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JCommon is a free general purpose Java class library that is used in several projects at www.jfree.org, including JFreeChart and JFreeReport.
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/* ========================================================================
* JCommon : a free general purpose class library for the Java(tm) platform
* ========================================================================
*
* (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
*
* Project Info: http://www.jfree.org/jcommon/index.html
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*
* [Java is a trademark or registered trademark of Sun Microsystems, Inc.
* in the United States and other countries.]
*
* ---------------------
* ObjectUtilitiess.java
* ---------------------
* (C) Copyright 2003-2005, by Object Refinery Limited.
*
* Original Author: David Gilbert (for Object Refinery Limited);
* Contributor(s): -;
*
* $Id: ObjectUtilities.java,v 1.21 2008/09/10 09:24:41 mungady Exp $
*
* Changes
* -------
* 25-Mar-2003 : Version 1 (DG);
* 15-Sep-2003 : Fixed bug in clone(List) method (DG);
* 25-Nov-2004 : Modified clone(Object) method to fail with objects that
* cannot be cloned, added new deepClone(Collection) method.
* Renamed ObjectUtils --> ObjectUtilities (DG);
* 11-Jan-2005 : Removed deprecated code in preparation for 1.0.0 release (DG);
* 18-Aug-2005 : Added casts to suppress compiler warnings, as suggested in
* patch 1260622 (DG);
*
*/
package org.jfree.util;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.StringTokenizer;
/**
* A collection of useful static utility methods for handling classes and object
* instantiation.
*
* @author Thomas Morgner
*/
public final class ObjectUtilities {
/**
* A constant for using the TheadContext as source for the classloader.
*/
public static final String THREAD_CONTEXT = "ThreadContext";
/**
* A constant for using the ClassContext as source for the classloader.
*/
public static final String CLASS_CONTEXT = "ClassContext";
/**
* By default use the thread context.
*/
private static String classLoaderSource = THREAD_CONTEXT;
/**
* The custom classloader to be used (if not null).
*/
private static ClassLoader classLoader;
/**
* Default constructor - private.
*/
private ObjectUtilities() {
}
/**
* Returns the internal configuration entry, whether the classloader of
* the thread context or the context classloader should be used.
*
* @return the classloader source, either THREAD_CONTEXT or CLASS_CONTEXT.
*/
public static String getClassLoaderSource() {
return classLoaderSource;
}
/**
* Defines the internal configuration entry, whether the classloader of
* the thread context or the context classloader should be used.
*
* This setting can only be defined using the API, there is no safe way
* to put this into an external configuration file.
*
* @param classLoaderSource the classloader source,
* either THREAD_CONTEXT or CLASS_CONTEXT.
*/
public static void setClassLoaderSource(final String classLoaderSource) {
ObjectUtilities.classLoaderSource = classLoaderSource;
}
/**
* Returns true if the two objects are equal OR both
* null.
*
* @param o1 object 1 (null permitted).
* @param o2 object 2 (null permitted).
* @return true or false.
*/
public static boolean equal(final Object o1, final Object o2) {
if (o1 == o2) {
return true;
}
if (o1 != null) {
return o1.equals(o2);
}
else {
return false;
}
}
/**
* Returns a hash code for an object, or zero if the object is
* null.
*
* @param object the object (null permitted).
* @return The object's hash code (or zero if the object is
* null).
*/
public static int hashCode(final Object object) {
int result = 0;
if (object != null) {
result = object.hashCode();
}
return result;
}
/**
* Returns a clone of the specified object, if it can be cloned, otherwise
* throws a CloneNotSupportedException.
*
* @param object the object to clone (null not permitted).
* @return A clone of the specified object.
* @throws CloneNotSupportedException if the object cannot be cloned.
*/
public static Object clone(final Object object)
throws CloneNotSupportedException {
if (object == null) {
throw new IllegalArgumentException("Null 'object' argument.");
}
if (object instanceof PublicCloneable) {
final PublicCloneable pc = (PublicCloneable) object;
return pc.clone();
}
else {
try {
final Method method = object.getClass().getMethod("clone",
(Class[]) null);
if (Modifier.isPublic(method.getModifiers())) {
return method.invoke(object, (Object[]) null);
}
}
catch (NoSuchMethodException e) {
Log.warn("Object without clone() method is impossible.");
}
catch (IllegalAccessException e) {
Log.warn("Object.clone(): unable to call method.");
}
catch (InvocationTargetException e) {
Log.warn("Object without clone() method is impossible.");
}
}
throw new CloneNotSupportedException("Failed to clone.");
}
/**
* Returns a new collection containing clones of all the items in the
* specified collection.
*
* @param collection the collection (null not permitted).
* @return A new collection containing clones of all the items in the
* specified collection.
* @throws CloneNotSupportedException if any of the items in the collection
* cannot be cloned.
*/
public static Collection deepClone(final Collection collection)
throws CloneNotSupportedException {
if (collection == null) {
throw new IllegalArgumentException("Null 'collection' argument.");
}
// all JDK-Collections are cloneable ...
// and if the collection is not clonable, then we should throw
// a CloneNotSupportedException anyway ...
final Collection result
= (Collection) ObjectUtilities.clone(collection);
result.clear();
final Iterator iterator = collection.iterator();
while (iterator.hasNext()) {
final Object item = iterator.next();
if (item != null) {
result.add(clone(item));
}
else {
result.add(null);
}
}
return result;
}
/**
* Redefines the custom classloader.
*
* @param classLoader the new classloader or null to use the default.
*/
public static synchronized void setClassLoader(
final ClassLoader classLoader) {
ObjectUtilities.classLoader = classLoader;
}
/**
* Returns the custom classloader or null, if no custom classloader is defined.
