| /* VMStackWalker.java -- Reference implementation of VM hooks for stack access |
| Copyright (C) 2005, 2006, 2010 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 02110-1301 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| package gnu.classpath; |
| |
| /** |
| * This class provides access to the classes on the Java stack |
| * for reflection and security purposes. |
| * |
| * <p> |
| * This class is only available to privileged code (i.e., code loaded |
| * by the bootstrap loader). |
| * |
| * @author John Keiser |
| * @author Eric Blake <ebb9@email.byu.edu> |
| * @author Archie Cobbs |
| */ |
| public final class VMStackWalker |
| { |
| |
| private VMStackWalker() {} // Prohibits instantiation. |
| |
| /** |
| * Get a list of all the classes currently executing methods on the |
| * Java stack. <code>getClassContext()[0]</code> is the class associated |
| * with the currently executing method, i.e., the method that called |
| * <code>VMStackWalker.getClassContext()</code> (possibly through |
| * reflection). So you may need to pop off these stack frames from |
| * the top of the stack: |
| * <ul> |
| * <li><code>VMStackWalker.getClassContext()</code> |
| * <li><code>Method.invoke()</code> |
| * </ul> |
| * |
| * @return an array of the declaring classes of each stack frame |
| */ |
| public static native Class[] getClassContext(); |
| |
| /** |
| * Get the class associated with the method invoking the method |
| * invoking this method, or <code>null</code> if the stack is not |
| * that deep (e.g., invoked via JNI invocation API). This method |
| * is an optimization for the expression <code>getClassContext()[1]</code> |
| * and should return the same result. |
| * |
| * <p> |
| * VM implementers are encouraged to provide a more efficient |
| * version of this method. |
| */ |
| public static Class getCallingClass() |
| { |
| Class[] ctx = getClassContext(); |
| if (ctx.length < 3) |
| return null; |
| return ctx[2]; |
| } |
| |
| /** |
| * Get the class loader associated with the Class returned by |
| * <code>getCallingClass()</code>, or <code>null</code> if no such class |
| * exists or it is the boot loader. This method is an optimization for the |
| * expression <code>VMStackWalker.getClassLoader(getClassContext()[1])</code> |
| * and should return the same result. |
| * |
| * <p> |
| * VM implementers are encouraged to provide a more efficient |
| * version of this method. |
| */ |
| public static ClassLoader getCallingClassLoader() |
| { |
| Class[] ctx = getClassContext(); |
| if (ctx.length < 3) |
| return null; |
| return getClassLoader(ctx[2]); |
| } |
| |
| /** |
| * Retrieve the class's ClassLoader, or <code>null</code> if loaded |
| * by the bootstrap loader. I.e., this should return the same thing |
| * as {@link java.lang.VMClass#getClassLoader}. This duplicate version |
| * is here to work around access permissions. |
| */ |
| public static native ClassLoader getClassLoader(Class cl); |
| |
| /** |
| * Walk up the stack and return the first non-null class loader. |
| * If there aren't any non-null class loaders on the stack, return null. |
| */ |
| public static ClassLoader firstNonNullClassLoader() |
| { |
| Class[] stack = getClassContext(); |
| for (int i = 0; i < stack.length; i++) |
| { |
| ClassLoader loader = getClassLoader(stack[i]); |
| if (loader != null) |
| return loader; |
| } |
| return null; |
| } |
| } |