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 Santiago.PericasGeertsen@sun.com */ class FactoryFinder { // Check we have access to package. private static final String DEFAULT_PACKAGE = "com.sun.xml.internal."; /** * 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 volatile 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 isnull, first try using the
* context class loader followed by the current (i.e. bootstrap) class
* loader.
*
* Use bootstrap classLoader if cl = null and useBSClsLoader is true
*/
static private Class getProviderClass(String className, ClassLoader cl,
boolean doFallback, boolean useBSClsLoader) throws ClassNotFoundException
{
try {
if (cl == null) {
if (useBSClsLoader) {
return Class.forName(className, true, FactoryFinder.class.getClassLoader());
} else {
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 used to load the factory class. If null
* current Thread's context classLoader is used to load the factory class.
*
* @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
{
return newInstance(className, cl, doFallback, false);
}
/**
* 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 used to load the factory class. If null
* current Thread's context classLoader is used to load the factory class.
*
* @param doFallback True if the current ClassLoader should be tried as
* a fallback if the class is not found using cl
*
* @param useBSClsLoader True if cl=null actually meant bootstrap classLoader. This parameter
* is needed since DocumentBuilderFactory/SAXParserFactory defined null as context classLoader.
*/
static Object newInstance(String className, ClassLoader cl, boolean doFallback, boolean useBSClsLoader)
throws ConfigurationError
{
// make sure we have access to restricted packages
if (System.getSecurityManager() != null) {
if (className != null && className.startsWith(DEFAULT_PACKAGE)) {
cl = null;
useBSClsLoader = true;
}
}
try {
Class providerClass = getProviderClass(className, cl, doFallback, useBSClsLoader);
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.
*
* @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
{
return find(factoryId, null, fallbackClassName);
}
/**
* 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 cl ClassLoader to be used to load the class, null means to use
* the bootstrap ClassLoader
*
* @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, ClassLoader cl, 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 read $java.home/lib/stax.properties followed by
// $java.home/lib/jaxp.properties if former not present
String configFile = null;
try {
String factoryClassName = null;
if (firstTime) {
synchronized (cacheProps) {
if (firstTime) {
configFile = ss.getSystemProperty("java.home") + File.separator +
"lib" + File.separator + "stax.properties";
File f = new File(configFile);
firstTime = false;
if (ss.doesFileExist(f)) {
dPrint("Read properties file "+f);
cacheProps.load(ss.getFileInputStream(f));
}
else {
configFile = ss.getSystemProperty("java.home") + File.separator +
"lib" + File.separator + "jaxp.properties";
f = new File(configFile);
if (ss.doesFileExist(f)) {
dPrint("Read properties file "+f);
cacheProps.load(ss.getFileInputStream(f));
}
}
}
}
}
factoryClassName = cacheProps.getProperty(factoryId);
if (factoryClassName != null) {
dPrint("found in " + configFile + " 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, cl, 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();
boolean useBSClsLoader = false;
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);
useBSClsLoader = true;
}
} else {
// No Context ClassLoader, try the current ClassLoader
cl = FactoryFinder.class.getClassLoader();
is = ss.getResourceAsStream(cl, serviceId);
useBSClsLoader = true;
}
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, useBSClsLoader);
}
// 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;
}
/**
* use the exception chaining mechanism of JDK1.4
*/
@Override
public Throwable getCause() {
return exception;
}
}
}