org.springframework.core.annotation
Class AnnotationUtils

java.lang.Object
  org.springframework.core.annotation.AnnotationUtils

public abstract class AnnotationUtils
extends Object

General utility methods for working with annotations, handling bridge methods (which the compiler generates for generic declarations) as well as super methods (for optional "annotation inheritance"). Note that none of this is provided by the JDK's introspection facilities themselves.

As a general rule for runtime-retained annotations (e.g. for transaction control, authorization or service exposure), always use the lookup methods on this class (e.g., findAnnotation(Method, Class), getAnnotation(Method, Class), and getAnnotations(Method)) instead of the plain annotation lookup methods in the JDK. You can still explicitly choose between lookup on the given class level only (getAnnotation(Method, Class)) and lookup in the entire inheritance hierarchy of the given method (findAnnotation(Method, Class)).

Since:

2.0

Author:

Rob Harrop, Juergen Hoeller, Sam Brannen, Mark Fisher, Chris Beams

See Also:

AccessibleObject.getAnnotations(), Method.getAnnotation(Class)

Constructor Summary

AnnotationUtils()

Method Summary

static <A extends Annotation> A	findAnnotation(Class<?> clazz, Class<A> annotationType) Find a single Annotation of annotationType from the supplied Class, traversing its interfaces and superclasses if no annotation can be found on the given class itself.
static <A extends Annotation> A	findAnnotation(Method method, Class<A> annotationType) Get a single Annotation of annotationType from the supplied Method, traversing its super methods if no annotation can be found on the given method itself.
static Class<?>	findAnnotationDeclaringClass(Class<? extends Annotation> annotationType, Class<?> clazz) Find the first Class in the inheritance hierarchy of the specified clazz (including the specified clazz itself) which declares an annotation for the specified annotationType, or null if not found.
static <T extends Annotation> T	getAnnotation(AnnotatedElement ae, Class<T> annotationType) Get a single Annotation of annotationType from the supplied Method, Constructor or Field.
static <A extends Annotation> A	getAnnotation(Method method, Class<A> annotationType) Get a single Annotation of annotationType from the supplied Method.
static Map<String,Object>	getAnnotationAttributes(Annotation annotation) Retrieve the given annotation's attributes as a Map, preserving all attribute types as-is.
static Map<String,Object>	getAnnotationAttributes(Annotation annotation, boolean classValuesAsString) Retrieve the given annotation's attributes as a Map.
static AnnotationAttributes	getAnnotationAttributes(Annotation annotation, boolean classValuesAsString, boolean nestedAnnotationsAsMap) Retrieve the given annotation's attributes as an AnnotationAttributes map structure.
static Annotation[]	getAnnotations(Method method) Get all Annotations from the supplied Method.
static Object	getDefaultValue(Annotation annotation) Retrieve the default value of the "value" attribute of a single-element Annotation, given an annotation instance.
static Object	getDefaultValue(Annotation annotation, String attributeName) Retrieve the default value of a named Annotation attribute, given an annotation instance.
static Object	getDefaultValue(Class<? extends Annotation> annotationType) Retrieve the default value of the "value" attribute of a single-element Annotation, given the annotation type.
static Object	getDefaultValue(Class<? extends Annotation> annotationType, String attributeName) Retrieve the default value of a named Annotation attribute, given the annotation type.
static Object	getValue(Annotation annotation) Retrieve the value of the "value" attribute of a single-element Annotation, given an annotation instance.
static Object	getValue(Annotation annotation, String attributeName) Retrieve the value of a named Annotation attribute, given an annotation instance.
static boolean	isAnnotationDeclaredLocally(Class<? extends Annotation> annotationType, Class<?> clazz) Determine whether an annotation for the specified annotationType is declared locally on the supplied clazz.
static boolean	isAnnotationInherited(Class<? extends Annotation> annotationType, Class<?> clazz) Determine whether an annotation for the specified annotationType is present on the supplied clazz and is inherited i.e., not declared locally for the class).

Methods inherited from class java.lang.Object

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

Constructor Detail

AnnotationUtils

public AnnotationUtils()

Method Detail

getAnnotation

public static <T extends Annotation> T getAnnotation(AnnotatedElement ae,
                                                     Class<T> annotationType)

Get a single Annotation of annotationType from the supplied Method, Constructor or Field. Meta-annotations will be searched if the annotation is not declared locally on the supplied element.

