/*

 * 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

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package com.sun.org.glassfish.gmbal.util;

import java.lang.reflect.Constructor ;

import java.security.AccessController;

import java.security.PrivilegedExceptionAction;

import java.util.logging.Level;

import java.util.logging.Logger;

/** Class that allows any class to be instantiated via any accessible constructor.

 * Really a short hand to avoid writing a bunch of reflective code.

 */

public class GenericConstructor<T> {

    private final Object lock = new Object() ;

    private String typeName ;

    private Class<T> resultType ;

    private Class<?> type ;

    private Class<?>[] signature ;

    // Use the raw type of the constructor here, because

    // MethodInfo can only return a raw type for a constructor.

    // It is not possible to have MethodInfo return a

    // Constructor<T> because T may not be known at compile time.

    private Constructor constructor ;

    /** Create a generic of type T for the untyped class cls.

     * Generally cls is a class that has been generated and loaded, so

     * no compiled code can depend on the class directly.  However, the

     * generated class probably implements some interface T, represented

     * here by Class<T>.

     * @param type The expected type of a create call.

     * @param className The name of the class to use for a constructor.

     * @param signature The signature of the desired constructor.

     * @throws IllegalArgumentException if cls is not a subclass of type.

     */

    public GenericConstructor( final Class<T> type, final String className,

        final Class<?>... signature ) {

        this.resultType = type ;

        this.typeName = className ;

        this.signature = signature.clone() ;

    }

    @SuppressWarnings("unchecked")

    private void getConstructor() {

        synchronized( lock ) {

            if ((type == null) || (constructor == null)) {

                try {

                    type = (Class<T>)Class.forName( typeName ) ;

                    constructor = AccessController.doPrivileged(

                        new PrivilegedExceptionAction<Constructor>() {

                            public Constructor run() throws Exception {

                                synchronized( lock ) {

                                    return type.getDeclaredConstructor( signature ) ;

                                }

                            }

                        } ) ;

                } catch (Exception exc) {

                    // Catch all for several checked exceptions: ignore findbugs

                    Logger.getLogger( "com.sun.org.glassfish.gmbal.util" ).log( Level.FINE,

                        "Failure in getConstructor", exc ) ;

                }

            }

        }

    }

    /** Create an instance of type T using the constructor that

     * matches the given arguments if possible.  The constructor

     * is cached, so an instance of GenericClass should always be

     * used for the same types of arguments.  If a call fails,

     * a check is made to see if a different constructor could

     * be used.

     * @param args The constructor arguments.

     * @return A new instance of the object.

     */

    public synchronized T create( Object... args ) {

        synchronized(lock) {

            T result = null ;

            for (int ctr=0; ctr<=1; ctr++) {

                getConstructor() ;

                if (constructor == null) {

                    break ;

                }

                try {

                    result = resultType.cast( constructor.newInstance( args ) ) ;

                    break ;

                } catch (Exception exc) {

                    // There are 4 checked exceptions here with identical handling.

                    // Ignore FindBugs complaints.

                    constructor = null ;

                    Logger.getLogger("com.sun.org.glassfish.gmbal.util").

                        log(Level.WARNING, "Error invoking constructor", exc );

                }

            }

            return result ;

        }

    }

}