NullPointerException when using CfnApi::getBinaryMediaTypes from Java

[ivoanjo]

Hello there! 👋

I've just run into an issue while trying to read the binaryMediaTypes for a SAM CfnApi. It looks like the Java generator does not properly handle when it gets a null for the underlying field.

Reproduction Steps

package com.myorg;

import software.amazon.awscdk.core.App;
import software.amazon.awscdk.services.sam.CfnApi;
import software.amazon.awscdk.services.sam.CfnApiProps;
import software.amazon.awscdk.core.Stack;
import java.util.Arrays;

public class HelloApp {
    public static void main(final String argv[]) {
        App app = new App();
        Stack stack = new Stack(app, "mystack", null);

        CfnApi cfnApi = new CfnApi(stack, "foo",
            CfnApiProps.builder().stageName("foo").build());

        cfnApi.getBinaryMediaTypes(); // <--- NullPointerException will happen inside here

        app.synth();
    }
}

What I expected: An empty collection returned from getBinaryMediaTypes() (I can live with a null too, it needed)

Error Log

java.lang.NullPointerException
    at java.util.Collections$UnmodifiableCollection.<init> (Collections.java:1026)
    at java.util.Collections$UnmodifiableList.<init> (Collections.java:1302)
    at java.util.Collections.unmodifiableList (Collections.java:1287)
    at software.amazon.awscdk.services.sam.CfnApi.getBinaryMediaTypes (CfnApi.java:195)
    at com.myorg.HelloApp.main (HelloApp.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:498)
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run (ExecJavaMojo.java:282)
    at java.lang.Thread.run (Thread.java:748)

Environment

• CLI Version : 1.10.0 (build 19ae072)
• Framework Version: 1.10.0.DEVPREVIEW
• OS : Ubuntu 16.04.6 LTS
• Language : Java (JDK 8)

---

This is 🐛 Bug Report

[RomainMuller]

Yeah - looks like we need to check for null before we try to make a collection unmodifiable... This is a bug in the jsii runtime for Java.

[nija-at]

This looks like a bug in our JSII Java bindings. Sending it @RomainMuller's way.