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package javax.ws.rs.client;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Iterator;
import java.util.Properties;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Factory finder utility class.
 *
 * @author Paul Sandoz
 * @author Marc Hadley
 * @author Marek Potociar
 * @since 2.0
 */
final class FactoryFinder {

    private static final Logger LOGGER = Logger.getLogger(FactoryFinder.class.getName());

    private FactoryFinder() {
        // prevents instantiation
    }

    static ClassLoader getContextClassLoader() {
        return AccessController.doPrivileged((PrivilegedAction) () -> {
            ClassLoader cl = null;
            try {
                cl = Thread.currentThread().getContextClassLoader();
            } catch (SecurityException ex) {
                LOGGER.log(
                        Level.WARNING,
                        "Unable to get context classloader instance.",
                        ex);
            }
            return cl;
        });
    }

    /**
     * Creates an instance of the specified class using the specified
     * {@code ClassLoader} object.
     *
     * @param className   name of the class to be instantiated.
     * @param classLoader class loader to be used.
     * @return instance of the specified class.
     * @throws ClassNotFoundException if the given class could not be found
     *                                or could not be instantiated.
     */
    private static Object newInstance(final String className, final ClassLoader classLoader) throws ClassNotFoundException {
        try {
            Class spiClass;
            if (classLoader == null) {
                spiClass = Class.forName(className);
            } else {
                try {
                    spiClass = Class.forName(className, false, classLoader);
                } catch (ClassNotFoundException ex) {
                    LOGGER.log(
                            Level.FINE,
                            "Unable to load provider class " + className
                            + " using custom classloader " + classLoader.getClass().getName()
                            + " trying again with current classloader.",
                            ex);
                    spiClass = Class.forName(className);
                }
            }
            return spiClass.getDeclaredConstructor().newInstance();
        } catch (ClassNotFoundException x) {
            throw x;
        } catch (Exception x) {
            throw new ClassNotFoundException("Provider " + className + " could not be instantiated: " + x, x);
        }
    }

    /**
     * Finds the implementation {@code Class} for the given factory name,
     * or if that fails, finds the {@code Class} for the given fallback
     * class name and create its instance. The arguments supplied MUST be
     * used in order. If using the first argument is successful, the second
     * one will not be used.
     * 

* This method is package private so that this code can be shared. * * @param factoryId the name of the factory to find, which is * a system property. * @param fallbackClassName the implementation class name, which is * to be used only if nothing else. * is found; {@code null} to indicate that * there is no fallback class name. * @param service service to be found. * @param type of the service to be found. * @return the instance of the specified service; may not be {@code null}. * @throws ClassNotFoundException if the given class could not be found * or could not be instantiated. */ static Object find(final String factoryId, final String fallbackClassName, Class service) throws ClassNotFoundException { ClassLoader classLoader = getContextClassLoader(); try { Iterator iterator = ServiceLoader.load(service, FactoryFinder.getContextClassLoader()).iterator(); if(iterator.hasNext()) { return iterator.next(); } } catch (Exception | ServiceConfigurationError ex) { LOGGER.log(Level.FINER, "Failed to load service " + factoryId + ".", ex); } try { Iterator iterator = ServiceLoader.load(service, FactoryFinder.class.getClassLoader()).iterator(); if(iterator.hasNext()) { return iterator.next(); } } catch (Exception | ServiceConfigurationError ex) { LOGGER.log(Level.FINER, "Failed to load service " + factoryId + ".", ex); } // try to read from $java.home/lib/jaxrs.properties FileInputStream inputStream = null; String configFile = null; try { String javah = System.getProperty("java.home"); configFile = javah + File.separator + "lib" + File.separator + "jaxrs.properties"; File f = new File(configFile); if (f.exists()) { Properties props = new Properties(); inputStream = new FileInputStream(f); props.load(inputStream); String factoryClassName = props.getProperty(factoryId); return newInstance(factoryClassName, classLoader); } } catch (Exception ex) { LOGGER.log(Level.FINER, "Failed to load service " + factoryId + " from $java.home/lib/jaxrs.properties", ex); } finally { if (inputStream != null) { try { inputStream.close(); } catch (IOException ex) { LOGGER.log(Level.FINER, String.format("Error closing %s file.", configFile), ex); } } } // Use the system property try { String systemProp = System.getProperty(factoryId); if (systemProp != null) { return newInstance(systemProp, classLoader); } } catch (SecurityException se) { LOGGER.log(Level.FINER, "Failed to load service " + factoryId + " from a system property", se); } if (fallbackClassName == null) { throw new ClassNotFoundException( "Provider for " + factoryId + " cannot be found", null); } return newInstance(fallbackClassName, classLoader); } }





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