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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

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 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

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 *

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package java.lang.reflect;

import java.security.AccessController;

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 -- <em>module boundaries</em>,

 * 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. Unlike access control specified

 * in the <cite>The Java&trade; Language Specification</cite> and

 * <cite>The Java Virtual Machine Specification</cite>, access checks

 * with reflected objects assume {@link Module#canRead readability}.

 *

 * <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.

 *

 * <p>By default, a reflected object is <em>not</em> accessible.

 *

 * @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.

     */

    private static final java.security.Permission ACCESS_PERMISSION =

        new ReflectPermission("suppressAccessChecks");

    static void checkPermission() {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) sm.checkPermission(ACCESS_PERMISSION);

    }

    /**

     * Convenience method to set the {@code accessible} flag for an

     * array of objects with a single security check (for efficiency).

     *

     * <p>This method cannot be used to enable access to an object that is a

     * {@link Member member} of a class in a different module to the caller and

     * where the class is in a package that is not exported to the caller's

     * module. Additionally, this method cannot be used to enable access to

     * non-public members of {@code AccessibleObject} or {@link Module}.

     *

     * <p>If there is a security manager, its

     * {@code checkPermission} method is first called with a

     * {@code ReflectPermission("suppressAccessChecks")} permission.

     *

     * <p>A {@code SecurityException} is also thrown if any of the elements of

     * the input {@code array} is a {@link java.lang.reflect.Constructor}

     * object for the class {@code java.lang.Class} and {@code flag} is true.

     *

     * @param array the array of AccessibleObjects

     * @param flag  the new value for the {@code accessible} flag

     *              in each object

     * @throws InaccessibleObjectException if access cannot be enabled

     * @throws SecurityException if the request is denied.

     * @see SecurityManager#checkPermission

     * @see ReflectPermission

     */

    @CallerSensitive

    public static void setAccessible(AccessibleObject[] array, boolean flag) {

        checkPermission();

        if (flag) {

            Class<?> caller = Reflection.getCallerClass();

            array = array.clone();

            for (AccessibleObject ao : array) {

                ao.checkCanSetAccessible(caller);

            }

        }

        for (AccessibleObject ao : array) {

            ao.setAccessible0(flag);

        }

    }

    /**

     * 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

     * while assuming readability (as noted in the class description).

     *

     * <p>This method cannot be used to enable access to an object that is a

     * {@link Member member} of a class in a different module to the caller and

     * where the class is in a package that is not exported to the caller's

     * module. Additionally, this method cannot be used to enable access to

     * non-public members of {@code AccessibleObject} or {@link Module}.

     *

     * <p>If there is a security manager, its

     * {@code checkPermission} method is first called with a

     * {@code ReflectPermission("suppressAccessChecks")} permission.

     *

     * @param flag the new value for the {@code accessible} flag

     * @throws InaccessibleObjectException if access cannot be enabled

     * @throws SecurityException if the request is denied

     * @see SecurityManager#checkPermission

     * @see ReflectPermission

     */

    public void setAccessible(boolean flag) {

        AccessibleObject.checkPermission();

        setAccessible0(flag);

    }

    void setAccessible0(boolean flag) {

        this.override = flag;

    }

   /**

    * If the given AccessibleObject is a {@code Constructor}, {@code Method}

    * or {@code Field} then checks that its declaring class is in a package

    * that can be accessed by the given caller of setAccessible.

    */

    void checkCanSetAccessible(Class<?> caller) {

        // do nothing, needs to be overridden by Constructor, Method, Field

    }

    void checkCanSetAccessible(Class<?> caller, Class<?> declaringClass) {

        Module callerModule = caller.getModule();

        Module declaringModule = declaringClass.getModule();

        if (callerModule != declaringModule

                && callerModule != Object.class.getModule()) {

            // check exports to target module

            String pn = packageName(declaringClass);

            if (!declaringModule.isExported(pn, callerModule)) {

                String msg = "Unable to make member of "

                        + declaringClass + " accessible:  "

                        + declaringModule + " does not export "

                        + pn + " to " + callerModule;

                Reflection.throwInaccessibleObjectException(msg);

            }

        }

        if (declaringClass == Module.class

                || declaringClass == AccessibleObject.class) {

            int modifiers;

            if (this instanceof Executable) {

                modifiers = ((Executable) this).getModifiers();

            } else {

                modifiers = ((Field) this).getModifiers();

            }

            if (!Modifier.isPublic(modifiers)) {

                String msg = "Cannot make a non-public member of "

                        + declaringClass + " accessible";

                Reflection.throwInaccessibleObjectException(msg);

            }

        }

    }

    /**

     * Returns the package name of the given class.

