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/*
 * Copyright 2014 - Present Rafael Winterhalter
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.bytebuddy.dynamic.loading;

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import net.bytebuddy.build.HashCodeAndEqualsPlugin;
import net.bytebuddy.matcher.ElementMatcher;
import net.bytebuddy.utility.nullability.MaybeNull;
import net.bytebuddy.utility.nullability.UnknownNull;

import java.io.IOException;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.*;

import static net.bytebuddy.matcher.ElementMatchers.is;
import static net.bytebuddy.matcher.ElementMatchers.not;

/**
 * 

* This {@link java.lang.ClassLoader} is capable of loading classes from multiple parents. This class loader * implicitly defines the bootstrap class loader to be its direct parent as it is required for all class loaders. * This can be useful when creating a type that inherits a super type and interfaces that are defined by different, * non-compatible class loaders. *

*

* Note: Instances of this class loader can have the same class loader as its parent multiple times, * either directly or indirectly by multiple parents sharing a common parent class loader. By definition, * this implies that the bootstrap class loader is {@code #(direct parents) + 1} times a parent of this class loader. * For the {@link java.lang.ClassLoader#getResources(java.lang.String)} method, this means that this class loader * might return the same url multiple times by representing the same class loader multiple times. *

*

* Important: This class loader does not support the location of packages from its multiple parents. This breaks * package equality when loading classes by either loading them directly via this class loader (e.g. by subclassing) or * by loading classes with child class loaders of this class loader. *

