1 /*
2  * Copyright (c) 2010, 2016, 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
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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
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19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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25 
26 /*
27  * This file is available under and governed by the GNU General Public
28  * License version 2 only, as published by the Free Software Foundation.
29  * However, the following notice accompanied the original version of this
30  * file, and Oracle licenses the original version of this file under the BSD
31  * license:
32  */
33 /*
34    Copyright 2009-2013 Attila Szegedi
35 
36    Redistribution and use in source and binary forms, with or without
37    modification, are permitted provided that the following conditions are
38    met:
39    * Redistributions of source code must retain the above copyright
40      notice, this list of conditions and the following disclaimer.
41    * Redistributions in binary form must reproduce the above copyright
42      notice, this list of conditions and the following disclaimer in the
43      documentation and/or other materials provided with the distribution.
44    * Neither the name of the copyright holder nor the names of
45      contributors may be used to endorse or promote products derived from
46      this software without specific prior written permission.
47 
48    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
49    IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
50    TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
51    PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
52    BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
53    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
54    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
55    BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
56    WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
57    OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
58    ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
59 */
60 
61 package jdk.dynalink.linker.support;
62 
63 import java.util.LinkedList;
64 import java.util.List;
65 import java.util.Objects;
66 import jdk.dynalink.linker.GuardedInvocation;
67 import jdk.dynalink.linker.GuardingDynamicLinker;
68 import jdk.dynalink.linker.LinkRequest;
69 import jdk.dynalink.linker.LinkerServices;
70 
71 /**
72  * A {@link GuardingDynamicLinker} that delegates sequentially to a list of
73  * other guarding dynamic linkers in its
74  * {@link #getGuardedInvocation(LinkRequest, LinkerServices)}.
75  */
76 public class CompositeGuardingDynamicLinker implements GuardingDynamicLinker {
77 
78     private final GuardingDynamicLinker[] linkers;
79 
80     /**
81      * Creates a new composite linker.
82      *
83      * @param linkers a list of component linkers.
84      * @throws NullPointerException if {@code linkers} or any of its elements
85      * are null.
86      */
CompositeGuardingDynamicLinker(final Iterable<? extends GuardingDynamicLinker> linkers)87     public CompositeGuardingDynamicLinker(final Iterable<? extends GuardingDynamicLinker> linkers) {
88         final List<GuardingDynamicLinker> l = new LinkedList<>();
89         for(final GuardingDynamicLinker linker: linkers) {
90             l.add(Objects.requireNonNull(linker));
91         }
92         this.linkers = l.toArray(new GuardingDynamicLinker[0]);
93     }
94 
95     /**
96      * Delegates the call to its component linkers. The first non-null value
97      * returned from a component linker is returned. If no component linker
98      * returns a non-null invocation, null is returned.
99      * @param linkRequest the object describing the request for linking a
100      * particular invocation
101      * @param linkerServices linker services
102      * @return the first non-null return value from a component linker, or null
103      * if none of the components returned a non-null.
104      */
105     @Override
getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices)106     public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices)
107             throws Exception {
108         for(final GuardingDynamicLinker linker: linkers) {
109             final GuardedInvocation invocation = linker.getGuardedInvocation(linkRequest, linkerServices);
110             if(invocation != null) {
111                 return invocation;
112             }
113         }
114         return null;
115     }
116 }
117