Generate Avro Schema from certain Java Object

** Example**

Pojo class

public class ExportData implements Serializable {
    private String body;
    // ... getters and setters
}

Serialize

File file = new File(fileName);
DatumWriter<ExportData> writer = new ReflectDatumWriter<>(ExportData.class);
DataFileWriter<ExportData> dataFileWriter = new DataFileWriter<>(writer);
Schema schema = ReflectData.get().getSchema(ExportData.class);
dataFileWriter.create(schema, file);
for (Row row : resultSet) {
    String rec = row.getString(0);
    dataFileWriter.append(new ExportData(rec));
}
dataFileWriter.close();

Deserialize

File file = new File(avroFilePath);
DatumReader<ExportData> datumReader = new ReflectDatumReader<>(ExportData.class);
DataFileReader<ExportData> dataFileReader = new DataFileReader<>(file, datumReader);
ExportData record = null;
while (dataFileReader.hasNext()){
    record = dataFileReader.next(record);
    // process record
}

Take a look at the Java reflection API.

Getting a schema looks like:

Schema schema = ReflectData.get().getSchema(T);

See the example from Doug on another question for a working example.

Credits of this answer belong to Sean Busby.

Here's how to Generate an Avro Schema from POJO definition

ObjectMapper mapper = new ObjectMapper(new AvroFactory());
AvroSchemaGenerator gen = new AvroSchemaGenerator();
mapper.acceptJsonFormatVisitor(RootType.class, gen);
AvroSchema schemaWrapper = gen.getGeneratedSchema();
org.apache.avro.Schema avroSchema = schemaWrapper.getAvroSchema();
String asJson = avroSchema.toString(true);