POST API in API Management renders 500 when the incoming body has header content-type:application/json

Question

POST API in API Management renders 500 when the incoming body has header content-type:application/json

Robert Heynen 50

I set up a POST API Operation in an API Management API. Anytime I try to submit a request with a Header Content-Type: application/json, I get a 500 Status code. I tried setting it as a representation and that did not work If I remove the header item, the call works without issue. The body is standard Json.

MuthuKumaranMurugaachari-MSFT 22,441 Reputation points Moderator

2023-04-14T15:29:20.0933333+00:00

Robert Heynen Thanks for posting your question in Microsoft Q&A. Based on your description in this thread as well as other thread, you got 500 error when submitting Post request via Postman and APIM portal test console works. It also works when you remove header Content-Type: application/json. If you can share correlation ID, timestamp for 500 error, it would help in reviewing the error.

I suspect how the request is being made in Postman might be the issue here. After you set the header in Postman, make sure to send body as raw with JSON (validate JSON using https://jsonlint.com/) and then check how HTTP POST request is generated using Code view https://learning.postman.com/docs/sending-requests/generate-code-snippets/#generating-code-snippets-in-postman.

If you still face the issue, share the sample request body JSON, and screenshot of how you are sending it via Postman after removing sensitive info (Correlation ID/timestamp also if possible).

Robert Heynen 50

@MuthuKumaranMurugaachari-MSFT In the tester within Azure APIM, if I add the header, it fails. It is only successful without the header. In Postman, as long as it is not in the header, it works with the exception of choosing "JSON" This works: User's image

This does not: User's image

The Representation is set as content-type: application/json User's image

Inside Azure API Test: Using: User's image

Yields error: User's image

Remove header: Success User's image

On a side note: In my policy, I am trying to read body and place into variables. The initial "RequestBody" variable was an attempt to deserialize the Body with plans to assign the variable values in the set-variable value, however I could not figure out how to access the "RequestBody" variable properly within the tags of the set-variable. I left the code in place with the intent to hopefully use it if needed...

<choose>
            <when condition="@(context.Request.Body != null)">
                <set-variable name="RequestBody" value="@(context.Request.Body.As<JObject>(preserveContent: true))" />
                <set-variable name="TaskName" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("TaskName"))" />
                <set-variable name="TaskLike" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("TaskLike"))" />
                <set-variable name="TaskList" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("TaskList"))" />
                <set-variable name="RequirementName" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("RequirementName"))" />
                <set-variable name="RequirementLike" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("RequirementLike"))" />
                <set-variable name="RequirementList" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("RequirementList"))" />
                <set-variable name="ItemName" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("ItemName"))" />
                <set-variable name="ItemLike" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("ItemLike"))" />
                <set-variable name="ItemList" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("ItemList"))" />
                <set-variable name="SupplierName" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("SupplierName"))" />
                <set-variable name="SupplierLike" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("SupplierLike"))" />
                <set-variable name="SupplierList" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("SupplierList"))" />
                <set-query-parameter name="TaskName" exists-action="append">
                    <value>@((string)context.Variables["TaskName"])</value>
                </set-query-parameter>
                <set-query-parameter name="TaskLike" exists-action="append">
                    <value>@((string)context.Variables["TaskLike"])</value>
                </set-query-parameter>
                <set-query-parameter name="TaskList" exists-action="append">
                    <value>@((string)context.Variables["TaskList"])</value>
                </set-query-parameter>
                <set-query-parameter name="RequirementName" exists-action="append">
                    <value>@((string)context.Variables["RequirementName"])</value>
                </set-query-parameter>
                <set-query-parameter name="RequirementLike" exists-action="append">
                    <value>@((string)context.Variables["RequirementLike"])</value>
                </set-query-parameter>
                <set-query-parameter name="RequirementList" exists-action="append">
                    <value>@((string)context.Variables["RequirementList"])</value>
                </set-query-parameter>
                <set-query-parameter name="ItemName" exists-action="append">
                    <value>@((string)context.Variables["ItemName"])</value>
                </set-query-parameter>
                <set-query-parameter name="ItemLike" exists-action="append">
                    <value>@((string)context.Variables["ItemLike"])</value>
                </set-query-parameter>
                <set-query-parameter name="ItemList" exists-action="append">
                    <value>@((string)context.Variables["ItemList"])</value>
                </set-query-parameter>
                <set-query-parameter name="SupplierName" exists-action="append">
                    <value>@((string)context.Variables["SupplierName"])</value>
                </set-query-parameter>
                <set-query-parameter name="SupplierLike" exists-action="append">
                    <value>@((string)context.Variables["SupplierLike"])</value>
                </set-query-parameter>
                <set-query-parameter name="SupplierList" exists-action="append">
                    <value>@((string)context.Variables["SupplierList"])</value>
                </set-query-parameter>
            </when>
        </choose>

Robert Heynen 50

Hi: The setting you describe above is the only one that fails. If I use other Postman raw settings (text, Javascript, HTML, XML) there is no issue and the API responds correctly. This is also the case in the Azure APIM API Test - when I include a header Content-Type:application/json It fails. When I remove the header, it works without issue. I have a Representation content-type:application/json set on the API, but even without this, it fails as stated. I have Azure applicationinsights set up but am not seeing the rejection in the exception log as I believe it may be being rejected before it gets to the policy for whatever reason? In my inbound policy, I am trying to see if there is a body, and if so, I am setting variables that can be used in a querystring on the backend URL It is unclear if this is causing the problem as the system is not trapping any exceptions when it fails. The sample code in the inbound policy is this:

