yesod - 获取 POST“Content-type: application/json”的请求正文
使用 yesod 0.8.0，我尝试从此示例请求中检索发布消息的正文：
curl -v -H "Accept: application/json" -H "Content-Type: application/json" -X POST -d '{"name":"oscar"}' http://localhost:3000/user/xyz
在我的处理程序中，我看到它的唯一方法是使用
(pp, files) <- runRequestBody
But 由于内容类型而失败。还有其他函数可以做到这一点吗？
Using yesod 0.8.0, I'm trying to retrieve the body of a post message from this example request:
curl -v -H "Accept: application/json" -H "Content-Type: application/json" -X POST -d '{"name":"oscar"}' http://localhost:3000/user/xyz
in my handler the only way I see it is to use
(pp, files) <- runRequestBody
But this fails because of the content type. Is there another function to do this?
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其他答案似乎很旧，并且是在添加下面使用的功能之前。
The other answers seem to be pretty old and from before the functions used below were added.
这是现在的操作方法。对于未来的版本，我希望添加一些方便的包装；感谢对此的意见。
解释：每个处理程序函数都位于 GGHandler sub master (Iteratee ByteString IO) monad 中。这相当复杂，但它的意思是它是一个围绕接收 ByteString 流的 Iteratee 的 Handler monad 转换器。该字节字符串流是原始请求正文。
因此，我们需要使用枚举器的消费函数来获取整个字节字符串流并将它们存储为列表。我们需要使用 lift 函数将其提升到内部 monad（Iteratee）。然后，L.fromChunks 将严格的 ByteString 列表转换为惰性 ByteString，您可以使用任何任意 JSON 库对其进行解析（Yesod 在 aeson 上进行标准化）。
我的猜测是，我可以提供的最方便的函数是 parseRequestJson :: GGHandler sm (Iteratee ByteString IO) (Maybe Data.Aeson.Value)。我可以在 yesod-json 的点发布中添加这一点。
Here's how to do it now. For future releases, I'm hoping to add some convenience wrappers; input on this is appreciated.
The explanation: Each handler function lives in a
GGHandler sub master (Iteratee ByteString IO)monad. That's fairly complicated, but what it means is that it's a Handler monad transformer around an Iteratee that receives a stream of ByteStrings. That stream of ByteStrings is the raw request body.So we need to use enumerator's consume function to take that entire stream of ByteStrings and store them as a list. And we need to use the lift function to lift this to the inner monad (the Iteratee). L.fromChunks then converts from a list of strict ByteStrings to a lazy ByteString, which you can parse with any arbitrary JSON library (Yesod is standardizing on aeson).
My guess is that the most convenient function I could provide would be
parseRequestJson :: GGHandler s m (Iteratee ByteString IO) (Maybe Data.Aeson.Value). I can add that in a point release of yesod-json.在 Yesod 1.0+（也许更早，不确定）中，以下内容似乎有效：
In Yesod 1.0+ (and maybe earlier, not sure), the following appears to work: