javassist.bytecode

Class AnnotationsAttribute

java.lang.Object

javassist.bytecode.AttributeInfo

javassist.bytecode.AnnotationsAttribute

public class AnnotationsAttribute
extends AttributeInfo

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, Annotation

Field Summary

Fields

Modifier and Type	Field and Description
static String	invisibleTag The name of the RuntimeInvisibleAnnotations attribute.
static String	visibleTag The name of the RuntimeVisibleAnnotations attribute.

Fields inherited from class javassist.bytecode.AttributeInfo

constPool

Constructor Summary

Constructors

Constructor and Description
AnnotationsAttribute(ConstPool cp, String attrname) Constructs an empty Runtime(In)VisibleAnnotations_attribute.
AnnotationsAttribute(ConstPool cp, String attrname, byte[] info) Constructs a Runtime(In)VisibleAnnotations_attribute.

Method Summary

Methods

Modifier and Type	Method and Description
void	addAnnotation(Annotation annotation) Adds an annotation.
AttributeInfo	copy(ConstPool newCp, Map classnames) Copies this attribute and returns a new copy.
Annotation	getAnnotation(String type) Parses the annotations and returns a data structure representing the annotation with the specified type.
Annotation[]	getAnnotations() Parses the annotations and returns a data structure representing that parsed annotations.
int	numAnnotations() Returns num_annotations.
void	setAnnotation(Annotation annotation) Changes the annotations.
void	setAnnotations(Annotation[] annotations) Changes the annotations represented by this object according to the given array of Annotation objects.
String	toString() Returns a string representation of this object.

Methods inherited from class javassist.bytecode.AttributeInfo

get, getConstPool, getName, length, set

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

visibleTag

public static final String visibleTag

The name of the RuntimeVisibleAnnotations attribute.

See Also:

Constant Field Values

invisibleTag

public static final String invisibleTag

The name of the RuntimeInvisibleAnnotations attribute.

See Also:

Constant Field Values

Constructor Detail

AnnotationsAttribute

public AnnotationsAttribute(ConstPool cp,
                    String attrname,
                    byte[] info)

Constructs a Runtime(In)VisibleAnnotations_attribute.

Parameters:

cp - constant pool

attrname - attribute name (visibleTag or invisibleTag).

info - the contents of this attribute. It does not include attribute_name_index or attribute_length.

AnnotationsAttribute

public AnnotationsAttribute(ConstPool cp,
                    String attrname)

Constructs an empty Runtime(In)VisibleAnnotations_attribute. A new annotation can be later added to the created attribute by setAnnotations().

Parameters:

cp - constant pool

attrname - attribute name (visibleTag or invisibleTag).

See Also:

setAnnotations(Annotation[])

Method Detail

numAnnotations

public int numAnnotations()

Returns num_annotations.

copy

public AttributeInfo copy(ConstPool newCp,
                 Map classnames)

Copies this attribute and returns a new copy.

Overrides:

copy in class AttributeInfo

Parameters:

newCp - the constant pool table used by the new copy.

classnames - pairs of replaced and substituted class names.

getAnnotation

public Annotation getAnnotation(String type)

Parses the annotations and returns a data structure representing the annotation with the specified type. See also getAnnotations() as to the returned data structure.

Parameters:

type - the annotation type.

Returns:

null if the specified annotation type is not included.

See Also:

getAnnotations()

addAnnotation

public void addAnnotation(Annotation annotation)

Adds an annotation. If there is an annotation with the same type, it is removed before the new annotation is added.

Parameters:

annotation - the added annotation.

getAnnotations

public Annotation[] getAnnotations()

Parses the annotations and returns a data structure representing that parsed annotations. Note that changes of the node values of the returned tree are not reflected on the annotations represented by this object unless the tree is copied back to this object by setAnnotations().

See Also:

setAnnotations(Annotation[])

setAnnotations

public void setAnnotations(Annotation[] annotations)

Changes the annotations represented by this object according to the given array of Annotation objects.

Parameters:

annotations - the data structure representing the new annotations.

setAnnotation

public void setAnnotation(Annotation annotation)

Changes the annotations. A call to this method is equivalent to:

setAnnotations(new Annotation[] { annotation })

Parameters:

annotation - the data structure representing the new annotation.

toString

public String toString()

Returns a string representation of this object.

Overrides:

toString in class Object