We will start with various ways to generate classes from Avro schema and end with example code.
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There are two ways to generate AVRO classes from Schema.
Let's generate Avro schema first to be used later in pragmatic generation or using maven plugin.
{
"type" : "record",
"name" : "Employee",
"namespace" : "cc.gaurav.blog.avro",
"doc" : "Schema to hold employee object",
"fields" : [{
"name" : "firstName",
"type" : "string"
},
{
"name" : "lastName",
"type" : "string"
},
{
"name" : "sex",
"type" : {
"name" : "SEX",
"type" : "enum",
"symbols" : ["MALE", "FEMALE"]
}
}]
}Classes can be generated for schema using SchemaCompiler. It has two constructors, one take Protocolas an argument and other take Schema as an argument.
public class PragmaticSchemaGeneration {
private static final Logger LOGGER = LoggerFactory.getLogger(PragmaticSchemaGeneration.class);
public static void main(String[] args) {
try {
// Point 1
SpecificCompiler compiler = new SpecificCompiler(new Schema.Parser().parse(new File("src/main/avro/employee.avsc")));
compiler.compileToDestination(new File("src/main/avro"), new File("src/main/java"));
} catch (IOException e) {
LOGGER.error("Exception occurred parsing schema: ", e);
}
}
}There is maven plugin which can generate schema for you. You need to add following configuration to your pom.xml.
<plugin>
<groupId>org.apache.avro</groupId>
<artifactId>avro-maven-plugin</artifactId>
<version>${avro.version}</version>
<executions>
<execution>
<id>schemas</id>
<phase>generate-sources</phase>
<goals>
<goal>schema</goal>
<goal>protocol</goal>
<goal>idl-protocol</goal>
</goals>
<configuration>
<sourceDirectory>${project.basedir}/src/main/avro/</sourceDirectory>
<outputDirectory>${project.basedir}/src/main/java/</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>This is how we can generate classes from Avro schema. I hope you find this post informative and helpful. You can find the full project on Github.