<choose>
            <when condition="@(context.Request.Body != null)">
                <set-variable name="RequestBody" value="@(context.Request.Body.As<JObject>(preserveContent: true))" />
                <set-variable name="TaskName" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("TaskName"))" />
                <set-variable name="TaskLike" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("TaskLike"))" />
                <set-variable name="TaskList" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("TaskList"))" />
                <set-variable name="RequirementName" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("RequirementName"))" />
                <set-variable name="RequirementLike" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("RequirementLike"))" />
                <set-variable name="RequirementList" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("RequirementList"))" />
                <set-variable name="ItemName" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("ItemName"))" />
                <set-variable name="ItemLike" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("ItemLike"))" />
                <set-variable name="ItemList" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("ItemList"))" />
                <set-variable name="SupplierName" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("SupplierName"))" />
                <set-variable name="SupplierLike" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("SupplierLike"))" />
                <set-variable name="SupplierList" value="@((string)context.Request.Body.As<JObject>(preserveContent: true).SelectToken("SupplierList"))" />
                <set-query-parameter name="TaskName" exists-action="append">
                    <value>@((string)context.Variables["TaskName"])</value>
                </set-query-parameter>
                <set-query-parameter name="TaskLike" exists-action="append">
                    <value>@((string)context.Variables["TaskLike"])</value>
                </set-query-parameter>
                <set-query-parameter name="TaskList" exists-action="append">
                    <value>@((string)context.Variables["TaskList"])</value>
                </set-query-parameter>
                <set-query-parameter name="RequirementName" exists-action="append">
                    <value>@((string)context.Variables["RequirementName"])</value>
                </set-query-parameter>
                <set-query-parameter name="RequirementLike" exists-action="append">
                    <value>@((string)context.Variables["RequirementLike"])</value>
                </set-query-parameter>
                <set-query-parameter name="RequirementList" exists-action="append">
                    <value>@((string)context.Variables["RequirementList"])</value>
                </set-query-parameter>
                <set-query-parameter name="ItemName" exists-action="append">
                    <value>@((string)context.Variables["ItemName"])</value>
                </set-query-parameter>
                <set-query-parameter name="ItemLike" exists-action="append">
                    <value>@((string)context.Variables["ItemLike"])</value>
                </set-query-parameter>
                <set-query-parameter name="ItemList" exists-action="append">
                    <value>@((string)context.Variables["ItemList"])</value>
                </set-query-parameter>
                <set-query-parameter name="SupplierName" exists-action="append">
                    <value>@((string)context.Variables["SupplierName"])</value>
                </set-query-parameter>
                <set-query-parameter name="SupplierLike" exists-action="append">
                    <value>@((string)context.Variables["SupplierLike"])</value>
                </set-query-parameter>
                <set-query-parameter name="SupplierList" exists-action="append">
                    <value>@((string)context.Variables["SupplierList"])</value>
                </set-query-parameter>
            </when>
        </choose>

If I try to send without a body, with content-type set to application/json, still fails.
I tried to set the body into a variable with the hopes that I could use that variable in the subsequent calls to set-variables....however I have not yet been able to get that to work. I left the code in to make sure it wasn't breaking anything.

MuthuKumaranMurugaachari-MSFT 22,441 Reputation points Moderator

2023-04-14T18:48:04.4433333+00:00

Thanks for sharing the additional details. Based on screenshot, success response has content-type returned as text/html whereas failed one showed as application/javascript. Have you tried Trace a call and see which section it failed (like backend)? If it fails in Inbound section, then review the error message where it is failing and troubleshoot accordingly. For further assistance, I might have to review trace and send an email to azcommunity@microsoft.com referencing this thread with your subscription ID, details and subject as "Attn: Muthu". I will assist you with next steps.

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MuthuKumaranMurugaachari-MSFT 22,441 Reputation points Moderator

2023-04-14T15:29:20.0933333+00:00

Robert Heynen Thanks for posting your question in Microsoft Q&A. Based on your description in this thread as well as other thread, you got 500 error when submitting Post request via Postman and APIM portal test console works. It also works when you remove header Content-Type: application/json. If you can share correlation ID, timestamp for 500 error, it would help in reviewing the error.

I suspect how the request is being made in Postman might be the issue here. After you set the header in Postman, make sure to send body as raw with JSON (validate JSON using https://jsonlint.com/) and then check how HTTP POST request is generated using Code view https://learning.postman.com/docs/sending-requests/generate-code-snippets/#generating-code-snippets-in-postman.

If you still face the issue, share the sample request body JSON, and screenshot of how you are sending it via Postman after removing sensitive info (Correlation ID/timestamp also if possible).
MuthuKumaranMurugaachari-MSFT 22,441 Reputation points Moderator

2023-04-14T18:48:04.4433333+00:00

Thanks for sharing the additional details. Based on screenshot, success response has content-type returned as text/html whereas failed one showed as application/javascript. Have you tried Trace a call and see which section it failed (like backend)? If it fails in Inbound section, then review the error message where it is failing and troubleshoot accordingly. For further assistance, I might have to review trace and send an email to azcommunity@microsoft.com referencing this thread with your subscription ID, details and subject as "Attn: Muthu". I will assist you with next steps.

Answer 1

MuthuKumaranMurugaachari-MSFT 22,441 Moderator

Robert Heynen Thanks again for sharing the details.

Update for the community:

Robert captured a trace using Trace a call and found that APIM generated a request with query parameters to backend, but backend API was rejecting the request when header content-type was set as application/json . He also validated the same via Postman as well. So, he overrides header value by setting content-type as text/plain in APIM policy and it worked. I hope this helps with your questions and let us know if you have any other.

Robert Heynen 50 Reputation points

2023-04-15T00:25:36.6033333+00:00

TY Muthu! Great response time!

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POST API in API Management renders 500 when the incoming body has header content-type:application/json

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