如何在Azure Functions中获取POST请求体的JSON字符串？

我用JavaScript客户端通过POST发送JSON数据，代码如下：

fetch("https://%$%$%%$.azurewebsites.net/api/JointPose?", {
    method: "POST",
    body: JSON.stringify({
        JointPose1: `${Joint1Pose}`,
        JointPose2: `${Joint2Pose}`,
        JointPose3: `${Joint3Pose}`,
        JointPose4: `${Joint4Pose}`,
        JointPose5: `${Joint5Pose}`,
        JointPose6: `${Joint6Pose}`,
        JointPose7: `${Joint7Pose}`
    }),
    headers: {
        "Content-Type": "application/json; charset=UTF-8",
    }
})
.then(response => {
    if (!response.ok) {
        throw new Error('Network response was not ok ' + response.statusText);
    }
    return response.json();
})
.then(data => {
    console.log('Success:', data);
})
.catch(error => {
    console.error('Error:', error);
});

尝试在Azure Functions的HTTP Trigger中获取请求体，初始代码如下：

public static async Task<IActionResult> Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = "JointPose")] HttpRequest req)
{
    MemoryStream ms = new MemoryStream();
    await req.Body.CopyToAsync(ms);
    string jointPoseData = ms.ToString();

    //using StreamReader reader = new(req.Body);
    //string bodyStr = await reader.ReadToEndAsync();
    //var jointPoseData = JsonConvert.DeserializeObject<JointPoseData>(bodyStr);

    return new OkObjectResult( new { Content = new StringContent(JsonConvert.SerializeObject(jointPoseData), Encoding.UTF8, "application/json") });
}

public class JointPoseData
{
    public string JointPose1 { get; set; }
    public string JointPose2 { get; set; }
    public string JointPose3 { get; set; }
    public string JointPose4 { get; set; }
    public string JointPose5 { get; set; }
    public string JointPose6 { get; set; }
    public string JointPose7 { get; set; }
}

打开URL后响应不符合预期，我期望输出类似JointPose1: 0.31, JointPose2: 0.32,.......。之后修改了函数代码：

[FunctionName("GetJointData")]
public static async Task<IActionResult> GetJointData(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = "JointPose")] HttpRequest req)
{
    using StreamReader reader = new(req.Body);
    string bodyStr = await reader.ReadToEndAsync();
    await serviceHubContext.Clients.All.SendAsync("jointPose", JsonConvert.SerializeObject(bodyStr));
    return new OkObjectResult(new
    {
        Content = JsonConvert.SerializeObject(bodyStr)
    });
}

但浏览器控制台显示Content为null，请求体数据无法正确获取，请问该怎么解决？

1. 最优实现：直接绑定模型读取请求体 #

Azure Functions支持直接将请求体反序列化为指定模型，无需手动处理流，这是最可靠的方式：

[FunctionName("GetJointData")]
public static async Task<IActionResult> GetJointData(
    [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "JointPose")] HttpRequest req,
    ILogger log)
{
    // 直接将请求体反序列化为JointPoseData模型
    var jointPoseData = await req.ReadFromJsonAsync<JointPoseData>();

    if (jointPoseData == null)
    {
        return new BadRequestObjectResult("无效的请求体格式");
    }

    // 发送数据到SignalR（保持你的业务逻辑）
    await serviceHubContext.Clients.All.SendAsync("jointPose", jointPoseData);

    // 返回符合预期格式的响应
    return new OkObjectResult(new
    {
        JointPose1 = jointPoseData.JointPose1,
        JointPose2 = jointPoseData.JointPose2,
        JointPose3 = jointPoseData.JointPose3,
        JointPose4 = jointPoseData.JointPose4,
        JointPose5 = jointPoseData.JointPose5,
        JointPose6 = jointPoseData.JointPose6,
        JointPose7 = jointPoseData.JointPose7
    });
}

public class JointPoseData
{
    public string JointPose1 { get; set; }
    public string JointPose2 { get; set; }
    public string JointPose3 { get; set; }
    public string JointPose4 { get; set; }
    public string JointPose5 { get; set; }
    public string JointPose6 { get; set; }
    public string JointPose7 { get; set; }
}

2. 原代码失败原因分析 #

• 初始代码中ms.ToString()不会读取内存流的内容，而是返回System.IO.MemoryStream字符串，完全不是请求体数据。
• 修改后的代码若返回null，大概率是请求体流读取后未重置位置，或客户端发送的JSON格式有误。手动读取流时必须重置位置：

  using StreamReader reader = new(req.Body);
  string bodyStr = await reader.ReadToEndAsync();
  req.Body.Position = 0; // 重置流位置，避免后续读取失败
  var jointPoseData = JsonConvert.DeserializeObject<JointPoseData>(bodyStr);
  

3. 额外检查项 #

• 确认客户端的Joint1Pose等变量有实际值，可在fetch前打印JSON.stringify(...)的结果验证。
• 确保HTTP Trigger只保留post方法（你不需要处理get请求，避免误触发）。

内容的提问来源于stack exchange，提问作者Astroboy