Android Retrofit实现GET请求返回空对象问题求助

核心问题 #

你遇到的问题根源在于GET请求的参数传递方式不匹配：

• Postman中你是把参数放在请求Body里发送GET请求（虽然不符合HTTP规范，但Postman支持这种非常规用法）
• 而Retrofit中用@Query是把参数拼接到URL的查询字符串中，服务端实际是从请求Body读取参数，自然找不到对应值，返回空对象。

另外你的代码里还有两处明显的类型错误，也会导致请求异常：

• boolean cod = "1";：boolean类型不能赋值字符串，类型不匹配
• float weight = "1";：float类型不能赋值字符串，类型不匹配

解决方案 #

方案1：按服务端要求用GET请求携带Body（适配Postman的调用方式） #

Retrofit默认不支持GET请求带Body，需要通过@HTTP注解自定义请求：

1. 创建参数实体类

public class ServiceabilityParams {
    @SerializedName("pickup_postcode")
    private String pickupPostcode;
    @SerializedName("delivery_postcode")
    private String deliveryPostcode;
    @SerializedName("cod")
    private String cod;
    @SerializedName("weight")
    private String weight;

    // 构造方法
    public ServiceabilityParams(String pickupPostcode, String deliveryPostcode, String cod, String weight) {
        this.pickupPostcode = pickupPostcode;
        this.deliveryPostcode = deliveryPostcode;
        this.cod = cod;
        this.weight = weight;
    }
}

2. 修改Retrofit接口

public interface ShipRocketServiceAbilityInterface {
    @HTTP(method = "GET", path = "courier/serviceability/", hasBody = true)
    Call<ShipRocketServiceabilityResponse> getService(@Body ServiceabilityParams params);
}

3. 修正调用代码的类型错误

// 修正类型错误，统一用String匹配参数格式
String pickupPostcode = "600114";
String deliveryPostcode = "600125";
String cod = "1";
String weight = "1";

Call<ShipRocketServiceabilityResponse> service = 
    shipRocket.getService(new ServiceabilityParams(pickupPostcode, deliveryPostcode, cod, weight));

service.enqueue(new Callback<ShipRocketServiceabilityResponse>() {
    @Override
    public void onResponse(Call<ShipRocketServiceabilityResponse> call, Response<ShipRocketServiceabilityResponse> response) {
        if (response.isSuccessful() && response.body() != null) {
            String currency = response.body().getCurrency();
            // 处理返回数据
        } else {
            Log.d("TAG", "请求失败，响应码：" + response.code());
        }
    }

    @Override
    public void onFailure(Call<ShipRocketServiceabilityResponse> call, Throwable t) {
        Log.d("TAG","请求失败：" + t.getMessage());
    }
});

方案2：改用URL查询参数传递（如果服务端支持） #

如果服务端实际兼容URL查询参数的传递方式，只需修正代码中的类型错误即可：

1. 保留原接口不变
2. 修正调用代码的类型错误

String pickupPostcode = "600114";
String deliveryPostcode = "600125";
String cod = "1"; // 改为String类型，匹配接口参数类型
String weight = "1"; // 改为String类型，或接口参数改为float时用float weight = 1.0f;

Call<ShipRocketServiceabilityResponse> service = 
    shipRocket.getService(pickupPostcode,deliveryPostcode,cod,weight);

// 后续回调代码同方案1

辅助排查建议 #

添加Retrofit日志拦截器，查看完整的请求/响应详情，确认参数是否正确传递：

OkHttpClient client = new OkHttpClient.Builder()
    .addInterceptor(new HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BODY))
    .build();

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("你的BaseURL")
    .client(client)
    .addConverterFactory(GsonConverterFactory.create())
    .build();

内容的提问来源于stack exchange，提问作者AMRESWAR V