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	/*
	* Copyright (c) 2010, 2013, 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.sql.rowset;

	import java.security.AccessController;
	import java.security.PrivilegedAction;
	import java.sql.SQLException;
	import java.util.PropertyPermission;
	import java.util.ServiceConfigurationError;
	import java.util.ServiceLoader;
	import sun.reflect.misc.ReflectUtil;

	/**
	* A factory API that enables applications to obtain a
	* {@code RowSetFactory} implementation that can be used to create different
	* types of {@code RowSet} implementations.
	* <p>
	* Example:
	* </p>
	* <pre>
	* RowSetFactory aFactory = RowSetProvider.newFactory();
	* CachedRowSet crs = aFactory.createCachedRowSet();
	* ...
	* RowSetFactory rsf = RowSetProvider.newFactory("com.sun.rowset.RowSetFactoryImpl", null);
	* WebRowSet wrs = rsf.createWebRowSet();
	* </pre>
	*<p>
	* Tracing of this class may be enabled by setting the System property
	* {@code javax.sql.rowset.RowSetFactory.debug} to any value but {@code false}.
	* </p>
	*
	* @author Lance Andersen
	* @since 1.7
	*/
	public class RowSetProvider {

	private static final String ROWSET_DEBUG_PROPERTY = "javax.sql.rowset.RowSetProvider.debug";
	private static final String ROWSET_FACTORY_IMPL = "com.sun.rowset.RowSetFactoryImpl";
	private static final String ROWSET_FACTORY_NAME = "javax.sql.rowset.RowSetFactory";
	/**
	* Internal debug flag.
	*/
	private static boolean debug = true;


	static {
	// Check to see if the debug property is set
	String val = getSystemProperty(ROWSET_DEBUG_PROPERTY);
	// Allow simply setting the prop to turn on debug
	debug = val != null && !"false".equals(val);
	}

	/**
	* RowSetProvider constructor
	*/
	protected RowSetProvider () {
	}

	/**
	* <p>Creates a new instance of a <code>RowSetFactory</code>
	* implementation. This method uses the following
	* look up order to determine
	* the <code>RowSetFactory</code> implementation class to load:</p>
	* <ul>
	* <li>
	* The System property {@code javax.sql.rowset.RowSetFactory}. For example:
	* <ul>
	* <li>
	* -Djavax.sql.rowset.RowSetFactory=com.sun.rowset.RowSetFactoryImpl
	* </li>
	* </ul>
	* <li>
	* The {@link ServiceLoader} API. The {@code ServiceLoader} API will look
	* for a class name in the file
	* {@code META-INF/services/javax.sql.rowset.RowSetFactory}
	* in jars available to the runtime. For example, to have the RowSetFactory
	* implementation {@code com.sun.rowset.RowSetFactoryImpl } loaded, the
	* entry in {@code META-INF/services/javax.sql.rowset.RowSetFactory} would be:
	* <ul>
	* <li>
	* {@code com.sun.rowset.RowSetFactoryImpl }
	* </li>
	* </ul>
	* </li>
	* <li>
	* Platform default <code>RowSetFactory</code> instance.
	* </li>
	* </ul>
	*
	* <p>Once an application has obtained a reference to a {@code RowSetFactory},
	* it can use the factory to obtain RowSet instances.</p>
	*
	* @return New instance of a <code>RowSetFactory</code>
	*
	* @throws SQLException if the default factory class cannot be loaded,
	* instantiated. The cause will be set to actual Exception
	*
	* @see ServiceLoader
	* @since 1.7
	*/
	public static RowSetFactory newFactory()
	throws SQLException {
	// Use the system property first
	RowSetFactory factory = null;
	String factoryClassName = null;
	try {
	trace("Checking for Rowset System Property...");
	factoryClassName = getSystemProperty(ROWSET_FACTORY_NAME);
	if (factoryClassName != null) {
	trace("Found system property, value=" + factoryClassName);
	if (factoryClassName.equals(ROWSET_FACTORY_IMPL)) {
	return defaultRowSetFactory();
	}
	// getFactoryClass takes care of adding the read edge if
	// necessary
	@SuppressWarnings("deprecation")
	Object o = getFactoryClass(factoryClassName, null, false).newInstance();
	factory = (RowSetFactory) o;
	}
	} catch (Exception e) {
	throw new SQLException( "RowSetFactory: " + factoryClassName +
	" could not be instantiated: ", e);
	}

	// Check to see if we found the RowSetFactory via a System property
	if (factory == null) {
	// If the RowSetFactory is not found via a System Property, now
	// look it up via the ServiceLoader API and if not found, use the
	// Java SE default.
	factory = loadViaServiceLoader();
	}
	return factory == null ? defaultRowSetFactory() : factory;
	}

	private static RowSetFactory defaultRowSetFactory() {
	return new com.sun.rowset.RowSetFactoryImpl();
	}

