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 import com.google.common.base.Charsets;
024
025 import java.io.IOException;
026 import java.io.InputStream;
027 import java.io.InputStreamReader;
028 import java.io.OutputStream;
029 import java.net.URL;
030 import java.nio.charset.Charset;
031 import java.util.List;
032
033 /**
034 * Provides utility methods for working with resources in the classpath.
035 * Note that even though these methods use {@link URL} parameters, they
036 * are usually not appropriate for HTTP or other non-classpath resources.
037 *
038 * <p>All method parameters must be non-null unless documented otherwise.
039 *
040 * @author Chris Nokleberg
041 * @author Ben Yu
042 * @since 1.0
043 */
044 @Beta
045 public final class Resources {
046 private Resources() {}
047
048 /**
049 * Returns a factory that will supply instances of {@link InputStream} that
050 * read from the given URL.
051 *
052 * @param url the URL to read from
053 * @return the factory
054 */
055 public static InputSupplier<InputStream> newInputStreamSupplier(
056 final URL url) {
057 checkNotNull(url);
058 return new InputSupplier<InputStream>() {
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 charset used to decode the input stream; see {@link
071 * Charsets} for helpful predefined constants
072 * @return the factory
073 */
074 public static InputSupplier<InputStreamReader> newReaderSupplier(
075 URL url, Charset charset) {
076 return CharStreams.newReaderSupplier(newInputStreamSupplier(url), charset);
077 }
078
079 /**
080 * Reads all bytes from a URL into a byte array.
081 *
082 * @param url the URL to read from
083 * @return a byte array containing all the bytes from the URL
084 * @throws IOException if an I/O error occurs
085 */
086 public static byte[] toByteArray(URL url) throws IOException {
087 return ByteStreams.toByteArray(newInputStreamSupplier(url));
088 }
089
090 /**
091 * Reads all characters from a URL into a {@link String}, using the given
092 * character set.
093 *
094 * @param url the URL to read from
095 * @param charset the charset used to decode the input stream; see {@link
096 * Charsets} for helpful predefined constants
097 * @return a string containing all the characters from the URL
098 * @throws IOException if an I/O error occurs.
099 */
100 public static String toString(URL url, Charset charset) throws IOException {
101 return CharStreams.toString(newReaderSupplier(url, charset));
102 }
103
104 /**
105 * Streams lines from a URL, stopping when our callback returns false, or we
106 * have read all of the lines.
107 *
108 * @param url the URL to read from
109 * @param charset the charset used to decode the input stream; see {@link
110 * Charsets} for helpful predefined constants
111 * @param callback the LineProcessor to use to handle the lines
112 * @return the output of processing the lines
113 * @throws IOException if an I/O error occurs
114 */
115 public static <T> T readLines(URL url, Charset charset,
116 LineProcessor<T> callback) throws IOException {
117 return CharStreams.readLines(newReaderSupplier(url, charset), callback);
118 }
119
120 /**
121 * Reads all of the lines from a URL. The lines do not include
122 * line-termination characters, but do include other leading and trailing
123 * whitespace.
124 *
125 * @param url the URL to read from
126 * @param charset the charset used to decode the input stream; see {@link
127 * Charsets} for helpful predefined constants
128 * @return a mutable {@link List} containing all the lines
129 * @throws IOException if an I/O error occurs
130 */
131 public static List<String> readLines(URL url, Charset charset)
132 throws IOException {
133 return CharStreams.readLines(newReaderSupplier(url, charset));
134 }
135
136 /**
137 * Copies all bytes from a URL to an output stream.
138 *
139 * @param from the URL to read from
140 * @param to the output stream
141 * @throws IOException if an I/O error occurs
142 */
143 public static void copy(URL from, OutputStream to) throws IOException {
144 ByteStreams.copy(newInputStreamSupplier(from), to);
145 }
146
147 /**
148 * Returns a {@code URL} pointing to {@code resourceName} if the resource is
149 * found in the class path. {@code Resources.class.getClassLoader()} is used
150 * to locate the resource.
151 *
152 * @throws IllegalArgumentException if resource is not found
153 */
154 public static URL getResource(String resourceName) {
155 URL url = Resources.class.getClassLoader().getResource(resourceName);
156 checkArgument(url != null, "resource %s not found.", resourceName);
157 return url;
158 }
159
160 /**
161 * Returns a {@code URL} pointing to {@code resourceName} that is relative to
162 * {@code contextClass}, if the resource is found in the class path.
163 *
164 * @throws IllegalArgumentException if resource is not found
165 */
166 public static URL getResource(Class<?> contextClass, String resourceName) {
167 URL url = contextClass.getResource(resourceName);
168 checkArgument(url != null, "resource %s relative to %s not found.",
169 resourceName, contextClass.getName());
170 return url;
171 }
172 }