https://openjdk.java.net/ 
/*
 * Copyright (c) 2014, 2021, 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).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.lang;

import java.io.IOException;
import java.io.InputStream;
import java.lang.annotation.Annotation;
import java.lang.module.Configuration;
import java.lang.module.ModuleReference;
import java.lang.module.ModuleDescriptor;
import java.lang.module.ModuleDescriptor.Exports;
import java.lang.module.ModuleDescriptor.Opens;
import java.lang.module.ModuleDescriptor.Version;
import java.lang.module.ResolvedModule;
import java.lang.reflect.AnnotatedElement;
import java.net.URI;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import jdk.internal.loader.BuiltinClassLoader;
import jdk.internal.loader.BootLoader;
import jdk.internal.loader.ClassLoaders;
import jdk.internal.misc.CDS;
import jdk.internal.module.ModuleLoaderMap;
import jdk.internal.module.ServicesCatalog;
import jdk.internal.module.Resources;
import jdk.internal.org.objectweb.asm.AnnotationVisitor;
import jdk.internal.org.objectweb.asm.Attribute;
import jdk.internal.org.objectweb.asm.ClassReader;
import jdk.internal.org.objectweb.asm.ClassVisitor;
import jdk.internal.org.objectweb.asm.ClassWriter;
import jdk.internal.org.objectweb.asm.ModuleVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;
import jdk.internal.reflect.CallerSensitive;
import jdk.internal.reflect.Reflection;
import jdk.internal.vm.annotation.Stable;
import sun.security.util.SecurityConstants;


Represents a run-time module, either named or unnamed. 
 Named modules have a name and are constructed by the Java Virtual Machine when a graph of modules is defined to the Java virtual machine to create a module layer. 


 An unnamed module does not have a name. There is an unnamed module for each ClassLoader, obtained by invoking its getUnnamedModule method. All types that are not in a named module are members of their defining class loader's unnamed module. 


 The package names that are parameters or returned by methods defined in
this class are the fully-qualified names of the packages as defined in
section {@jls 6.5.3} of The Java Language Specification, for example, "java.lang". 


 Unless otherwise specified, passing a null argument to a method in this class causes a NullPointerException to be thrown. 


See Also:
Since:9
@jls7.7 Module Declarations
/**
 * Represents a run-time module, either {@link #isNamed() named} or unnamed.
 *
 * <p> Named modules have a {@link #getName() name} and are constructed by the
 * Java Virtual Machine when a graph of modules is defined to the Java virtual
 * machine to create a {@linkplain ModuleLayer module layer}. </p>
 *
 * <p> An unnamed module does not have a name. There is an unnamed module for
 * each {@link ClassLoader ClassLoader}, obtained by invoking its {@link
 * ClassLoader#getUnnamedModule() getUnnamedModule} method. All types that are
 * not in a named module are members of their defining class loader's unnamed
 * module. </p>
 *
 * <p> The package names that are parameters or returned by methods defined in
 * this class are the fully-qualified names of the packages as defined in
 * section {@jls 6.5.3} of <cite>The Java Language Specification</cite>, for
 * example, {@code "java.lang"}. </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>
 *
 * @since 9
 * @see Class#getModule()
 * @jls 7.7 Module Declarations
 */

public final class Module implements AnnotatedElement {

    // the layer that contains this module, can be null
    private final ModuleLayer layer;

    // module name and loader, these fields are read by VM
    private final String name;
    private final ClassLoader loader;

    // the module descriptor
    private final ModuleDescriptor descriptor;

    // true, if this module allows restricted native access
    @Stable
    private boolean enableNativeAccess;

    
Creates a new named Module. The resulting Module will be defined to the
VM but will not read any other modules, will not have any exports setup
and will not be registered in the service catalog.

/**
     * Creates a new named Module. The resulting Module will be defined to the
     * VM but will not read any other modules, will not have any exports setup
     * and will not be registered in the service catalog.
     */
    Module(ModuleLayer layer,
           ClassLoader loader,
           ModuleDescriptor descriptor,
           URI uri)
    {
        this.layer = layer;
        this.name = descriptor.name();
        this.loader = loader;
        this.descriptor = descriptor;

        // define module to VM

        boolean isOpen = descriptor.isOpen() || descriptor.isAutomatic();
        Version version = descriptor.version().orElse(null);
        String vs = Objects.toString(version, null);
        String loc = Objects.toString(uri, null);
        Object[] packages = descriptor.packages().toArray();
        defineModule0(this, isOpen, vs, loc, packages);
        if (loader == null || loader == ClassLoaders.platformClassLoader()) {
            // boot/builtin modules are always native
            implAddEnableNativeAccess();
        }
    }


    
Create the unnamed Module for the given ClassLoader.

