REST API的XHTTP请求

Question

I have this API 我有这个API

[HttpGet("data")]
public dynamic GetData(){
    return context.DataTable.ToList();
}

I tried calling it on my Javascript using this snippet; 我尝试使用此代码段在Javascript上调用它；

function getData(){
    var xhttp = XMLHttpRequest();
    xhttp.open("GET", "api/myclass/data", true);
    xhttp.setRequestHeader("Content-type","application/json");
    xhttp.send();
    var resp = xhttp.responseText;
}

However, it only returns empty XMLHttpRequest . 但是，它仅返回空的XMLHttpRequest 。

I think what's wrong there is the URL. 我认为URL出了问题。 How I may able to call the API to my Javascript? 我怎么能调用我的Javascript API？

Answer 1

The request may take time to receive the response so you have to wait. 该请求可能需要一些时间才能收到响应，因此您必须等待。 Something like this. 这样的事情。

function getData(){
    var xhttp = XMLHttpRequest();
    xhttp.open("GET", "api/myclass/data", true); //the request is asynchronous
    xhttp.onreadystatechange = function(){
       if(this.readyState == 4 && this.state == 200){ //**this** is xhttp
          //data are received and ready to use
          var resp = this.responseText;
          //do whatever you want with resp but never try to **return** it from the function
       }
    }
    xhttp.setRequestHeader("Content-type","application/json");
    xhttp.send();
    //var resp = xhttp.responseText; //too early ;(
}

Answer 2

Since u have not cheked the response of ur answer, i susspect there is something wrong in ur backend. 由于您尚未检查您回答的答复，因此我怀疑您的后端出了点问题。 But, here is a sample of functional solution: 但是，这是功能解决方案的示例：

 <!DOCTYPE html> <html> <body> <h2>Using the XMLHttpRequest Object</h2> <div id="demo"> <button type="button" onclick="loadXMLDoc()">Change Content</button> </div> <script> function loadXMLDoc() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { console.log("Status is: "+this.status); if (this.readyState == 4 && this.status == 200) { document.getElementById("demo").innerHTML = this.responseText; } }; xhttp.open("GET", "xmlhttp_info.txt", true); xhttp.send(); } </script> </body> </html>

You van find more info here . 您可以在此处找到更多信息。 But in the line 但是在行

xhttp.open("GET", "api/myclass/data", true);

The second parameter is the address of a file in ur server. 第二个参数是ur服务器中文件的地址。 ru sure u have wrotten the correct format? 您确定您输入了正确的格式吗？ what is the extension of ur data file. ur data文件的扩展名是什么。

I guess, both backend and front end should be reconsidered. 我想，后端和前端都应该重新考虑。 To do it: 去做吧：

Try to send a reuqest using postman to backend 尝试使用邮递员发送请求到后端
in frontend check the status of response using my answer 在前端使用我的答案检查响应状态
To make sure make it async = false with 为了确保使其与async = false
xhttp.open("GET", "api/myclass/data", false); xhttp.open（“ GET”，“ api / myclass / data”，false）;

Therefore, there wouldn't be a delay as @Alex Kudryashev pointed 因此，@ Alex Kudryashev指出，不会有延迟

Solution: 解：

You need to first find the result of line 您需要先找到line的结果

console.log("Status is: "+this.status);

in ur browser's console. 在您的浏览器控制台中。

If u get the responseText as empty it may come because u have sent an empty string from backend,(we are not sure because u have not tested ur backend with postman) but it is crucial to know the status of response. 如果您将responseText设为空，则可能是因为您从后端发送了一个空字符串（我们不确定，因为您尚未使用邮递员测试您的后端）， 但是了解响应的状态至关重要。

REST API的XHTTP请求

问题描述

2 个解决方案

解决方案1
1 2017-11-12 20:27:15

解决方案2
1 已采纳 2017-11-12 20:36:36

REST API的XHTTP请求

问题描述

2 个解决方案

解决方案1 1 2017-11-12 20:27:15

解决方案2 1 已采纳 2017-11-12 20:36:36

解决方案1
1 2017-11-12 20:27:15

解决方案2
1 已采纳 2017-11-12 20:36:36