1 /*
   2  * Copyright (c) 2003, 2020, 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 sun.reflect.generics.repository;
  27 
  28 import java.lang.reflect.TypeVariable;
  29 import sun.reflect.generics.factory.GenericsFactory;
  30 import sun.reflect.generics.tree.FormalTypeParameter;
  31 import sun.reflect.generics.tree.Signature;
  32 import sun.reflect.generics.visitor.Reifier;
  33 
  34 
  35 
  36 /**
  37  * This class represents the generic type information for a generic
  38  * declaration.
  39  * The code is not dependent on a particular reflective implementation.
  40  * It is designed to be used unchanged by at least core reflection and JDI.
  41  */
  42 public abstract class GenericDeclRepository<S extends Signature>
  43     extends AbstractRepository<S> {
  44 
  45     /** The formal type parameters.  Lazily initialized. */
  46     private volatile TypeVariable<?>[] typeParameters;
  47 
  48     protected GenericDeclRepository(String rawSig, GenericsFactory f) {
  49         super(rawSig, f);
  50     }
  51 
  52     /*
  53      * When queried for a particular piece of type information, the
  54      * general pattern is to consult the corresponding cached value.
  55      * If the corresponding field is non-null, it is returned.
  56      * If not, it is created lazily. This is done by selecting the appropriate
  57      * part of the tree and transforming it into a reflective object
  58      * using a visitor, which is created by feeding it the factory
  59      * with which the repository was created.
  60      */
  61 
  62     /**
  63      * Returns the formal type parameters of this generic declaration.
  64      * @return the formal type parameters of this generic declaration
  65      */
  66     public TypeVariable<?>[] getTypeParameters() {
  67         TypeVariable<?>[] value = typeParameters;
  68         if (value == null) {
  69             value = computeTypeParameters();
  70             typeParameters = value;
  71         }
  72         return value.clone();
  73     }
  74 
  75     private TypeVariable<?>[] computeTypeParameters() {
  76         // first, extract type parameter subtree(s) from AST
  77         FormalTypeParameter[] ftps = getTree().getFormalTypeParameters();
  78         // create array to store reified subtree(s)
  79         int length = ftps.length;
  80         TypeVariable<?>[] typeParameters = new TypeVariable<?>[length];
  81         // reify all subtrees
  82         for (int i = 0; i < length; i++) {
  83             Reifier r = getReifier(); // obtain visitor
  84             ftps[i].accept(r); // reify subtree
  85             // extract result from visitor and store it
  86             typeParameters[i] = (TypeVariable<?>) r.getResult();
  87         }
  88         return typeParameters;
  89     }
  90 }