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package java.lang.reflect;

import java.security.AccessController;
import sun.reflect.ReflectionFactory;
import java.lang.annotation.Annotation;


The AccessibleObject class is the base class for Field, Method and
Constructor objects.  It provides the ability to flag a reflected
object as suppressing default Java language access control checks
when it is used.  The access checks--for public, default (package)
access, protected, and private members--are performed when Fields,
Methods or Constructors are used to set or get fields, to invoke
methods, or to create and initialize new instances of classes,
respectively.

Setting the accessible flag in a reflected object 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. 
See Also:
Since:1.2
/**
 * The AccessibleObject class is the base class for Field, Method and
 * Constructor objects.  It provides the ability to flag a reflected
 * object as suppressing default Java language access control checks
 * when it is used.  The access checks--for public, default (package)
 * access, protected, and private members--are performed when Fields,
 * Methods or Constructors are used to set or get fields, to invoke
 * methods, or to create and initialize new instances of classes,
 * respectively.
 *
 * <p>Setting the {@code accessible} flag in a reflected object
 * 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.
 *
 * @see Field
 * @see Method
 * @see Constructor
 * @see ReflectPermission
 *
 * @since 1.2
 */
public class AccessibleObject implements AnnotatedElement {

    
The Permission object that is used to check whether a client
has sufficient privilege to defeat Java language access
control checks.

/**
     * The Permission object that is used to check whether a client
     * has sufficient privilege to defeat Java language access
     * control checks.
     */
    static final private java.security.Permission ACCESS_PERMISSION =
        new ReflectPermission("suppressAccessChecks");

    
Convenience method to set the accessible flag for an array of objects with a single security check (for efficiency). 
First, if there is a security manager, its checkPermission method is called with a ReflectPermission("suppressAccessChecks") permission. 
A SecurityException is raised if flag is true but accessibility of any of the elements of the input array may not be changed (for example, if the element object is a Constructor object for the class Class). In the event of such a SecurityException, the accessibility of objects is set to flag for array elements upto (and excluding) the element for which the exception occurred; the accessibility of elements beyond (and including) the element for which the exception occurred is unchanged. 
Params:
  • array – the array of AccessibleObjects
  • flag –  the new value for the accessible flag in each object
Throws:
See Also:
/**
     * Convenience method to set the {@code accessible} flag for an
     * array of objects with a single security check (for efficiency).
     *
     * <p>First, if there is a security manager, its
     * {@code checkPermission} method is called with a
     * {@code ReflectPermission("suppressAccessChecks")} permission.
     *
     * <p>A {@code SecurityException} is raised if {@code flag} is
     * {@code true} but accessibility of any of the elements of the input
     * {@code array} may not be changed (for example, if the element
     * object is a {@link Constructor} object for the class {@link
     * java.lang.Class}).  In the event of such a SecurityException, the
     * accessibility of objects is set to {@code flag} for array elements
     * upto (and excluding) the element for which the exception occurred; the
     * accessibility of elements beyond (and including) the element for which
     * the exception occurred is unchanged.
     *
     * @param array the array of AccessibleObjects
     * @param flag  the new value for the {@code accessible} flag
     *              in each object
     * @throws SecurityException if the request is denied.
     * @see SecurityManager#checkPermission
     * @see java.lang.RuntimePermission
     */
    public static void setAccessible(AccessibleObject[] array, boolean flag)
        throws SecurityException {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) sm.checkPermission(ACCESS_PERMISSION);
        for (int i = 0; i < array.length; i++) {
            setAccessible0(array[i], flag);
        }
    }

    
Set the accessible flag for this object to the indicated boolean value. A value of true indicates that the reflected object should suppress Java language access checking when it is used. A value of false indicates that the reflected object should enforce Java language access checks. 
First, if there is a security manager, its checkPermission method is called with a ReflectPermission("suppressAccessChecks") permission. 
A SecurityException is raised if flag is true but accessibility of this object may not be changed (for example, if this element object is a Constructor object for the class Class). 
A SecurityException is raised if this object is a Constructor object for the class java.lang.Class, and flag is true. 
Params:
  • flag – the new value for the accessible flag
Throws:
See Also:
/**
     * Set the {@code accessible} flag for this object to
     * the indicated boolean value.  A value of {@code true} indicates that
     * the reflected object should suppress Java language access
     * checking when it is used.  A value of {@code false} indicates
     * that the reflected object should enforce Java language access checks.
     *
     * <p>First, if there is a security manager, its
     * {@code checkPermission} method is called with a
     * {@code ReflectPermission("suppressAccessChecks")} permission.
     *
     * <p>A {@code SecurityException} is raised if {@code flag} is
     * {@code true} but accessibility of this object may not be changed
     * (for example, if this element object is a {@link Constructor} object for
     * the class {@link java.lang.Class}).
     *
     * <p>A {@code SecurityException} is raised if this object is a {@link
     * java.lang.reflect.Constructor} object for the class
     * {@code java.lang.Class}, and {@code flag} is true.
     *
     * @param flag the new value for the {@code accessible} flag
     * @throws SecurityException if the request is denied.
     * @see SecurityManager#checkPermission
     * @see java.lang.RuntimePermission
     */
    public void setAccessible(boolean flag) throws SecurityException {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) sm.checkPermission(ACCESS_PERMISSION);
        setAccessible0(this, flag);
    }

    /* Check that you aren't exposing java.lang.Class.<init>. */
    private static void setAccessible0(AccessibleObject obj, boolean flag)
        throws SecurityException
    {
        if (obj instanceof Constructor && flag == true) {
            Constructor c = (Constructor)obj;
            if (c.getDeclaringClass() == Class.class) {
                throw new SecurityException("Can not make a java.lang.Class" +
                                            " constructor accessible");
            }
        }
        obj.override = flag;
    }

    
Get the value of the accessible flag for this object. 
Returns:the value of the object's accessible flag
/**
     * Get the value of the {@code accessible} flag for this object.
     *
     * @return the value of the object's {@code accessible} flag
     */
    public boolean isAccessible() {
        return override;
    }

    
Constructor: only used by the Java Virtual Machine.

/**
     * Constructor: only used by the Java Virtual Machine.
     */
    protected AccessibleObject() {}

    // Indicates whether language-level access checks are overridden
    // by this object. Initializes to "false". This field is used by
    // Field, Method, and Constructor.
    //
    // NOTE: for security purposes, this field must not be visible
    // outside this package.
    boolean override;

    // Reflection factory used by subclasses for creating field,
    // method, and constructor accessors. Note that this is called
    // very early in the bootstrapping process.
    static final ReflectionFactory reflectionFactory =
        AccessController.doPrivileged(
            new sun.reflect.ReflectionFactory.GetReflectionFactoryAction());

    
Throws:
  • NullPointerException – {@inheritDoc}
Since:1.5
/**
     * @throws NullPointerException {@inheritDoc}
     * @since 1.5
     */
    public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
        throw new AssertionError("All subclasses should override this method");
    }

    
Throws:
  • NullPointerException – {@inheritDoc}
Since:1.5
/**
     * @throws NullPointerException {@inheritDoc}
     * @since 1.5
     */
    public boolean isAnnotationPresent(
        Class<? extends Annotation> annotationClass) {
        return getAnnotation(annotationClass) != null;
    }

    
Since:1.5
/**
     * @since 1.5
     */
    public Annotation[] getAnnotations() {
        return getDeclaredAnnotations();
    }

    
Since:1.5
/**
     * @since 1.5
     */
    public Annotation[] getDeclaredAnnotations()  {
        throw new AssertionError("All subclasses should override this method");
    }
}