使用Retrofit发送Multipart图片时遇Json Data未完全消费错误

问题背景 #

使用Retrofit以Multipart形式发送图片时，出现「Json Data Was not fully consumed」错误，Postman测试API正常，但代码实现报错，已尝试Stack Overflow方案无效。

相关代码 #

ApiHandler类 #

public class ApiHandler {

    private static final String BASE_URL = "https://aaplasevak.com/";

    private static Retrofit retrofit;

    public static Retrofit getRetrofitInstance() {


        if(retrofit == null){

            OkHttpClient client = new OkHttpClient.Builder().build();

            Gson gson = new GsonBuilder().setLenient().create();

            retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .client(client)
                    .addConverterFactory(GsonConverterFactory.create(gson))
                    .build();
        }

        return retrofit;
    }
   
}

Api Interface类 #

@Multipart
    @POST("whatsapp_api.php")
    Call<WhatsAppApiResponseData> sentWhatsAppMessage(
            @Part("series_id") RequestBody seriesId,
            @Part("colony_id") RequestBody  colonyId,
            @Part("row_id") RequestBody  rowId,
            @Part("watersupply_id") RequestBody  waterSupplyId,
            @Part("constituency") RequestBody  constituency,
            @Part("city_village") RequestBody  cityVillage,
            @Part("zone") RequestBody  zone,
            @Part("prabhag_ward") RequestBody  prabhagWard,
            @Part("template_desc") RequestBody  templateDesc,
            @Part MultipartBody.Part file
    );

API实现代码 #

private void sentWhatsAppMessage() {
        ApiInterface apiInterface = getRetrofitInstance().create(ApiInterface.class);

        RequestBody seriesId = RequestBody.create(MediaType.parse("multipart/form-data"), String.valueOf(spinner_series.getSelectedItemPosition()));
        RequestBody colonyId = RequestBody.create(MediaType.parse("multipart/form-data"), String.valueOf(spinner_colony.getSelectedItemPosition() + 1));
        RequestBody rowId = RequestBody.create(MediaType.parse("multipart/form-data"), String.valueOf(spinner_row.getSelectedItemPosition() + 1));
        RequestBody waterSupplyId = RequestBody.create(MediaType.parse("multipart/form-data"), String.valueOf(spinner_water_Supply.getSelectedItemPosition()));
        RequestBody zoneId = RequestBody.create(MediaType.parse("multipart/form-data"), String.valueOf(spinner_zone.getSelectedItemPosition()));
        RequestBody wardId = RequestBody.create(MediaType.parse("multipart/form-data"), String.valueOf(spinner_ward.getSelectedItemPosition()));
        RequestBody constituencyId = RequestBody.create(MediaType.parse("multipart/form-data"), String.valueOf(spinner_constituency.getSelectedItemPosition()));
        RequestBody cityVillageId = RequestBody.create(MediaType.parse("multipart/form-data"), String.valueOf(spinner_city_village.getSelectedItemPosition()));
        RequestBody message = RequestBody.create(MediaType.parse("multipart/form-data"),  etMessage.getText().toString());


        File file = new File(getRealPathFromURI(selectedUri));
        RequestBody requestFile = RequestBody.create(MediaType.parse("multipart/form-data"), file);
        MultipartBody.Part body = MultipartBody.Part.createFormData("file", file.getName(), requestFile);


        Call<WhatsAppApiResponseData> call = apiInterface.sentWhatsAppMessage(seriesId,colonyId,rowId,waterSupplyId,constituencyId,cityVillageId,zoneId,wardId,message,body);
        //Log.d("Api Response", "WhatsApp: " + whatsAppApiBody.toString());


        call.enqueue(new Callback<WhatsAppApiResponseData>() {
            @Override
            public void onResponse(Call<WhatsAppApiResponseData> call, retrofit2.Response<WhatsAppApiResponseData> response) {
                if (response.isSuccessful()) {
                    WhatsAppApiResponseData responseData = response.body();
                    String status = responseData.toString();
                    Toast.makeText(WhatsappActivity.this, "Success!! " + status, Toast.LENGTH_SHORT).show();
                    Log.d("Api Response","data: " + status);
                    finish();
                } else {
                    Toast.makeText(WhatsappActivity.this, "Response Error..!!", Toast.LENGTH_SHORT).show();
                    Log.e("Api Response", "Response Error..");
                }
            }

