A class to simplify access to resources through the classloader
/*
* Copyright 2004 Clinton Begin
*
* 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.
*/
import java.io.*;
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.
*/
public class Resources extends Object {
private static ClassLoader defaultClassLoader;
/**
* Charset to use when calling getResourceAsReader.
* null means use the system default.
*/
private static Charset charset;
private Resources() {
}
/**
* Returns the default classloader (may be null).
*
* @return The default classloader
*/
public static ClassLoader getDefaultClassLoader() {
return defaultClassLoader;
}
/**
* Sets the default classloader
*
* @param defaultClassLoader - the new default ClassLoader
*/
public static void setDefaultClassLoader(ClassLoader defaultClassLoader) {
Resources.defaultClassLoader = defaultClassLoader;
}
/**
* Returns the URL of the resource on the classpath
*
* @param resource The resource to find
* @return The resource
* @throws IOException If the resource cannot be found or read
*/
public static URL getResourceURL(String resource) throws IOException {
return getResourceURL(getClassLoader(), resource);
}
/**
* Returns the URL of the resource on the classpath
*
* @param loader The classloader used to load the resource
* @param resource The resource to find
* @return The resource
* @throws IOException If the resource cannot be found or read
*/
public static URL getResourceURL(ClassLoader loader, String resource) throws IOException {
URL url = null;
if (loader != null) url = loader.getResource(resource);
if (url == null) url = ClassLoader.getSystemResource(resource);
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 IOException If the resource cannot be found or read
*/
public static InputStream getResourceAsStream(String resource) throws IOException {
return getResourceAsStream(getClassLoader(), resource);
}
/**
* Returns a resource on the classpath as a Stream object
*
* @param loader The classloader used to load the resource
* @param resource The resource to find
* @return The resource
* @throws IOException If the resource cannot be found or read
*/
public static InputStream getResourceAsStream(ClassLoader loader, String resource) throws IOException {
InputStream in = null;
if (loader != null) in = loader.getResourceAsStream(resource);
if (in == null) in = ClassLoader.getSystemResourceAsStream(resource);
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 IOException If the resource cannot be found or read
*/
public static Properties getResourceAsProperties(String resource)
throws IOException {
Properties props = new Properties();
InputStream in = null;
String propfile = resource;
in = getResourceAsStream(propfile);
props.load(in);
in.close();
return props;
}
/**
* Returns a resource on the classpath as a Properties object
*
* @param loader The classloader used to load the resource
* @param resource The resource to find
* @return The resource
* @throws IOException If the resource cannot be found or read
*/
public static Properties getResourceAsProperties(ClassLoader loader, String resource)
throws IOException {
Properties props = new Properties();
InputStream in = null;
String propfile = resource;
in = getResourceAsStream(loader, propfile);
props.load(in);
in.close();
return props;
}
/**
* Returns a resource on the classpath as a Reader object
*
* @param resource The resource to find
* @return The resource
* @throws 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 load the resource
* @param resource The resource to find
* @return The resource
* @throws 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 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 load the resource
* @param resource - the resource to find
* @return The resource
* @throws 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 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 IOException If the resource cannot be found or read
*/
public static Reader getUrlAsReader(String urlString) throws IOException {
return new InputStreamReader(getUrlAsStream(urlString));
}
/**
* Gets a URL as a Properties object
*
* @param urlString - the URL to get
* @return A Properties object with the data from the URL
* @throws IOException If the resource cannot be found or read
*/
public static Properties getUrlAsProperties(String urlString) throws IOException {
Properties props = new Properties();
InputStream in = null;
String propfile = urlString;
in = getUrlAsStream(propfile);
props.load(in);
in.close();
return props;
}
/**
* Loads a class
*
* @param className - the class to load
* @return The loaded class
* @throws ClassNotFoundException If the class cannot be found (duh!)
*/
public static Class classForName(String className) throws ClassNotFoundException {
Class clazz = null;
try {
clazz = getClassLoader().loadClass(className);
} catch (Exception e) {
// Ignore. Failsafe below.
}
if (clazz == null) {
clazz = Class.forName(className);
}
return clazz;
}
/**
* Creates an instance of a class
*
* @param className - the class to create
* @return An instance of the class
* @throws ClassNotFoundException If the class cannot be found (duh!)
* @throws InstantiationException If the class cannot be instantiaed
* @throws IllegalAccessException If the class is not public, or other access problems arise
*/
public static Object instantiate(String className)
throws ClassNotFoundException, InstantiationException, IllegalAccessException {
return instantiate(classForName(className));
}
/**
* Creates an instance of a class
*
* @param clazz - the class to create
* @return An instance of the class
* @throws InstantiationException If the class cannot be instantiaed
* @throws IllegalAccessException If the class is not public, or other access problems arise
*/
public static Object instantiate(Class clazz) throws InstantiationException, IllegalAccessException {
try {
return clazz.newInstance();
} catch (Exception e) {
// Try alternative...theoretically should fail for the exact same
// reason, but in case of a weird security manager, this will help
// some cases.
//return clazz.newInstance();
return clazz.newInstance();
}
}
private static ClassLoader getClassLoader() {
if (defaultClassLoader != null) {
return defaultClassLoader;
} else {
return Thread.currentThread().getContextClassLoader();
}
}
public static Charset getCharset() {
return charset;
}
/**
* Use this method to set the Charset to be used when
* calling the getResourceAsReader methods. This will
* allow iBATIS to function properly when the system default
* encoding doesn't deal well with unicode (IBATIS-340, IBATIS-349)
*
* @param charset
*/
public static void setCharset(Charset charset) {
Resources.charset = charset;
}
}
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