See Also:
  • getUnnamedModule.getUnnamedModule
/**
     * Create the unnamed Module for the given ClassLoader.
     *
     * @see ClassLoader#getUnnamedModule
     */
    Module(ClassLoader loader) {
        this.layer = null;
        this.name = null;
        this.loader = loader;
        this.descriptor = null;
    }


    
Creates a named module but without defining the module to the VM.

API Note:This constructor is for VM white-box testing.
/**
     * Creates a named module but without defining the module to the VM.
     *
     * @apiNote This constructor is for VM white-box testing.
     */
    Module(ClassLoader loader, ModuleDescriptor descriptor) {
        this.layer = null;
        this.name = descriptor.name();
        this.loader = loader;
        this.descriptor = descriptor;
    }


    
Returns true if this module is a named module. 
See Also:
Returns:true if this is a named module
@jls7.7.5 Unnamed Modules
/**
     * Returns {@code true} if this module is a named module.
     *
     * @return {@code true} if this is a named module
     *
     * @see ClassLoader#getUnnamedModule()
     * @jls 7.7.5 Unnamed Modules
     */
    public boolean isNamed() {
        return name != null;
    }

    
Returns the module name or null if this module is an unnamed module. 
Returns:The module name
/**
     * Returns the module name or {@code null} if this module is an unnamed
     * module.
     *
     * @return The module name
     */
    public String getName() {
        return name;
    }

    
Returns the ClassLoader for this module. 
 If there is a security manager then its checkPermission method if first called with a RuntimePermission("getClassLoader") permission to check that the caller is allowed to get access to the class loader. 


Throws:
Returns:The class loader for this module
/**
     * Returns the {@code ClassLoader} for this module.
     *
     * <p> If there is a security manager then its {@code checkPermission}
     * method if first called with a {@code RuntimePermission("getClassLoader")}
     * permission to check that the caller is allowed to get access to the
     * class loader. </p>
     *
     * @return The class loader for this module
     *
     * @throws SecurityException
     *         If denied by the security manager
     */
    public ClassLoader getClassLoader() {
        @SuppressWarnings("removal")
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
        }
        return loader;
    }

    
Returns the module descriptor for this module or null if this module is an unnamed module. 
Returns:The module descriptor for this module
/**
     * Returns the module descriptor for this module or {@code null} if this
     * module is an unnamed module.
     *
     * @return The module descriptor for this module
     */
    public ModuleDescriptor getDescriptor() {
        return descriptor;
    }

    
Returns the module layer that contains this module or null if this module is not in a module layer. A module layer contains named modules and therefore this method always returns null when invoked on an unnamed module. 
 Dynamic modules are
named modules that are generated at runtime. A dynamic module may or may
not be in a module layer. 


See Also:
Returns:The module layer that contains this module
/**
     * Returns the module layer that contains this module or {@code null} if
     * this module is not in a module layer.
     *
     * A module layer contains named modules and therefore this method always
     * returns {@code null} when invoked on an unnamed module.
     *
     * <p> <a href="reflect/Proxy.html#dynamicmodule">Dynamic modules</a> are
     * named modules that are generated at runtime. A dynamic module may or may
     * not be in a module layer. </p>
     *
     * @return The module layer that contains this module
     *
     * @see java.lang.reflect.Proxy
     */
    public ModuleLayer getLayer() {
        if (isNamed()) {
            ModuleLayer layer = this.layer;
            if (layer != null)
                return layer;

            // special-case java.base as it is created before the boot layer
            if (loader == null && name.equals("java.base")) {
                return ModuleLayer.boot();
            }
        }
        return null;
    }

    
Update this module to allow access to restricted methods.

/**
     * Update this module to allow access to restricted methods.
     */
    Module implAddEnableNativeAccess() {
        enableNativeAccess = true;
        return this;
    }

    
Update all unnamed modules to allow access to restricted methods.

/**
     * Update all unnamed modules to allow access to restricted methods.
     */
    static void implAddEnableNativeAccessAllUnnamed() {
        ALL_UNNAMED_MODULE.enableNativeAccess = true;
    }

    
Returns true if module m can access restricted methods.

