Java tutorial
/** * Copyright 2009-2018 the original author or 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 org.apache.ibatis.io; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.Reader; import java.net.URL; import java.net.URLConnection; import java.nio.charset.Charset; import java.util.Properties; /** * A class to simplify access to resources through the classloader. * * @author Clinton Begin */ public class Resources { private static ClassLoaderWrapper classLoaderWrapper = new ClassLoaderWrapper(); /** * Charset to use when calling getResourceAsReader. * null means use the system default. */ private static Charset charset; Resources() { } /** * Returns the default classloader (may be null). * * @return The default classloader */ public static ClassLoader getDefaultClassLoader() { return classLoaderWrapper.defaultClassLoader; } /** * Sets the default classloader * * @param defaultClassLoader - the new default ClassLoader */ public static void setDefaultClassLoader(ClassLoader defaultClassLoader) { classLoaderWrapper.defaultClassLoader = defaultClassLoader; } /** * Returns the URL of the resource on the classpath * * @param resource The resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static URL getResourceURL(String resource) throws IOException { // issue #625 return getResourceURL(null, resource); } /** * Returns the URL of the resource on the classpath * * @param loader The classloader used to fetch the resource * @param resource The resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static URL getResourceURL(ClassLoader loader, String resource) throws IOException { URL url = classLoaderWrapper.getResourceAsURL(resource, loader); if (url == null) { throw new IOException("Could not find resource " + resource); } return url; } /** * Returns a resource on the classpath as a Stream object * * @param resource The resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static InputStream getResourceAsStream(String resource) throws IOException { return getResourceAsStream(null, resource); } /** * Returns a resource on the classpath as a Stream object * * @param loader The classloader used to fetch the resource * @param resource The resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static InputStream getResourceAsStream(ClassLoader loader, String resource) throws IOException { InputStream in = classLoaderWrapper.getResourceAsStream(resource, loader); if (in == null) { throw new IOException("Could not find resource " + resource); } return in; } /** * Returns a resource on the classpath as a Properties object * * @param resource The resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static Properties getResourceAsProperties(String resource) throws IOException { Properties props = new Properties(); try (InputStream in = getResourceAsStream(resource)) { props.load(in); } return props; } /** * Returns a resource on the classpath as a Properties object * * @param loader The classloader used to fetch the resource * @param resource The resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static Properties getResourceAsProperties(ClassLoader loader, String resource) throws IOException { Properties props = new Properties(); try (InputStream in = getResourceAsStream(loader, resource)) { props.load(in); } return props; } /** * Returns a resource on the classpath as a Reader object * * @param resource The resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static Reader getResourceAsReader(String resource) throws IOException { Reader reader; if (charset == null) { reader = new InputStreamReader(getResourceAsStream(resource)); } else { reader = new InputStreamReader(getResourceAsStream(resource), charset); } return reader; } /** * Returns a resource on the classpath as a Reader object * * @param loader The classloader used to fetch the resource * @param resource The resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static Reader getResourceAsReader(ClassLoader loader, String resource) throws IOException { Reader reader; if (charset == null) { reader = new InputStreamReader(getResourceAsStream(loader, resource)); } else { reader = new InputStreamReader(getResourceAsStream(loader, resource), charset); } return reader; } /** * Returns a resource on the classpath as a File object * * @param resource The resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static File getResourceAsFile(String resource) throws IOException { return new File(getResourceURL(resource).getFile()); } /** * Returns a resource on the classpath as a File object * * @param loader - the classloader used to fetch the resource * @param resource - the resource to find * @return The resource * @throws java.io.IOException If the resource cannot be found or read */ public static File getResourceAsFile(ClassLoader loader, String resource) throws IOException { return new File(getResourceURL(loader, resource).getFile()); } /** * Gets a URL as an input stream * * @param urlString - the URL to get * @return An input stream with the data from the URL * @throws java.io.IOException If the resource cannot be found or read */ public static InputStream getUrlAsStream(String urlString) throws IOException { URL url = new URL(urlString); URLConnection conn = url.openConnection(); return conn.getInputStream(); } /** * Gets a URL as a Reader * * @param urlString - the URL to get * @return A Reader with the data from the URL * @throws java.io.IOException If the resource cannot be found or read */ public static Reader getUrlAsReader(String urlString) throws IOException { Reader reader; if (charset == null) { reader = new InputStreamReader(getUrlAsStream(urlString)); } else { reader = new InputStreamReader(getUrlAsStream(urlString), charset); } return reader; } /** * Gets a URL as a Properties object * * @param urlString - the URL to get * @return A Properties object with the data from the URL * @throws java.io.IOException If the resource cannot be found or read */ public static Properties getUrlAsProperties(String urlString) throws IOException { Properties props = new Properties(); try (InputStream in = getUrlAsStream(urlString)) { props.load(in); } return props; } /** * Loads a class * * @param className - the class to fetch * @return The loaded class * @throws ClassNotFoundException If the class cannot be found (duh!) */ public static Class<?> classForName(String className) throws ClassNotFoundException { return classLoaderWrapper.classForName(className); } public static Charset getCharset() { return charset; } public static void setCharset(Charset charset) { Resources.charset = charset; } }