*
* @return the custom classloader or null to use the default.
*/
public static ClassLoader getClassLoader() {
return classLoader;
}
/**
* Returns the classloader, which was responsible for loading the given
* class.
*
* @param c the classloader, either an application class loader or the
* boot loader.
* @return the classloader, never null.
* @throws SecurityException if the SecurityManager does not allow to grab
* the context classloader.
*/
public static ClassLoader getClassLoader(final Class c) {
final String localClassLoaderSource;
synchronized(ObjectUtilities.class)
{
if (classLoader != null) {
return classLoader;
}
localClassLoaderSource = classLoaderSource;
}
if ("ThreadContext".equals(localClassLoaderSource)) {
final ClassLoader threadLoader = Thread.currentThread().getContextClassLoader();
if (threadLoader != null) {
return threadLoader;
}
}
// Context classloader - do not cache ..
final ClassLoader applicationCL = c.getClassLoader();
if (applicationCL == null) {
return ClassLoader.getSystemClassLoader();
}
else {
return applicationCL;
}
}
/**
* Returns the resource specified by the absolute name.
*
* @param name the name of the resource
* @param c the source class
* @return the url of the resource or null, if not found.
*/
public static URL getResource(final String name, final Class c) {
final ClassLoader cl = getClassLoader(c);
if (cl == null) {
return null;
}
return cl.getResource(name);
}
/**
* Returns the resource specified by the relative name.
*
* @param name the name of the resource relative to the given class
* @param c the source class
* @return the url of the resource or null, if not found.
*/
public static URL getResourceRelative(final String name, final Class c) {
final ClassLoader cl = getClassLoader(c);
final String cname = convertName(name, c);
if (cl == null) {
return null;
}
return cl.getResource(cname);
}
/**
* Transform the class-relative resource name into a global name by
* appending it to the classes package name. If the name is already a
* global name (the name starts with a "/"), then the name is returned
* unchanged.
*
* @param name the resource name
* @param c the class which the resource is relative to
* @return the tranformed name.
*/
private static String convertName(final String name, Class c) {
if (name.startsWith("/")) {
// strip leading slash..
return name.substring(1);
}
// we cant work on arrays, so remove them ...
while (c.isArray()) {
c = c.getComponentType();
}
// extract the package ...
final String baseName = c.getName();
final int index = baseName.lastIndexOf('.');
if (index == -1) {
return name;
}
final String pkgName = baseName.substring(0, index);
return pkgName.replace('.', '/') + "/" + name;
}
/**
* Returns the inputstream for the resource specified by the
* absolute name.
*
* @param name the name of the resource
* @param context the source class
* @return the url of the resource or null, if not found.
*/
public static InputStream getResourceAsStream(final String name,
final Class context) {
final URL url = getResource(name, context);
if (url == null) {
return null;
}
try {
return url.openStream();
}
catch (IOException e) {
return null;
}
}
/**
* Returns the inputstream for the resource specified by the
* relative name.
*
* @param name the name of the resource relative to the given class
* @param context the source class
* @return the url of the resource or null, if not found.
*/
public static InputStream getResourceRelativeAsStream
(final String name, final Class context) {
final URL url = getResourceRelative(name, context);
if (url == null) {
return null;
}
try {
return url.openStream();
}
catch (IOException e) {
return null;
}
}
/**
* Tries to create a new instance of the given class. This is a short cut
* for the common bean instantiation code.
*
* @param className the class name as String, never null.
* @param source the source class, from where to get the classloader.
* @return the instantiated object or null, if an error occured.
*/
public static Object loadAndInstantiate(final String className,
final Class source) {
try {
final ClassLoader loader = getClassLoader(source);
final Class c = loader.loadClass(className);
return c.newInstance();
}
catch (Exception e) {
return null;
}
}
/**
* Tries to create a new instance of the given class. This is a short cut
* for the common bean instantiation code. This method is a type-safe method
* and will not instantiate the class unless it is an instance of the given
* type.
*
* @param className the class name as String, never null.
* @param source the source class, from where to get the classloader.
* @param type the type.
* @return the instantiated object or null, if an error occurred.
*/
public static Object loadAndInstantiate(final String className,
final Class source,
final Class type) {
try {
final ClassLoader loader = getClassLoader(source);
final Class c = loader.loadClass(className);
if (type.isAssignableFrom(c)) {
return c.newInstance();
}
}
catch (Exception e) {
return null;
}
return null;
}
/**
* Returns true if this is version 1.4 or later of the
* Java runtime.
*
* @return A boolean.
*/
public static boolean isJDK14() {
try {
final ClassLoader loader = getClassLoader(ObjectUtilities.class);
if (loader != null) {
try {
loader.loadClass("java.util.RandomAccess");
return true;
}
catch (ClassNotFoundException e) {
return false;
}
catch(Exception e) {
// do nothing, but do not crash ...
}
}
}
catch (Exception e) {
// cant do anything about it, we have to accept and ignore it ..
}
// OK, the quick and dirty, but secure way failed. Lets try it
// using the standard way.
try {
final String version = System.getProperty
("java.vm.specification.version");
// parse the beast...
if (version == null) {
return false;
}
String[] versions = parseVersions(version);
String[] target = new String[]{ "1", "4" };
return (ArrayUtilities.compareVersionArrays(versions, target) >= 0);
}
catch(Exception e) {
return false;
}
}
private static String[] parseVersions (String version)
{
if (version == null)
{
return new String[0];
}
final ArrayList versions = new ArrayList();
final StringTokenizer strtok = new StringTokenizer(version, ".");
while (strtok.hasMoreTokens())
{
versions.add (strtok.nextToken());
}
return (String[]) versions.toArray(new String[versions.size()]);
}
}