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Posted to commits@xalan.apache.org by il...@apache.org on 2003/08/14 18:29:19 UTC
cvs commit: xml-xalan/java/src/org/apache/xml/utils ObjectFactory.java
ilene 2003/08/14 09:29:19
Added: java/src/org/apache/xml/utils ObjectFactory.java
Log:
Applying Igor Malinin's (igor@widespace.ee) patch for more convenient (centralized)
classloading. See bugzilla #16675.
Revision Changes Path
1.1 xml-xalan/java/src/org/apache/xml/utils/ObjectFactory.java
Index: ObjectFactory.java
===================================================================
/*
* The Apache Software License, Version 1.1
*
*
* Copyright (c) 2001, 2002 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The name "Apache Software Foundation" must not be used to endorse or
* promote products derived from this software without prior written
* permission. For written permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache",
* nor may "Apache" appear in their name, without prior written
* permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation and was
* originally based on software copyright (c) 1999-2001, Sun Microsystems,
* Inc., http://www.sun.com. For more information on the Apache Software
* Foundation, please see <http://www.apache.org/>.
*/
package org.apache.xml.utils;
import java.io.InputStream;
import java.io.IOException;
import java.io.File;
import java.io.FileInputStream;
import java.util.Properties;
import java.io.BufferedReader;
import java.io.InputStreamReader;
/**
* This class is duplicated for each JAXP subpackage so keep it in sync.
* It is package private and therefore is not exposed as part of the JAXP
* API.
* <p>
* This code is designed to implement the JAXP 1.1 spec pluggability
* feature and is designed to run on JDK version 1.1 and
* later, and to compile on JDK 1.2 and onward.
* The code also runs both as part of an unbundled jar file and
* when bundled as part of the JDK.
* <p>
* This class was moved from the <code>javax.xml.parsers.ObjectFactory</code>
* class and modified to be used as a general utility for creating objects
* dynamically.
*
* @version $Id: $
*/
public class ObjectFactory {
//
// Constants
//
// name of default properties file to look for in JDK's jre/lib directory
private static final String DEFAULT_PROPERTIES_FILENAME = "xalan.properties";
/** Set to true for debugging */
private static final boolean DEBUG = false;
/** cache the contents of the xalan.properties file.
* Until an attempt has been made to read this file, this will
* be null; if the file does not exist or we encounter some other error
* during the read, this will be empty.
*/
private static Properties fXalanProperties = null;
/***
* Cache the time stamp of the xalan.properties file so
* that we know if it's been modified and can invalidate
* the cache when necessary.
*/
private static long fLastModified = -1;
//
// Public static methods
//
/**
* Finds the implementation Class object in the specified order. The
* specified order is the following:
* <ol>
* <li>query the system property using <code>System.getProperty</code>
* <li>read <code>META-INF/services/<i>factoryId</i></code> file
* <li>use fallback classname
* </ol>
*
* @return Class object of factory, never null
*
* @param factoryId Name of the factory to find, same as
* a property name
* @param fallbackClassName Implementation class name, if nothing else
* is found. Use null to mean no fallback.
*
* @exception ObjectFactory.ConfigurationError
*/
public static Object createObject(String factoryId, String fallbackClassName)
throws ConfigurationError {
return createObject(factoryId, null, fallbackClassName);
} // createObject(String,String):Object
/**
* Finds the implementation Class object in the specified order. The
* specified order is the following:
* <ol>
* <li>query the system property using <code>System.getProperty</code>
* <li>read <code>$java.home/lib/<i>propertiesFilename</i></code> file
* <li>read <code>META-INF/services/<i>factoryId</i></code> file
* <li>use fallback classname
* </ol>
*
* @return Class object of factory, never null
*
* @param factoryId Name of the factory to find, same as
* a property name
* @param propertiesFilename The filename in the $java.home/lib directory
* of the properties file. If none specified,
* ${java.home}/lib/xalan.properties will be used.
* @param fallbackClassName Implementation class name, if nothing else
* is found. Use null to mean no fallback.
