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 
26 package jdk.internal.module;
27 
28 import java.lang.module.ModuleDescriptor;
29 import java.lang.module.ModuleDescriptor.Provides;
30 import java.util.ArrayList;
31 import java.util.List;
32 import java.util.Map;
33 import java.util.Objects;
34 import java.util.concurrent.ConcurrentHashMap;
35 import java.util.concurrent.CopyOnWriteArrayList;
36 
37 import jdk.internal.loader.ClassLoaderValue;
38 
39 /**
40  * A <em>services catalog</em>. Each {@code ClassLoader} and {@code Layer} has
41  * an optional {@code ServicesCatalog} for modules that provide services.
42  *
43  * @apiNote This class will be replaced once the ServiceLoader is further
44  *          specified
45  */
46 public final class ServicesCatalog {
47 
48     /**
49      * Represents a service provider in the services catalog.
50      */
51     public final class ServiceProvider {
52         private final Module module;
53         private final String providerName;
54 
ServiceProvider(Module module, String providerName)55         public ServiceProvider(Module module, String providerName) {
56             this.module = module;
57             this.providerName = providerName;
58         }
59 
module()60         public Module module() {
61             return module;
62         }
63 
providerName()64         public String providerName() {
65             return providerName;
66         }
67 
68         @Override
hashCode()69         public int hashCode() {
70             return Objects.hash(module, providerName);
71         }
72 
73         @Override
equals(Object ob)74         public boolean equals(Object ob) {
75             if (!(ob instanceof ServiceProvider))
76                 return false;
77             ServiceProvider that = (ServiceProvider)ob;
78             return Objects.equals(this.module, that.module)
79                     && Objects.equals(this.providerName, that.providerName);
80         }
81     }
82 
83     // service name -> list of providers
84     private final Map<String, List<ServiceProvider>> map = new ConcurrentHashMap<>();
85 
ServicesCatalog()86     private ServicesCatalog() { }
87 
88     /**
89      * Creates a ServicesCatalog that supports concurrent registration and
90      * and lookup
91      */
create()92     public static ServicesCatalog create() {
93         return new ServicesCatalog();
94     }
95 
96     /**
97      * Returns the list of service provides for the given service type
98      * name, creating it if needed.
99      */
providers(String service)100     private List<ServiceProvider> providers(String service) {
101         // avoid computeIfAbsent here
102         List<ServiceProvider> list = map.get(service);
103         if (list == null) {
104             list = new CopyOnWriteArrayList<>();
105             List<ServiceProvider> prev = map.putIfAbsent(service, list);
106             if (prev != null)
107                 list = prev;  // someone else got there
108         }
109         return list;
110     }
111 
112     /**
113      * Registers the providers in the given module in this services catalog.
114      */
register(Module module)115     public void register(Module module) {
116         ModuleDescriptor descriptor = module.getDescriptor();
117         for (Provides provides : descriptor.provides()) {
118             String service = provides.service();
119             List<String> providerNames = provides.providers();
120             int count = providerNames.size();
121             if (count == 1) {
122                 String pn = providerNames.get(0);
123                 providers(service).add(new ServiceProvider(module, pn));
124             } else {
125                 List<ServiceProvider> list = new ArrayList<>(count);
126                 for (String pn : providerNames) {
127                     list.add(new ServiceProvider(module, pn));
128                 }
129                 providers(service).addAll(list);
130             }
131         }
132     }
133 
134     /**
135      * Add a provider in the given module to this services catalog
136      *
137      * @apiNote This method is for use by java.lang.instrument
138      */
addProvider(Module module, Class<?> service, Class<?> impl)139     public void addProvider(Module module, Class<?> service, Class<?> impl) {
140         List<ServiceProvider> list = providers(service.getName());
141         list.add(new ServiceProvider(module, impl.getName()));
142     }
143 
144     /**
145      * Returns the (possibly empty) list of service providers that implement
146      * the given service type.
147      */
findServices(String service)148     public List<ServiceProvider> findServices(String service) {
149         return map.getOrDefault(service, List.of());
150     }
151 
152     /**
153      * Returns the ServicesCatalog for the given class loader or {@code null}
154      * if there is none.
155      */
getServicesCatalogOrNull(ClassLoader loader)156     public static ServicesCatalog getServicesCatalogOrNull(ClassLoader loader) {
157         return CLV.get(loader);
158     }
159 
160     /**
161      * Returns the ServicesCatalog for the given class loader, creating it if
162      * needed.
163      */
getServicesCatalog(ClassLoader loader)164     public static ServicesCatalog getServicesCatalog(ClassLoader loader) {
165         // CLV.computeIfAbsent(loader, (cl, clv) -> create());
166         ServicesCatalog catalog = CLV.get(loader);
167         if (catalog == null) {
168             catalog = create();
169             ServicesCatalog previous = CLV.putIfAbsent(loader, catalog);
170             if (previous != null) catalog = previous;
171         }
172         return catalog;
173     }
174 
175     // the ServicesCatalog registered to a class loader
176     private static final ClassLoaderValue<ServicesCatalog> CLV = new ClassLoaderValue<>();
177 }
178