ToolProvider.java revision 2721:f7ce2cfa4cdb 
1/*
2 * Copyright (c) 2005, 2014, 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 javax.tools;
27
28import java.lang.ref.Reference;
29import java.lang.ref.WeakReference;
30import java.util.HashMap;
31import java.util.Locale;
32import java.util.Map;
33import java.util.logging.Logger;
34import java.util.logging.Level;
35
36import static java.util.logging.Level.*;
37
38/**
39 * Provides methods for locating tool providers, for example,
40 * providers of compilers.  This class complements the
41 * functionality of {@link java.util.ServiceLoader}.
42 *
43 * @author Peter von der Ahé
44 * @since 1.6
45 */
46public class ToolProvider {
47
48    private static final String propertyName = "sun.tools.ToolProvider";
49    private static final String loggerName   = "javax.tools";
50
51    /*
52     * Define the system property "sun.tools.ToolProvider" to enable
53     * debugging:
54     *
55     *     java ... -Dsun.tools.ToolProvider ...
56     */
57    static <T> T trace(Level level, Object reason) {
58        // NOTE: do not make this method private as it affects stack traces
59        try {
60            if (System.getProperty(propertyName) != null) {
61                StackTraceElement[] st = Thread.currentThread().getStackTrace();
62                String method = "???";
63                String cls = ToolProvider.class.getName();
64                if (st.length > 2) {
65                    StackTraceElement frame = st[2];
66                    method = String.format((Locale)null, "%s(%s:%s)",
67                                           frame.getMethodName(),
68                                           frame.getFileName(),
69                                           frame.getLineNumber());
70                    cls = frame.getClassName();
71                }
72                Logger logger = Logger.getLogger(loggerName);
73                if (reason instanceof Throwable) {
74                    logger.logp(level, cls, method,
75                                reason.getClass().getName(), (Throwable)reason);
76                } else {
77                    logger.logp(level, cls, method, String.valueOf(reason));
78                }
79            }
80        } catch (SecurityException ex) {
81            System.err.format((Locale)null, "%s: %s; %s%n",
82                              ToolProvider.class.getName(),
83                              reason,
84                              ex.getLocalizedMessage());
85        }
86        return null;
87    }
88
89    private static final String systemJavaCompilerName
90        = "com.sun.tools.javac.api.JavacTool";
91
92    /**
93     * Returns the Java&trade; programming language compiler provided
94     * with this platform.
95     * @return the compiler provided with this platform or
96     * {@code null} if no compiler is provided
97     */
98    public static JavaCompiler getSystemJavaCompiler() {
99        return instance().getSystemTool(JavaCompiler.class, systemJavaCompilerName);
100    }
101
102    private static final String systemDocumentationToolName
103        = "com.sun.tools.javadoc.api.JavadocTool";
104
105    /**
106     * Returns the Java&trade; programming language documentation tool provided
107     * with this platform.
108     * @return the documentation tool provided with this platform or
109     * {@code null} if no documentation tool is provided
110     */
111    public static DocumentationTool getSystemDocumentationTool() {
112        return instance().getSystemTool(DocumentationTool.class, systemDocumentationToolName);
113    }
114
115    /**
116     * Returns the class loader for tools provided with this platform.
117     * This does not include user-installed tools.  Use the
118     * {@linkplain java.util.ServiceLoader service provider mechanism}
119     * for locating user installed tools.
120     *
121     * @return the class loader for tools provided with this platform
122     * or {@code null} if no tools are provided
123     */
124    public static ClassLoader getSystemToolClassLoader() {
125        return ClassLoader.getSystemClassLoader();
126    }
127
128
129    private static ToolProvider instance;
130
131    private static synchronized ToolProvider instance() {
132        if (instance == null)
133            instance = new ToolProvider();
134        return instance;
135    }
136
137    // Cache for tool classes.
138    // Use weak references to avoid keeping classes around unnecessarily
139    private final Map<String, Reference<Class<?>>> toolClasses = new HashMap<>();
140
141    private ToolProvider() { }
142
143    private <T> T getSystemTool(Class<T> clazz, String name) {
144        Class<? extends T> c = getSystemToolClass(clazz, name);
145        try {
146            return c.asSubclass(clazz).newInstance();
147        } catch (InstantiationException | IllegalAccessException | RuntimeException | Error e) {
148            return trace(WARNING, e);
149        }
150    }
151
152    private <T> Class<? extends T> getSystemToolClass(Class<T> clazz, String name) {
153        Reference<Class<?>> refClass = toolClasses.get(name);
154        Class<?> c = (refClass == null ? null : refClass.get());
155        if (c == null) {
156            try {
157                c = Class.forName(name, false, ClassLoader.getSystemClassLoader());
158            } catch (ClassNotFoundException | RuntimeException | Error e) {
159                return trace(WARNING, e);
160            }
161            toolClasses.put(name, new WeakReference<>(c));
162        }
163        return c.asSubclass(clazz);
164    }
165}
166