第6章 Spring的工具类AnnotationMetadata

最新推荐文章于 2026-01-04 17:28:49 发布

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这篇博客介绍了如何利用Spring的AnnotationMetadata类来访问和处理类上的注解。通过示例代码展示了如何检查注解的存在，获取注解属性以及遍历注解的方法。文章还包含了针对DirectAnnotation、NestAnnotation和Scope等自定义注解的测试。

Spring提供许多工具类，AnnotationMetadata 就是其中之一。AnnotationMetadata 是用来访问指定类上的注解，处理注解非常方便。本章节就是来学习一些API。

前置条件

maven需要引入Spring、assertj-core包。

代码

public class AnnotationMetadataTest {

    @Test
    void standardAnnotationMetadata() {
        AnnotationMetadata metadata = AnnotationMetadata.introspect(AnnotatedComponent.class);
        doTestAnnotationInfo(metadata);
    }

    private void doTestAnnotationInfo(AnnotationMetadata metadata) {
        assertThat(metadata.getClassName()).isEqualTo(AnnotatedComponent.class.getName());
        assertThat(metadata.isInterface()).isFalse();
        assertThat(metadata.isAbstract()).isFalse();
        assertThat(metadata.isAnnotation()).isFalse();
        assertThat(metadata.hasSuperClass()).isTrue();
        assertThat(metadata.getSuperClassName()).isEqualTo(Object.class.getName());

        assertThat(metadata.isAnnotated(DirectAnnotation.class.getName())).isTrue();
        assertThat(metadata.isAnnotated(NestAnnotation.class.getName())).isTrue();
        assertThat(metadata.isAnnotated(Scope.class.getName())).isTrue();

        assertThat(metadata.hasAnnotation(DirectAnnotation.class.getName())).isTrue();
        assertThat(metadata.hasAnnotation(NestAnnotation.class.getName())).isTrue();
        assertThat(metadata.hasAnnotation(Scope.class.getName())).isFalse();

        assertThat(metadata.getAnnotationTypes()).containsExactlyInAnyOrder(
                DirectAnnotation.class.getName(),
                NestAnnotation.class.getName()
        );

        AnnotationAttributes direAttrs = (AnnotationAttributes) metadata.getAnnotationAttributes(DirectAnnotation.class.getName());
        assertThat(direAttrs).hasSize(2);
        assertThat(direAttrs.getString("value")).isEqualTo("hello");
        assertThat(direAttrs.getStringArray("additionArray")).containsExactlyInAnyOrder("HHH", "KKK");

        Set<MethodMetadata> annotatedMethods = metadata.getAnnotatedMethods(Scope.class.getName());
        assertThat(annotatedMethods).hasSize(1);
        MethodMetadata next = annotatedMethods.iterator().next();
        assertThat(next.isAbstract()).isFalse();
        assertThat(next.isStatic()).isFalse();
        assertThat(next.isAnnotated(Scope.class.getName())).isTrue();
    }

    // ------------------------------------
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface DirectAnnotation {
        String value() default "value";

        String[] additionArray() default "direct";
    }

    @Target({ElementType.TYPE, ElementType.METHOD})
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Scope {

    }

    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    @Scope
    public @interface NestAnnotation {

    }

    @DirectAnnotation(value = "hello", additionArray = {"HHH", "KKK"})
    @NestAnnotation
    private static class AnnotatedComponent implements Serializable {

        @Scope
        public void test() {}
    }
}