	/**
	* <p>Creates a new instance of a <code>RowSetFactory</code> from the
	* specified factory class name.
	* This function is useful when there are multiple providers in the classpath.
	* It gives more control to the application as it can specify which provider
	* should be loaded.</p>
	*
	* <p>Once an application has obtained a reference to a <code>RowSetFactory</code>
	* it can use the factory to obtain RowSet instances.</p>
	*
	* @param factoryClassName fully qualified factory class name that
	* provides an implementation of <code>javax.sql.rowset.RowSetFactory</code>.
	*
	* @param cl <code>ClassLoader</code> used to load the factory
	* class. If <code>null</code> current <code>Thread</code>'s context
	* classLoader is used to load the factory class.
	*
	* @return New instance of a <code>RowSetFactory</code>
	*
	* @throws SQLException if <code>factoryClassName</code> is
	* <code>null</code>, or the factory class cannot be loaded, instantiated.
	*
	* @see #newFactory()
	*
	* @since 1.7
	*/
	public static RowSetFactory newFactory(String factoryClassName, ClassLoader cl)
	throws SQLException {

	trace("***In newInstance()");

	if(factoryClassName == null) {
	throw new SQLException("Error: factoryClassName cannot be null");
	}
	try {
	ReflectUtil.checkPackageAccess(factoryClassName);
	} catch (java.security.AccessControlException e) {
	throw new SQLException("Access Exception",e);
	}

	try {
	// getFactoryClass takes care of adding the read edge if
	// necessary
	Class<?> providerClass = getFactoryClass(factoryClassName, cl, false);
	@SuppressWarnings("deprecation")
	RowSetFactory instance = (RowSetFactory) providerClass.newInstance();
	if (debug) {
	trace("Created new instance of " + providerClass +
	" using ClassLoader: " + cl);
	}
	return instance;
	} catch (ClassNotFoundException x) {
	throw new SQLException(
	"Provider " + factoryClassName + " not found", x);
	} catch (Exception x) {
	throw new SQLException(
	"Provider " + factoryClassName + " could not be instantiated: " + x,
	x);
	}
	}

	/*
	* Returns the class loader to be used.
	* @return The ClassLoader to use.
	*
	*/
	static private ClassLoader getContextClassLoader() throws SecurityException {
	return AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {

	public ClassLoader run() {
	ClassLoader cl = null;

	cl = Thread.currentThread().getContextClassLoader();

	if (cl == null) {
	cl = ClassLoader.getSystemClassLoader();
	}

	return cl;
	}
	});
	}

	/**
	* 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 class loader.
	* @return The class which was loaded
	*/
	static private Class<?> getFactoryClass(String factoryClassName, ClassLoader cl,
	boolean doFallback) throws ClassNotFoundException {
	Class<?> factoryClass = null;

	try {
	if (cl == null) {
	cl = getContextClassLoader();
	if (cl == null) {
	throw new ClassNotFoundException();
	} else {
	factoryClass = cl.loadClass(factoryClassName);
	}
	} else {
	factoryClass = cl.loadClass(factoryClassName);
	}
	} catch (ClassNotFoundException e) {
	if (doFallback) {
	// Use current class loader
	factoryClass = Class.forName(factoryClassName, true, RowSetFactory.class.getClassLoader());
	} else {
	throw e;
	}
	}

	ReflectUtil.checkPackageAccess(factoryClass);
	return factoryClass;
	}

	/**
	* Use the ServiceLoader mechanism to load the default RowSetFactory
	* @return default RowSetFactory Implementation
	*/
	static private RowSetFactory loadViaServiceLoader() throws SQLException {
	RowSetFactory theFactory = null;
	try {
	trace("***in loadViaServiceLoader():");
	for (RowSetFactory factory : ServiceLoader.load(javax.sql.rowset.RowSetFactory.class)) {
	trace(" Loading done by the java.util.ServiceLoader :" + factory.getClass().getName());
	theFactory = factory;
	break;
	}
	} catch (ServiceConfigurationError e) {
	throw new SQLException(
	"RowSetFactory: Error locating RowSetFactory using Service "
	+ "Loader API: " + e, e);
	}
	return theFactory;

	}

	/**
	* Returns the requested System Property. If a {@code SecurityException}
	* occurs, just return NULL
	* @param propName - System property to retrieve
	* @return The System property value or NULL if the property does not exist
	* or a {@code SecurityException} occurs.
	*/
	static private String getSystemProperty(final String propName) {
	String property = null;
	try {
	property = AccessController.doPrivileged(new PrivilegedAction<String>() {

	public String run() {
	return System.getProperty(propName);
	}
	}, null, new PropertyPermission(propName, "read"));
	} catch (SecurityException se) {
	trace("error getting " + propName + ": "+ se);
	if (debug) {
	se.printStackTrace();
	}
	}
	return property;
	}

	/**
	* Debug routine which will output tracing if the System Property
	* -Djavax.sql.rowset.RowSetFactory.debug is set
	* @param msg - The debug message to display
	*/
	private static void trace(String msg) {
	if (debug) {
	System.err.println("###RowSets: " + msg);
	}
	}
	}

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