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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.util;
import static java.nio.charset.StandardCharsets.UTF_8;
import com.google.common.io.ByteStreams;
import java.io.IOException;
import java.io.InputStream;
/**
* A little utility to load resources (property files) from jars or the classpath. Recommended for
* longer texts that do not fit nicely into a piece of Java code - e.g. a template for a lengthy
* email.
*/
public final class ResourceFileLoader {
private ResourceFileLoader() {}
public static boolean resourceExists(Class<?> relativeToClass, String resourceName) {
try (InputStream resourceStream = getResourceAsStream(relativeToClass, resourceName)) {
return resourceStream != null;
} catch (IOException e) {
return false;
}
}
/**
* Loads a text resource that is located in a directory on the Java classpath that corresponds to
* the package of <code>relativeToClass</code> using UTF8 encoding. E.g. <code>
* loadResource(Class.forName("com.google.foo.Foo", "bar.txt"))</code> will look for <code>
* com/google/foo/bar.txt</code> in the classpath.
*/
public static String loadResource(Class<?> relativeToClass, String resourceName)
throws IOException {
try (InputStream stream = getResourceAsStream(relativeToClass, resourceName)) {
if (stream == null) {
throw new IOException(resourceName + " not found.");
}
return new String(ByteStreams.toByteArray(stream), UTF_8);
}
}
private static InputStream getResourceAsStream(Class<?> relativeToClass, String resourceName) {
ClassLoader loader = relativeToClass.getClassLoader();
String resource = resolveResource(relativeToClass, resourceName);
return loader.getResourceAsStream(resource);
}
/**
* Converts a relative resource name and Java class to a full resource path, using the same logic
* as {@link #loadResource}.
*/
public static String resolveResource(Class<?> relativeToClass, String resourceName) {
// TODO(bazel-team): use relativeToClass.getPackage().getName().
String className = relativeToClass.getName();
String packageName = className.substring(0, className.lastIndexOf('.'));
String path = packageName.replace('.', '/');
return path + '/' + resourceName;
}
}