java: Can't satisfy List<Object> parameters in Cfn*Props.Builder methods

[mbulman]

When creating a Cfn*Props builder, methods that accept a List<Object> parameter don't seem to behave properly (or I'm doing something wrong).

As an example, when setting up an API Gateway Usage Plan, I want the resulting template to look something like:

UsagePlan:
    Type: AWS::ApiGateway::UsagePlan
    Properties:
        UsagePlanName: MyUsagePlan
        ApiStages:
            - Stage: Foo
              ApiId: Bar

The property I have trouble with is ApiStages, which is a list of objects (Maps, specifically). My first attempt was the following Java code:

Map<String, String> stage = ImmutableMap.of(
        "ApiId", "Foo"
        "Stage", "Bar");

ArrayList<Object> stages = new ArrayList<Object>();
stages.add(stage);

CfnUsagePlan usagePlan = new CfnUsagePlan(this, "UsagePlan", CfnUsagePlanProps.builder()
        .withUsagePlanName("MyUsagePlan")
        .withApiStages(stages)
        .build());

...but this yields:

UsagePlan:
    Type: AWS::ApiGateway::UsagePlan
    Properties:
        UsagePlanName: MyUsagePlan
        ApiStages:
            - {}

If I use addPropertyOverride instead, I am able to get the expected result:

Map<String, String> stage = ImmutableMap.of(
        "ApiId", "Foo"
        "Stage", "Bar");

ArrayList<Object> stages = new ArrayList<Object>();
stages.add(stage);

CfnUsagePlan usagePlan = new CfnUsagePlan(this, "UsagePlan", CfnUsagePlanProps.builder()
        .withUsagePlanName("MyUsagePlan")
        .build());
        
usagePlan.addPropertyOverride("ApiStages", stages);

I've seen this behavior on multiple Cfn*Props Builders that expect List types, so it isn't specific to CfnUsagePlan.

Let me know what other info or things I can do that would be helpful. Thanks

[nija-at]

This is a bug on our side, specifically in jsii. It turns out jsii is not properly identifying the types of nested property bags and is silently ignoring them.

We've recently identified this from a similar Python issue. Here's the link to the JSII issue for more details and which will track to fix this - aws/jsii#822

---

Pasting a full CDK Java app where I was able to reproduce this bug -

package com.myorg;

import software.amazon.awscdk.core.App;
import software.amazon.awscdk.core.Stack;
import software.amazon.awscdk.services.apigateway.CfnUsagePlan;
import software.amazon.awscdk.services.apigateway.CfnUsagePlanProps;

import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.HashMap;

public class HelloApp {
    public static void main(final String argv[]) {
        App app = new App();

        Map<String, String> stage = new HashMap<>();
        stage.put("key1", "value1");
        List<Object> stages = new ArrayList<>();
        stages.add(stage);
        Stack stack = new Stack(app, "mystack", null);
        CfnUsagePlanProps props = CfnUsagePlanProps.builder().usagePlanName("myusageplan").apiStages(stages).build();
        new CfnUsagePlan(stack, "myusageplan", props);

        // required until https://github.com/aws/jsii/issues/456 is resolved
        app.synth();
    }
}