*
* @exception ObjectFactory.ConfigurationError
*/
public static Object createObject(String factoryId,
String propertiesFilename,
String fallbackClassName)
throws ConfigurationError
{
debugPrintln("debug is on");
SecuritySupport ss = SecuritySupport.getInstance();
ClassLoader cl = findClassLoader();
// Use the system property first
try {
String systemProp = ss.getSystemProperty(factoryId);
if (systemProp != null) {
debugPrintln("found system property, value=" + systemProp);
return newInstance(systemProp, cl, true);
}
} catch (SecurityException se) {
// Ignore and continue w/ next location
}
// Try to read from propertiesFilename, or $java.home/lib/xalan.properties
String factoryClassName = null;
// no properties file name specified; use $JAVA_HOME/lib/xalan.properties:
if (propertiesFilename == null) {
File propertiesFile = null;
boolean propertiesFileExists = false;
try {
String javah = ss.getSystemProperty("java.home");
propertiesFilename = javah + File.separator +
"lib" + File.separator + DEFAULT_PROPERTIES_FILENAME;
propertiesFile = new File(propertiesFilename);
propertiesFileExists = ss.getFileExists(propertiesFile);
} catch (SecurityException e) {
// try again...
fLastModified = -1;
fXalanProperties = null;
}
synchronized (ObjectFactory.class) {
boolean loadProperties = false;
try {
// file existed last time
if(fLastModified >= 0) {
if(propertiesFileExists &&
(fLastModified < (fLastModified = ss.getLastModified(propertiesFile)))) {
loadProperties = true;
} else {
// file has stopped existing...
if(!propertiesFileExists) {
fLastModified = -1;
fXalanProperties = null;
} // else, file wasn't modified!
}
} else {
// file has started to exist:
if(propertiesFileExists) {
loadProperties = true;
fLastModified = ss.getLastModified(propertiesFile);
} // else, nothing's changed
}
if(loadProperties) {
// must never have attempted to read xalan.properties before (or it's outdeated)
fXalanProperties = new Properties();
FileInputStream fis = ss.getFileInputStream(propertiesFile);
fXalanProperties.load(fis);
fis.close();
}
} catch (Exception x) {
fXalanProperties = null;
fLastModified = -1;
// assert(x instanceof FileNotFoundException
// || x instanceof SecurityException)
// In both cases, ignore and continue w/ next location
}
}
if(fXalanProperties != null) {
factoryClassName = fXalanProperties.getProperty(factoryId);
}
} else {
try {
FileInputStream fis = ss.getFileInputStream(new File(propertiesFilename));
Properties props = new Properties();
props.load(fis);
fis.close();
factoryClassName = props.getProperty(factoryId);
} catch (Exception x) {
// assert(x instanceof FileNotFoundException
// || x instanceof SecurityException)
// In both cases, ignore and continue w/ next location
}
}
if (factoryClassName != null) {
debugPrintln("found in " + propertiesFilename + ", value=" + factoryClassName);
return newInstance(factoryClassName, cl, true);
}
// Try Jar Service Provider Mechanism
Object provider = findJarServiceProvider(factoryId);
if (provider != null) {
return provider;
}
if (fallbackClassName == null) {
throw new ConfigurationError(
"Provider for " + factoryId + " cannot be found", null);
}
debugPrintln("using fallback, value=" + fallbackClassName);
return newInstance(fallbackClassName, cl, true);
} // createObject(String,String,String):Object
//
// Private static methods
//
/** Prints a message to standard error if debugging is enabled. */
private static void debugPrintln(String msg) {
if (DEBUG) {
System.err.println("JAXP: " + msg);
}
} // debugPrintln(String)
/**
* Figure out which ClassLoader to use. For JDK 1.2 and later use
* the context ClassLoader.
*/
public static ClassLoader findClassLoader()
throws ConfigurationError
{
SecuritySupport ss = SecuritySupport.getInstance();
// Figure out which ClassLoader to use for loading the provider
// class. If there is a Context ClassLoader then use it.
ClassLoader context = ss.getContextClassLoader();
ClassLoader system = ss.getSystemClassLoader();
ClassLoader chain = system;
while (true) {
if (context == chain) {
// Assert: we are on JDK 1.1 or we have no Context ClassLoader
// or any Context ClassLoader in chain of system classloader
// (including extension ClassLoader) so extend to widest
// ClassLoader (always look in system ClassLoader if Xalan
// is in boot/extension/system classpath and in current
// ClassLoader otherwise); normal classloaders delegate
// back to system ClassLoader first so this widening doesn't
// change the fact that context ClassLoader will be consulted
ClassLoader current = ObjectFactory.class.getClassLoader();
chain = system;
while (true) {
if (current == chain) {
// Assert: Current ClassLoader in chain of
// boot/extension/system ClassLoaders
return system;
}
if (chain == null) {
break;
}
chain = ss.getParentClassLoader(chain);
}
// Assert: Current ClassLoader not in chain of
// boot/extension/system ClassLoaders
return current;
}
if (chain == null) {
// boot ClassLoader reached
break;
}
// Check for any extension ClassLoaders in chain up to
// boot ClassLoader
chain = ss.getParentClassLoader(chain);
};
// Assert: Context ClassLoader not in chain of
// boot/extension/system ClassLoaders
return context;
} // findClassLoader():ClassLoader
/**
* Create an instance of a class using the specified ClassLoader
*/
public static Object newInstance(String className, ClassLoader cl,
boolean doFallback)
throws ConfigurationError
{
// assert(className != null);
try{
Class providerClass = findProviderClass(className, cl, doFallback);
Object instance = providerClass.newInstance();
debugPrintln("created new instance of " + providerClass +
" using ClassLoader: " + cl);
return instance;
} catch (ClassNotFoundException x) {
throw new ConfigurationError(
"Provider " + className + " not found", x);
} catch (Exception x) {
throw new ConfigurationError(
"Provider " + className + " could not be instantiated: " + x,
x);
}
}
/**
* Find a Class using the specified ClassLoader
*/
public static Class findProviderClass(String className, ClassLoader cl,
boolean doFallback)
throws ClassNotFoundException, ConfigurationError
{
Class providerClass;
if (cl == null) {
// XXX Use the bootstrap ClassLoader. There is no way to
// load a class using the bootstrap ClassLoader that works
// in both JDK 1.1 and Java 2. However, this should still
// work b/c the following should be true:
//
// (cl == null) iff current ClassLoader == null
//
// Thus Class.forName(String) will use the current
// ClassLoader which will be the bootstrap ClassLoader.
