A class representing
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 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 Also: AnnotationDefaultAttribute
See Also: javassist.bytecode.annotation.Annotation | 