1 /*
   2  * Copyright (c) 2015, 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 package jdk.nashorn.api.scripting;
  27 
  28 import jdk.nashorn.internal.runtime.JSType;
  29 
  30 /**
  31  * Default implementation of {@link JSObject#getDefaultValue(Class)}. Isolated into a separate class mostly so
  32  * that we can have private static instances of function name arrays, something we couldn't declare without it
  33  * being visible in {@link JSObject} interface.
  34  */
  35 class DefaultValueImpl {
  36     private static final String[] DEFAULT_VALUE_FNS_NUMBER = new String[] { "valueOf", "toString" };
  37     private static final String[] DEFAULT_VALUE_FNS_STRING = new String[] { "toString", "valueOf" };
  38 
  39     static Object getDefaultValue(final JSObject jsobj, final Class<?> hint) throws UnsupportedOperationException {
  40         final boolean isNumber = hint == null || hint == Number.class;
  41         for(final String methodName: isNumber ? DEFAULT_VALUE_FNS_NUMBER : DEFAULT_VALUE_FNS_STRING) {
  42             final Object objMember = jsobj.getMember(methodName);
  43             if (objMember instanceof JSObject) {
  44                 final JSObject member = (JSObject)objMember;
  45                 if (member.isFunction()) {
  46                     final Object value = member.call(jsobj);
  47                     if (JSType.isPrimitive(value)) {
  48                         return value;
  49                     }
  50                 }
  51             }
  52         }
  53         throw new UnsupportedOperationException(isNumber ? "cannot.get.default.number" : "cannot.get.default.string");
  54     }
  55 }