SpringBoot bootBuildInfo fails with a NullPointerException when an additional property has a null value

If you attempt to add additional properties to buildInfo which could be null at runtime, coersion to string fails with a NPE

Sample build.gradle entry

springBoot {
    buildInfo {
        properties {
            def testProp = project.hasProperty("sdhjksad") ? project.getProperty("sdhjksad").toString() : null
            additional = [
                'nullable': testProp
            ]
        }
    }
}

Stack Trace

Caused by: java.lang.NullPointerException
        at org.springframework.boot.gradle.tasks.buildinfo.BuildInfo.lambda$coerceToStringValues$0(BuildInfo.java:111)
        at org.springframework.boot.gradle.tasks.buildinfo.BuildInfo.coerceToStringValues(BuildInfo.java:111)
        at org.springframework.boot.gradle.tasks.buildinfo.BuildInfo.generateBuildProperties(BuildInfo.java:64)

Offending code

• https://github.com/spring-projects/spring-boot/blob/main/spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/buildinfo/BuildInfo.java#L111

    private Map<String, String> coerceToStringValues(Map<String, Object> input) {
        Map<String, String> output = new HashMap<>();
        input.forEach((key, value) -> output.put(key, value.toString()));   // add null check, and filter when value is null
        return output;
    }

Comment From: pruidong

def testProp = project.hasProperty("sdhjksad") ? project.getProperty("sdhjksad").toString() : ""

I think you can replace null with "" to avoid this error.

Calling toString() with null results in an NPE.

I want to submit a fix to Spring Boot.

Comment From: wilkinsona

See https://github.com/spring-projects/spring-boot/issues/6724, https://github.com/spring-projects/spring-boot/issues/12382, and https://github.com/spring-projects/spring-boot/pull/16583 for background.

I think we should avoid the NPE, but we should not do that by filtering out the values. As described in the related issues, a property being null could indicate a mistake that will then be silently ignored if we filter it out.

For consistency with Maven, I think we should leave the value as null so that it fails with a more informative error:

* What went wrong:
Execution failed for task ':bootBuildInfo'.
> Additional property 'nullable' is illegal as its value is null