WebAPI 暂时从 OnActionExecuted 覆盖 JsonFormatter

Question

我正在尝试创建一个属性，该属性将以不同方式从操作return序列化数据

public override void OnActionExecuted(HttpActionExecutedContext filterContext)
{
    var content = (filterContext.Response.Content as ObjectContent);

    if (content == null)
    {
        return;
    }

    if (content.ObjectType.IsGenericType 
        && content.ObjectType.GetGenericTypeDefinition() == typeof (Page<>))
    {
        var pageObject = (content.Value as IPage);
        var jsonFormatterRule = new JsonFormatterRule();
        var pageJson = JsonConvert.SerializeObject(pageObject.ItemsArray, 
                                                jsonFormatterRule.GetPascalCasedSettings());

       //How do I set the content that \/ doesn't compile?
       //filterContext.Response.Content = pageJson;
   }
}

这是 JsonFormatterRules，任何人都想看。

public JsonSerializerSettings GetDefaultSettings()
{
    var settings = new JsonSerializerSettings()
    {
        Formatting = Formatting.Indented,
        ContractResolver = new CamelCasePropertyNamesContractResolver(),
        DateTimeZoneHandling = DateTimeZoneHandling.RoundtripKind,
    };

    settings.Converters.AddRange(defaultConfiguredConverters);
    return settings;
}

public JsonSerializerSettings GetPascalCasedSettings()
{
    var settings = this.GetDefaultSettings();
    settings.ContractResolver = new DefaultContractResolver();

    return settings;
}

如何设置动作执行时的内容？我无法将默认序列化器全局更改为 DefaultContract，因为它可能会出现线程问题。

此外，我不希望创建新的响应并从旧响应中复制 Headers，这似乎太过分了。

Answer 1

实现此目的的一种方法是定义自定义格式化程序。

首先，定义您的属性：

[AttributeUsage(AttributeTargets.Class)]
public sealed class SpecialSerializeAttribute : Attribute
{
}

现在创建一个将找到属性的格式化程序：

public class SpecialSerializeFormatter : MediaTypeFormatter
{
    public SpecialSerializeFormatter()
    {
        //You can add any other supported types here.
        this.SupportedMediaTypes.Add(new MediaTypeHeaderValue("application/json"));
    }

    public override bool CanReadType(Type type)
    {
        //you can just return false if you don't want to read any differently than your default way
        //if you return true here, you should override the ReadFromStreamAsync method to do custom deserialize
        return type.IsDefined(typeof(SpecialSerializeAttribute), true));
    }

    public override bool CanWriteType(Type type)
    {
        return type.IsDefined(typeof(SpecialSerializeAttribute), true));
    }

    public override async Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content,
        TransportContext transportContext)
    {

        //value will be your object that you want to serialize

        //add any custom serialize settings here
        var json = JsonConvert.SerializeObject(value);

        //Use the right encoding for your application here
        var byteArray = Encoding.UTF8.GetBytes(json);
        await writeStream.WriteAsync(byteArray, 0, byteArray.Length);
    }
}

在你注册格式化程序WebApiConfig.cs

您也可以直接为每个类型构建一个格式化程序，然后您不必执行属性。只需更改您的 CanRead 和 CanWrite 方法。我发现基于这些直接类型会得到更好的结果，因为它不是一个通用的格式化程序，您可能需要根据类型应用自定义逻辑，但上面的答案应该能满足您的需求。

Answer 2

如果有人想知道，Response Content 是一个 HTTPContent，它继承自 ByteArrayContent。因此，如果您已经将 JSON 序列化，您所要做的就是将其放入字节数组中。

filterContext.ActionContext.Response.Content = new ByteArrayContent(Encoding.ASCII.GetBytes(pageJson));

WebAPI 暂时从 OnActionExecuted 覆盖 JsonFormatter

WebAPI Temporarily Override JsonFormatter from OnActionExecuted

c#

action-filter

onactionexecuted

asp.net-web-api