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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>

  <!-- 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