1 /*
   2  * Copyright (c) 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 package java.lang;
  26 
  27 import java.lang.module.Configuration;
  28 import java.lang.module.ModuleReference;
  29 import java.lang.reflect.Module;
  30 import java.net.URI;
  31 
  32 /**
  33  * A NamedPackage represents a package by name in a specific module.
  34  *
  35  * A class loader will automatically create NamedPackage for each
  36  * package when a class is defined.  Package object is lazily
  37  * defined until Class::getPackage, Package::getPackage(s), or
  38  * ClassLoader::getDefinedPackage(s) method is called.
  39  *
  40  * NamedPackage allows ClassLoader to keep track of the runtime
  41  * packages with minimal footprint and avoid constructing Package
  42  * object.
  43  */
  44 class NamedPackage {
  45     private final String name;
  46     private final Module module;
  47 
  48     NamedPackage(String pn, Module module) {
  49         if (pn.isEmpty() && module.isNamed()) {
  50             throw new InternalError("unnamed package in  " + module);
  51         }
  52         this.name = pn.intern();
  53         this.module = module;
  54     }
  55 
  56     /**
  57      * Returns the name of this package.
  58      */
  59     String packageName() {
  60         return name;
  61     }
  62 
  63     /**
  64      * Returns the module of this named package.
  65      */
  66     Module module() {
  67         return module;
  68     }
  69 
  70     /**
  71      * Returns the location of the module if this named package is in
  72      * a named module; otherwise, returns null.
  73      */
  74     URI location() {
  75         if (module.isNamed() && module.getLayer() != null) {
  76             Configuration cf = module.getLayer().configuration();
  77             ModuleReference mref
  78                 = cf.findModule(module.getName()).getWhenPresent().reference();
  79             return mref.location().orElse(null);
  80         }
  81         return null;
  82     }
  83 
  84     /**
  85      * Creates a Package object of the given name and module.
  86      */
  87     static Package toPackage(String name, Module module) {
  88         return new Package(name, module);
  89     }
  90 }