AnnotatedElement
Executable
, Field
public class AccessibleObject extends Object implements AnnotatedElement
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)
).
Modifier | Constructor | Description |
---|---|---|
protected |
Deprecated. |
Modifier and Type | Method | Description |
---|---|---|
final boolean |
canAccess |
Test if the caller can access this reflected object. |
<T extends Annotation> |
getAnnotation |
Returns this element's annotation for the specified type if such an annotation is present, else null. |
Annotation[] |
getAnnotations() |
Returns annotations that are present on this element. |
<T extends Annotation> |
getAnnotationsByType |
Returns annotations that are associated with this element. |
<T extends Annotation> |
getDeclaredAnnotation |
Returns this element's annotation for the specified type if such an annotation is directly present, else null. |
Annotation[] |
getDeclaredAnnotations() |
Returns annotations that are directly present on this element. |
<T extends Annotation> |
getDeclaredAnnotationsByType |
Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present. |
boolean |
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. |
boolean |
isAnnotationPresent |
Returns true if an annotation for the specified type is present on this element, else false. |
void |
setAccessible |
Set the accessible flag for this reflected object to the indicated boolean value. |
static void |
setAccessible |
Convenience method to set the accessible flag for an array of reflected objects with a single security check (for efficiency). |
final boolean |
trySetAccessible() |
Set the accessible flag for this reflected object to true if possible. |
@Deprecated(since="17") protected AccessibleObject()
public static void setAccessible(AccessibleObject[] array, boolean flag)
accessible
flag for an array of reflected objects with a single security check (for efficiency). 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)
.
If there is a security manager, its checkPermission
method is first called with a ReflectPermission("suppressAccessChecks")
permission.
A SecurityException
is also thrown if any of the elements of the input array
is a Constructor
object for the class java.lang.Class
and flag
is true.
array
- the array of AccessibleObjectsflag
- the new value for the accessible
flag in each objectInaccessibleObjectException
- if access cannot be enabled for all objects in the arraySecurityException
- if the request is denied by the security manager or an element in the array is a constructor for
java.lang.Class
public void setAccessible(boolean flag)
accessible
flag for this reflected object to the indicated boolean value. A value of true
indicates that the reflected object should suppress checks for Java language access control when it is used. A value of false
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 a member
of declaring class
D
if any of the following hold:
C
and D
are in the same module. public
and D
is public
in a package that the module containing D
exports
to at least the module containing C
. protected
static
, D
is public
in a package that the module containing D
exports to at least the module containing C
, and C
is a subclass of D
. D
is in a package that the module containing D
opens
to at least the module containing C
. All packages in unnamed and open modules are open to all modules and so this method always succeeds when D
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
of declaring class
D
if and only if:
public
and D
is public
in a package that the module containing D
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:
The accessible
flag when true
suppresses Java language access control checks to only enable read access to these non-modifiable final fields.
If there is a security manager, its checkPermission
method is first called with a ReflectPermission("suppressAccessChecks")
permission.
flag
- the new value for the accessible
flagInaccessibleObjectException
- if access cannot be enabledSecurityException
- if the request is denied by the security managerpublic final boolean trySetAccessible()
accessible
flag for this reflected object to true
if possible. This method sets the accessible
flag, as if by invoking setAccessible(true)
, and returns the possibly-updated value for the accessible
flag. If access cannot be enabled, i.e. the checks or Java language access control cannot be suppressed, this method returns false
(as opposed to
setAccessible(true)
throwing InaccessibleObjectException
when it fails). This method is a no-op if the accessible
flag for this reflected object is true
.
For example, a caller can invoke trySetAccessible
on a Method
object for a private instance method p.T::privateMethod
to suppress the checks for Java language access control when the Method
is invoked. If p.T
class is in a different module to the caller and package p
is open to at least the caller's module, the code below successfully sets the accessible
flag to true
.
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.
If there is a security manager, its checkPermission
method is first called with a ReflectPermission("suppressAccessChecks")
permission.
true
if the accessible
flag is set to true
; false
if access cannot be enabled.SecurityException
- if the request is denied by the security manager@Deprecated(since="9") public boolean isAccessible()
false
on a reflected object that is accessible to the caller. To test if this reflected object is accessible, it should use canAccess(Object)
.accessible
flag for this reflected object.accessible
flagpublic final boolean canAccess(Object obj)
obj
with the reflected object. For instance methods or fields then the obj
argument must be an instance of the declaring class
. For static members and constructors then obj
must be null
. This method returns true
if the accessible
flag is set to true
, 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 returns true
if the member and the declaring class are public, and the class is in a package that is exported unconditionally.
obj
- an instance object of the declaring class of this reflected object if it is an instance method or fieldtrue
if the caller can access this reflected object.IllegalArgumentException
- obj
is non-null
, or obj
is null
or of type that is not a subclass of the declaring class
of the member.public <T extends Annotation> T getAnnotation(Class<T> annotationClass)
Note that any annotation returned by this method is a declaration annotation.
getAnnotation
in interface AnnotatedElement
UnsupportedOperationException
; subclasses should override this method.T
- the type of the annotation to query for and return if presentannotationClass
- the Class object corresponding to the annotation typeNullPointerException
- if the given annotation class is nullpublic boolean isAnnotationPresent(Class<? extends Annotation> annotationClass)
The truth value returned by this method is equivalent to: getAnnotation(annotationClass) != null
isAnnotationPresent
in interface AnnotatedElement
annotationClass
- the Class object corresponding to the annotation typeNullPointerException
- if the given annotation class is nullpublic <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass)
AnnotatedElement.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.
getAnnotationsByType
in interface AnnotatedElement
UnsupportedOperationException
; subclasses should override this method.T
- the type of the annotation to query for and return if presentannotationClass
- the Class object corresponding to the annotation typeNullPointerException
- if the given annotation class is nullpublic Annotation[] getAnnotations()
Note that any annotations returned by this method are declaration annotations.
getAnnotations
in interface AnnotatedElement
public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass)
Note that any annotation returned by this method is a declaration annotation.
getDeclaredAnnotation
in interface AnnotatedElement
T
- the type of the annotation to query for and return if directly presentannotationClass
- the Class object corresponding to the annotation typeNullPointerException
- if the given annotation class is nullpublic <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass)
AnnotatedElement.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.
getDeclaredAnnotationsByType
in interface AnnotatedElement
T
- the type of the annotation to query for and return if directly or indirectly presentannotationClass
- the Class object corresponding to the annotation typeNullPointerException
- if the given annotation class is nullpublic Annotation[] getDeclaredAnnotations()
Note that any annotations returned by this method are declaration annotations.
getDeclaredAnnotations
in interface AnnotatedElement
UnsupportedOperationException
; subclasses should override this method.
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