javax.xml.parsers.FactoryFinder Maven / Gradle / Ivy
/*
* The contents of this file are subject to the terms
* of the Common Development and Distribution License
* (the "License"). You may not use this file except
* in compliance with the License.
*
* You can obtain a copy of the license at
* https://jaxp.dev.java.net/CDDLv1.0.html.
* See the License for the specific language governing
* permissions and limitations under the License.
*
* When distributing Covered Code, include this CDDL
* HEADER in each file and include the License file at
* https://jaxp.dev.java.net/CDDLv1.0.html
* If applicable add the following below this CDDL HEADER
* with the fields enclosed by brackets "[]" replaced with
* your own identifying information: Portions Copyright
* [year] [name of copyright owner]
*/
/*
* $Id: FactoryFinder.java,v 1.5 2006/10/06 14:43:07 spericas Exp $
* %W% %E%
*
* Copyright 2005 Sun Microsystems, Inc. All Rights Reserved.
*/
package javax.xml.parsers;
import java.io.File;
import java.io.FileInputStream;
import java.util.Properties;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
/**
* Implements pluggable Datatypes.
*
* This class is duplicated for each JAXP subpackage so keep it in
* sync. It is package private for secure class loading.
*
* @author [email protected]
*/
class FactoryFinder {
/**
* Internal debug flag.
*/
private static boolean debug = false;
/**
* Cache for properties in java.home/lib/jaxp.properties
*/
static Properties cacheProps = new Properties();
/**
* Flag indicating if properties from java.home/lib/jaxp.properties
* have been cached.
*/
static boolean firstTime = true;
/**
* Security support class use to check access control before
* getting certain system resources.
*/
static SecuritySupport ss = new SecuritySupport();
// Define system property "jaxp.debug" to get output
static {
// Use try/catch block to support applets, which throws
// SecurityException out of this code.
try {
String val = ss.getSystemProperty("jaxp.debug");
// Allow simply setting the prop to turn on debug
debug = val != null && !"false".equals(val);
}
catch (SecurityException se) {
debug = false;
}
}
private static void dPrint(String msg) {
if (debug) {
System.err.println("JAXP: " + msg);
}
}
/**
* Attempt to load a class using the class loader supplied. If that fails
* and fall back is enabled, the current (i.e. bootstrap) class loader is
* tried.
*
* If the class loader supplied is null, first try using the
* context class loader followed by the current (i.e. bootstrap) class
* loader.
*/
static private Class getProviderClass(String className, ClassLoader cl,
boolean doFallback) throws ClassNotFoundException
{
try {
if (cl == null) {
cl = ss.getContextClassLoader();
if (cl == null) {
throw new ClassNotFoundException();
}
else {
return cl.loadClass(className);
}
}
else {
return cl.loadClass(className);
}
}
catch (ClassNotFoundException e1) {
if (doFallback) {
// Use current class loader - should always be bootstrap CL
return Class.forName(className, true, FactoryFinder.class.getClassLoader());
}
else {
throw e1;
}
}
}
/**
* Create an instance of a class. Delegates to method
* getProviderClass() in order to load the class.
*
* @param className Name of the concrete class corresponding to the
* service provider
*
* @param cl ClassLoader to use to load the class, null means to use
* the bootstrap ClassLoader
*
* @param doFallback True if the current ClassLoader should be tried as
* a fallback if the class is not found using cl
*/
static Object newInstance(String className, ClassLoader cl, boolean doFallback)
throws ConfigurationError
{
try {
Class providerClass = getProviderClass(className, cl, doFallback);
Object instance = providerClass.newInstance();
if (debug) { // Extra check to avoid computing cl strings
dPrint("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);
}
}
/**
* Finds the implementation Class object in the specified order. Main
* entry point.
* @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.
*
* Package private so this code can be shared.
*/
static Object find(String factoryId, String fallbackClassName)
throws ConfigurationError
{
dPrint("find factoryId =" + factoryId);
// Use the system property first
try {
String systemProp = ss.getSystemProperty(factoryId);
if (systemProp != null) {
dPrint("found system property, value=" + systemProp);
return newInstance(systemProp, null, true);
}
}
catch (SecurityException se) {
if (debug) se.printStackTrace();
}
// try to read from $java.home/lib/jaxp.properties
try {
String factoryClassName = null;
if (firstTime) {
synchronized (cacheProps) {
if (firstTime) {
String configFile = ss.getSystemProperty("java.home") + File.separator +
"lib" + File.separator + "jaxp.properties";
File f = new File(configFile);
firstTime = false;
if (ss.doesFileExist(f)) {
dPrint("Read properties file "+f);
cacheProps.load(ss.getFileInputStream(f));
}
}
}
}
factoryClassName = cacheProps.getProperty(factoryId);
if (factoryClassName != null) {
dPrint("found in $java.home/jaxp.properties, value=" + factoryClassName);
return newInstance(factoryClassName, null, true);
}
}
catch (Exception ex) {
if (debug) ex.printStackTrace();
}
// 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);
}
dPrint("loaded from fallback value: " + fallbackClassName);
return newInstance(fallbackClassName, null, true);
}
/*
* 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
{
String serviceId = "META-INF/services/" + factoryId;
InputStream is = null;
// First try the Context ClassLoader
ClassLoader cl = ss.getContextClassLoader();
if (cl != null) {
is = ss.getResourceAsStream(cl, serviceId);
// If no provider found then try the current ClassLoader
if (is == null) {
cl = FactoryFinder.class.getClassLoader();
is = ss.getResourceAsStream(cl, serviceId);
}
} else {
// No Context ClassLoader, try the current ClassLoader
cl = FactoryFinder.class.getClassLoader();
is = ss.getResourceAsStream(cl, serviceId);
}
if (is == null) {
// No provider found
return null;
}
if (debug) { // Extra check to avoid computing cl strings
dPrint("found jar resource=" + serviceId + " using ClassLoader: " + cl);
}
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)) {
dPrint("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;
}
static class ConfigurationError extends Error {
private Exception exception;
/**
* Construct a new instance with the specified detail string and
* exception.
*/
ConfigurationError(String msg, Exception x) {
super(msg);
this.exception = x;
}
Exception getException() {
return exception;
}
}
}