ConfluentSchemaRegistry无法更新现有模式

在使用Confluent SchemaRegistry时，如果您尝试更新现有模式时出现问题，请按照以下步骤进行排除：

1. 确保您具有正确的权限来更新现有模式。
2. 检查您尝试更新的模式是否已经被注册。
3. 确保您的代码使用正确的模式ID进行更新操作。

以下是一个Java代码示例，它演示了如何使用Confluent SchemaRegistry来更新模式：

import io.confluent.kafka.schemaregistry.client.CachedSchemaRegistryClient;
import io.confluent.kafka.schemaregistry.client.SchemaMetadata;
import io.confluent.kafka.schemaregistry.client.rest.exceptions.RestClientException;
import org.apache.avro.Schema;

import java.io.IOException;

public class SchemaRegistryExample {

    private static final String SCHEMA_REGISTRY_URL = "http://localhost:8081";
    private static final String SUBJECT_NAME = "my_subject";

    public static void main(String[] args) throws IOException, RestClientException {

        // create a schema registry client
        CachedSchemaRegistryClient client = new CachedSchemaRegistryClient(SCHEMA_REGISTRY_URL, 10);

        // register a new schema
        String newSchemaString = "{ \"type\": \"record\", \"name\": \"my_record\", \"fields\": [{ \"name\": \"field1\", \"type\": \"string\" }] }";
        Schema newSchema = new Schema.Parser().parse(newSchemaString);
        int schemaId = client.register(SUBJECT_NAME, newSchema);

        // update the schema
        String updatedSchemaString = "{ \"type\": \"record\", \"name\": \"my_record\", \"fields\": [{ \"name\": \"field1\", \"type\": \"string\" }, { \"name\": \"field2\", \"type\": \"int\" }] }";
        Schema updatedSchema = new Schema.Parser().parse(updatedSchemaString);
        client.updateSchemaMetadata(schemaId, SUBJECT_NAME, updatedSchema);

        // retrieve the schema metadata
        SchemaMetadata schemaMetadata = client.getLatestSchemaMetadata(SUBJECT_NAME);

        // print the schema metadata
        System.out.println("Latest schema ID: " + schemaMetadata.getId());