            @Override
            public void onFailure(Call<WhatsAppApiResponseData> call, Throwable throwable) {
                Log.e("Api Response", "Error.." + throwable.getLocalizedMessage());
                Toast.makeText(WhatsappActivity.this, "Error.." + throwable.getLocalizedMessage(), Toast.LENGTH_SHORT).show();
                throwable.printStackTrace();
            }
        });

    }

getRealPathFromUri方法 #

private String getRealPathFromURI(Uri contentUri) {

        String[] projection = {MediaStore.Images.Media.DATA};
        Cursor cursor = getContentResolver().query(contentUri, projection, null, null, null);
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        cursor.moveToFirst();
        String filePath = cursor.getString(column_index);
        cursor.close();
        return filePath;

    }

错误原因分析 #

1. RequestBody媒体类型错误：所有表单字段都指定multipart/form-data类型，但Multipart请求中普通字段无需手动指定该类型，错误设置会导致请求格式异常；图片文件未使用对应MIME类型（如image/jpeg），服务器无法正确识别文件内容，返回异常响应。
2. 响应解析不匹配：服务器返回的响应可能包含非JSON内容（如调试信息、HTML冗余字符），Gson转换器无法完全消耗响应体，触发错误。
3. 文件路径适配问题：getRealPathFromURI方法在Android 10及以上系统无法正确获取文件真实路径，导致文件读取异常，间接引发响应解析错误。

解决办法 #

1. 修正RequestBody媒体类型 #

• 普通表单字段使用text/plain类型，或不指定MediaType（Retrofit会自动处理）；图片文件使用对应MIME类型：

// 普通字段示例
RequestBody seriesId = RequestBody.create(MediaType.parse("text/plain"), String.valueOf(spinner_series.getSelectedItemPosition()));

// 文件字段示例：自动获取图片MIME类型
String mimeType = getContentResolver().getType(selectedUri);
RequestBody requestFile = RequestBody.create(MediaType.parse(mimeType), file);
MultipartBody.Part body = MultipartBody.Part.createFormData("file", file.getName(), requestFile);

2. 排查服务器响应内容 #

• 在onResponse中打印错误响应体，确认是否存在非JSON内容：

@Override
public void onResponse(Call<WhatsAppApiResponseData> call, retrofit2.Response<WhatsAppApiResponseData> response) {
    if (!response.isSuccessful()) {
        try {
            String errorBody = response.errorBody().string();
            Log.e("Api Response", "Error Body: " + errorBody);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

• 若响应存在冗余内容，需要求后端修正响应格式为纯JSON，或自定义ConverterFactory过滤多余字符。

3. 优化Gson解析配置 #

• 放宽Gson解析规则，忽略未知字段和格式不严谨问题：

Gson gson = new GsonBuilder()
        .setLenient()
        .ignoreUnknownFields()
        .create();

4. 适配Android 10+文件读取 #

• 替换getRealPathFromURI方法，改用ContentResolver读取文件流：

private RequestBody getFileRequestBody(Uri uri) throws IOException {
    InputStream inputStream = getContentResolver().openInputStream(uri);
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int length;
    while ((length = inputStream.read(buffer)) != -1) {
        outputStream.write(buffer, 0, length);
    }
    byte[] fileBytes = outputStream.toByteArray();
    inputStream.close();
    outputStream.close();
    return RequestBody.create(MediaType.parse(getContentResolver().getType(uri)), fileBytes);
}

内容的提问来源于stack exchange，提问作者Mamta