1 /* 2 * Copyright (c) 2006, 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 27 28 package com.sun.org.glassfish.gmbal.util; 29 30 import java.lang.reflect.Constructor ; 31 import java.security.AccessController; 32 import java.security.PrivilegedExceptionAction; 33 import java.util.logging.Level; 34 import java.util.logging.Logger; 35 36 /** Class that allows any class to be instantiated via any accessible constructor. 37 * Really a short hand to avoid writing a bunch of reflective code. 38 */ 39 public class GenericConstructor<T> { 40 private final Object lock = new Object() ; 41 42 private String typeName ; 43 private Class<T> resultType ; 44 private Class<?> type ; 45 private Class<?>[] signature ; 46 47 // Use the raw type of the constructor here, because 48 // MethodInfo can only return a raw type for a constructor. 49 // It is not possible to have MethodInfo return a 50 // Constructor<T> because T may not be known at compile time. 51 private Constructor constructor ; 52 53 /** Create a generic of type T for the untyped class cls. 54 * Generally cls is a class that has been generated and loaded, so 55 * no compiled code can depend on the class directly. However, the 56 * generated class probably implements some interface T, represented 57 * here by Class<T>. 58 * @param type The expected type of a create call. 59 * @param className The name of the class to use for a constructor. 60 * @param signature The signature of the desired constructor. 61 * @throws IllegalArgumentException if cls is not a subclass of type. 62 */ 63 public GenericConstructor( final Class<T> type, final String className, 64 final Class<?>... signature ) { 65 this.resultType = type ; 66 this.typeName = className ; 67 this.signature = signature.clone() ; 68 } 69 70 @SuppressWarnings("unchecked") 71 private void getConstructor() { 72 synchronized( lock ) { 73 if ((type == null) || (constructor == null)) { 74 try { 75 type = (Class<T>)Class.forName( typeName ) ; 76 constructor = AccessController.doPrivileged( 77 new PrivilegedExceptionAction<Constructor>() { 78 public Constructor run() throws Exception { 79 synchronized( lock ) { 80 return type.getDeclaredConstructor( signature ) ; 81 } 82 } 83 } ) ; 84 } catch (Exception exc) { 85 // Catch all for several checked exceptions: ignore findbugs 86 Logger.getLogger( "com.sun.org.glassfish.gmbal.util" ).log( Level.FINE, 87 "Failure in getConstructor", exc ) ; 88 } 89 } 90 } 91 } 92 93 /** Create an instance of type T using the constructor that 94 * matches the given arguments if possible. The constructor 95 * is cached, so an instance of GenericClass should always be 96 * used for the same types of arguments. If a call fails, 97 * a check is made to see if a different constructor could 98 * be used. 99 * @param args The constructor arguments. 100 * @return A new instance of the object. 101 */ 102 public synchronized T create( Object... args ) { 103 synchronized(lock) { 104 T result = null ; 105 106 for (int ctr=0; ctr<=1; ctr++) { 107 getConstructor() ; 108 if (constructor == null) { 109 break ; 110 } 111 112 try { 113 result = resultType.cast( constructor.newInstance( args ) ) ; 114 break ; 115 } catch (Exception exc) { 116 // There are 4 checked exceptions here with identical handling. 117 // Ignore FindBugs complaints. 118 constructor = null ; 119 Logger.getLogger("com.sun.org.glassfish.gmbal.util"). 120 log(Level.WARNING, "Error invoking constructor", exc ); 121 } 122 } 123 124 return result ; 125 } 126 } 127 }