java - 提取给定方法句柄的@Nullable/@NonNull 注释

Question

我正在玩 CheckerFramework 并想提取方法的返回值和参数的有效 @Nullable/@NonNull 注释，例如some.package.Thing: Object compute(Object,Collection)。到目前为止，我发现的唯一方法是生成在不同空值上下文中使用此方法的源代码，以便我可以从检查器结果中推断出注释。但是我很确定有一种方法可以扩展 NullnessChecker，这样我就可以在类路径上给它一个方法句柄（通过反射获得）并导出有效的空值注释。谁能给我一些关于从哪里开始的提示？

Answer 1

As background, the Checker Framework lets you write annotations on types, such as List<@NonNull String>, but it also applies defaulting and inference.

The final type annotation is written to the class file. Therefore, you can use tools that read the class file.

• javap -v MyFile.class will show you a lot of information including the type annotations.

• The Annotation File Utilities read annotations from, and write annotations to, .java files, .class files, and text files. This is what I would use, but I am not sure of your use case. I would compile the .java file, then run extract-annotations mypackage.MyClass to create a text file mypackage.MyClass.jaif. A human or a tool can read that file.

• If the annotations have run-time retention (most annotations, such as @Nullable, do), you can also obtain them via reflection. This requires you to load the class under analysis, however. You can see a tutorial or another Stack Overflow question.