jaxp/src/share/classes/javax/xml/transform/FactoryFinder.java
changeset 12005 a754d69d5e60
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jaxp/src/share/classes/javax/xml/transform/FactoryFinder.java	Sun Mar 04 11:55:34 2012 -0800
@@ -0,0 +1,327 @@
+/*
+ * Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package javax.xml.transform;
+
+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;
+
+/**
+ * <p>Implements pluggable Datatypes.</p>
+ *
+ * <p>This class is duplicated for each JAXP subpackage so keep it in
+ * sync.  It is package private for secure class loading.</p>
+ *
+ * @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 is <code>null</code>, 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
+     * <code>getProviderClass()</code> 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;
+        }
+    }
+
+}