我试图为Kafka主题提供数据。作为需求的一部分，我从数据库中提取数据并将其Map到avro模式。我知道如何解析数据，因为模式很简单，如下所示：
简单avro模式：

{
    "type":"record",
    "namespace":"demo",
    "name":"coreloader330",
    "doc":"sample avro schema file for core loader 330",
    "fields":[
        { "name" : "HEALTH_PLAN", "type" : ["null", "string"]}
    ]
}

通用生成器java：

public GenericRecordBuilder getGenericBuilder() {
        GenericRecordBuilder builder = null;
        Schema.Parser parser = new Schema.Parser();
        try {
            Schema schema = parser.parse(new File("src/main/resources/coreloader.avsc"));
           builder = new GenericRecordBuilder(schema);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return builder;

将值Map到生成器：

public void produceMessage(){
        //Create Producer
        KafkaProducer<String, GenericRecord> producer = new KafkaProducer<String, GenericRecord>(props);
        try{
            while(rs.next()){
               // System.out.println(rs.getString("HEALTH_PLAN"));
                builder.set("HEALTH_PLAN", rs.getString("HEALTH_PLAN")); ---> mapping values to avro schema field
                GenericData.Record  data = builder.build();
                ProducerRecord<String, GenericRecord> record = new ProducerRecord<String, GenericRecord>(topic, data);
                producer.send(record);
                producer.flush();
            }

但是，如果模式很复杂，如何Map值，如何到达Map的嵌套字段？
假设我有下面这样的模式，如何遍历并将值Map到sourcesystem字段？

"type": "record",
"name": "demo",
"namespace": "example",
"fields": [
    {
        "name": "data",
        "type": {
            "type": "record",
            "name": "Data",
            "fields": [
                {
                    "name": "SourceSystem",
                    "type": [
                        "null",
                        "string"
                    ],
                    "default": null
                }
            ]
        }
    }

在下面的代码中，我的Map应该是什么？

builder.set(<?>, rs.getString("source system")); ---> mapping values to avro schema field