>
</dependency>

These dependencies are optional. Include them only if your generated classes use features like Optional<T> fields (Jackson) or ImmutableList and ImmutableSet types (Guava).

Related pages

Official Avro Java Getting Started Guide