Parameters:

ae - the Method, Constructor or Field from which to get the annotation

annotationType - the annotation class to look for, both locally and as a meta-annotation

Returns:

the matching annotation or null if not found

Since:

3.1

getAnnotations

public static Annotation[] getAnnotations(Method method)

Get all Annotations from the supplied Method.

Correctly handles bridge Methods generated by the compiler.

Parameters:

method - the method to look for annotations on

Returns:

the annotations found

See Also:

BridgeMethodResolver.findBridgedMethod(Method)

getAnnotation

public static <A extends Annotation> A getAnnotation(Method method,
                                                     Class<A> annotationType)

Get a single Annotation of annotationType from the supplied Method.

Correctly handles bridge Methods generated by the compiler.

Parameters:

method - the method to look for annotations on

annotationType - the annotation class to look for

Returns:

the annotations found

See Also:

BridgeMethodResolver.findBridgedMethod(Method)

findAnnotation

public static <A extends Annotation> A findAnnotation(Method method,
                                                      Class<A> annotationType)

Get a single Annotation of annotationType from the supplied Method, traversing its super methods if no annotation can be found on the given method itself.

Annotations on methods are not inherited by default, so we need to handle this explicitly.

Parameters:

method - the method to look for annotations on

annotationType - the annotation class to look for

Returns:

the annotation found, or null if none found

findAnnotation

public static <A extends Annotation> A findAnnotation(Class<?> clazz,
                                                      Class<A> annotationType)

Find a single Annotation of annotationType from the supplied Class, traversing its interfaces and superclasses if no annotation can be found on the given class itself.

This method explicitly handles class-level annotations which are not declared as inherited as well as annotations on interfaces.

The algorithm operates as follows: Searches for an annotation on the given class and returns it if found. Else searches all interfaces that the given class declares, returning the annotation from the first matching candidate, if any. Else proceeds with introspection of the superclass of the given class, checking the superclass itself; if no annotation found there, proceeds with the interfaces that the superclass declares. Recursing up through the entire superclass hierarchy if no match is found.

Parameters:

clazz - the class to look for annotations on

annotationType - the annotation class to look for

Returns:

the annotation found, or null if none found

findAnnotationDeclaringClass

public static Class<?> findAnnotationDeclaringClass(Class<? extends Annotation> annotationType,
                                                    Class<?> clazz)

Find the first Class in the inheritance hierarchy of the specified clazz (including the specified clazz itself) which declares an annotation for the specified annotationType, or null if not found. If the supplied clazz is null, null will be returned.

If the supplied clazz is an interface, only the interface itself will be checked; the inheritance hierarchy for interfaces will not be traversed.

The standard Class API does not provide a mechanism for determining which class in an inheritance hierarchy actually declares an Annotation, so we need to handle this explicitly.

Parameters:

annotationType - the Class object corresponding to the annotation type

clazz - the Class object corresponding to the class on which to check for the annotation, or null

Returns:

the first Class in the inheritance hierarchy of the specified clazz which declares an annotation for the specified annotationType, or null if not found

See Also:

Class.isAnnotationPresent(Class), Class.getDeclaredAnnotations()

isAnnotationDeclaredLocally

public static boolean isAnnotationDeclaredLocally(Class<? extends Annotation> annotationType,
                                                  Class<?> clazz)

Determine whether an annotation for the specified annotationType is declared locally on the supplied clazz. The supplied Class may represent any type.

Note: This method does not determine if the annotation is inherited. For greater clarity regarding inherited annotations, consider using isAnnotationInherited(Class, Class) instead.

Parameters:

annotationType - the Class object corresponding to the annotation type

clazz - the Class object corresponding to the class on which to check for the annotation

Returns:

true if an annotation for the specified annotationType is declared locally on the supplied clazz

See Also:

Class.getDeclaredAnnotations(), isAnnotationInherited(Class, Class)

isAnnotationInherited

public static boolean isAnnotationInherited(Class<? extends Annotation> annotationType,
                                            Class<?> clazz)

Determine whether an annotation for the specified annotationType is present on the supplied clazz and is inherited i.e., not declared locally for the class).

If the supplied clazz is an interface, only the interface itself will be checked. In accordance with standard meta-annotation semantics, the inheritance hierarchy for interfaces will not be traversed. See the JavaDoc for the @Inherited meta-annotation for further details regarding annotation inheritance.

