001 /*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package com.google.common.io;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkNotNull;
021
022 import com.google.common.annotations.Beta;
023
024 import java.io.IOException;
025 import java.io.InputStream;
026 import java.io.InputStreamReader;
027 import java.io.OutputStream;
028 import java.net.URL;
029 import java.nio.charset.Charset;
030 import java.util.List;
031
032 /**
033 * Provides utility methods for working with resources in the classpath.
034 * Note that even though these methods use {@link URL} parameters, they
035 * are usually not appropriate for HTTP or other non-classpath resources.
036 *
037 * <p>All method parameters must be non-null unless documented otherwise.
038 *
039 * @author Chris Nokleberg
040 * @author Ben Yu
041 * @since 1
042 */
043 @Beta
044 public final class Resources {
045 private Resources() {}
046
047 /**
048 * Returns a factory that will supply instances of {@link InputStream} that
049 * read from the given URL.
050 *
051 * @param url the URL to read from
052 * @return the factory
053 */
054 public static InputSupplier<InputStream> newInputStreamSupplier(
055 final URL url) {
056 checkNotNull(url);
057 return new InputSupplier<InputStream>() {
058 @Override
059 public InputStream getInput() throws IOException {
060 return url.openStream();
061 }
062 };
063 }
064
065 /**
066 * Returns a factory that will supply instances of
067 * {@link InputStreamReader} that read a URL using the given character set.
068 *
069 * @param url the URL to read from
070 * @param charset the character set used when reading the URL contents
071 * @return the factory
072 */
073 public static InputSupplier<InputStreamReader> newReaderSupplier(
074 URL url, Charset charset) {
075 return CharStreams.newReaderSupplier(newInputStreamSupplier(url), charset);
076 }
077
078 /**
079 * Reads all bytes from a URL into a byte array.
080 *
081 * @param url the URL to read from
082 * @return a byte array containing all the bytes from the URL
083 * @throws IOException if an I/O error occurs
084 */
085 public static byte[] toByteArray(URL url) throws IOException {
086 return ByteStreams.toByteArray(newInputStreamSupplier(url));
087 }
088
089 /**
090 * Reads all characters from a URL into a {@link String}, using the given
091 * character set.
092 *
093 * @param url the URL to read from
094 * @param charset the character set used when reading the URL
095 * @return a string containing all the characters from the URL
096 * @throws IOException if an I/O error occurs.
097 */
098 public static String toString(URL url, Charset charset) throws IOException {
099 return CharStreams.toString(newReaderSupplier(url, charset));
100 }
101
102 /**
103 * Streams lines from a URL, stopping when our callback returns false, or we
104 * have read all of the lines.
105 *
106 * @param url the URL to read from
107 * @param charset the character set used when reading the URL
108 * @param callback the LineProcessor to use to handle the lines
109 * @return the output of processing the lines
110 * @throws IOException if an I/O error occurs
111 */
112 public static <T> T readLines(URL url, Charset charset,
113 LineProcessor<T> callback) throws IOException {
114 return CharStreams.readLines(newReaderSupplier(url, charset), callback);
115 }
116
117 /**
118 * Reads all of the lines from a URL. The lines do not include
119 * line-termination characters, but do include other leading and trailing
120 * whitespace.
121 *
122 * @param url the URL to read from
123 * @param charset the character set used when writing the file
124 * @return a mutable {@link List} containing all the lines
125 * @throws IOException if an I/O error occurs
126 */
127 public static List<String> readLines(URL url, Charset charset)
128 throws IOException {
129 return CharStreams.readLines(newReaderSupplier(url, charset));
130 }
131
132 /**
133 * Copies all bytes from a URL to an output stream.
134 *
135 * @param from the URL to read from
136 * @param to the output stream
137 * @throws IOException if an I/O error occurs
138 */
139 public static void copy(URL from, OutputStream to) throws IOException {
140 ByteStreams.copy(newInputStreamSupplier(from), to);
141 }
142
143 /**
144 * Returns a {@code URL} pointing to {@code resourceName} if the resource is
145 * found in the class path. {@code Resources.class.getClassLoader()} is used
146 * to locate the resource.
147 *
148 * @throws IllegalArgumentException if resource is not found
149 */
150 public static URL getResource(String resourceName) {
151 URL url = Resources.class.getClassLoader().getResource(resourceName);
152 checkArgument(url != null, "resource %s not found.", resourceName);
153 return url;
154 }
155
156 /**
157 * Returns a {@code URL} pointing to {@code resourceName} that is relative to
158 * {@code contextClass}, if the resource is found in the class path.
159 *
160 * @throws IllegalArgumentException if resource is not found
161 */
162 public static URL getResource(Class<?> contextClass, String resourceName) {
163 URL url = contextClass.getResource(resourceName);
164 checkArgument(url != null, "resource %s relative to %s not found.",
165 resourceName, contextClass.getName());
166 return url;
167 }
168 }