我有一个工作代码,其中我的改装客户端可以从api中检索对象列表(国家/地区)。问题是,如果我以前检索所有国家/地区,则api使用的参数返回ARRAY,然后当我想查询单个国家/地区时它返回单个OBJECT。结果显示以下异常。
java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 4 column 17 path $.RestResponse.result
顺便说一句,我使用的是Retrofit 2.
我在这个帖子中尝试了接受的答案 How to handle parameters that can be an ARRAY or OBJECT in Retrofit on Android?
但它仍然没有奏效。这是我的实施。
API
http://services.groupkt.com/country/get/all
http://services.groupkt.com/country/get/iso2code/{alpha2_code}
ApiInterface
public interface ApiInterface {
@GET("country/get/all")
Call<Example> getCountry();
@GET("country/get/iso2code/{alpha2_code}")
Call<Example> searchCountryByIso2Code(@Path("alpha2_code") String alpha2Code);
@GET("country/get/iso3code/{alpha3_code}")
Call<Example> searchCountryByIso3Code(@Path("alpha3_code") String alpha3Code);
@GET("country/search?text={text to search}")
Call<Example> searchCountry(@Path("text to search") String searchText);
}
CountryTypeAdapter
public class CountryTypeAdapter extends TypeAdapter<RestResponse> {
private Gson mGson = new Gson();
@Override
public void write(JsonWriter jsonWriter, RestResponse restResponse) throws IOException {
mGson.toJson(restResponse, RestResponse.class, jsonWriter);
}
@Override
public RestResponse read(JsonReader jsonReader) throws IOException {
RestResponse result;
jsonReader.beginObject();
jsonReader.nextName();
if (jsonReader.peek() == JsonToken.BEGIN_ARRAY) {
result = new RestResponse((Result[]) mGson.fromJson(jsonReader, Result.class));
} else if (jsonReader.peek() == JsonToken.BEGIN_OBJECT) {
result = new RestResponse((Result) mGson.fromJson(jsonReader, Result.class));
} else {
throw new JsonParseException("Unexpected token " + jsonReader.peek());
}
jsonReader.endObject();
return result;
}
}
ApiClient
public class ApiClient {
public static final String BASE_URL = "http://services.groupkt.com/";
private static Retrofit mRetrofit;
public static Retrofit getmRetrofitClient(){
if (mRetrofit == null) {
mRetrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create(new GsonBuilder().registerTypeAdapter(CountryTypeAdapter.class, new CountryTypeAdapter()).create()))
.build();
}
return mRetrofit;
}
}
编辑: RestResponse
public class RestResponse {
@SerializedName("messages")
@Expose
private List<String> messages = null;
@SerializedName("result")
@Expose
private List<Result> result = null;
public RestResponse() {
}
public RestResponse(List<String> messages, List<Result> result) {
this.messages = messages;
this.result = result;
}
public RestResponse(Result... result) {
this.result = Arrays.asList(result);
}
public List<String> getMessages() {
return messages;
}
public void setMessages(List<String> messages) {
this.messages = messages;
}
public List<Result> getResult() {
return result;
}
public void setResult(List<Result> result) {
this.result = result;
}
}
答案 0 :(得分:2)
您的代码中存在一些问题,其中一些问题可以修复或重新设计,以简化许多操作。首先,我们来看看服务(名称不同)。对于具有查询参数但不是@Query
的请求,Retrofit界面必须使用@Path
。此外,您的服务方法必须返回Call
,其T
声明实际结果类型,提供有关该方法返回的内容的一些信息。您提到的服务可以返回单个元素或不返回(但由于某种原因从不返回HTTP 404),或者根据端点URL返回列表。假设,单个值和无值都不是1或0大小的列表:
interface IService {
@GET("country/get/all")
Call<List<Country>> getCountries();
@GET("country/get/iso2code/{code}")
Call<Country> getCountryByIso2Code(
@Path("code") String code
);
@GET("country/get/iso3code/{code}")
Call<Country> getCountryByIso3Code(
@Path("code") String code
);
@GET("country/search")
Call<List<Country>> searchCountries(
@Query("text") String query
);
}
接下来,Country
类可能如下所示:
final class Country {
@SerializedName("name")
final String name = null;
@SerializedName("alpha2_code")
final String code2 = null;
@SerializedName("alpha3_code")
final String code3 = null;
@Override
public String toString() {
return name + '(' + code2 + ',' + code3 + ')';
}
}
请注意@SerializedName
可以将外部名称映射到本地字段名称,字段为final