/**
     * Returns true if module m can access restricted methods.
     */
    boolean implIsEnableNativeAccess() {
        return isNamed() ?
                enableNativeAccess :
                ALL_UNNAMED_MODULE.enableNativeAccess;
    }

    // --

    // special Module to mean "all unnamed modules"
    private static final Module ALL_UNNAMED_MODULE;
    private static final Set<Module> ALL_UNNAMED_MODULE_SET;

    // special Module to mean "everyone"
    private static final Module EVERYONE_MODULE;
    private static final Set<Module> EVERYONE_SET;

    private static class ArchivedData {
        private static ArchivedData archivedData;
        private final Module allUnnamedModule;
        private final Set<Module> allUnnamedModules;
        private final Module everyoneModule;
        private final Set<Module> everyoneSet;

        private ArchivedData() {
            this.allUnnamedModule = ALL_UNNAMED_MODULE;
            this.allUnnamedModules = ALL_UNNAMED_MODULE_SET;
            this.everyoneModule = EVERYONE_MODULE;
            this.everyoneSet = EVERYONE_SET;
        }

        static void archive() {
            archivedData = new ArchivedData();
        }

        static ArchivedData get() {
            return archivedData;
        }

        static {
            CDS.initializeFromArchive(ArchivedData.class);
        }
    }

    static {
        ArchivedData archivedData = ArchivedData.get();
        if (archivedData != null) {
            ALL_UNNAMED_MODULE = archivedData.allUnnamedModule;
            ALL_UNNAMED_MODULE_SET = archivedData.allUnnamedModules;
            EVERYONE_MODULE = archivedData.everyoneModule;
            EVERYONE_SET = archivedData.everyoneSet;
        } else {
            ALL_UNNAMED_MODULE = new Module(null);
            ALL_UNNAMED_MODULE_SET = Set.of(ALL_UNNAMED_MODULE);
            EVERYONE_MODULE = new Module(null);
            EVERYONE_SET = Set.of(EVERYONE_MODULE);
            ArchivedData.archive();
        }
    }

    
The holder of data structures to support readability, exports, and
service use added at runtime with the reflective APIs.

/**
     * The holder of data structures to support readability, exports, and
     * service use added at runtime with the reflective APIs.
     */
    private static class ReflectionData {
        
A module (1st key) reads another module (2nd key)

/**
         * A module (1st key) reads another module (2nd key)
         */
        static final WeakPairMap<Module, Module, Boolean> reads =
            new WeakPairMap<>();

        
A module (1st key) exports or opens a package to another module
(2nd key). The map value is a map of package name to a boolean
that indicates if the package is opened.

/**
         * A module (1st key) exports or opens a package to another module
         * (2nd key). The map value is a map of package name to a boolean
         * that indicates if the package is opened.
         */
        static final WeakPairMap<Module, Module, Map<String, Boolean>> exports =
            new WeakPairMap<>();

        
A module (1st key) uses a service (2nd key)

/**
         * A module (1st key) uses a service (2nd key)
         */
        static final WeakPairMap<Module, Class<?>, Boolean> uses =
            new WeakPairMap<>();
    }


    // -- readability --

    // the modules that this module reads
    private volatile Set<Module> reads;

    
Indicates if this module reads the given module. This method returns true if invoked to test if this module reads itself. It also returns true if invoked on an unnamed module (as unnamed modules read all modules). 
Params:
  • other – 
        The other module
See Also:
Returns:true if this module reads other
/**
     * Indicates if this module reads the given module. This method returns
     * {@code true} if invoked to test if this module reads itself. It also
     * returns {@code true} if invoked on an unnamed module (as unnamed
     * modules read all modules).
     *
     * @param  other
     *         The other module
     *
     * @return {@code true} if this module reads {@code other}
     *
     * @see #addReads(Module)
     */
    public boolean canRead(Module other) {
        Objects.requireNonNull(other);

        // an unnamed module reads all modules
        if (!this.isNamed())
            return true;

        // all modules read themselves
        if (other == this)
            return true;

        // check if this module reads other
        if (other.isNamed()) {
            Set<Module> reads = this.reads; // volatile read
            if (reads != null && reads.contains(other))
                return true;
        }

        // check if this module reads the other module reflectively
        if (ReflectionData.reads.containsKeyPair(this, other))
            return true;