Parameters:

annotationType - the Class object corresponding to the annotation type

clazz - the Class object corresponding to the class on which to check for the annotation

Returns:

true if an annotation for the specified annotationType is present on the supplied clazz and is inherited

See Also:

Class.isAnnotationPresent(Class), isAnnotationDeclaredLocally(Class, Class)

getAnnotationAttributes

public static Map<String,Object> getAnnotationAttributes(Annotation annotation)

Retrieve the given annotation's attributes as a Map, preserving all attribute types as-is.

Note: As of Spring 3.1.1, the returned map is actually an AnnotationAttributes instance, however the Map signature of this method has been preserved for binary compatibility.

Parameters:

annotation - the annotation to retrieve the attributes for

Returns:

the Map of annotation attributes, with attribute names as keys and corresponding attribute values as values

getAnnotationAttributes

public static Map<String,Object> getAnnotationAttributes(Annotation annotation,
                                                         boolean classValuesAsString)

Retrieve the given annotation's attributes as a Map. Equivalent to calling getAnnotationAttributes(Annotation, boolean, boolean) with the nestedAnnotationsAsMap parameter set to false.

Note: As of Spring 3.1.1, the returned map is actually an AnnotationAttributes instance, however the Map signature of this method has been preserved for binary compatibility.

Parameters:

annotation - the annotation to retrieve the attributes for

classValuesAsString - whether to turn Class references into Strings (for compatibility with AnnotationMetadata or to preserve them as Class references

Returns:

the Map of annotation attributes, with attribute names as keys and corresponding attribute values as values

getAnnotationAttributes

public static AnnotationAttributes getAnnotationAttributes(Annotation annotation,
                                                           boolean classValuesAsString,
                                                           boolean nestedAnnotationsAsMap)

Retrieve the given annotation's attributes as an AnnotationAttributes map structure. Implemented in Spring 3.1.1 to provide fully recursive annotation reading capabilities on par with that of the reflection-based StandardAnnotationMetadata.

Parameters:

annotation - the annotation to retrieve the attributes for

classValuesAsString - whether to turn Class references into Strings (for compatibility with AnnotationMetadata or to preserve them as Class references

nestedAnnotationsAsMap - whether to turn nested Annotation instances into AnnotationAttributes maps (for compatibility with AnnotationMetadata or to preserve them as Annotation instances

Returns:

the annotation attributes (a specialized Map) with attribute names as keys and corresponding attribute values as values

Since:

3.1.1

getValue

public static Object getValue(Annotation annotation)

Retrieve the value of the "value" attribute of a single-element Annotation, given an annotation instance.

Parameters:

annotation - the annotation instance from which to retrieve the value

Returns:

the attribute value, or null if not found

See Also:

getValue(Annotation, String)

getValue

public static Object getValue(Annotation annotation,
                              String attributeName)

Retrieve the value of a named Annotation attribute, given an annotation instance.

Parameters:

annotation - the annotation instance from which to retrieve the value

attributeName - the name of the attribute value to retrieve

Returns:

the attribute value, or null if not found

See Also:

getValue(Annotation)

getDefaultValue

public static Object getDefaultValue(Annotation annotation)

Retrieve the default value of the "value" attribute of a single-element Annotation, given an annotation instance.

Parameters:

annotation - the annotation instance from which to retrieve the default value

Returns:

the default value, or null if not found

See Also:

getDefaultValue(Annotation, String)

getDefaultValue

public static Object getDefaultValue(Annotation annotation,
                                     String attributeName)

Retrieve the default value of a named Annotation attribute, given an annotation instance.

Parameters:

annotation - the annotation instance from which to retrieve the default value

attributeName - the name of the attribute value to retrieve

Returns:

the default value of the named attribute, or null if not found

See Also:

getDefaultValue(Class, String)

getDefaultValue

public static Object getDefaultValue(Class<? extends Annotation> annotationType)

Retrieve the default value of the "value" attribute of a single-element Annotation, given the annotation type.

Parameters:

annotationType - the annotation type for which the default value should be retrieved

Returns:

the default value, or null if not found

See Also:

getDefaultValue(Class, String)

getDefaultValue

public static Object getDefaultValue(Class<? extends Annotation> annotationType,
                                     String attributeName)

Retrieve the default value of a named Annotation attribute, given the annotation type.

Parameters:

annotationType - the annotation type for which the default value should be retrieved

attributeName - the name of the attribute value to retrieve.

Returns:

the default value of the named attribute, or null if not found

See Also:

getDefaultValue(Annotation, String)