本文主要是介绍MetadataReader，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

MetadataReader

/**
 * Simple facade for accessing class metadata,
 * as read by an ASM {@link org.springframework.asm.ClassReader}.
 *
 * @author Juergen Hoeller
 * @since 2.5
 */
public interface MetadataReader {

	/**
	 * Return the resource reference for the class file.
	 */
	Resource getResource();

	/**
	 * Read basic class metadata for the underlying class.
	 */
	ClassMetadata getClassMetadata();

	/**
	 * Read full annotation metadata for the underlying class,
	 * including metadata for annotated methods.
	 */
	AnnotationMetadata getAnnotationMetadata();

}

SimpleMetadataReader

/** 把resource通过asm读取出来信息
 * {@link MetadataReader} implementation based on an ASM
 * {@link org.springframework.asm.ClassReader}.
 *
 * @author Juergen Hoeller
 * @author Costin Leau
 * @since 2.5
 */
final class SimpleMetadataReader implements MetadataReader {

	private static final int PARSING_OPTIONS = ClassReader.SKIP_DEBUG
			| ClassReader.SKIP_CODE | ClassReader.SKIP_FRAMES;

	private final Resource resource;

	private final AnnotationMetadata annotationMetadata;


	SimpleMetadataReader(Resource resource, @Nullable ClassLoader classLoader) throws IOException {
		SimpleAnnotationMetadataReadingVisitor visitor = new SimpleAnnotationMetadataReadingVisitor(classLoader);
		getClassReader(resource).accept(visitor, PARSING_OPTIONS);
		this.resource = resource;
		this.annotationMetadata = visitor.getMetadata();
	}

	private static ClassReader getClassReader(Resource resource) throws IOException {
		try (InputStream is = resource.getInputStream()) {
			try {
				return new ClassReader(is);
			}
			catch (IllegalArgumentException ex) {
				throw new NestedIOException("ASM ClassReader failed to parse class file - " +
						"probably due to a new Java class file version that isn't supported yet: " + resource, ex);
			}
		}
	}


	@Override
	public Resource getResource() {
		return this.resource;
	}

	@Override
	public ClassMetadata getClassMetadata() {
		return this.annotationMetadata;
	}

	@Override
	public AnnotationMetadata getAnnotationMetadata() {
		return this.annotationMetadata;
	}

}

类图

调试值

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