RuntimeVisibleAnnotations_attribute and RuntimeInvisibleAnnotations_attribute. To obtain an AnnotationAttribute object, invoke getAttribute(AnnotationsAttribute.visibleTag) in ClassFile, MethodInfo, or FieldInfo. The obtained attribute is a runtime visible annotations attribute. If the parameter is AnnotationAttribute.invisibleTag, then the obtained attribute is a runtime invisible one.
For example,
import org.jboss.forge.furnace.proxy.javassist.bytecode.annotation.Annotation; : CtMethod m = ... ; MethodInfo minfo = m.getMethodInfo(); AnnotationsAttribute attr = (AnnotationsAttribute) minfo.getAttribute(AnnotationsAttribute.invisibleTag); Annotation an = attr.getAnnotation("Author"); String s = ((StringMemberValue)an.getMemberValue("name")).getValue(); System.out.println("@Author(name=" + s + ")"); This code snippet retrieves an annotation of the type Author from the MethodInfo object specified by minfo. Then, it prints the value of name in Author.
If the annotation type Author is annotated by a meta annotation:
@Retention(RetentionPolicy.RUNTIME)
Then Author is visible at runtime. Therefore, the third statement of the code snippet above must be changed into:
AnnotationsAttribute attr = (AnnotationsAttribute) minfo.getAttribute(AnnotationsAttribute.visibleTag);
The attribute tag must be visibleTag instead of invisibleTag.
If the member value of an annotation is not specified, the default value is used as that member value. If so, getMemberValue() in Annotation returns null since the default value is not included in the AnnotationsAttribute. It is included in the AnnotationDefaultAttribute of the method declared in the annotation type.
If you want to record a new AnnotationAttribute object, execute the following snippet:
ClassFile cf = ... ; ConstPool cp = cf.getConstPool(); AnnotationsAttribute attr = new AnnotationsAttribute(cp, AnnotationsAttribute.visibleTag); Annotation a = new Annotation("Author", cp); a.addMemberValue("name", new StringMemberValue("Chiba", cp)); attr.setAnnotation(a); cf.addAttribute(attr); cf.setVersionToJava5(); The last statement is necessary if the class file was produced by Javassist or JDK 1.4. Otherwise, it is not necessary. @see AnnotationDefaultAttribute @see org.jboss.forge.furnace.proxy.javassist.bytecode.annotation.Annotation
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