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cloud:aws:apigateway [2023/11/01 07:13] – removed - external edit (Unknown date) 127.0.0.1cloud:aws:apigateway [2023/11/01 07:13] (current) – ↷ Page moved from business_process_management:camunda:cloud:aws:apigateway to cloud:aws:apigateway skipidar
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 +===== API Gateway =====
 +
 +
 +Real-time applications with API Gateway WebSockets and AWS Lambda
 +https://serverless.com/blog/api-gateway-websockets-support/
 +
 +
 +
 +Calling API gateways via generated SDKs
 +https://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-generate-sdk-javascript.html
 +
 +
 +
 +
 +
 +
 +===== REST API vs HTTP API =====
 +https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-vs-rest.html
 +
 +REST-Api has more functionality regarding inspection.
 +
 +
 +===== 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**. 
 +ONe can see much more exceptions in there.
 +
 +{{https://s3.eu-central-1.amazonaws.com/alf-digital-wiki-pics/sharex/gDyYDmOwNf.png}}
 +
 +{{https://s3.eu-central-1.amazonaws.com/alf-digital-wiki-pics/sharex/0SwqtTPgvP.png}}
 +
 +==== Java Lambda behind the API gateway ====
 +https://www.baeldung.com/aws-lambda-api-gateway
 +
 +
 +Example: https://github.com/skipidar/aws-javalambda-behind-apigateway
 +
 +=== Java signature ===
 +There are obligations on the Java-Lambda signature, when executed behind Gateway.
 +
 +It is important to have 
 +  * InputStream inputStream, 
 +  * OutputStream outputStream
 +
 +in the interface of the Lambda - otherwise the API Gateway will throw exceptions
 +
 +
 +Dependencies
 +<code>
 +
 +dependencies {
 +    implementation 'com.amazonaws:aws-lambda-java-core:1.2.1'
 +    implementation 'com.google.code.gson:gson:2.8.6'
 +    testImplementation 'org.apache.logging.log4j:log4j-api:2.13.0'
 +    testImplementation 'org.apache.logging.log4j:log4j-core:2.13.0'
 +    testImplementation 'org.apache.logging.log4j:log4j-slf4j18-impl:2.13.0'
 +    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.6.0'
 +    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.6.0'
 +
 +    compile 'com.googlecode.json-simple:json-simple:1.1.1'
 +}
 +</code>
 +
 +
 +
 +<sxh java>
 +package example;
 +
 +import com.amazonaws.services.lambda.runtime.Context;
 +import com.amazonaws.services.lambda.runtime.LambdaLogger;
 +import com.amazonaws.services.lambda.runtime.RequestStreamHandler;
 +import com.google.gson.Gson;
 +import com.google.gson.GsonBuilder;
 +import com.nimbusds.oauth2.sdk.TokenRequest;
 +import no.nav.security.mock.oauth2.MockOAuth2Server;
 +import no.nav.security.mock.oauth2.token.OAuth2TokenCallback;
 +import org.jetbrains.annotations.NotNull;
 +import org.jetbrains.annotations.Nullable;
 +import org.json.simple.JSONObject;
 +import org.json.simple.parser.JSONParser;
 +import org.json.simple.parser.ParseException;
 +
 +import java.io.*;
 +import java.util.Arrays;
 +import java.util.Collections;
 +import java.util.List;
 +import java.util.Map;
 +import java.util.concurrent.TimeUnit;
 +
 +
 +// Handler value: example.Handler
 +public class Handler implements RequestStreamHandler {
 +
 +    /**
 +     * The handleRequest interface, as below,
 +     * with InputStream, OutputStream
 +     *
 +     * when Lambda is used with the API Gateway - is required.
 +     *
 +     * https://www.baeldung.com/aws-lambda-api-gateway
 +     *
 +     * @param inputStream
 +     * @param outputStream
 +     * @param context
 +     * @throws IOException
 +     */
 +    public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) throws IOException {
 +        JSONParser parser = new JSONParser();
 +        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
 +        JSONObject responseJson = new JSONObject();
 +
 +        JSONObject event = null;
 +        try {
 +            event = (JSONObject) parser.parse(reader);
 +
 +            handleEvent(event,
 +                    responseJson,
 +                    inputStream,
 +                    outputStream,
 +                    context);
 +
 +        } catch (ParseException e) {
 +            responseJson.put("statusCode", 400);
 +            responseJson.put("exception", e);
 +        }
 +        
 +        // example response
 +        JSONObject obj2 = new JSONObject();
 +        obj2.put("Content-Type", "application/json");
 +        responseJson.put("statusCode", 200);
 +        responseJson.put("headers", obj2);
 +        responseJson.put("body", "hello world");
 +
 +        // writing the result into the
 +        OutputStreamWriter writer = new OutputStreamWriter(outputStream, "UTF-8");
 +        writer.write(responseJson.toString());
 +        writer.close();
 +    }
 +</sxh>
 +
 +
 +=== 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>
 +
 +// Handler value: example.Handler
 +public class Handler implements RequestStreamHandler {
 +    public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) throws IOException {
 +        // example response
 +        JSONObject obj2 = new JSONObject();
 +        obj2.put("Content-Type", "application/json");
 +        responseJson.put("statusCode", 200);
 +        responseJson.put("headers", obj2);
 +        responseJson.put("body", "hello world");
 +
 +        // writing the result into the
 +        OutputStreamWriter writer = new OutputStreamWriter(outputStream, "UTF-8");
 +        writer.write(responseJson.toString());
 +        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}}
 +