1 /*
   2  * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.xml.internal.ws.api.pipe;
  27 
  28 import java.security.AccessController;
  29 import java.security.PrivilegedAction;
  30 
  31 /**
  32  * Interception for {@link Fiber} context switch.
  33  *
  34  * <p>
  35  * Even though pipeline runs asynchronously, sometimes it's desirable
  36  * to bind some state to the current thread running a fiber. Such state
  37  * may include security subject (in terms of {@link AccessController#doPrivileged}),
  38  * or a transaction.
  39  *
  40  * <p>
  41  * This mechanism makes it possible to do such things, by allowing
  42  * some code to be executed before and after a thread executes a fiber.
  43  *
  44  * <p>
  45  * The design also encapsulates the entire fiber execution in a single
  46  * opaque method invocation {@link Work#execute}, allowing the use of
  47  * {@code finally} block.
  48  *
  49  *
  50  * @author Kohsuke Kawaguchi
  51  */
  52 public interface FiberContextSwitchInterceptor {
  53     /**
  54      * Allows the interception of the fiber execution.
  55      *
  56      * <p>
  57      * This method needs to be implemented like this:
  58      *
  59      * <pre>
  60      * &lt;R,P> R execute( Fiber f, P p, Work&lt;R,P> work ) {
  61      *   // do some preparation work
  62      *   ...
  63      *   try {
  64      *     // invoke
  65      *     return work.execute(p);
  66      *   } finally {
  67      *     // do some clean up work
  68      *     ...
  69      *   }
  70      * }
  71      * </pre>
  72      *
  73      * <p>
  74      * While somewhat unintuitive,
  75      * this interception mechanism enables the interceptor to wrap
  76      * the whole fiber execution into a {@link AccessController#doPrivileged(PrivilegedAction)},
  77      * for example.
  78      *
  79      * @param f
  80      *      {@link Fiber} to be executed.
  81      * @param p
  82      *      The opaque parameter value for {@link Work}. Simply pass this value to
  83      *      {@link Work#execute(Object)}.
  84      * @return
  85      *      The opaque return value from the the {@link Work}. Simply return
  86      *      the value from {@link Work#execute(Object)}.
  87      */
  88     <R,P> R execute( Fiber f, P p, Work<R,P> work );
  89 
  90     /**
  91      * Abstraction of the execution that happens inside the interceptor.
  92      */
  93     interface Work<R,P> {
  94         /**
  95          * Have the current thread executes the current fiber,
  96          * and returns when it stops doing so.
  97          *
  98          * <p>
  99          * The parameter and the return value is controlled by the
 100          * JAX-WS runtime, and interceptors should simply treat
 101          * them as opaque values.
 102          */
 103         R execute(P param);
 104     }
 105 }
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