com.google.gson.internal.LinkedTreeMap无法转换为com.google.gson.internal.LinkedTreeMap

Question

我编写了一个Java类，使用feignHttp从架构注册表中检索架构。当我尝试检索架构时，抛出以上异常。

客户端类：

import com.google.gson.internal.LinkedTreeMap;
import feign.Feign;
import feign.FeignException;
import feign.gson.GsonDecoder;
import feign.gson.GsonEncoder;
import feign.okhttp.OkHttpClient;
import org.apache.avro.Schema;
import org.apache.avro.SchemaParseException;

public class SchemaRegistryReader {
    public Schema getSchemaFromID(String registryURL, String schemaID) throws SchemaParseException, FeignException {
        SchemaRegistryClient registryClient = Feign.builder()
                .client(new OkHttpClient())
                .encoder(new GsonEncoder())
                .decoder(new GsonDecoder())
                .target(SchemaRegistryClient.class, registryURL);
        Object returnedSchema = registryClient.findByID(schemaID);
        LinkedTreeMap jsonSchemaObject = ((LinkedTreeMap) returnedSchema);
        String jsonSchema = jsonSchemaObject.get("schema").toString();
        return new Schema.Parser().parse(jsonSchema);
    }
}

方法界面：

import feign.Headers;
import feign.Param;
import feign.RequestLine;

public interface SchemaRegistryClient {
    @RequestLine("GET")
    Object connect();

    @RequestLine("GET /schemas/ids/{id}")
    @Headers("Content-Type: application/json")
    Object findByID(@Param("id") String id);
}

引发异常：

java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to com.google.gson.internal.LinkedTreeMap at org.wso2.extension.siddhi.map.avro.util.schema.SchemaRegistryReader.getSchemaFromID(SchemaRegistryReader.java:41)

如果可以找到造成这种情况的原因，将会提供很大的帮助。