c# - 不同的 "translated"JsonProperty 名称

Question

我想将 JSON 中使用的键翻译成不同的语言。

我知道在设计接口(interface)、API 等时，从技术角度来看这似乎是无稽之谈。为什么不首先只使用英语？嗯，这个需求不是我写的 ;)

/// <summary>serialization language</summary>
public enum Language
{
   /// <summary>English</summary>
   EN,
   /// <summary>German</summary>
   DE
   // some more ...
}

实现这一点的最简单方法可能是一个属性:

/// <summary>An Attribute to add different "translations"</summary>
public class TranslatedFieldName : Attribute
{
   public string Name { get; }
   public Language Lang{ get; }
   // actually there might be a dictionary with lang-name pairs later on; but let's keep it simple
   public TranslatedFieldName(string translatedName, Language lang)
   {
       this.Lang = lang;
       this.Name = translatedName;
    }
}

然后我将这个属性添加到我想要序列化的类中:

/// <summary>I want to serialize classes of this kind to json in different languages </summary>
public class TranslatableObject
{
    [TranslatedFieldName("deutscher_schluessel", Language.DE)]
    public string english_key;
}

并调用JsonConvert.SerializeObject(...)

public void SerializationMethod()
{
    TranslatableObject to = new TranslatableObject()
    {
        english_key = "foo bar"
    };
    string englishJson = JsonConvert.SerializeObject(to); // == { "english_key": "foo bar" }
    string germanJson = JsonConvert.SerializeObject(to, new MultiLangConverter(Language.DE); // == { "deutscher_schluessel": "foo bar" }
}

我不知道使用过的 MultiLangConverter 实际上应该是什么样子:

public class MultiLangConverter : JsonConverter
{
    private readonly Language _lang,

    public MultiLangConverter() : this(Language.EN) { }

    public MultiLangConverter(Language lang)
    {
        _lang = lang;
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        throw new NotImplementedException("Out of scope for now");
    }

    public override bool CanRead
    {
        get { return false; } // out of scope for now
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        // what goes here?
    }
}

我尝试过的所有尝试似乎都过于复杂。我真的需要 JsonConverter 吗？还是 ContractResolver 更适合？

Answer 1

我认为您使用属性来表示翻译后的字段名称是正确的，但我认为您最终会希望使用自定义 ContractResolver 来处理翻译而不是 JsonConverter，尤其是当您需要对多个模型类进行翻译时(似乎很有可能)。

这是解析器的样子:

public class MultiLangResolver : DefaultContractResolver
{
    public Language Language { get; set; }

    public MultiLangResolver(Language lang)
    {
        Language = lang;
    }

    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        JsonProperty prop = base.CreateProperty(member, memberSerialization);

        // See if there is a [TranslatedFieldName] attribute applied to the property 
        // for the requested language
        var att = prop.AttributeProvider.GetAttributes(true)
                                        .OfType<TranslatedFieldNameAttribute>()
                                        .FirstOrDefault(a => a.Lang == Language);

        // if so, change the property name to the one from the attribute
        if (att != null)
        {
            prop.PropertyName = att.Name;
        }
        return prop;
    }
}

下面是如何使用解析器序列化:

public static string Serialize(object obj, Language lang)
{
    var settings = new JsonSerializerSettings
    {
        ContractResolver = new MultiLangResolver(lang),
        Formatting = Formatting.Indented
    };
    var json = JsonConvert.SerializeObject(obj, settings);
    return json;
}

另一个注意事项:您需要使用 [AttributeUsage] 属性标记您的 TranslatedFieldNameAttribute 类，这表明它可以用于属性并且可以多次应用(针对您要支持的每种不同语言一次):

[AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = true)]
public class TranslatedFieldNameAttribute : Attribute
{
    ...
}

工作演示:https://dotnetfiddle.net/lIQaJc