android – 如何通过Retrofit在@Query中传递自定义枚举？

我有一个简单的枚举：

public enum Season {
    @SerializedName("0")
    AUTUMN,@SerializedName("1")
    SPRING;
}

从某个版本开始,GSON就能够解析这些枚举.为了确保,我这样做了：

final String s = gson.toJson(Season.AUTUMN);

它按我的预期工作.输出为“0”.所以,我尝试在我的Retrofit服务中使用它：

@GET("index.PHP?page[api]=test")
Observable<List<Month>> getMonths(@Query("season_lookup") Season season);
/*...some files later...*/
service.getMonths(Season.AUTUMN);

并且还添加了日志以确定其结果：

HttpLoggingInterceptor httpLoggingInterceptor = new HttpLoggingInterceptor();
httpLoggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);

OkHttpClient httpClient = new OkHttpClient.Builder()
        .addInterceptor(httpLoggingInterceptor)
        .build();

但它失败了. @Query完全忽略@SerializedName并改为使用.toString(),所以日志显示为… / index.PHP？page [api] = test& season_lookup = AUTUMN.

我跟踪了Retrofit源代码并找到了带有行的文件RequestFactoryParser：

Converter<?,String> converter = 
    retrofit.stringConverter(parameterType,parameterAnnotations);
action = new RequestAction.Query<>(name,converter,encoded);

似乎,就像它根本不关心枚举一样.在这些行之前,它将rawParameterType.isArray()测试为数组或Iterable.class.isAssignableFrom(),仅此而已.

改造实例创建是：

retrofit = new Retrofit.Builder()
                .baseUrl(ApiConstants.API_ENDPOINT)
                .client(httpClient)
                .addConverterFactory(GsonConverterFactory.create(gson))
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .build();

gson是GsonBuilder().create().我偷看了源代码,其中有枚举的预定义ENUM_TypeAdapters.ENUM_FACTORY,所以我保持原样.

问题是我该怎么办,以防止在我的枚举上使用toString()并使用@SerializedName？我将toString()用于其他目的.

解决方法

正如@DawidSzydło所提到的,我在Retrofit中误解了Gson的用法.它仅用于响应/请求解码/编码,但不用于@Query / @ Url / @ Path e.t.c.对于他们来说,Retrofit使用Converter.Factory将任何类型转换为String.
以下是将@SerializedName作为任何Enum的值传递给Retrofit服务时自动使用的代码.

转换器：

public class EnumRetrofitConverterFactory extends Converter.Factory {
    @Override
    public Converter<?,String> stringConverter(Type type,Annotation[] annotations,Retrofit retrofit) {
        Converter<?,String> converter = null;
        if (type instanceof Class && ((Class<?>)type).isEnum()) {
            converter = value -> EnumUtils.GetSerializedNameValue((Enum) value);
        }
        return converter;
    }
}

EnumUtils：

public class EnumUtils {
    @Nullable
    static public <E extends Enum<E>> String GetSerializedNameValue(E e) {
        String value = null;
        try {
            value = e.getClass().getField(e.name()).getAnnotation(SerializedName.class).value();
        } catch (NoSuchFieldException exception) {
            exception.printStackTrace();
        }
        return value;
    }
}

改造创造：

retrofit = new Retrofit.Builder()
        .baseUrl(ApiConstants.API_ENDPOINT)
        .client(httpClient)
        .addConverterFactory(GsonConverterFactory.create(gson))
        .addConverterFactory(new EnumRetrofitConverterFactory())
        .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
        .build();

08.18更新添加kotlin类似物：

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val httpLoggingInterceptor = HttpLoggingInterceptor()
        httpLoggingInterceptor.level = HttpLoggingInterceptor.Level.BODY

        val httpClient = OkHttpClient.Builder()
                .addInterceptor(httpLoggingInterceptor)
                .build()

        val gson = GsonBuilder().create()

        val retrofit = Retrofit.Builder()
                .baseUrl(Api.ENDPOINT)
                .client(httpClient)
                .addConverterFactory(GsonConverterFactory.create(gson))
                .addConverterFactory(EnumConverterFactory())
                .build()

        val service = retrofit.create(Api::class.java)
        service.getMonths(Season.AUTUMN).enqueue(object : Callback<List<String>> {
            override fun onFailure(call: Call<List<String>>?,t: Throwable?) {
                /* ignore */
            }

            override fun onResponse(call: Call<List<String>>?,response: Response<List<String>>?) {
                /* ignore */
            }
        })
    }
}

class EnumConverterFactory : Converter.Factory() {
    override fun stringConverter(type: Type?,annotations: Array<out Annotation>?,retrofit: Retrofit?): Converter<*,String>? {
        if (type is Class<*> && type.isEnum) {
            return Converter<Any?,String> { value -> getSerializedNameValue(value as Enum<*>) }
        }
        return null
    }
}

fun <E : Enum<*>> getSerializedNameValue(e: E): String {
    try {
        return e.javaClass.getField(e.name).getAnnotation(SerializedName::class.java).value
    } catch (exception: NoSuchFieldException) {
        exception.printStackTrace()
    }

    return ""
}

enum class Season {
    @SerializedName("0")
    AUTUMN,@SerializedName("1")
    SPRING
}

interface Api {
    @GET("index.PHP?page[api]=test")
    fun getMonths(@Query("season_lookup") season: Season): Call<List<String>>

    companion object {
        const val ENDPOINT = "http://127.0.0.1"
    }
}

在日志中,您将看到：

D/OkHttp: --> GET http://127.0.0.1/index.PHP?page[api]=test&season_lookup=0 
D/OkHttp: --> END GET 
D/OkHttp: <-- HTTP Failed: java.net.ConnectException: Failed to connect to /127.0.0.1:80

使用的依赖项是：

implementation 'com.squareup.retrofit2:retrofit:2.4.0'
implementation 'com.google.code.gson:gson:2.8.5'
implementation 'com.squareup.okhttp3:logging-interceptor:3.11.0'
implementation 'com.squareup.retrofit2:converter-gson:2.4.0'

android – 如何通过Retrofit在@Query中传递自定义枚举？

解决方法

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