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* Copyright (c) 2014, 2016, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
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*
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package java.lang.reflect;
import java.lang.module.Configuration;
import java.lang.module.ModuleDescriptor;
import java.lang.module.ModuleDescriptor.Provides;
import java.lang.module.ResolvedModule;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;
import java.util.function.Function;
import java.util.stream.Collectors;
import jdk.internal.loader.Loader;
import jdk.internal.loader.LoaderPool;
import jdk.internal.misc.SharedSecrets;
import jdk.internal.module.ServicesCatalog;
import jdk.internal.module.ServicesCatalog.ServiceProvider;
import sun.security.util.SecurityConstants;
/**
* A layer of modules in the Java virtual machine.
*
* <p> A layer is created from a graph of modules that is the {@link
* Configuration} and a function that maps each module to a {@link ClassLoader}.
* Creating a layer informs the Java virtual machine about the classes that
* may be loaded from modules so that the Java virtual machine knows which
* module that each class is a member of. Each layer, except the {@link
* #empty() empty} layer, has a {@link #parent() parent}. </p>
*
* <p> Creating a layer creates a {@link Module} object for each {@link
* ResolvedModule} in the configuration. For each resolved module that is
* {@link ResolvedModule#reads() read}, the {@code Module} {@link
* Module#canRead reads} the corresponding run-time {@code Module}, which may
* be in the same layer or a parent layer. The {@code Module} {@link
* Module#isExported(String) exports} the packages described by its {@link
* ModuleDescriptor}. </p>
*
* <p> The {@link #defineModulesWithOneLoader defineModulesWithOneLoader} and
* {@link #defineModulesWithManyLoaders defineModulesWithManyLoaders} methods
* provide convenient ways to create a {@code Layer} where all modules are
* mapped to a single class loader or where each module is mapped to its own
* class loader. The {@link #defineModules defineModules} method is for more
* advanced cases where modules are mapped to custom class loaders by means of
* a function specified to the method. </p>
*
* <p> A Java virtual machine has at least one non-empty layer, the {@link
* #boot() boot} layer, that is created when the Java virtual machine is
* started. The <em>system modules</em>, including {@code java.base}, are in
* the boot layer. The modules in the boot layer are mapped to the bootstrap
* class loader and other class loaders that are built-in into the Java virtual
* machine. The boot layer will often be the {@link #parent() parent} when
* creating additional layers. </p>
*
* <p> As when creating a {@code Configuration},
* {@link ModuleDescriptor#isAutomatic() automatic} modules receive
* <a href="../module/Configuration.html#automaticmoduleresolution">special
* treatment</a> when creating a layer. An automatic module is created in the
* Java virtual machine as a {@code Module} that reads every unnamed {@code
* Module} in the Java virtual machine. </p>
*
* <p> Unless otherwise specified, passing a {@code null} argument to a method
* in this class causes a {@link NullPointerException NullPointerException} to
* be thrown. </p>
*
* <h3> Example usage: </h3>
*
* <p> This example creates a configuration by resolving a module named
* "{@code myapp}" with the configuration for the boot layer as the parent. It
* then creates a new layer with the modules in this configuration. All modules
* are defined to the same class loader. </p>
*
* <pre>{@code
* ModuleFinder finder = ModuleFinder.of(dir1, dir2, dir3);
*
* Layer parent = Layer.boot();
*
* Configuration cf = parent.configuration()
* .resolveRequires(finder, ModuleFinder.of(), Set.of("myapp"));
*
* ClassLoader scl = ClassLoader.getSystemClassLoader();
*
* Layer layer = parent.defineModulesWithOneLoader(cf, scl);
*
* Class<?> c = layer.findLoader("myapp").loadClass("app.Main");
* }</pre>
*
* @since 9
* @see Module#getLayer()
*/
public final class Layer {
// the empty Layer
private static final Layer EMPTY_LAYER
= new Layer(Configuration.empty(), null, null);
// the configuration from which this Layer was created
private final Configuration cf;
// parent layer, null in the case of the empty layer
private final Layer parent;
// maps module name to jlr.Module
private final Map<String, Module> nameToModule;
/**
* Creates a new Layer from the modules in the given configuration.