        // if other is an unnamed module then check if this module reads
        // all unnamed modules
        if (!other.isNamed()
            && ReflectionData.reads.containsKeyPair(this, ALL_UNNAMED_MODULE))
            return true;

        return false;
    }

    
If the caller's module is this module then update this module to read the given module. This method is a no-op if other is this module (all modules read themselves), this module is an unnamed module (as unnamed modules read all modules), or this module already reads other. 
Params:
  • other – 
        The other module
Throws:
See Also:
Implementation Note:Read edges added by this method are weak and do not prevent other from being GC'ed when this module is strongly reachable.
Returns:this module
/**
     * If the caller's module is this module then update this module to read
     * the given module.
     *
     * This method is a no-op if {@code other} is this module (all modules read
     * themselves), this module is an unnamed module (as unnamed modules read
     * all modules), or this module already reads {@code other}.
     *
     * @implNote <em>Read edges</em> added by this method are <em>weak</em> and
     * do not prevent {@code other} from being GC'ed when this module is
     * strongly reachable.
     *
     * @param  other
     *         The other module
     *
     * @return this module
     *
     * @throws IllegalCallerException
     *         If this is a named module and the caller's module is not this
     *         module
     *
     * @see #canRead
     */
    @CallerSensitive
    public Module addReads(Module other) {
        Objects.requireNonNull(other);
        if (this.isNamed()) {
            Module caller = getCallerModule(Reflection.getCallerClass());
            if (caller != this) {
                throw new IllegalCallerException(caller + " != " + this);
            }
            implAddReads(other, true);
        }
        return this;
    }

    
Updates this module to read another module.

API Note:Used by the --add-reads command line option.
/**
     * Updates this module to read another module.
     *
     * @apiNote Used by the --add-reads command line option.
     */
    void implAddReads(Module other) {
        implAddReads(other, true);
    }

    
Updates this module to read all unnamed modules.

API Note:Used by the --add-reads command line option.
/**
     * Updates this module to read all unnamed modules.
     *
     * @apiNote Used by the --add-reads command line option.
     */
    void implAddReadsAllUnnamed() {
        implAddReads(Module.ALL_UNNAMED_MODULE, true);
    }

    
Updates this module to read another module without notifying the VM.

API Note:This method is for VM white-box testing.
/**
     * Updates this module to read another module without notifying the VM.
     *
     * @apiNote This method is for VM white-box testing.
     */
    void implAddReadsNoSync(Module other) {
        implAddReads(other, false);
    }

    
Makes the given Module readable to this module. If syncVM is true then the VM is notified. 
/**
     * Makes the given {@code Module} readable to this module.
     *
     * If {@code syncVM} is {@code true} then the VM is notified.
     */
    private void implAddReads(Module other, boolean syncVM) {
        Objects.requireNonNull(other);
        if (!canRead(other)) {
            // update VM first, just in case it fails
            if (syncVM) {
                if (other == ALL_UNNAMED_MODULE) {
                    addReads0(this, null);
                } else {
                    addReads0(this, other);
                }
            }

            // add reflective read
            ReflectionData.reads.putIfAbsent(this, other, Boolean.TRUE);
        }
    }


    // -- exported and open packages --

    // the packages are open to other modules, can be null
    // if the value contains EVERYONE_MODULE then the package is open to all
    private volatile Map<String, Set<Module>> openPackages;

    // the packages that are exported, can be null
    // if the value contains EVERYONE_MODULE then the package is exported to all
    private volatile Map<String, Set<Module>> exportedPackages;

    
Returns true if this module exports the given package to at least the given module. 
 This method returns true if invoked to test if a package in this module is exported to itself. It always returns true when invoked on an unnamed module. A package that is open to the given module is considered exported to that module at run-time and so this method returns true if the package is open to the given module. 


 This method does not check if the given module reads this module. 


Params:
  • pn – 
        The package name
  • other – 
        The other module
See Also:
Returns:true if this module exports the package to at least the given module
/**
     * Returns {@code true} if this module exports the given package to at
     * least the given module.
     *
     * <p> This method returns {@code true} if invoked to test if a package in
     * this module is exported to itself. It always returns {@code true} when
     * invoked on an unnamed module. A package that is {@link #isOpen open} to
     * the given module is considered exported to that module at run-time and
     * so this method returns {@code true} if the package is open to the given
     * module. </p>
     *
     * <p> This method does not check if the given module reads this module. </p>
     *
     * @param  pn
     *         The package name
     * @param  other
     *         The other module
     *
     * @return {@code true} if this module exports the package to at least the
     *         given module
     *
     * @see ModuleDescriptor#exports()
     * @see #addExports(String,Module)
     */
    public boolean isExported(String pn, Module other) {
        Objects.requireNonNull(pn);
        Objects.requireNonNull(other);
        return implIsExportedOrOpen(pn, other, /*open*/false);
    }

    
Returns true if this module has opened a package to at
least the given module.