*/ public class MultipleParentClassLoader extends InjectionClassLoader { /* * Register class loader as parallel capable if the current VM supports it. */ static { doRegisterAsParallelCapable(); } /** * Registers class loader as parallel capable if possible. */ @SuppressFBWarnings(value = "DP_DO_INSIDE_DO_PRIVILEGED", justification = "Must be invoked from targeting class loader type.") private static void doRegisterAsParallelCapable() { try { Method method = ClassLoader.class.getDeclaredMethod("registerAsParallelCapable"); method.setAccessible(true); method.invoke(null); } catch (Throwable ignored) { /* do nothing */ } } /** * The parents of this class loader in their application order. */ private final List parents; /** * Creates a new class loader with multiple parents. * * @param parents The parents of this class loader in their application order. This list must not contain {@code null}, * i.e. the bootstrap class loader which is an implicit parent of any class loader. */ public MultipleParentClassLoader(List parents) { this(ClassLoadingStrategy.BOOTSTRAP_LOADER, parents); } /** * Creates a new class loader with multiple parents. * * @param parent An explicit parent in compliance with the class loader API. This explicit parent should only be set if * the current platform does not allow creating a class loader that extends the bootstrap loader. * @param parents The parents of this class loader in their application order. This list must not contain {@code null}, * i.e. the bootstrap class loader which is an implicit parent of any class loader. */ public MultipleParentClassLoader(@MaybeNull ClassLoader parent, List parents) { this(parent, parents, true); } /** * Creates a new class loader with multiple parents. * * @param parent An explicit parent in compliance with the class loader API. This explicit parent should only be set if * the current platform does not allow creating a class loader that extends the bootstrap loader. * @param parents The parents of this class loader in their application order. This list must not contain {@code null}, * i.e. the bootstrap class loader which is an implicit parent of any class loader. * @param sealed {@code true} if the class loader is sealed for injection of additional classes. */ public MultipleParentClassLoader(@MaybeNull ClassLoader parent, List parents, boolean sealed) { super(parent, sealed); this.parents = parents; } /** * {@inheritDoc} */ protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException { for (ClassLoader parent : parents) { try { Class type = parent.loadClass(name); if (resolve) { resolveClass(type); } return type; } catch (ClassNotFoundException ignored) { /* try next class loader */ } } return super.loadClass(name, resolve); } /** * {@inheritDoc} */ public URL getResource(String name) { for (ClassLoader parent : parents) { URL url = parent.getResource(name); if (url != null) { return url; } } return super.getResource(name); } /** * {@inheritDoc} */ public Enumeration getResources(String name) throws IOException { List> enumerations = new ArrayList>(parents.size() + 1); for (ClassLoader parent : parents) { enumerations.add(parent.getResources(name)); } enumerations.add(super.getResources(name)); return new CompoundEnumeration(enumerations); } @Override protected Map> doDefineClasses(Map typeDefinitions) { Map> types = new HashMap>(); for (Map.Entry entry : typeDefinitions.entrySet()) { types.put(entry.getKey(), defineClass(entry.getKey(), entry.getValue(), 0, entry.getValue().length)); } return types; } /** * A compound URL enumeration. */ protected static class CompoundEnumeration implements Enumeration { /** * Indicates the first index of a list. */ private static final int FIRST = 0; /** * The remaining lists of enumerations. */ private final List> enumerations; /** * The currently represented enumeration or {@code null} if no such enumeration is currently selected. */ @UnknownNull private Enumeration current; /** * Creates a compound enumeration. * * @param enumerations The enumerations to represent. */ protected CompoundEnumeration(List> enumerations) { this.enumerations = enumerations; } /** * {@inheritDoc} */ public boolean hasMoreElements() { if (current != null && current.hasMoreElements()) { return true; } else if (!enumerations.isEmpty()) { current = enumerations.remove(FIRST); return hasMoreElements(); } else { return false; } } /** * {@inheritDoc} */ @SuppressFBWarnings(value = "UWF_FIELD_NOT_INITIALIZED_IN_CONSTRUCTOR", justification = "Null reference is avoided by element check.") public URL nextElement() { if (hasMoreElements()) { return current.nextElement(); } else { throw new NoSuchElementException(); } } } /** * A builder to collect class loader and that creates a * {@link net.bytebuddy.dynamic.loading.MultipleParentClassLoader} only if multiple or no * {@link java.lang.ClassLoader}s are found in the process. If exactly a single class loader is found, * this class loader is returned. All class loaders are applied in their collection order with the exception * of the bootstrap class loader which is represented by {@code null} and which is an implicit parent of any * class loader. */ @HashCodeAndEqualsPlugin.Enhance public static class Builder { /** * {@code true} if the created class loader is sealed. */ private final boolean sealed; /** * The class loaders that were collected. */ private final List classLoaders; /** * Creates a new builder without any class loaders. */ public Builder() { this(true); } /** * Creates a new builder without any class loaders. * * @param sealed {@code true} if the created class loader is sealed. */ public Builder(boolean sealed) { this(Collections.emptyList(), sealed); } /** * Creates a new builder. * * @param classLoaders The class loaders that were collected until now. * @param sealed {@code true} if the created class loader is sealed. */ private Builder(List classLoaders, boolean sealed) { this.classLoaders = classLoaders; this.sealed = sealed; } /** * Appends the class loaders of the given types. The bootstrap class loader is implicitly skipped as * it is an implicit parent of any class loader. * * @param type The types of which to collect the class loaders. * @return A new builder instance with the additional class loaders of the provided types if they were not * yet collected. */ public Builder append(Class... type) { return append(Arrays.asList(type)); } /** * Appends the class loaders of the given types if those class loaders were not yet collected. The bootstrap class * loader is implicitly skipped as it is an implicit parent of any class loader. * * @param types The types of which to collect the class loaders. * @return A new builder instance with the additional class loaders. */ public Builder append(Collection> types) { List classLoaders = new ArrayList(types.size()); for (Class type : types) { classLoaders.add(type.getClassLoader()); } return append(classLoaders); } /** * Appends the given class loaders if they were not yet collected. The bootstrap class loader is implicitly * skipped as it is an implicit parent of any class loader. * * @param classLoader The class loaders to be collected. * @return A new builder instance with the additional class loaders. */ public Builder append(ClassLoader... classLoader) { return append(Arrays.asList(classLoader)); } /** * Appends the given class loaders if they were not yet appended. The bootstrap class loader is never appended as * it is an implicit parent of any class loader. * * @param classLoaders The class loaders to collected. * @return A new builder instance with the additional class loaders. */ public Builder append(List classLoaders) { List filtered = new ArrayList(this.classLoaders.size() + classLoaders.size()); filtered.addAll(this.classLoaders); Set registered = new HashSet(this.classLoaders); for (ClassLoader classLoader : classLoaders) { if (classLoader != null && registered.add(classLoader)) { filtered.add(classLoader); } } return new Builder(filtered, sealed); } /** * Appends the class loaders of the given types but filters any duplicates within the hierarchy of class loaders. * The bootstrap class loader is implicitly skipped as it is an implicit parent of any class loader. Class loaders * are prepended to the list of class loaders. * * @param type The types of which to collect the class loaders. * @return A new builder instance with the additional class loaders of the provided types if they were not * yet collected. */ public Builder appendMostSpecific(Class... type) { return appendMostSpecific(Arrays.asList(type)); } /** * Appends the class loaders of the given types but filters any duplicates within the hierarchy of class loaders. * The bootstrap class loader is implicitly skipped as it is an implicit parent of any class loader. Class loaders * are prepended to the list of class loaders. * * @param types The types of which to collect the class loaders. * @return A new builder instance with the additional class loaders. */ public Builder appendMostSpecific(Collection> types) { List classLoaders = new ArrayList(types.size()); for (Class type : types) { classLoaders.add(type.getClassLoader()); } return appendMostSpecific(classLoaders); } /** * Appends the given class loaders but removes any class loaders that are the parent of any previously registered class loader. * The bootstrap class loader is implicitly skipped as it is an implicit parent of any class loader. * * @param classLoader The class loaders to be collected. * @return A new builder instance with the additional class loaders. */ public Builder appendMostSpecific(ClassLoader... classLoader) { return appendMostSpecific(Arrays.asList(classLoader)); } /** * Appends the given class loaders but removes any class loaders that are the parent of any previously registered class loader. * The bootstrap class loader is implicitly skipped as it is an implicit parent of any class loader. * * @param classLoaders The class loaders to collected. * @return A new builder instance with the additional class loaders. */ public Builder appendMostSpecific(List classLoaders) { List filtered = new ArrayList(this.classLoaders.size() + classLoaders.size()); filtered.addAll(this.classLoaders); consideration: for (ClassLoader classLoader : classLoaders) { if (classLoader == null) { continue; } ClassLoader candidate = classLoader; do { Iterator iterator = filtered.iterator(); while (iterator.hasNext()) { ClassLoader previous = iterator.next(); if (previous.equals(candidate)) { iterator.remove(); } } } while ((candidate = candidate.getParent()) != null); for (ClassLoader previous : filtered) { do { if (previous.equals(classLoader)) { continue consideration; } } while ((previous = previous.getParent()) != null); } filtered.add(classLoader); } return new Builder(filtered, sealed); } /** * Only retains all class loaders that match the given matcher. * * @param matcher The matcher to be used for filtering. * @return A builder that does not longer consider any appended class loaders that matched the provided matcher. */ public Builder filter(ElementMatcher matcher) { List classLoaders = new ArrayList(this.classLoaders.size()); for (ClassLoader classLoader : this.classLoaders) { if (matcher.matches(classLoader)) { classLoaders.add(classLoader); } } return new Builder(classLoaders, sealed); } /** *