*/
private Layer(Configuration cf,
Layer parent,
Function<String, ClassLoader> clf)
{
this.cf = cf;
this.parent = parent;
Map<String, Module> map;
if (parent == null) {
map = Collections.emptyMap();
} else {
map = Module.defineModules(cf, clf, this);
}
this.nameToModule = map; // no need to do defensive copy
}
/**
* Creates a new layer, with this layer as its parent, by defining the
* modules in the given {@code Configuration} to the Java virtual machine.
* This method creates one class loader and defines all modules to that
* class loader.
*
* <p> The class loader created by this method implements <em>direct
* delegation</em> when loading types from modules. When its {@link
* ClassLoader#loadClass(String, boolean) loadClass} method is invoked to
* load a class then it uses the package name of the class to map it to a
* module. This may be a module in this layer and hence defined to the same
* class loader. It may be a package in a module in a parent layer that is
* exported to one or more of the modules in this layer. The class
* loader delegates to the class loader of the module, throwing {@code
* ClassNotFoundException} if not found by that class loader.
*
* When {@code loadClass} is invoked to load classes that do not map to a
* module then it delegates to the parent class loader. </p>
*
* <p> Attempting to create a layer with all modules defined to the same
* class loader can fail for the following reasons:
*
* <ul>
*
* <li><p> <em>Overlapping packages</em>: Two or more modules in the
* configuration have the same package (exported or concealed). </p></li>
*
* <li><p> <em>Split delegation</em>: The resulting class loader would
* need to delegate to more than one class loader in order to load types
* in a specific package. </p></li>
*
* </ul>
*
* <p> If there is a security manager then the class loader created by
* this method will load classes and resources with privileges that are
* restricted by the calling context of this method. </p>
*
* @param cf
* The configuration for the layer
* @param parentLoader
* The parent class loader for the class loader created by this
* method; may be {@code null} for the bootstrap class loader
*
* @return The newly created layer
*
* @throws IllegalArgumentException
* If the parent of the given configuration is not the configuration
* for this layer
* @throws LayerInstantiationException
* If all modules cannot be defined to the same class loader for any
* of the reasons listed above
* @throws SecurityException
* If {@code RuntimePermission("createClassLoader")} or
* {@code RuntimePermission("getClassLoader")} is denied by
* the security manager
*
* @see #findLoader
*/
public Layer defineModulesWithOneLoader(Configuration cf,
ClassLoader parentLoader)
{
checkConfiguration(cf);
checkCreateClassLoaderPermission();
checkGetClassLoaderPermission();
Loader loader;
try {
loader = new Loader(cf.modules(), parentLoader);
loader.initRemotePackageMap(cf, this);
} catch (IllegalArgumentException e) {
throw new LayerInstantiationException(e.getMessage());
}
return new Layer(cf, this, mn -> loader);
}
/**
* Creates a new layer, with this layer as its parent, by defining the
* modules in the given {@code Configuration} to the Java virtual machine.
* Each module is defined to its own {@link ClassLoader} created by this
* method. The {@link ClassLoader#getParent() parent} of each class loader
* is the given parent class loader.
*
* <p> The class loaders created by this method implement <em>direct
* delegation</em> when loading types from modules. When {@link
* ClassLoader#loadClass(String, boolean) loadClass} method is invoked to
* load a class then it uses the package name of the class to map it to a
* module. The package may be in the module defined to the class loader.
* The package may be exported by another module in this layer to the
* module defined to the class loader. It may be in a package exported by a
* module in a parent layer. The class loader delegates to the class loader
* of the module, throwing {@code ClassNotFoundException} if not found by
* that class loader.
*
* When {@code loadClass} is invoked to load classes that do not map to a
* module then it delegates to the parent class loader. </p>
*
* <p> If there is a security manager then the class loaders created by
* this method will load classes and resources with privileges that are
* restricted by the calling context of this method. </p>
*
* @param cf
* The configuration for the layer
* @param parentLoader
* The parent class loader for each of the class loaders created by
* this method; may be {@code null} for the bootstrap class loader
*
* @return The newly created layer
*
* @throws IllegalArgumentException
* If the parent of the given configuration is not the configuration
* for this layer
* @throws SecurityException
* If {@code RuntimePermission("createClassLoader")} or
* {@code RuntimePermission("getClassLoader")} is denied by
* the security manager
*
* @see #findLoader
*/
public Layer defineModulesWithManyLoaders(Configuration cf,
ClassLoader parentLoader)
{
checkConfiguration(cf);
checkCreateClassLoaderPermission();
checkGetClassLoaderPermission();
LoaderPool pool = new LoaderPool(cf, this, parentLoader);
return new Layer(cf, this, pool::loaderFor);
}
/**
* Creates a new layer, with this layer as its parent, by defining the
* modules in the given {@code Configuration} to the Java virtual machine.
