ToolProvider.java revision 4104:4012b3f11f0d 
1/*
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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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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
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24 */
25
26package javax.tools;
27
28import java.lang.reflect.InvocationTargetException;
29import java.lang.reflect.Method;
30import java.security.AccessController;
31import java.security.PrivilegedAction;
32import java.util.Iterator;
33import java.util.ServiceConfigurationError;
34import java.util.ServiceLoader;
35
36/**
37 * Provides methods for locating tool providers, for example,
38 * providers of compilers.  This class complements the
39 * functionality of {@link java.util.ServiceLoader}.
40 *
41 * @author Peter von der Ahé
42 * @since 1.6
43 */
44public class ToolProvider {
45
46    private static final String systemJavaCompilerModule = "jdk.compiler";
47    private static final String systemJavaCompilerName   = "com.sun.tools.javac.api.JavacTool";
48
49    /**
50     * Returns the Java™ programming language compiler provided
51     * with this platform.
52     * <p>The file manager returned by calling
53     * {@link JavaCompiler#getStandardFileManager getStandardFileManager}
54     * on this compiler supports paths provided by any
55     * {@linkplain java.nio.file.FileSystem filesystem}.</p>
56     * @return the compiler provided with this platform or
57     * {@code null} if no compiler is provided
58     * @implNote This implementation returns the compiler provided
59     * by the {@code jdk.compiler} module if that module is available,
60     * and {@code null} otherwise.
61     */
62    public static JavaCompiler getSystemJavaCompiler() {
63        return getSystemTool(JavaCompiler.class,
64                systemJavaCompilerModule, systemJavaCompilerName);
65    }
66
67    private static final String systemDocumentationToolModule = "jdk.javadoc";
68    private static final String systemDocumentationToolName = "jdk.javadoc.internal.api.JavadocTool";
69
70    /**
71     * Returns the Java&trade; programming language documentation tool provided
72     * with this platform.
73     * <p>The file manager returned by calling
74     * {@link DocumentationTool#getStandardFileManager getStandardFileManager}
75     * on this tool supports paths provided by any
76     * {@linkplain java.nio.file.FileSystem filesystem}.</p>
77     * @return the documentation tool provided with this platform or
78     * {@code null} if no documentation tool is provided
79     * @implNote This implementation returns the tool provided
80     * by the {@code jdk.javadoc} module if that module is available,
81     * and {@code null} otherwise.
82     */
83    public static DocumentationTool getSystemDocumentationTool() {
84        return getSystemTool(DocumentationTool.class,
85                systemDocumentationToolModule, systemDocumentationToolName);
86    }
87
88    /**
89     * Returns a class loader that may be used to load system tools,
90     * or {@code null} if no such special loader is provided.
91     * @implSpec This implementation always returns {@code null}.
92     * @deprecated This method is subject to removal in a future version of
93     * Java SE.
94     * Use the {@link java.util.spi.ToolProvider system tool provider} or
95     * {@link java.util.ServiceLoader service loader} mechanisms to
96     * locate system tools as well as user-installed tools.
97     * @return a class loader, or {@code null}
98     */
99    @Deprecated
100    public static ClassLoader getSystemToolClassLoader() {
101        return null;
102    }
103
104    private static final boolean useLegacy;
105
106    static {
107        Class<?> c = null;
108        try {
109            c = Class.forName("java.lang.Module");
110        } catch (Throwable t) {
111        }
112        useLegacy = (c == null);
113    }
114
115    /**
116     * Get an instance of a system tool using the service loader.
117     * @implNote         By default, this returns the implementation in the specified module.
118     *                   For limited backward compatibility, if this code is run on an older version
119     *                   of the Java platform that does not support modules, this method will
120     *                   try and create an instance of the named class. Note that implies the
121     *                   class must be available on the system class path.
122     * @param <T>        the interface of the tool
123     * @param clazz      the interface of the tool
124     * @param moduleName the name of the module containing the desired implementation
125     * @param className  the class name of the desired implementation
126     * @return the specified implementation of the tool
127     */
128    private static <T> T getSystemTool(Class<T> clazz, String moduleName, String className) {
129        if (useLegacy) {
130            try {
131                return Class.forName(className, true, ClassLoader.getSystemClassLoader()).
132                    asSubclass(clazz).getConstructor().newInstance();
133            } catch (ReflectiveOperationException e) {
134                throw new Error(e);
135            }
136        }
137
138        try {
139            ServiceLoader<T> sl = ServiceLoader.load(clazz, ClassLoader.getSystemClassLoader());
140            for (Iterator<T> iter = sl.iterator(); iter.hasNext(); ) {
141                T tool = iter.next();
142                if (matches(tool, moduleName))
143                    return tool;
144            }
145        } catch (ServiceConfigurationError e) {
146            throw new Error(e);
147        }
148        return null;
149    }
150
151    /**
152     * Determine if this is the desired tool instance.
153     * @param <T>        the interface of the tool
154     * @param tool       the instance of the tool
155     * @param moduleName the name of the module containing the desired implementation
156     * @return true if and only if the tool matches the specified criteria
157     */
158    private static <T> boolean matches(T tool, String moduleName) {
159        PrivilegedAction<Boolean> pa = () -> {
160            // for now, use reflection to implement
161            //      return moduleName.equals(tool.getClass().getModule().getName());
162            try {
163                Method getModuleMethod = Class.class.getDeclaredMethod("getModule");
164                Object toolModule = getModuleMethod.invoke(tool.getClass());
165                Method getNameMethod = toolModule.getClass().getDeclaredMethod("getName");
166                String toolModuleName = (String) getNameMethod.invoke(toolModule);
167                return moduleName.equals(toolModuleName);
168            } catch (InvocationTargetException | NoSuchMethodException | IllegalAccessException e) {
169                return false;
170            }
171        };
172        return AccessController.doPrivileged(pa);
173    }
174}
175