AWS API Gateway Not Applying Mapping Template to DELETE request with empty body

Question

I have an API gateway endpoint setup that is hooked up to a Lambda function. I've configured a mapping template for the integration between my endpoint and my lambda function which looks like this:

{  
   "httpMethod":"$context.httpMethod",
   "body":"$input.json('$')",
   "queryParams":"$input.params().querystring",
   "headerParams":"$input.params().header",
   "headerParamNames":"$input.params().header.keySet()",
   "contentTypeValue":"$input.params().header.get('Content-Type')",
   "cognitoIdentityId":"$context.identity.cognitoIdentityId",
   "cognitoIdentityPoolId":"$context.identity.cognitoIdentityPoolId",
   "id":"$input.params('id')"
}

I've set up a /{id} path that supports GET and DELETE, both of which have the above mapping template configured.

When I make a GET request, I can see in my CloudWatch logs that the API gateway gets a null request body, processing my mapping, and sends a transformed request body to my lambda with all the expected information filled in.

Method request body before transformations: null
....
Endpoint request body after transformations: {"httpMethod":"GET","body":{},"queryParams":"{}","headerParams":"{....

When I make a DELETE request to the same resource, I see different behavior:

Method request body before transformations: null
....
Endpoint request body after transformations: null

So it seems like there is an issue with the DELETE portion of the API gateway in that it can't handle a null body (an empty body in a DELETE request should be valid as per the HTTP spec).

It all seems to work fine if I pass in an empty body to the DELETE (e.g. set the body to {}). However the API Gateway JavaScript SDK has no way that I can see to pass an empty JSON object; if I pass the generated delete method an empty body it just sets the body of the DELETE request to be null instead of the empty JSON object.

Ka Hou Ieong Ka Hou Ieong · Accepted Answer · 2016-03-13T04:03:31

Would you mind trying to pass in an empty body in string format ("{}")? You might try to use cURL to test your API. Sometime, you might have to pass in Content-Type in header.

I hope those can help you to debug your API.

AWS API Gateway Not Applying Mapping Template to DELETE request with empty body

1 Answers