* Each module is mapped, by name, to its class loader by means of the
* given function. The class loader delegation implemented by these class
* loaders must respect module readability. In addition, the caller needs
* to arrange that the class loaders are ready to load from these module
* before there are any attempts to load classes or resources.
*
* <p> Creating a {@code Layer} can fail for the following reasons: </p>
*
* <ul>
*
* <li><p> Two or more modules with the same package (exported or
* concealed) are mapped to the same class loader. </p></li>
*
* <li><p> A module is mapped to a class loader that already has a
* module of the same name defined to it. </p></li>
*
* <li><p> A module is mapped to a class loader that has already
* defined types in any of the packages in the module. </p></li>
*
* </ul>
*
* <p> If the function to map a module name to class loader throws an error
* or runtime exception then it is propagated to the caller of this method.
* </p>
*
* @apiNote It is implementation specific as to whether creating a Layer
* with this method is an atomic operation or not. Consequentially it is
* possible for this method to fail with some modules, but not all, defined
* to Java virtual machine.
*
* @param cf
* The configuration for the layer
* @param clf
* The function to map a module name to a class loader
*
* @return The newly created layer
*
* @throws IllegalArgumentException
* If the parent of the given configuration is not the configuration
* for this layer
* @throws LayerInstantiationException
* If creating the {@code Layer} fails for any of the reasons
* listed above
* @throws SecurityException
* If {@code RuntimePermission("getClassLoader")} is denied by
* the security manager
*/
public Layer defineModules(Configuration cf,
Function<String, ClassLoader> clf)
{
checkConfiguration(cf);
Objects.requireNonNull(clf);
checkGetClassLoaderPermission();
// For now, no two modules in the boot Layer may contain the same
// package so we use a simple check for the boot Layer to keep
// the overhead at startup to a minimum
if (boot() == null) {
checkBootModulesForDuplicatePkgs(cf);
} else {
checkForDuplicatePkgs(cf, clf);
}
try {
return new Layer(cf, this, clf);
} catch (IllegalArgumentException iae) {
// IAE is thrown by VM when defining the module fails
throw new LayerInstantiationException(iae.getMessage());
}
}
private void checkConfiguration(Configuration cf) {
Objects.requireNonNull(cf);
Optional<Configuration> oparent = cf.parent();
if (!oparent.isPresent() || oparent.get() != this.configuration()) {
throw new IllegalArgumentException(
"Parent of configuration != configuration of this Layer");
}
}
private static void checkCreateClassLoaderPermission() {
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkPermission(SecurityConstants.CREATE_CLASSLOADER_PERMISSION);
}
private static void checkGetClassLoaderPermission() {
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
}
/**
* Checks a configuration for the boot Layer to ensure that no two modules
* have the same package.
*
* @throws LayerInstantiationException
*/
private static void checkBootModulesForDuplicatePkgs(Configuration cf) {
Map<String, String> packageToModule = new HashMap<>();
for (ResolvedModule resolvedModule : cf.modules()) {
ModuleDescriptor descriptor = resolvedModule.reference().descriptor();
String name = descriptor.name();
for (String p : descriptor.packages()) {
String other = packageToModule.putIfAbsent(p, name);
if (other != null) {
throw fail("Package " + p + " in both module "
+ name + " and module " + other);
}
}
}
}
/**
* Checks a configuration and the module-to-loader mapping to ensure that
* no two modules mapped to the same class loader have the same package.
* It also checks that no two automatic modules have the same package.
*
* @throws LayerInstantiationException
*/
private static void checkForDuplicatePkgs(Configuration cf,
Function<String, ClassLoader> clf)
{
// HashMap allows null keys
Map<ClassLoader, Set<String>> loaderToPackages = new HashMap<>();
for (ResolvedModule resolvedModule : cf.modules()) {
ModuleDescriptor descriptor = resolvedModule.reference().descriptor();
ClassLoader loader = clf.apply(descriptor.name());
Set<String> loaderPackages
= loaderToPackages.computeIfAbsent(loader, k -> new HashSet<>());
for (String pkg : descriptor.packages()) {
boolean added = loaderPackages.add(pkg);
if (!added) {
throw fail("More than one module with package %s mapped" +
" to the same class loader", pkg);
}
}
}
}
/**
* Creates a LayerInstantiationException with the a message formatted from
* the given format string and arguments.
