Spring nullable annotation generates unknown enum constant warning

Question

In my app, whenever I add @Nullable (which imports from org.springframework.lang.Nullable) to any of the fields, I get a build warning:

Warning:java: unknown enum constant javax.annotation.meta.When.MAYBE reason: class file for javax.annotation.meta.When not found

@NonNull and other null safety annoations from spring compile without any warnings as its implementation doesn't import import javax.annotation.meta.When.

The application runs just fine but the warning is just annoying. I am using spring boot 2.1.0 and java version 1.8.0_191

Answer 1

This warning is caused by the javax.annotation.meta.When enum not being available to your projects runtime (org.springframework.lang.Nullable references this enum but it is not made available automatically). You need to bring in a JSR305 implementation to fix this warning.

the Google find bugs repo includes a JSR305 implementation that should fix the problem: https://mvnrepository.com/artifact/com.google.code.findbugs/jsr305

since you are using gradle, add the dependency to your build.gradle script:

...
dependencies {
    ...

     // https://mvnrepository.com/artifact/com.google.code.findbugs/jsr305
    implementation 'com.google.code.findbugs:jsr305:3.0.2'

    ...
}
...

do a clean build and the error should go away

---

If you do not want to use the com.google.code.findbugs group's artifact you can try another from this list: https://mvnrepository.com/search?q=JSR305

references:

• Strange Eclipse IDE error javax.annotation.meta.When #Java
• What happened to Java's @OverridingMethodMustCallSuper?
• https://github.com/sbrannen/runtime-annotations/blob/master/src/main/java/org/example/SpringApplication.java

Answer 2

it's bothered me too. just try this in your pom:

    <dependency>
        <groupId>com.google.code.findbugs</groupId>
        <artifactId>annotations</artifactId>
        <version>3.0.1</version>
    </dependency>

it's work for me.