Class AccessibleObject
- All Implemented Interfaces:
AnnotatedElement
- Direct Known Subclasses:
Executable
,Field
AccessibleObject
class is the base class for Field
,
Method
, and Constructor
objects (known as reflected
objects). It provides the ability to flag a reflected object as
suppressing checks for Java language access control when it is used. This
permits sophisticated applications with sufficient privilege, such as Java
Object Serialization or other persistence mechanisms, to manipulate objects
in a manner that would normally be prohibited.
Java language access control prevents use of private members outside
their top-level class; package access members outside their package; protected members
outside their package or subclasses; and public members outside their
module unless they are declared in an exported
package and the user reads
their module. By
default, Java language access control is enforced (with one variation) when
Field
s, Method
s, or Constructor
s are used to get or
set fields, to invoke methods, or to create and initialize new instances of
classes, respectively. Every reflected object checks that the code using it
is in an appropriate class, package, or module. The check when invoked by
JNI code with no Java
class on the stack only succeeds if the member and the declaring class are
public, and the class is in a package that is exported to all modules.
The one variation from Java language access control is that the checks by reflected objects assume readability. That is, the module containing the use of a reflected object is assumed to read the module in which the underlying field, method, or constructor is declared.
Whether the checks for Java language access control can be suppressed
(and thus, whether access can be enabled) depends on whether the reflected
object corresponds to a member in an exported or open package
(see setAccessible(boolean)
).
- See Java Language Specification:
-
6.6 Access Control
- Since:
- 1.2
- External Specifications
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Constructor Summary
-
Method Summary
Modifier and TypeMethodDescriptionfinal boolean
Test if the caller can access this reflected object.<T extends Annotation>
TgetAnnotation
(Class<T> annotationClass) Returns this element's annotation for the specified type if such an annotation is present, else null.Returns annotations that are present on this element.<T extends Annotation>
T[]getAnnotationsByType
(Class<T> annotationClass) Returns annotations that are associated with this element.<T extends Annotation>
TgetDeclaredAnnotation
(Class<T> annotationClass) Returns this element's annotation for the specified type if such an annotation is directly present, else null.Returns annotations that are directly present on this element.<T extends Annotation>
T[]getDeclaredAnnotationsByType
(Class<T> annotationClass) Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present.boolean
Deprecated.This method is deprecated because its name hints that it checks if the reflected object is accessible when it actually indicates if the checks for Java language access control are suppressed.boolean
isAnnotationPresent
(Class<? extends Annotation> annotationClass) Returns true if an annotation for the specified type is present on this element, else false.void
setAccessible
(boolean flag) Set theaccessible
flag for this reflected object to the indicated boolean value.static void
setAccessible
(AccessibleObject[] array, boolean flag) Convenience method to set theaccessible
flag for an array of reflected objects.final boolean
Set theaccessible
flag for this reflected object totrue
if possible.
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Constructor Details
-
AccessibleObject
Deprecated.Constructor: only used by the Java Virtual Machine.
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-
Method Details
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setAccessible
Convenience method to set theaccessible
flag for an array of reflected objects.This method may be used to enable access to all reflected objects in the array when access to each reflected object can be enabled as specified by
setAccessible(boolean)
.A
SecurityException
is thrown if any of the elements of the inputarray
is aConstructor
object for the classjava.lang.Class
andflag
is true.- Parameters:
array
- the array of AccessibleObjectsflag
- the new value for theaccessible
flag in each object- Throws:
InaccessibleObjectException
- if access cannot be enabled for all objects in the arraySecurityException
- if an element in the array is a constructor forjava.lang.Class
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setAccessible
public void setAccessible(boolean flag) Set theaccessible
flag for this reflected object to the indicated boolean value. A value oftrue
indicates that the reflected object should suppress checks for Java language access control when it is used. A value offalse
indicates that the reflected object should enforce checks for Java language access control when it is used, with the variation noted in the class description.This method may be used by a caller in class
C
to enable access to amember
ofdeclaring class
D
if any of the following hold:-
C
andD
are in the same module. - The member is
public
andD
ispublic
in a package that the module containingD
exports
to at least the module containingC
. - The member is
protected
static
,D
ispublic
in a package that the module containingD
exports to at least the module containingC
, andC
is a subclass ofD
. -
D
is in a package that the module containingD
opens
to at least the module containingC
. All packages in unnamed and open modules are open to all modules and so this method always succeeds whenD
is in an unnamed or open module.
This method may be used by JNI code with no caller class on the stack to enable access to a
member
ofdeclaring class
D
if and only if:- The member is
public
andD
ispublic
in a package that the module containingD
exports
unconditionally.
This method cannot be used to enable access to private members, members with default (package) access, protected instance members, or protected constructors when the declaring class is in a different module to the caller and the package containing the declaring class is not open to the caller's module.