*/
private static LayerInstantiationException fail(String fmt, Object ... args) {
String msg = String.format(fmt, args);
return new LayerInstantiationException(msg);
}
/**
* Returns the configuration for this layer.
*
* @return The configuration for this layer
*/
public Configuration configuration() {
return cf;
}
/**
* Returns this layer's parent unless this is the {@linkplain #empty empty
* layer}, which has no parent.
*
* @return This layer's parent
*/
public Optional<Layer> parent() {
return Optional.ofNullable(parent);
}
/**
* Returns a set of the modules in this layer.
*
* @return A possibly-empty unmodifiable set of the modules in this layer
*/
public Set<Module> modules() {
return Collections.unmodifiableSet(
nameToModule.values().stream().collect(Collectors.toSet()));
}
/**
* Returns the module with the given name in this layer, or if not in this
* layer, the {@linkplain #parent parent} layer.
*
* @param name
* The name of the module to find
*
* @return The module with the given name or an empty {@code Optional}
* if there isn't a module with this name in this layer or any
* parent layer
*/
public Optional<Module> findModule(String name) {
Module m = nameToModule.get(Objects.requireNonNull(name));
if (m != null)
return Optional.of(m);
return parent().flatMap(l -> l.findModule(name));
}
/**
* Returns the {@code ClassLoader} for the module with the given name. If
* a module of the given name is not in this layer then the {@link #parent}
* layer is checked.
*
* <p> If there is a security manager then its {@code checkPermission}
* method is called with a {@code RuntimePermission("getClassLoader")}
* permission to check that the caller is allowed to get access to the
* class loader. </p>
*
* @apiNote This method does not return an {@code Optional<ClassLoader>}
* because `null` must be used to represent the bootstrap class loader.
*
* @param name
* The name of the module to find
*
* @return The ClassLoader that the module is defined to
*
* @throws IllegalArgumentException if a module of the given name is not
* defined in this layer or any parent of this layer
*
* @throws SecurityException if denied by the security manager
*/
public ClassLoader findLoader(String name) {
Module m = nameToModule.get(Objects.requireNonNull(name));
if (m != null)
return m.getClassLoader();
Optional<Layer> ol = parent();
if (ol.isPresent())
return ol.get().findLoader(name);
throw new IllegalArgumentException("Module " + name
+ " not known to this layer");
}
/**
* Returns the <em>empty</em> layer. There are no modules in the empty
* layer. It has no parent.
*
* @return The empty layer
*/
public static Layer empty() {
return EMPTY_LAYER;
}
/**
* Returns the boot layer. The boot layer contains at least one module,
* {@code java.base}. Its parent is the {@link #empty() empty} layer.
*
* @apiNote This method returns {@code null} during startup and before
* the boot layer is fully initialized.
*
* @return The boot layer
*/
public static Layer boot() {
return SharedSecrets.getJavaLangAccess().getBootLayer();
}
/**
* Returns the ServicesCatalog for this Layer, creating it if not
* already created.
*/
ServicesCatalog getServicesCatalog() {
ServicesCatalog servicesCatalog = this.servicesCatalog;
if (servicesCatalog != null)
return servicesCatalog;
Map<String, Set<ServiceProvider>> map = new HashMap<>();
for (Module m : nameToModule.values()) {
ModuleDescriptor descriptor = m.getDescriptor();
for (Provides provides : descriptor.provides().values()) {
String service = provides.service();
Set<ServiceProvider> providers
= map.computeIfAbsent(service, k -> new HashSet<>());
for (String pn : provides.providers()) {
providers.add(new ServiceProvider(m, pn));
}
}
}
ServicesCatalog catalog = new ServicesCatalog() {
@Override
public void register(Module module) {
throw new UnsupportedOperationException();
}
@Override
public Set<ServiceProvider> findServices(String service) {
Set<ServiceProvider> providers = map.get(service);
if (providers == null) {
return Collections.emptySet();
} else {
return Collections.unmodifiableSet(providers);
}
}
};
synchronized (this) {
servicesCatalog = this.servicesCatalog;
if (servicesCatalog == null) {
this.servicesCatalog = servicesCatalog = catalog;
}
}
return servicesCatalog;
}
private volatile ServicesCatalog servicesCatalog;
}