ServiceProxy.java revision 2571:10fc81ac75b4 
1/*
2 * Copyright (c) 2006, 2012, 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 com.sun.tools.javac.processing;
27
28import java.io.BufferedReader;
29import java.io.FileNotFoundException;
30import java.io.IOException;
31import java.io.InputStream;
32import java.io.InputStreamReader;
33import java.net.MalformedURLException;
34import java.net.URL;
35
36/**
37 * Utility class to determine if a service can be found on the
38 * path that might be used to create a class loader.
39 *
40 * <p><b>This is NOT part of any supported API.
41 * If you write code that depends on this, you do so at your own risk.
42 * This code and its internal interfaces are subject to change or
43 * deletion without notice.</b>
44 *
45 */
46// based on sun.misc.Service
47class ServiceProxy {
48    static class ServiceConfigurationError extends Error {
49        static final long serialVersionUID = 7732091036771098303L;
50
51        ServiceConfigurationError(String msg) {
52            super(msg);
53        }
54    }
55
56    private static final String prefix = "META-INF/services/";
57
58    private static void fail(Class<?> service, String msg)
59            throws ServiceConfigurationError {
60        throw new ServiceConfigurationError(service.getName() + ": " + msg);
61    }
62
63    private static void fail(Class<?> service, URL u, int line, String msg)
64            throws ServiceConfigurationError {
65        fail(service, u + ":" + line + ": " + msg);
66    }
67
68    /**
69     * Parse the content of the given URL as a provider-configuration file.
70     *
71     * @param  service
72     *         The service class for which providers are being sought;
73     *         used to construct error detail strings
74     *
75     * @param  u
76     *         The URL naming the configuration file to be parsed
77     *
78     * @return true if the name of a service is found
79     *
80     * @throws ServiceConfigurationError
81     *         If an I/O error occurs while reading from the given URL, or
82     *         if a configuration-file format error is detected
83     */
84    private static boolean parse(Class<?> service, URL u) throws ServiceConfigurationError {
85        InputStream in = null;
86        BufferedReader r = null;
87        try {
88            in = u.openStream();
89            r = new BufferedReader(new InputStreamReader(in, "utf-8"));
90            int lc = 1;
91            String ln;
92            while ((ln = r.readLine()) != null) {
93                int ci = ln.indexOf('#');
94                if (ci >= 0) ln = ln.substring(0, ci);
95                ln = ln.trim();
96                int n = ln.length();
97                if (n != 0) {
98                    if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0))
99                        fail(service, u, lc, "Illegal configuration-file syntax");
100                    int cp = ln.codePointAt(0);
101                    if (!Character.isJavaIdentifierStart(cp))
102                        fail(service, u, lc, "Illegal provider-class name: " + ln);
103                    for (int i = Character.charCount(cp); i < n; i += Character.charCount(cp)) {
104                        cp = ln.codePointAt(i);
105                        if (!Character.isJavaIdentifierPart(cp) && (cp != '.'))
106                            fail(service, u, lc, "Illegal provider-class name: " + ln);
107                    }
108                    return true;
109                }
110            }
111        } catch (FileNotFoundException x) {
112            return false;
113        } catch (IOException x) {
114            fail(service, ": " + x);
115        } finally {
116            try {
117                if (r != null) r.close();
118            } catch (IOException y) {
119                fail(service, ": " + y);
120            }
121            try {
122                if (in != null) in.close();
123            } catch (IOException y) {
124                fail(service, ": " + y);
125            }
126        }
127        return false;
128    }
129
130    /**
131     * Return true if a description for at least one service is found in the
132     * service configuration files in the given URLs.
133     */
134    public static boolean hasService(Class<?> service, URL[] urls)
135            throws ServiceConfigurationError {
136        for (URL url: urls) {
137            try {
138                String fullName = prefix + service.getName();
139                URL u = new URL(url, fullName);
140                boolean found = parse(service, u);
141                if (found)
142                    return true;
143            } catch (MalformedURLException e) {
144                // should not happen; ignore it if it does
145            }
146        }
147        return false;
148    }
149}
150