和null
ified - Gson可以自行处理它们。接下来,我假设你并不真正关心响应结构,只需要分别调整$.Response.result
。 TypeAdapterFactory
是您所需要的,可以与任何回复合作,不一定适用于各个国家/地区:
final class ResponseExtractorTypeAdapterFactory
implements TypeAdapterFactory {
private final Gson gson;
private ResponseExtractorTypeAdapterFactory(final Gson gson) {
this.gson = gson;
}
static TypeAdapterFactory getResponseExtractorTypeAdapterFactory(final Gson gson) {
return new ResponseExtractorTypeAdapterFactory(gson);
}
@Override
public <T> TypeAdapter<T> create(final Gson responseGson, final TypeToken<T> typeToken) {
// Using responseGson would result in infinite recursion since this type adapter factory overrides any type
return new ResponseExtractorTypeAdapter<>(gson, typeToken.getType());
}
private static final class ResponseExtractorTypeAdapter<T>
extends TypeAdapter<T> {
private final Gson gson;
private final Type type;
private ResponseExtractorTypeAdapter(final Gson gson, final Type type) {
this.gson = gson;
this.type = type;
}
@Override
public void write(final JsonWriter out, final T value) {
throw new UnsupportedOperationException();
}
@Override
public T read(final JsonReader in)
throws IOException {
T result = null;
// Strip the top most enclosing { for $
in.beginObject();
final String name1 = in.nextName();
switch ( name1 ) {
case "RestResponse":
// RestResponse { for $.Response
in.beginObject();
while ( in.hasNext() ) {
final String name2 = in.nextName();
switch ( name2 ) {
case "messages":
// If it's just $.Response.message, then skip it
in.skipValue();
break;
case "result":
// If it's $.Response.result, then delegate it to "real" Gson
result = gson.fromJson(in, type);
break;
default:
throw new MalformedJsonException("Unexpected at $.RestResponse: " + name2);
}
}
// RestResponse } for $.Response
in.endObject();
break;
default:
throw new MalformedJsonException("Unexpected at $: " + name1);
}
// Strip the top most enclosing } for $
in.endObject();
return result;
}
}
}
全部放在一起:
public static void main(final String... args) {
final Gson gson = new GsonBuilder()
// configure whatever you like
.create();
final Gson responseGson = new GsonBuilder()
.registerTypeAdapterFactory(getResponseExtractorTypeAdapterFactory(gson))
.create();
final Retrofit retrofit = new Builder()
.baseUrl("http://services.groupkt.com/")
.addConverterFactory(GsonConverterFactory.create(responseGson))
.build();
final IService apiInterface = retrofit.create(IService.class);
apiInterface.getCountries().enqueue(callback("getCountries()")); // http://services.groupkt.com/country/get/all
apiInterface.getCountryByIso2Code("UA").enqueue(callback("getCountryByIso2Code()")); // http://services.groupkt.com/country/get/iso2code/UA
apiInterface.getCountryByIso3Code("UKR").enqueue(callback("getCountryByIso3Code()")); // http://services.groupkt.com/country/get/iso3code/UKR
apiInterface.searchCountries("land").enqueue(callback("searchCountries()")); // http://services.groupkt.com/country/search?text=land
}
private static <T> Callback<T> callback(final String name) {
return new Callback<T>() {
@Override
public void onResponse(final Call<T> call, final Response<T> response) {
// Just make sure the output is not written in middle
synchronized ( System.out ) {
System.out.print(name);
System.out.print(": ");
System.out.println(response.body());
System.out.println();
}
}
@Override
public void onFailure(final Call<T> call, final Throwable ex) {
ex.printStackTrace(System.err);
}
};
}
结果(假设响应被接收并且后续处理+长响应被删除):
getCountries():[阿富汗(AF,AFG),奥兰群岛(AX,ALA),阿尔巴尼亚(AL,ALB),......,也门(YE,YEM),赞比亚(ZM,ZMB),津巴布韦( ZW,ZWE)]
getCountryByIso2Code():乌克兰(UA,UKR)
getCountryByIso3Code():乌克兰(UA,UKR)
searchCountries():[奥兰群岛(AX,ALA),布维岛(BV,BVT),开曼群岛(KY,CYM),...,美国本土外小岛屿(UM,UMI),维尔京群岛(英国)(VG,VGB),维尔京群岛(美国)(VI,VIR)]