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在action方法内部引发httpResponseException时处理httpResponseMessage及其内容

idisposable asp.net-web-api asp.net c#

3

Enrico Massone · 技术社区 · 6 年前

我问题的来源是以下代码,它是包含在 Microsoft documentation 对于ASP.NET Web API中的异常处理:

var resp = new HttpResponseMessage(HttpStatusCode.NotFound)
{
    Content = new StringContent(string.Format("No product with ID = {0}", id)),
    ReasonPhrase = "Product ID Not Found"
};
throw new HttpResponseException(resp);

两个 HttpResponseMessage 和 StringContent 实施 IDisposable 接口,但上述代码中没有人调用方法 IDisposable.Dispose .
这是个问题吗?不处置这些物品会有什么副作用吗?

根据 this article 可能的解决方案是将上述代码更改为以下代码:

var content = new StringContent(string.Format("No product with ID = {0}", id));
var resp = new HttpResponseMessage(HttpStatusCode.NotFound)
{
    Content = content,
    ReasonPhrase = "Product ID Not Found"
};

this.Request.RegisterForDispose(content);
this.Request.RegisterForDispose(resp);

throw new HttpResponseException(resp);

这真的有必要吗,还是可以避免(根据Microsoft文档中显示的内容)?

2 回复 | 直到 6 年前

1

Evk 6 年前

响应由包装 HttpResponseException 将由ASP.NET框架处理,就像从操作返回的任何其他响应一样。您可以通过创建虚拟响应消息来轻松测试这一点:

class DummyResponse : HttpResponseMessage {
    public DummyResponse(HttpStatusCode statusCode) : base(statusCode) {
    }

    protected override void Dispose(bool disposing) {
        Console.WriteLine("dispose called");
        base.Dispose(disposing);
    }
}

然后扔 HTT响应例外 并将断点放入 Dispose 覆盖。你会注意到的 处置 调用,如果查看调用堆栈,您将看到 HttpControllerHandler 负责执行此操作(在ASP.NET Web API控制器中)。

请注意,此异常被捕获 ApiControllerActionInvoker ,负责调用API控制器操作的类。然后它就抓住了 yourException.Response 并通过管道将其向前推,因此抛出这个异常与从API控制器操作返回相应的响应没有什么不同。很明显,我认为框架在处理完这些响应之后,会处理掉它们。否则它的设计会很差。

所以,不要把代码和那些 RegisterForDispose 让框架为您处理这个问题。

2

3

Robert Harvey 6 年前

检查 Microsoft Source for HttpResponseMessage.CS :

protected virtual void Dispose(bool disposing)
{
    // The reason for this type to implement IDisposable is that it contains instances of 
    // types that implement IDisposable (content). 
    if (disposing && !_disposed)
    {
        _disposed = true;
        if (_content != null)
        {
            _content.Dispose();
        }
    }
}

content 是httpcontent类型。检查 Microsoft Source for HttpContent.cs :

protected override void Dispose(bool disposing)
{
    Debug.Assert(_buffer != null);

    ArrayPool<byte>.Shared.Return(_buffer);
    _buffer = null;

    base.Dispose(disposing);
}

的评论 ArrayPool 说:

/// Renting and returning buffers with an <see cref="ArrayPool{T}"/> can increase performance
/// in situations where arrays are created and destroyed frequently, resulting in significant
/// memory pressure on the garbage collector.

检查arrayPool的来源会得到这个可爱的宝石:

    /// <summary>
    /// Retrieves a shared <see cref="ArrayPool{T}"/> instance.
    /// </summary>
    /// <remarks>
    /// The shared pool provides a default implementation of <see cref="ArrayPool{T}"/>
    /// that's intended for general applicability.  It maintains arrays of multiple sizes, and 
    /// may hand back a larger array than was actually requested, but will never hand back a smaller 
    /// array than was requested. Renting a buffer from it with <see cref="Rent"/> will result in an 
    /// existing buffer being taken from the pool if an appropriate buffer is available or in a new 
    /// buffer being allocated if one is not available.
    /// </remarks>
    public static ArrayPool<T> Shared
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        get { return Volatile.Read(ref s_sharedInstance) ?? EnsureSharedCreated(); }
    }

ArrayPool 不使用 WeakReference 或任何类似机制,以确保正确处置。如果你从 ArrayPool.Shared ,您必须返回它,否则将导致内存泄漏。

所以是的,我要说尊重 IDisposable 在这里很重要。