Spring Boot 2 - servlet not properly initialized

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/FilterChainManager.java の、issue で説明されている ServletExecutionFilter のチェックから始めます。その動作を GenericServlet#getServletInfo および CamelHttpTransportServlet の初期化と比較し、その後 Apache Camel の route シナリオを再現します。サーブレットが初期化され、POST /test エンドポイントが 404 ではなく 200 を返せば完了です。

Serverless Java Container version: 1.5.2

Implementations: Spring Boot 2

Framework version: Spring Boot 2.4.4

Frontend service: REST API using Apache Camel

Deployment method: Console

Scenario

Trying to test a simple /test REST endpoint served by Apache Camel.

Expected behavior

The /test should return a status code of 200 and the expected result.

Actual behavior

The endpoint returns a 404.

Steps to reproduce

Configure a simple Spring Boot 2 app with Apache Camel and define a route for it.

Example servlet config:

@Bean
ServletRegistrationBean<CamelHttpTransportServlet> servletRegistrationBean() {
	ServletRegistrationBean<CamelHttpTransportServlet> servlet =
			new ServletRegistrationBean<>(new CamelHttpTransportServlet(), "/*");
	servlet.setName("CamelServlet");
	return servlet;
}

Example route:

@Override
public void configure() throws Exception {
	rest("/")
		.produces("application/json")
		.post("test")
		.route()
		.bean(new Test())
		.endRest();
}

Full log output

2021-03-23T17:37:03.821+02:00	START RequestId: 6d29b2b7-ac66-4e9d-a199-32f15d7cf084 Version: $LATEST
2021-03-23T17:37:05.330+02:00	15:37:03.814 [main] INFO com.amazonaws.serverless.proxy.internal.LambdaContainerHandler - Starting Lambda Container Handler
2021-03-23T17:37:05.330+02:00	. ____ _ __ _ _
2021-03-23T17:37:05.331+02:00	/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
2021-03-23T17:37:05.331+02:00	( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
2021-03-23T17:37:05.331+02:00	\\/ ___)| |_)| | | | | || (_| | ) ) ) )
2021-03-23T17:37:05.331+02:00	' |____| .__|_| |_|_| |_\__, | / / / /
2021-03-23T17:37:05.344+02:00	=========|_|==============|___/=/_/_/_/
2021-03-23T17:37:05.723+02:00	:: Spring Boot ::
2021-03-23T17:37:05.724+02:00	2021-03-23 15:37:05.717 INFO 8 --- [ main] lambdainternal.AWSLambda : Starting AWSLambda using Java 11.0.9.1 on 169.254.168.21 with PID 8 (/var/runtime/lib/aws-lambda-java-runtime-0.2.0.jar started by sbx_user1051 in /var/task)
2021-03-23T17:37:08.325+02:00	2021-03-23 15:37:05.724 INFO 8 --- [ main] lambdainternal.AWSLambda : No active profile set, falling back to default profiles: default
2021-03-23T17:37:08.326+02:00	2021-03-23 15:37:08.325 INFO 8 --- [ main] c.a.s.p.i.servlet.AwsServletContext : Initializing Spring embedded WebApplicationContext
2021-03-23T17:37:09.349+02:00	2021-03-23 15:37:08.325 INFO 8 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 2458 ms
2021-03-23T17:37:11.867+02:00	2021-03-23 15:37:09.349 INFO 8 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2021-03-23T17:37:11.890+02:00	2021-03-23 15:37:11.867 INFO 8 --- [ main] c.s.b.CamelSpringBootApplicationListener : Starting CamelMainRunController to ensure the main thread keeps running
2021-03-23T17:37:11.890+02:00	2021-03-23 15:37:11.885 INFO 8 --- [ main] o.a.c.impl.engine.AbstractCamelContext : Routes startup summary (total:1 started:1)
2021-03-23T17:37:11.890+02:00	2021-03-23 15:37:11.890 INFO 8 --- [ main] o.a.c.impl.engine.AbstractCamelContext : Started route1 (rest://post:/:test)
2021-03-23T17:37:11.910+02:00	2021-03-23 15:37:11.890 INFO 8 --- [ main] o.a.c.impl.engine.AbstractCamelContext : Apache Camel 3.8.0 (camel-1) started in 707ms (build:82ms init:588ms start:37ms)
2021-03-23T17:37:11.931+02:00	2021-03-23 15:37:11.910 INFO 8 --- [ main] lambdainternal.AWSLambda : Started AWSLambda in 7.494 seconds (JVM running for 8.904)
2021-03-23T17:37:11.931+02:00	2021-03-23 15:37:11.930 INFO 8 --- [ main] c.a.s.p.i.servlet.AwsServletContext : Initializing Spring DispatcherServlet 'dispatcherServlet'
2021-03-23T17:37:11.932+02:00	2021-03-23 15:37:11.931 INFO 8 --- [ main] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2021-03-23T17:37:11.932+02:00	2021-03-23 15:37:11.932 INFO 8 --- [ main] o.s.web.servlet.DispatcherServlet : Completed initialization in 1 ms
2021-03-23T17:37:52.051+02:00	START RequestId: ee55b2df-c918-40e6-8bf0-fd98f7c76c70 Version: $LATEST
2021-03-23T17:37:52.305+02:00	2021-03-23 15:37:52.304 INFO 8 --- [ main] c.a.s.p.internal.LambdaContainerHandler : 127.0.0.1 null- null [09/04/2015:12:34:56Z] "POST /test HTTP/1.1" 404 - "-" "Custom User Agent String" combined
2021-03-23T17:37:52.306+02:00	END RequestId: ee55b2df-c918-40e6-8bf0-fd98f7c76c70
2021-03-23T17:37:52.306+02:00	REPORT RequestId: ee55b2df-c918-40e6-8bf0-fd98f7c76c70 Duration: 244.04 ms Billed Duration: 245 ms Memory Size: 512 MB Max Memory Used: 215 MB

Implementation details

The problem is caused by this check from ServletExecutionFilter.

By default, getServletInfo() returns an empty string, not null. The servlet used by Apache Camel, CamelHttpTransportServlet, does not override that method.

Because of this, ServletExecutionFilter thinks that the servlet is already initialized and it never calls its init() method. Consequently, the servlet resolve strategy is not initialized and the consumer for a specific request is never found.

Workaround

This can be worked around by overriding the getServletInfo() method:

public class CustomCamelHttpTransportServlet extends CamelHttpTransportServlet {

    @Override
    public String getServletInfo() {
        return null;
    }
}