1 /*
   2  * Copyright (c) 1998, 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 com.sun.jdi;
  27 
  28 import java.util.List;
  29 
  30 /**
  31  * A class loader object from the target VM.
  32  * A ClassLoaderReference is an {@link ObjectReference} with additional
  33  * access to classloader-specific information from the target VM. Instances
  34  * ClassLoaderReference are obtained through calls to
  35  * {@link ReferenceType#classLoader}
  36  *
  37  * @see ObjectReference
  38  *
  39  * @author Gordon Hirsch
  40  * @since  1.3
  41  */
  42 public interface ClassLoaderReference extends ObjectReference {
  43 
  44     /**
  45      * Returns a list of all classes defined by this class loader.
  46      * No ordering of this list guaranteed.
  47      * The returned list will include all reference types, including
  48      * {@link Class#isHidden hidden classes or interfaces}, loaded
  49      * at least to the point of preparation and types (like array)
  50      * for which preparation is not defined.
  51      *
  52      * @return a {@code List} of {@link ReferenceType} objects mirroring types
  53      * defined by this class loader. The list has length 0 if no types
  54      * have been defined by this classloader.
  55      */
  56     List<ReferenceType> definedClasses();
  57 
  58     /**
  59      * Returns a list of all classes which this class loader
  60      * can find by name via {@link ClassLoader#loadClass(String, boolean)
  61      * ClassLoader::loadClass}, {@link Class#forName(String) Class::forName}
  62      * and bytecode linkage in the target VM.  That is, this class loader
  63      * has been recorded as an initiating loader of these classes.
  64      * <p>
  65      * Each class in the returned list was created by this class loader
  66      * either by defining it directly or by delegation to another class loader
  67      * (see JVMS {@jvms 5.3}).
  68      *
  69      * The returned list does not include {@link Class#isHidden() <em>hidden</em>}
  70      * classes or interfaces that are created by the invocation of
  71      * {@link java.lang.invoke.MethodHandles.Lookup#defineHiddenClass(byte[], boolean, java.lang.invoke.MethodHandles.Lookup.ClassOption...)
  72      * Lookup::defineHiddenClass} because:
  73      * <ul>
  74      * <li>A hidden class or interface cannot be referenced by the constant pools
  75      *     of other classes and interfaces.
  76      * <li>A hidden class or interface cannot be discovered by any class loader.
  77      * </ul>
  78      * <p>
  79      * In addition, the returned list does not include array classes whose
  80      * {@linkplain ArrayType#componentType() element type} is a
  81      * {@link Class#isHidden() hidden class or interface} as they cannot
  82      * be discovered by this class loader.
  83      * <p>
  84      * The visible class list has useful properties with respect to
  85      * the type namespace. A particular type name will occur at most
  86      * once in the list. Each field or variable declared with that
  87      * type name in a class defined by
  88      * this class loader must be resolved to that single type.
  89      * <p>
  90      * No ordering of the returned list is guaranteed.
  91      * <p>
  92      * Note that unlike {@link #definedClasses()}
  93      * and {@link VirtualMachine#allClasses()},
  94      * some of the returned reference types may not be prepared.
  95      * Attempts to perform some operations on unprepared reference types
  96      * (e.g. {@link ReferenceType#fields() fields()}) will throw
  97      * a {@link ClassNotPreparedException}.
  98      * Use {@link ReferenceType#isPrepared()} to determine if
  99      * a reference type is prepared.
 100      *
 101      * @return a {@code List} of {@link ReferenceType} objects mirroring
 102      * classes which this class loader can find by name. The list
 103      * has length 0 if no classes are visible to this classloader.
 104      *
 105      * @jvms 5.3 Creation and Loading
 106      */
 107     List<ReferenceType> visibleClasses();
 108 }