providerClass = Class.forName(className);
} else {
try {
providerClass = cl.loadClass(className);
} catch (ClassNotFoundException x) {
if (doFallback) {
// Fall back to current classloader
ClassLoader current = ObjectFactory.class.getClassLoader();
if (current == null) {
providerClass = Class.forName(className);
} else if (cl != current) {
cl = current;
providerClass = cl.loadClass(className);
} else {
throw x;
}
} else {
throw x;
}
}
}
return providerClass;
}
/*
* Try to find provider using Jar Service Provider Mechanism
*
* @return instance of provider class if found or null
*/
private static Object findJarServiceProvider(String factoryId)
throws ConfigurationError
{
SecuritySupport ss = SecuritySupport.getInstance();
String serviceId = "META-INF/services/" + factoryId;
InputStream is = null;
// First try the Context ClassLoader
ClassLoader cl = findClassLoader();
is = ss.getResourceAsStream(cl, serviceId);
// If no provider found then try the current ClassLoader
if (is == null) {
ClassLoader current = ObjectFactory.class.getClassLoader();
if (cl != current) {
cl = current;
is = ss.getResourceAsStream(cl, serviceId);
}
}
if (is == null) {
// No provider found
return null;
}
debugPrintln("found jar resource=" + serviceId +
" using ClassLoader: " + cl);
// Read the service provider name in UTF-8 as specified in
// the jar spec. Unfortunately this fails in Microsoft
// VJ++, which does not implement the UTF-8
// encoding. Theoretically, we should simply let it fail in
// that case, since the JVM is obviously broken if it
// doesn't support such a basic standard. But since there
// are still some users attempting to use VJ++ for
// development, we have dropped in a fallback which makes a
// second attempt using the platform's default encoding. In
// VJ++ this is apparently ASCII, which is a subset of
// UTF-8... and since the strings we'll be reading here are
// also primarily limited to the 7-bit ASCII range (at
// least, in English versions), this should work well
// enough to keep us on the air until we're ready to
// officially decommit from VJ++. [Edited comment from
// jkesselm]
BufferedReader rd;
try {
rd = new BufferedReader(new InputStreamReader(is, "UTF-8"));
} catch (java.io.UnsupportedEncodingException e) {
rd = new BufferedReader(new InputStreamReader(is));
}
String factoryClassName = null;
try {
// XXX Does not handle all possible input as specified by the
// Jar Service Provider specification
factoryClassName = rd.readLine();
rd.close();
} catch (IOException x) {
// No provider found
return null;
}
if (factoryClassName != null &&
! "".equals(factoryClassName)) {
debugPrintln("found in resource, value="
+ factoryClassName);
// Note: here we do not want to fall back to the current
// ClassLoader because we want to avoid the case where the
// resource file was found using one ClassLoader and the
// provider class was instantiated using a different one.
return newInstance(factoryClassName, cl, false);
}
// No provider found
return null;
}
//
// Classes
//
/**
* A configuration error.
*/
public static class ConfigurationError
extends Error {
//
// Data
//
/** Exception. */
private Exception exception;
//
// Constructors
//
/**
* Construct a new instance with the specified detail string and
* exception.
*/
public ConfigurationError(String msg, Exception x) {
super(msg);
this.exception = x;
} // <init>(String,Exception)
//
// Public methods
//
/** Returns the exception associated to this error. */
public Exception getException() {
return exception;
} // getException():Exception
} // class ConfigurationError
} // class ObjectFactory
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