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26 package java.lang.reflect;
28 import java.security.AccessController;
29 import sun.reflect.Reflection;
30 import sun.reflect.ReflectionFactory;
31 import java.lang.annotation.Annotation;
34 * The AccessibleObject class is the base class for Field, Method and
35 * Constructor objects. It provides the ability to flag a reflected
36 * object as suppressing default Java language access control checks
37 * when it is used. The access checks--for public, default (package)
38 * access, protected, and private members--are performed when Fields,
39 * Methods or Constructors are used to set or get fields, to invoke
40 * methods, or to create and initialize new instances of classes,
43 * <p>Setting the {@code accessible} flag in a reflected object
44 * permits sophisticated applications with sufficient privilege, such
45 * as Java Object Serialization or other persistence mechanisms, to
46 * manipulate objects in a manner that would normally be prohibited.
48 * <p>By default, a reflected object is <em>not</em> accessible.
53 * @see ReflectPermission
57 public class AccessibleObject implements AnnotatedElement {
60 * The Permission object that is used to check whether a client
61 * has sufficient privilege to defeat Java language access
64 static final private java.security.Permission ACCESS_PERMISSION =
65 new ReflectPermission("suppressAccessChecks");
68 * Convenience method to set the {@code accessible} flag for an
69 * array of objects with a single security check (for efficiency).
71 * <p>First, if there is a security manager, its
72 * {@code checkPermission} method is called with a
73 * {@code ReflectPermission("suppressAccessChecks")} permission.
75 * <p>A {@code SecurityException} is raised if {@code flag} is
76 * {@code true} but accessibility of any of the elements of the input
77 * {@code array} may not be changed (for example, if the element
78 * object is a {@link Constructor} object for the class {@link
79 * java.lang.Class}). In the event of such a SecurityException, the
80 * accessibility of objects is set to {@code flag} for array elements
81 * upto (and excluding) the element for which the exception occurred; the
82 * accessibility of elements beyond (and including) the element for which
83 * the exception occurred is unchanged.
85 * @param array the array of AccessibleObjects
86 * @param flag the new value for the {@code accessible} flag
88 * @throws SecurityException if the request is denied.
89 * @see SecurityManager#checkPermission
90 * @see java.lang.RuntimePermission
92 public static void setAccessible(AccessibleObject[] array, boolean flag)
93 throws SecurityException {
94 SecurityManager sm = System.getSecurityManager();
95 if (sm != null) sm.checkPermission(ACCESS_PERMISSION);
96 for (int i = 0; i < array.length; i++) {
97 setAccessible0(array[i], flag);
102 * Set the {@code accessible} flag for this object to
103 * the indicated boolean value. A value of {@code true} indicates that
104 * the reflected object should suppress Java language access
105 * checking when it is used. A value of {@code false} indicates
106 * that the reflected object should enforce Java language access checks.
108 * <p>First, if there is a security manager, its
109 * {@code checkPermission} method is called with a
110 * {@code ReflectPermission("suppressAccessChecks")} permission.
112 * <p>A {@code SecurityException} is raised if {@code flag} is
113 * {@code true} but accessibility of this object may not be changed
114 * (for example, if this element object is a {@link Constructor} object for
115 * the class {@link java.lang.Class}).
117 * <p>A {@code SecurityException} is raised if this object is a {@link
118 * java.lang.reflect.Constructor} object for the class
119 * {@code java.lang.Class}, and {@code flag} is true.
121 * @param flag the new value for the {@code accessible} flag
122 * @throws SecurityException if the request is denied.
123 * @see SecurityManager#checkPermission
124 * @see java.lang.RuntimePermission
126 public void setAccessible(boolean flag) throws SecurityException {
127 SecurityManager sm = System.getSecurityManager();
128 if (sm != null) sm.checkPermission(ACCESS_PERMISSION);
129 setAccessible0(this, flag);
132 /* Check that you aren't exposing java.lang.Class.<init>. */
133 private static void setAccessible0(AccessibleObject obj, boolean flag)
134 throws SecurityException
136 if (obj instanceof Constructor && flag == true) {
137 Constructor<?> c = (Constructor<?>)obj;
138 if (c.getDeclaringClass() == Class.class) {
139 throw new SecurityException("Can not make a java.lang.Class" +
140 " constructor accessible");
147 * Get the value of the {@code accessible} flag for this object.