     */

    private static String packageName(Class<?> c) {

        while (c.isArray()) {

            c = c.getComponentType();

        }

        String pn = c.getPackageName();

        return (pn != null) ? pn : "";

    }

    /**

     * 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.

     */

    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(

    /**

     * @throws NullPointerException {@inheritDoc}

     * @since 1.5

     */

    public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {

        throw new AssertionError("All subclasses should override this method");

    }

    /**

     * {@inheritDoc}

     * @throws NullPointerException {@inheritDoc}

     * @since 1.5

     */

    @Override

    public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {

        return AnnotatedElement.super.isAnnotationPresent(annotationClass);

    }

   /**

     * @throws NullPointerException {@inheritDoc}

     * @since 1.8

     */

    @Override

    public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {

        throw new AssertionError("All subclasses should override this method");

    }

    /**

     * @since 1.5

     */

    public Annotation[] getAnnotations() {

        return getDeclaredAnnotations();

    }

    /**

     * @throws NullPointerException {@inheritDoc}

     * @since 1.8

     */

    @Override

    public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {

        // Only annotations on classes are inherited, for all other

        // objects getDeclaredAnnotation is the same as

        // getAnnotation.

        return getAnnotation(annotationClass);

    }

    /**

     * @throws NullPointerException {@inheritDoc}

     * @since 1.8

     */

    @Override

    public <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {

        // Only annotations on classes are inherited, for all other

        // objects getDeclaredAnnotationsByType is the same as

        // getAnnotationsByType.

        return getAnnotationsByType(annotationClass);

    }

    /**

     * @since 1.5

     */

    public Annotation[] getDeclaredAnnotations()  {

        throw new AssertionError("All subclasses should override this method");

    }

    // Shared access checking logic.

    // For non-public members or members in package-private classes,

    // it is necessary to perform somewhat expensive security checks.

    // If the security check succeeds for a given class, it will

    // always succeed (it is not affected by the granting or revoking

    // of permissions); we speed up the check in the common case by

    // remembering the last Class for which the check succeeded.

    //

    // The simple security check for Constructor is to see if

    // the caller has already been seen, verified, and cached.

    // (See also Class.newInstance(), which uses a similar method.)

    //

    // A more complicated security check cache is needed for Method and Field

    // The cache can be either null (empty cache), a 2-array of {caller,target},

    // or a caller (with target implicitly equal to this.clazz).

    // In the 2-array case, the target is always different from the clazz.

    volatile Object securityCheckCache;

    void checkAccess(Class<?> caller, Class<?> clazz, Object obj, int modifiers)

        throws IllegalAccessException

    {

        if (caller == clazz) {  // quick check

            return;             // ACCESS IS OK

        }

        Object cache = securityCheckCache;  // read volatile

        Class<?> targetClass = clazz;

        if (obj != null

            && Modifier.isProtected(modifiers)

            && ((targetClass = obj.getClass()) != clazz)) {

            // Must match a 2-list of { caller, targetClass }.

            if (cache instanceof Class[]) {

                Class<?>[] cache2 = (Class<?>[]) cache;

                if (cache2[1] == targetClass &&

                    cache2[0] == caller) {

                    return;     // ACCESS IS OK

                }

                // (Test cache[1] first since range check for [1]

                // subsumes range check for [0].)

            }

        } else if (cache == caller) {

            // Non-protected case (or obj.class == this.clazz).

            return;             // ACCESS IS OK

        }

        // If no return, fall through to the slow path.

        slowCheckMemberAccess(caller, clazz, obj, modifiers, targetClass);

    }

    // Keep all this slow stuff out of line:

    void slowCheckMemberAccess(Class<?> caller, Class<?> clazz, Object obj, int modifiers,

                               Class<?> targetClass)

        throws IllegalAccessException

    {

        Reflection.ensureMemberAccess(caller, clazz, obj, modifiers);

        // Success: Update the cache.

        Object cache = ((targetClass == clazz)

                        ? caller

                        : new Class<?>[] { caller, targetClass });

        // Note:  The two cache elements are not volatile,

        // but they are effectively final.  The Java memory model

        // guarantees that the initializing stores for the cache

        // elements will occur before the volatile write.

        securityCheckCache = cache;         // write volatile

    }

}