* Returns the only class loader that was appended if exactly one class loader was appended or a multiple parent class loader as * a parent of all supplied class loader and with the bootstrap class loader as an implicit parent. If no class loader was appended, * a new class loader is created that declares no parents. If a class loader is created, its explicit parent is set to be the * bootstrap class loader. *

*

* Important: Byte Buddy does not provide any access control for the creation of the class loader. It is the responsibility * of the user of this builder to provide such privileges. *

* * @return A suitable class loader. */ public ClassLoader build() { return classLoaders.size() == 1 ? classLoaders.get(0) : doBuild(ClassLoadingStrategy.BOOTSTRAP_LOADER); } /** *

* Returns the only class loader that was appended if exactly one class loader was appended or a multiple parent class loader as * a parent of all supplied class loader and with the bootstrap class loader as an implicit parent. If no class loader was appended, * or if only the supplied parent to this method was included, this class loader is returned, *

*

* Important: Byte Buddy does not provide any access control for the creation of the class loader. It is the responsibility * of the user of this builder to provide such privileges. *

* * @param parent The class loader's contractual parent which is accessible via {@link ClassLoader#getParent()}. If this class loader * is also included in the appended class loaders, it is not * @return A suitable class loader. */ public ClassLoader build(ClassLoader parent) { return classLoaders.isEmpty() || classLoaders.size() == 1 && classLoaders.contains(parent) ? parent : filter(not(is(parent))).doBuild(parent); } /** * Creates a multiple parent class loader with an explicit parent. * * @param parent The explicit parent class loader. * @return A multiple parent class loader that includes all collected class loaders and the explicit parent. */ @SuppressFBWarnings(value = "DP_CREATE_CLASSLOADER_INSIDE_DO_PRIVILEGED", justification = "Assuring privilege is explicit user responsibility.") private ClassLoader doBuild(@MaybeNull ClassLoader parent) { return new MultipleParentClassLoader(parent, classLoaders, sealed); } } }




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