 This method returns true if invoked to test if a package in this module is open to itself. It returns true when invoked on an open module with a package in the module. It always returns true when invoked on an unnamed module. 


 This method does not check if the given module reads this module. 


Params:
  • pn – 
        The package name
  • other – 
        The other module
See Also:
Returns:true if this module has opened the package
        to at least the given module
/**
     * Returns {@code true} if this module has <em>opened</em> a package to at
     * least the given module.
     *
     * <p> This method returns {@code true} if invoked to test if a package in
     * this module is open to itself. It returns {@code true} when invoked on an
     * {@link ModuleDescriptor#isOpen open} module with a package in the module.
     * It always returns {@code true} when invoked on an unnamed module. </p>
     *
     * <p> This method does not check if the given module reads this module. </p>
     *
     * @param  pn
     *         The package name
     * @param  other
     *         The other module
     *
     * @return {@code true} if this module has <em>opened</em> the package
     *         to at least the given module
     *
     * @see ModuleDescriptor#opens()
     * @see #addOpens(String,Module)
     * @see java.lang.reflect.AccessibleObject#setAccessible(boolean)
     * @see java.lang.invoke.MethodHandles#privateLookupIn
     */
    public boolean isOpen(String pn, Module other) {
        Objects.requireNonNull(pn);
        Objects.requireNonNull(other);
        return implIsExportedOrOpen(pn, other, /*open*/true);
    }

    
Returns true if this module exports the given package unconditionally. 
 This method always returns true when invoked on an unnamed module. A package that is opened unconditionally is considered exported unconditionally at run-time and so this method returns true if the package is opened unconditionally. 


 This method does not check if the given module reads this module. 


Params:
  • pn – 
        The package name
See Also:
Returns:true if this module exports the package unconditionally
/**
     * Returns {@code true} if this module exports the given package
     * unconditionally.
     *
     * <p> This method always returns {@code true} when invoked on an unnamed
     * module. A package that is {@link #isOpen(String) opened} unconditionally
     * is considered exported unconditionally at run-time and so this method
     * returns {@code true} if the package is opened unconditionally. </p>
     *
     * <p> This method does not check if the given module reads this module. </p>
     *
     * @param  pn
     *         The package name
     *
     * @return {@code true} if this module exports the package unconditionally
     *
     * @see ModuleDescriptor#exports()
     */
    public boolean isExported(String pn) {
        Objects.requireNonNull(pn);
        return implIsExportedOrOpen(pn, EVERYONE_MODULE, /*open*/false);
    }

    
Returns true if this module has opened a package
unconditionally.

 This method always returns true when invoked on an unnamed module. Additionally, it always returns true when invoked on an open module with a package in the module. 


 This method does not check if the given module reads this module. 


Params:
  • pn – 
        The package name
See Also:
Returns:true if this module has opened the package
        unconditionally
/**
     * Returns {@code true} if this module has <em>opened</em> a package
     * unconditionally.
     *
     * <p> This method always returns {@code true} when invoked on an unnamed
     * module. Additionally, it always returns {@code true} when invoked on an
     * {@link ModuleDescriptor#isOpen open} module with a package in the
     * module. </p>
     *
     * <p> This method does not check if the given module reads this module. </p>
     *
     * @param  pn
     *         The package name
     *
     * @return {@code true} if this module has <em>opened</em> the package
     *         unconditionally
     *
     * @see ModuleDescriptor#opens()
     */
    public boolean isOpen(String pn) {
        Objects.requireNonNull(pn);
        return implIsExportedOrOpen(pn, EVERYONE_MODULE, /*open*/true);
    }


    
Returns true if this module exports or opens the given package to the given module. If the other module is EVERYONE_MODULE then this method tests if the package is exported or opened unconditionally. 
/**
     * Returns {@code true} if this module exports or opens the given package
     * to the given module. If the other module is {@code EVERYONE_MODULE} then
     * this method tests if the package is exported or opened unconditionally.
     */
    private boolean implIsExportedOrOpen(String pn, Module other, boolean open) {
        // all packages in unnamed modules are open
        if (!isNamed())
            return true;

        // all packages are exported/open to self
        if (other == this && descriptor.packages().contains(pn))
            return true;

        // all packages in open and automatic modules are open
        if (descriptor.isOpen() || descriptor.isAutomatic())
            return descriptor.packages().contains(pn);

