com.google.common.io.Resources Maven / Gradle / Ivy
/*
* Copyright (C) 2007 The Guava Authors
*
* 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.common.io;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.Beta;
import com.google.common.base.Charsets;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.List;
/**
* Provides utility methods for working with resources in the classpath.
* Note that even though these methods use {@link URL} parameters, they
* are usually not appropriate for HTTP or other non-classpath resources.
*
* All method parameters must be non-null unless documented otherwise.
*
* @author Chris Nokleberg
* @author Ben Yu
* @since 1.0
*/
@Beta
public final class Resources {
private Resources() {}
/**
* Returns a factory that will supply instances of {@link InputStream} that
* read from the given URL.
*
* @param url the URL to read from
* @return the factory
*/
public static InputSupplier newInputStreamSupplier(
final URL url) {
checkNotNull(url);
return new InputSupplier() {
@Override
public InputStream getInput() throws IOException {
return url.openStream();
}
};
}
/**
* Returns a factory that will supply instances of
* {@link InputStreamReader} that read a URL using the given character set.
*
* @param url the URL to read from
* @param charset the charset used to decode the input stream; see {@link
* Charsets} for helpful predefined constants
* @return the factory
*/
public static InputSupplier newReaderSupplier(
URL url, Charset charset) {
return CharStreams.newReaderSupplier(newInputStreamSupplier(url), charset);
}
/**
* Reads all bytes from a URL into a byte array.
*
* @param url the URL to read from
* @return a byte array containing all the bytes from the URL
* @throws IOException if an I/O error occurs
*/
public static byte[] toByteArray(URL url) throws IOException {
return ByteStreams.toByteArray(newInputStreamSupplier(url));
}
/**
* Reads all characters from a URL into a {@link String}, using the given
* character set.
*
* @param url the URL to read from
* @param charset the charset used to decode the input stream; see {@link
* Charsets} for helpful predefined constants
* @return a string containing all the characters from the URL
* @throws IOException if an I/O error occurs.
*/
public static String toString(URL url, Charset charset) throws IOException {
return CharStreams.toString(newReaderSupplier(url, charset));
}
/**
* Streams lines from a URL, stopping when our callback returns false, or we
* have read all of the lines.
*
* @param url the URL to read from
* @param charset the charset used to decode the input stream; see {@link
* Charsets} for helpful predefined constants
* @param callback the LineProcessor to use to handle the lines
* @return the output of processing the lines
* @throws IOException if an I/O error occurs
*/
public static T readLines(URL url, Charset charset,
LineProcessor callback) throws IOException {
return CharStreams.readLines(newReaderSupplier(url, charset), callback);
}
/**
* Reads all of the lines from a URL. The lines do not include
* line-termination characters, but do include other leading and trailing
* whitespace.
*
* @param url the URL to read from
* @param charset the charset used to decode the input stream; see {@link
* Charsets} for helpful predefined constants
* @return a mutable {@link List} containing all the lines
* @throws IOException if an I/O error occurs
*/
public static List readLines(URL url, Charset charset)
throws IOException {
return CharStreams.readLines(newReaderSupplier(url, charset));
}
/**
* Copies all bytes from a URL to an output stream.
*
* @param from the URL to read from
* @param to the output stream
* @throws IOException if an I/O error occurs
*/
public static void copy(URL from, OutputStream to) throws IOException {
ByteStreams.copy(newInputStreamSupplier(from), to);
}
/**
* Returns a {@code URL} pointing to {@code resourceName} if the resource is
* found in the class path. {@code Resources.class.getClassLoader()} is used
* to locate the resource.
*
* @throws IllegalArgumentException if resource is not found
*/
public static URL getResource(String resourceName) {
URL url = Resources.class.getClassLoader().getResource(resourceName);
checkArgument(url != null, "resource %s not found.", resourceName);
return url;
}
/**
* Returns a {@code URL} pointing to {@code resourceName} that is relative to
* {@code contextClass}, if the resource is found in the class path.
*
* @throws IllegalArgumentException if resource is not found
*/
public static URL getResource(Class contextClass, String resourceName) {
URL url = contextClass.getResource(resourceName);
checkArgument(url != null, "resource %s relative to %s not found.",
resourceName, contextClass.getName());
return url;
}
}