149 * @return the value of the object's {@code accessible} flag
151 public boolean isAccessible() {
156 * Constructor: only used by the Java Virtual Machine.
158 protected AccessibleObject() {}
160 // Indicates whether language-level access checks are overridden
161 // by this object. Initializes to "false". This field is used by
162 // Field, Method, and Constructor.
164 // NOTE: for security purposes, this field must not be visible
165 // outside this package.
168 // Reflection factory used by subclasses for creating field,
169 // method, and constructor accessors. Note that this is called
170 // very early in the bootstrapping process.
171 static final ReflectionFactory reflectionFactory =
172 AccessController.doPrivileged(
173 new sun.reflect.ReflectionFactory.GetReflectionFactoryAction());
176 * @throws NullPointerException {@inheritDoc}
179 public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
180 throw new AssertionError("All subclasses should override this method");
184 * @throws NullPointerException {@inheritDoc}
187 public boolean isAnnotationPresent(
188 Class<? extends Annotation> annotationClass) {
189 return getAnnotation(annotationClass) != null;
195 public Annotation[] getAnnotations() {
196 return getDeclaredAnnotations();
202 public Annotation[] getDeclaredAnnotations() {
203 throw new AssertionError("All subclasses should override this method");
207 // Shared access checking logic.
209 // For non-public members or members in package-private classes,
210 // it is necessary to perform somewhat expensive security checks.
211 // If the security check succeeds for a given class, it will
212 // always succeed (it is not affected by the granting or revoking
213 // of permissions); we speed up the check in the common case by
214 // remembering the last Class for which the check succeeded.
216 // The simple security check for Constructor is to see if
217 // the caller has already been seen, verified, and cached.
218 // (See also Class.newInstance(), which uses a similar method.)
220 // A more complicated security check cache is needed for Method and Field
221 // The cache can be either null (empty cache), a 2-array of {caller,target},
222 // or a caller (with target implicitly equal to this.clazz).
223 // In the 2-array case, the target is always different from the clazz.
224 volatile Object securityCheckCache;
226 void checkAccess(Class<?> caller, Class<?> clazz, Object obj, int modifiers)
227 throws IllegalAccessException
229 if (caller == clazz) { // quick check
230 return; // ACCESS IS OK
232 Object cache = securityCheckCache; // read volatile
233 Class<?> targetClass = clazz;
235 && Modifier.isProtected(modifiers)
236 && ((targetClass = obj.getClass()) != clazz)) {
237 // Must match a 2-list of { caller, targetClass }.
238 if (cache instanceof Class[]) {
239 Class<?>[] cache2 = (Class<?>[]) cache;
240 if (cache2[1] == targetClass &&
241 cache2[0] == caller) {
242 return; // ACCESS IS OK
244 // (Test cache[1] first since range check for [1]
245 // subsumes range check for [0].)
247 } else if (cache == caller) {
248 // Non-protected case (or obj.class == this.clazz).
249 return; // ACCESS IS OK
252 // If no return, fall through to the slow path.
253 slowCheckMemberAccess(caller, clazz, obj, modifiers, targetClass);
256 // Keep all this slow stuff out of line:
257 void slowCheckMemberAccess(Class<?> caller, Class<?> clazz, Object obj, int modifiers,
258 Class<?> targetClass)
259 throws IllegalAccessException
261 Reflection.ensureMemberAccess(caller, clazz, obj, modifiers);
263 // Success: Update the cache.
264 Object cache = ((targetClass == clazz)
266 : new Class<?>[] { caller, targetClass });
268 // Note: The two cache elements are not volatile,
269 // but they are effectively final. The Java memory model
270 // guarantees that the initializing stores for the cache
271 // elements will occur before the volatile write.
272 securityCheckCache = cache; // write volatile