1/*
2 * Copyright (c) 2014, 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
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
26package java.lang.module;
27
28import java.io.IOException;
29import java.net.URI;
30import java.util.Objects;
31import java.util.Optional;
32
33
34/**
35 * A reference to a module's content.
36 *
37 * <p> A module reference is a concrete implementation of this class that
38 * implements the abstract methods defined by this class. It contains the
39 * module's descriptor and its location, if known.  It also has the ability to
40 * create a {@link ModuleReader} in order to access the module's content, which
41 * may be inside the Java run-time system itself or in an artifact such as a
42 * modular JAR file.
43 *
44 * @see ModuleFinder
45 * @see ModuleReader
46 * @since 9
47 * @spec JPMS
48 */
49
50public abstract class ModuleReference {
51
52    private final ModuleDescriptor descriptor;
53    private final URI location;
54
55    /**
56     * Constructs a new instance of this class.
57     *
58     * @param descriptor
59     *        The module descriptor
60     * @param location
61     *        The module location or {@code null} if not known
62     */
63    protected ModuleReference(ModuleDescriptor descriptor, URI location) {
64        this.descriptor = Objects.requireNonNull(descriptor);
65        this.location = location;
66    }
67
68    /**
69     * Returns the module descriptor.
70     *
71     * @return The module descriptor
72     */
73    public final ModuleDescriptor descriptor() {
74        return descriptor;
75    }
76
77    /**
78     * Returns the location of this module's content, if known.
79     *
80     * <p> This URI, when present, can be used as the {@linkplain
81     * java.security.CodeSource#getLocation location} value of a {@link
82     * java.security.CodeSource CodeSource} so that a module's classes can be
83     * granted specific permissions when loaded by a {@link
84     * java.security.SecureClassLoader SecureClassLoader}.
85     *
86     * @return The location or an empty {@code Optional} if not known
87     */
88    public final Optional<URI> location() {
89        return Optional.ofNullable(location);
90    }
91
92    /**
93     * Opens the module content for reading.
94     *
95     * @return A {@code ModuleReader} to read the module
96     *
97     * @throws IOException
98     *         If an I/O error occurs
99     * @throws SecurityException
100     *         If denied by the security manager
101     */
102    public abstract ModuleReader open() throws IOException;
103}
104