org.apache.lucene.analysis.util.ClasspathResourceLoader.java Source code

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Here is the source code for org.apache.lucene.analysis.util.ClasspathResourceLoader.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.lucene.analysis.util;

import java.io.IOException;
import java.io.InputStream;

import org.apache.lucene.util.SuppressForbidden;

/**
 * Simple {@link ResourceLoader} that uses {@link ClassLoader#getResourceAsStream(String)}
 * and {@link Class#forName(String,boolean,ClassLoader)} to open resources and
 * classes, respectively.
 */
public final class ClasspathResourceLoader implements ResourceLoader {
    private final Class<?> clazz;
    private final ClassLoader loader;

    /**
     * Creates an instance using the context classloader to load resources and classes.
     * Resource paths must be absolute.
     * 
     * @deprecated You should not use this ctor, because it uses the thread's context
     * class loader, which is bad programming style. Please specify a reference class or
     * a {@link ClassLoader} instead.
     * @see #ClasspathResourceLoader(ClassLoader)
     * @see #ClasspathResourceLoader(Class)
     */
    @Deprecated
    @SuppressForbidden(reason = "Deprecated method uses thread's context classloader, but there for backwards compatibility")
    public ClasspathResourceLoader() {
        this(Thread.currentThread().getContextClassLoader());
    }

    /**
     * Creates an instance using the given classloader to load Resources and classes.
     * Resource paths must be absolute.
     */
    public ClasspathResourceLoader(ClassLoader loader) {
        this(null, loader);
    }

    /**
     * Creates an instance using the context classloader to load Resources and classes
     * Resources are resolved relative to the given class, if path is not absolute.
     */
    public ClasspathResourceLoader(Class<?> clazz) {
        this(clazz, clazz.getClassLoader());
    }

    private ClasspathResourceLoader(Class<?> clazz, ClassLoader loader) {
        this.clazz = clazz;
        this.loader = loader;
    }

    @Override
    public InputStream openResource(String resource) throws IOException {
        final InputStream stream = (clazz != null) ? clazz.getResourceAsStream(resource)
                : loader.getResourceAsStream(resource);
        if (stream == null)
            throw new IOException("Resource not found: " + resource);
        return stream;
    }

    @Override
    public <T> Class<? extends T> findClass(String cname, Class<T> expectedType) {
        try {
            return Class.forName(cname, true, loader).asSubclass(expectedType);
        } catch (Exception e) {
            throw new RuntimeException("Cannot load class: " + cname, e);
        }
    }

    @Override
    public <T> T newInstance(String cname, Class<T> expectedType) {
        Class<? extends T> clazz = findClass(cname, expectedType);
        try {
            return clazz.newInstance();
        } catch (Exception e) {
            throw new RuntimeException("Cannot create instance: " + cname, e);
        }
    }
}