1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
|
/*
* Copyright 2019 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.auto.value.processor;
import static java.util.stream.Collectors.toList;
import com.google.common.collect.ImmutableList;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.StandardCharsets;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.ServiceConfigurationError;
/**
* A replacement for {@link java.util.ServiceLoader} that avoids certain long-standing bugs. This
* simpler implementation does not bother with lazy loading but returns all the service
* implementations in one list. It makes sure that {@link URLConnection#setUseCaches} is called to
* turn off jar caching, since that tends to lead to problems in versions before JDK 9.
*
* @see <a href="https://github.com/google/auto/issues/718">Issue #718</a>
* @see <a href="https://bugs.openjdk.java.net/browse/JDK-8156014">JDK-8156014</a>
*/
public final class SimpleServiceLoader {
private SimpleServiceLoader() {}
public static <T> ImmutableList<T> load(Class<? extends T> service, ClassLoader loader) {
String resourceName = "META-INF/services/" + service.getName();
List<URL> resourceUrls;
try {
resourceUrls = Collections.list(loader.getResources(resourceName));
} catch (IOException e) {
throw new ServiceConfigurationError("Could not look up " + resourceName, e);
}
ImmutableList.Builder<T> providers = ImmutableList.builder();
for (URL resourceUrl : resourceUrls) {
try {
providers.addAll(providersFromUrl(resourceUrl, service, loader));
} catch (IOException e) {
throw new ServiceConfigurationError("Could not read " + resourceUrl, e);
}
}
return providers.build();
}
private static <T> ImmutableList<T> providersFromUrl(
URL resourceUrl, Class<T> service, ClassLoader loader) throws IOException {
ImmutableList.Builder<T> providers = ImmutableList.builder();
URLConnection urlConnection = resourceUrl.openConnection();
urlConnection.setUseCaches(false);
try (InputStream in = urlConnection.getInputStream();
BufferedReader reader =
new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8))) {
for (String line : reader.lines().collect(toList())) {
Optional<String> maybeClassName = parseClassName(line);
if (maybeClassName.isPresent()) {
String className = maybeClassName.get();
Class<?> c;
try {
c = Class.forName(className, false, loader);
} catch (ClassNotFoundException e) {
throw new ServiceConfigurationError("Could not load " + className, e);
}
if (!service.isAssignableFrom(c)) {
throw new ServiceConfigurationError(
"Class " + className + " is not assignable to " + service.getName());
}
try {
Object provider = c.getConstructor().newInstance();
providers.add(service.cast(provider));
} catch (ReflectiveOperationException e) {
throw new ServiceConfigurationError("Could not construct " + className, e);
}
}
}
return providers.build();
}
}
private static Optional<String> parseClassName(String line) {
int hash = line.indexOf('#');
if (hash >= 0) {
line = line.substring(0, hash);
}
line = line.trim();
return line.isEmpty() ? Optional.empty() : Optional.of(line);
}
}
|
