Cors Issues Accessing API

[pradeepperi]

Hi,

I am facing issues in accessing an api from my PCF Control (calling the api from componentDidMount method). I am getting the below error message while calling the api. Surprisingly , this is not the error that occurs each time. Most of the time api call succeeeds and gets the data, but 20% of the api calls are failing with this error from the control. we are allowing ".dynamics.com" to send requests. Please note that this problem does not occur all the times, but pretty randomly some times ~20% times. 

Access to fetch at '*********' from origin '******' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

[HemantG]

Is it specific to one browser ? I dont think this is realted to react as such but can be quick validated using a standard control . Can you check the browser console logs and network traffic to see if this is missing header and any difference in the failed and sucessful calls ? 

Here are some other pointers which might help.

Browser caching -  https://stackoverflow.com/questions/21104810/what-could-explain-the-browser-intermittently-not-loadi...

https://stackoverflow.com/questions/51128176/reactjs-api-data-fetching-cors-error

Chrome extension can be used for testing CORS - https://chrome.google.com/webstore/detail/allow-control-allow-origi/nlfbmbojpeacfghkpbjhddihlkkiljbi

hemant

[pradeepperi]

Thanks for your help Hemant, it was not an issue with React i solved the problem at api. Many Thanks!

---

@HemantG wrote:

Is it specific to one browser ? I dont think this is realted to react as such but can be quick validated using a standard control . Can you check the browser console logs and network traffic to see if this is missing header and any difference in the failed and sucessful calls ? 

Here are some other pointers which might help.

Browser caching -  https://stackoverflow.com/questions/21104810/what-could-explain-the-browser-intermittently-not-loadi...

https://stackoverflow.com/questions/51128176/reactjs-api-data-fetching-cors-error

Chrome extension can be used for testing CORS - https://chrome.google.com/webstore/detail/allow-control-allow-origi/nlfbmbojpeacfghkpbjhddihlkkiljbi

hemant

---

[HemantG]

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@pradeepperi wrote:

Thanks for your help Hemant, it was not an issue with React i solved the problem at api. Many Thanks!

---

@HemantG wrote:

Is it specific to one browser ? I dont think this is realted to react as such but can be quick validated using a standard control . Can you check the browser console logs and network traffic to see if this is missing header and any difference in the failed and sucessful calls ? 

Here are some other pointers which might help.

Browser caching -  https://stackoverflow.com/questions/21104810/what-could-explain-the-browser-intermittently-not-loadi...

https://stackoverflow.com/questions/51128176/reactjs-api-data-fetching-cors-error

Chrome extension can be used for testing CORS - https://chrome.google.com/webstore/detail/allow-control-allow-origi/nlfbmbojpeacfghkpbjhddihlkkiljbi

hemant

---

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@pradeepperi , do you mind sharing some details on solution and sample code snippet? Might help someone in future 🙂

hemant 

[Mili12]

@pradeepperi- Can you please share what was done to resolve this issue? I am facing a similar issue too.  Thanks in advance!

-Mili

[HemantG]

are you able to use the API just using simple html from different domain ? That setup can be used for debugging. I had pointed some resources in the thread which might be useful 

Hemant

[pradeepperi]

Thanks Hemant, i have restructured the api calling functionality to a custom action and calling the custom action from the control. So, it works correctly now. Thanks again!

[Mili12]

Pradeep, 

Which library have you used to invoke the custom action from type script?  The standard way to invoke from JS is to use execute.online function but in type script what is the counterpart?  I failed when I tried to use the xrm-webapi-client library. Can you share the code at a high level for reference?  I am sure many others too have similar issue.

-Mili

[ben-thompson]

This should show you what you need to do 

refreshLicense(product:string) : Promise<Xrm.RetrieveMultipleResult>{
        'use strict';	
		var clientUrl =(<any>this.context).page.getClientUrl();
		var thisRef=this;
		var req = new XMLHttpRequest();
		req.open("POST", clientUrl + "/api/data/v9.1/hdn_ValidateLicense", true);
		req.setRequestHeader("OData-MaxVersion", "4.0");
		req.setRequestHeader("OData-Version", "4.0");
		req.setRequestHeader("Accept", "application/json");
		req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
		req.onreadystatechange = function() {
			if (this.readyState === 4) {
				req.onreadystatechange = null;
				
				if (this.status === 200) {
					return this.response;

					
				} else {

					return Promise.reject(error);
				}
			}
		};
		var body=	"{'ProductName': '"+product+"'}";
		req.send(body);
	}

[a33ik]

I found an alternative way of calling messages using execute of standard WebApi wrapper. Execute method is not exposed but it is available. Here is how I use it:

const youractionrequest = {
	getMetadata: function() {
	return {
		boundParameter: null,
		parameterTypes: {},
		operationType: 0,
		operationName: "nameofyouractionhere"
		};
	}
};

(<any>context.webAPI).execute(youractionrequest).then((result: any) => {
		result.json().then((response: any) => {
			//use your parsed response here
		});
	}, 
	(e: any) => {
		//Handle reject here
	});