Get field class in annotations processor

最新推荐文章于 2023-11-20 16:44:37 发布

转载最新推荐文章于 2023-11-20 16:44:37 发布 · 641 阅读

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本文介绍如何使用注解处理器处理特定类型的注解，并通过示例代码展示了如何获取被注解的字段及其类型。此外还讲解了在注解处理过程中进行验证的方法。

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When running your annotation processor, you don't have access to the compiled classes. The point of annotation processing is that it happens pre-compile.

Instead, you need to create an annotation processor that specifically handles your annotation type, then use the mirror API to access the field. For example:

@SupportedAnnotationTypes("com.example.MyAnnotation")
public class CompileTimeAnnotationProcessor extends AbstractProcessor {

    @Override
    public boolean process(Set<? extends TypeElement> annotations, 
                           RoundEnvironment roundEnv) {
        // Only one annotation, so just use annotations.iterator().next();
        Set<? extends Element> elements = roundEnv.getElementsAnnotatedWith(
                annotations.iterator().next());
        Set<VariableElement> fields = ElementFilter.fieldsIn(elements);
        for (VariableElement field : fields) {
            TypeMirror fieldType = field.asType();
            String fullTypeClassName = fieldType.toString();
            // Validate fullTypeClassName
        }
        return true;
    }
}

For the validation, you cannot use any classes which have yet to be compiled (including those that are about to be compiled with the annotation) using something like MyType.class. For these, you must use strings only. That is because annotation processing occurs during a pre-compiling phase known as "source generation", which is what allows you to generate source code before the compiler runs using annotations.

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http://stackoverflow.com/questions/17660469/get-field-class-in-annotations-processor

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