This method cannot be used to enable write access to a non-modifiable final field. The following fields are non-modifiable:
- static final fields declared in any class or interface
- final fields declared in a hidden class
- final fields declared in a record
The
accessible
flag whentrue
suppresses Java language access control checks to only enable read access to these non-modifiable final fields.- Parameters:
flag
- the new value for theaccessible
flag- Throws:
InaccessibleObjectException
- if access cannot be enabled- External Specifications
- See Also:
-
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trySetAccessible
public final boolean trySetAccessible()Set theaccessible
flag for this reflected object totrue
if possible. This method sets theaccessible
flag, as if by invokingsetAccessible(true)
, and returns the possibly-updated value for theaccessible
flag. If access cannot be enabled, i.e. the checks or Java language access control cannot be suppressed, this method returnsfalse
(as opposed tosetAccessible(true)
throwingInaccessibleObjectException
when it fails).This method is a no-op if the
accessible
flag for this reflected object istrue
.For example, a caller can invoke
trySetAccessible
on aMethod
object for a private instance methodp.T::privateMethod
to suppress the checks for Java language access control when theMethod
is invoked. Ifp.T
class is in a different module to the caller and packagep
is open to at least the caller's module, the code below successfully sets theaccessible
flag totrue
.p.T obj = ....; // instance of p.T : Method m = p.T.class.getDeclaredMethod("privateMethod"); if (m.trySetAccessible()) { m.invoke(obj); } else { // package p is not opened to the caller to access private member of T ... }
If this method is invoked by JNI code with no caller class on the stack, the
accessible
flag can only be set if the member and the declaring class are public, and the class is in a package that is exported unconditionally.- Returns:
true
if theaccessible
flag is set totrue
;false
if access cannot be enabled.- Since:
- 9
- External Specifications
- See Also:
-
isAccessible
Deprecated.This method is deprecated because its name hints that it checks if the reflected object is accessible when it actually indicates if the checks for Java language access control are suppressed. This method may returnfalse
on a reflected object that is accessible to the caller. To test if this reflected object is accessible, it should usecanAccess(Object)
.Get the value of theaccessible
flag for this reflected object.- Returns:
- the value of the object's
accessible
flag
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canAccess
Test if the caller can access this reflected object. If this reflected object corresponds to an instance method or field then this method tests if the caller can access the givenobj
with the reflected object. For instance methods or fields then theobj
argument must be an instance of thedeclaring class
. For static members and constructors thenobj
must benull
.This method returns
true
if theaccessible
flag is set totrue
, i.e. the checks for Java language access control are suppressed, or if the caller can access the member as specified in The Java Language Specification, with the variation noted in the class description. If this method is invoked by JNI code with no caller class on the stack, this method returnstrue
if the member and the declaring class are public, and the class is in a package that is exported unconditionally.- Parameters:
obj
- an instance object of the declaring class of this reflected object if it is an instance method or field- Returns:
true
if the caller can access this reflected object.- Throws:
IllegalArgumentException
-- if this reflected object is a static member or constructor and
the given
obj
is non-null
, or - if this reflected object is an instance method or field
and the given
obj
isnull
or of type that is not a subclass of thedeclaring class
of the member.
- if this reflected object is a static member or constructor and
the given
- See Java Language Specification:
-
6.6 Access Control
- Since:
- 9
- External Specifications
- See Also:
-
getAnnotation
Returns this element's annotation for the specified type if such an annotation is present, else null.Note that any annotation returned by this method is a declaration annotation.
- Specified by:
getAnnotation
in interfaceAnnotatedElement
- Implementation Requirements:
- The default implementation throws
UnsupportedOperationException
; subclasses should override this method. - Type Parameters:
T
- the type of the annotation to query for and return if present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- this element's annotation for the specified annotation type if present on this element, else null
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.5
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isAnnotationPresent
Returns true if an annotation for the specified type is present on this element, else false. This method is designed primarily for convenient access to marker annotations.The truth value returned by this method is equivalent to:
getAnnotation(annotationClass) != null
- Specified by:
isAnnotationPresent
in interfaceAnnotatedElement
- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- true if an annotation for the specified annotation type is present on this element, else false
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.5
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getAnnotationsByType
Returns annotations that are associated with this element. If there are no annotations associated with this element, the return value is an array of length 0. The difference between this method andAnnotatedElement.getAnnotation(Class)
is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getAnnotationsByType
in interfaceAnnotatedElement
- Implementation Requirements:
- The default implementation throws
UnsupportedOperationException
; subclasses should override this method. - Type Parameters:
T
- the type of the annotation to query for and return if present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- all this element's annotations for the specified annotation type if associated with this element, else an array of length zero
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.8
-
getAnnotations
Returns annotations that are present on this element. If there are no annotations present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getAnnotations
in interfaceAnnotatedElement
- Returns:
- annotations present on this element
- Since:
- 1.5
-
getDeclaredAnnotation
Returns this element's annotation for the specified type if such an annotation is directly present, else null. This method ignores inherited annotations. (Returns null if no annotations are directly present on this element.)Note that any annotation returned by this method is a declaration annotation.
- Specified by:
getDeclaredAnnotation
in interfaceAnnotatedElement
- Type Parameters:
T
- the type of the annotation to query for and return if directly present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- this element's annotation for the specified annotation type if directly present on this element, else null
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.8
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getDeclaredAnnotationsByType
Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present. This method ignores inherited annotations. If there are no specified annotations directly or indirectly present on this element, the return value is an array of length 0. The difference between this method andAnnotatedElement.getDeclaredAnnotation(Class)
is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation if one is present. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getDeclaredAnnotationsByType
in interfaceAnnotatedElement
- Type Parameters:
T
- the type of the annotation to query for and return if directly or indirectly present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- all this element's annotations for the specified annotation type if directly or indirectly present on this element, else an array of length zero
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.8
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getDeclaredAnnotations
Returns annotations that are directly present on this element. This method ignores inherited annotations. If there are no annotations directly present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getDeclaredAnnotations
in interfaceAnnotatedElement
- Implementation Requirements:
- The default implementation throws
UnsupportedOperationException
; subclasses should override this method. - Returns:
- annotations directly present on this element
- Since:
- 1.5
-