Using Null Analysis annotations in Java8

Question

In Java, I use the 'null analysis' using annotations. I don't use Eclipse's default annotations and I have defined my owns.

For each package, I used to add a global NonNullByDefault annotation in the package-info.java file.

With Java version <= Java7, the code below has no problem, everything works fine.

@my.package.annotations.NonNullByDefault
package my.foo.package;

But when I set Eclipse to be Java8 compliant (the only JDK installed on my system is Java8), then an error occurs:

A default nullness annotation has not been specified for the package my.foo.package - Java Problem

My annotation is declared in the following way:

@Retention(RetentionPolicy.CLASS)
@Target({ ElementType.PACKAGE, ElementType.TYPE, 
          ElementType.METHOD, ElementType.CONSTRUCTOR })
public @interface NonNullByDefault { 
    // marker annotation
}

What's new in Java8 about that? Can someone explain me the good way to use my annotations?

Please provide a full definition of your NonNullByDefault annotation. — Tagir Valeev
– Tagir Valeev, Commented May 9, 2015 at 10:08
The annotation is just used to check if it's present or not. There is no code in. @Retention(RetentionPolicy.CLASS) @Target({ ElementType.PACKAGE, ElementType.TYPE, ElementType.METHOD, ElementType.CONSTRUCTOR }) public @interface NonNullByDefault { // marker annotation } And it's works fine using the Java7 compliance — hiveship
– hiveship, Commented May 9, 2015 at 10:30

Stephan Herrmann · Accepted Answer · 2015-06-22 10:13:40Z

1

JDT's own annotations have significantly changed between versions 1.x and 2.x of org.eclipse.jdt.annotation. To fully leverage the greater precision of type annotations in Java 8, @NonNullByDefault now has an attribute of type DefaultLocation[], specifying where exactly the default should apply.

Rebuilding your own annotations with the same level of details and making JDT understand your own annotations will be cumbersome.

Still, an attribute-less @NonNullByDefault should be understood in the "default" way (see the default value of org.eclipse.jdt.annotation.NonNullByDefault.value). Apparently there's a bug in the evaluation of such custom annotations in Java 8 projects.

answered Jun 22, 2015 at 10:13

Stephan Herrmann

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Comments

akhil_mittal · Accepted Answer · 2015-05-09 10:00:59Z

0

Can you please try the following:

Put a file name package-info.java into each of your Java packages
Enter the following in the file:

@NonNullByDefault package your.package; import org.eclipse.jdt.annotation.NonNullByDefault;

This will specify that you don't want to accept null anywhere for any argument and you will also not be putting loads of @NonNull in the code. You may get a warning like A default nullness annotation has not been specified for the package my.foo.package if you create a new package but forget to copy the file.

answered May 9, 2015 at 10:00

akhil_mittal

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2 Comments

hiveship Over a year ago

That is exactly what I am already doing. I juste use my own annotation instead of org.eclipse.jdt.annotation.NonNullByDefault. My code has no problem using the Java7 compliance.

akhil_mittal Over a year ago

Okay. It should be working because when I had similar problem this was what I did and it worked for me. Anyways then I may not find any other problem.

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