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 { + + /** + * 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 isnull, 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;
+ }
+ /**
+ * use the exception chaining mechanism of JDK1.4
+ */
+ @Override
+ public Throwable getCause() {
+ return exception;
+ }
+ }
+
+}