Differences

This shows you the differences between two versions of the page.

--- cloud:aws:apigateway [2021/04/29 13:39] – [Java Lambda behind the API gateway] skipidar
+++ cloud:aws:apigateway [2023/11/01 07:13] (current) – ↷ Page moved from business_process_management:camunda:cloud:aws:apigateway to cloud:aws:apigateway skipidar
@@ Line 22: / Line 22: @@
 ===== Lambda behind the API gateway =====
+https://docs.aws.amazon.com/lambda/latest/dg/API_Invoke.html#API_Invoke_RequestSyntax
+====  Fallpit: Invoke Lambda POST ====
+The API must invoke the backend Lambda function using the **HTTP method POST**.
+https://docs.aws.amazon.com/lambda/latest/dg/API_Invoke.html#API_Invoke_RequestSyntax
+Otherwise you will get
+  * a 500 error on the Gateway
+  * a 403 error on the Lambda, behind the Gateway https://aws.amazon.com/premiumsupport/knowledge-center/api-gateway-lambda-template-invoke-error/
 ==== Debugging ====
-If a Lambda does not behave as intended - use the Test button.
+If a Lambda does not behave as intended - use the **Test button**.
 ONe can see much more exceptions in there.
@@ Line 35: / Line 47: @@
 https://www.baeldung.com/aws-lambda-api-gateway
+Example: https://github.com/skipidar/aws-javalambda-behind-apigateway
 === Java signature ===
@@ Line 140: / Line 154: @@
-=== Return structure ===
+=== Return format of Lambda ===
 Lambdas needs to return JSON, to be capable to be used from the gateway.
+https://docs.amazonaws.cn/en_us/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html#api-gateway-simple-proxy-for-lambda-output-format
 <sxh java>
@@ Line 161: / Line 176: @@
         writer.close();
 </sxh>
+====  Use Lambda Proxy integration ====
+When a client submits an API request, API Gateway passes to the integrated Lambda function the raw request as-is:
+That means, that the option `Use Lambda Proxy integration`
+  * **deactivates** the **"Mapping Templates"**
+  * https://aws.amazon.com/premiumsupport/knowledge-center/custom-headers-api-gateway-lambda/
+{{https://s3.eu-central-1.amazonaws.com/alf-digital-wiki-pics/sharex/vC2XDM5VDx.png}}
+This is the most powerful integration:
+  - **\{{proxy}}** sends all resources - to the Lambda
+  - **ANY** - accepts all methods
+https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-set-up-simple-proxy.html#api-gateway-proxy-resource%3Ficmpid=docs_apigateway_console
+{{https://s3.eu-central-1.amazonaws.com/alf-digital-wiki-pics/sharex/M51LDfQis7.png}}
+  * <color #ed1c24>Still the API must be deployed to a "stage"</color>
+  * <color #ed1c24>Minimum one resource must be present after the stage - or you will get "{"message":"Missing Authentication Token"}"</color>
+After that the lambda reacts on
+<code>
+curl -X POST https://s5oi8r61hk.execute-api.eu-west-1.amazonaws.com/stage/someresourcehere/1/2/bla/blub/enigma21/
+curl -X GET https://s5oi8r61hk.execute-api.eu-west-1.amazonaws.com/stage/2/
+</code>
+==== Mapping Templates ====
+Can be used to add custom headers
+from the API gateway
+to the Lambda
+https://aws.amazon.com/premiumsupport/knowledge-center/custom-headers-api-gateway-lambda/
+==== Token Exchange =====
+The token exchange is possible with 2 pieces:
+  * obtain a new token at the lambda authorizer
+  * set the header via VLT as in
+https://stackoverflow.com/questions/40585016/is-it-possible-to-add-an-http-header-from-aws-custom-auth-on-api-gateway
+===== A Detailed Overview of AWS API Gateway =====
+An overview of the API gateway functions.
+https://www.alexdebrie.com/posts/api-gateway-elements/
+{{https://s3.eu-central-1.amazonaws.com/alf-digital-wiki-pics/sharex/44ovAxhCbW.png}}
+{{https://s3.eu-central-1.amazonaws.com/alf-digital-wiki-pics/sharex/QuF6kGfybF.png}}