        // exported/opened via module declaration/descriptor
        if (isStaticallyExportedOrOpen(pn, other, open))
            return true;

        // exported via addExports/addOpens
        if (isReflectivelyExportedOrOpen(pn, other, open))
            return true;

        // not exported or open to other
        return false;
    }

    
Returns true if this module exports or opens a package to the given module via its module declaration or CLI options. 
/**
     * Returns {@code true} if this module exports or opens a package to
     * the given module via its module declaration or CLI options.
     */
    private boolean isStaticallyExportedOrOpen(String pn, Module other, boolean open) {
        // test if package is open to everyone or <other>
        Map<String, Set<Module>> openPackages = this.openPackages;
        if (openPackages != null && allows(openPackages.get(pn), other)) {
            return true;
        }

        if (!open) {
            // test package is exported to everyone or <other>
            Map<String, Set<Module>> exportedPackages = this.exportedPackages;
            if (exportedPackages != null && allows(exportedPackages.get(pn), other)) {
                return true;
            }
        }

        return false;
    }

    
Returns true if targets is non-null and contains EVERYONE_MODULE or the given module. Also returns true if the given module is an unnamed module and targets contains ALL_UNNAMED_MODULE. 
/**
     * Returns {@code true} if targets is non-null and contains EVERYONE_MODULE
     * or the given module. Also returns true if the given module is an unnamed
     * module and targets contains ALL_UNNAMED_MODULE.
     */
    private boolean allows(Set<Module> targets, Module module) {
       if (targets != null) {
           if (targets.contains(EVERYONE_MODULE))
               return true;
           if (module != EVERYONE_MODULE) {
               if (targets.contains(module))
                   return true;
               if (!module.isNamed() && targets.contains(ALL_UNNAMED_MODULE))
                   return true;
           }
        }
        return false;
    }

    
Returns true if this module reflectively exports or opens the given package to the given module. 
/**
     * Returns {@code true} if this module reflectively exports or opens the
     * given package to the given module.
     */
    private boolean isReflectivelyExportedOrOpen(String pn, Module other, boolean open) {
        // exported or open to all modules
        Map<String, Boolean> exports = ReflectionData.exports.get(this, EVERYONE_MODULE);
        if (exports != null) {
            Boolean b = exports.get(pn);
            if (b != null) {
                boolean isOpen = b.booleanValue();
                if (!open || isOpen) return true;
            }
        }

        if (other != EVERYONE_MODULE) {

            // exported or open to other
            exports = ReflectionData.exports.get(this, other);
            if (exports != null) {
                Boolean b = exports.get(pn);
                if (b != null) {
                    boolean isOpen = b.booleanValue();
                    if (!open || isOpen) return true;
                }
            }

            // other is an unnamed module && exported or open to all unnamed
            if (!other.isNamed()) {
                exports = ReflectionData.exports.get(this, ALL_UNNAMED_MODULE);
                if (exports != null) {
                    Boolean b = exports.get(pn);
                    if (b != null) {
                        boolean isOpen = b.booleanValue();
                        if (!open || isOpen) return true;
                    }
                }
            }

        }

        return false;
    }

    
Returns true if this module reflectively exports the given package to the given module. 
/**
     * Returns {@code true} if this module reflectively exports the
     * given package to the given module.
     */
    boolean isReflectivelyExported(String pn, Module other) {
        return isReflectivelyExportedOrOpen(pn, other, false);
    }

    
Returns true if this module reflectively opens the given package to the given module. 
/**
     * Returns {@code true} if this module reflectively opens the
     * given package to the given module.
     */
    boolean isReflectivelyOpened(String pn, Module other) {
        return isReflectivelyExportedOrOpen(pn, other, true);
    }


    
If the caller's module is this module then update this module to export
the given package to the given module.

 This method has no effect if the package is already exported (or
open) to the given module. 


Params:
  • pn – 
        The package name
  • other – 
        The module
Throws:
See Also:
API Note:As specified in section {@jvms 5.4.3} of the The Java
Virtual Machine Specification , if an attempt to resolve a
symbolic reference fails because of a linkage error, then subsequent
attempts to resolve the reference always fail with the same error that
was thrown as a result of the initial resolution attempt.
Returns:this module
@jvms5.4.3 Resolution
/**
     * If the caller's module is this module then update this module to export
     * the given package to the given module.
     *
     * <p> This method has no effect if the package is already exported (or
     * <em>open</em>) to the given module. </p>
     *
     * @apiNote As specified in section {@jvms 5.4.3} of the <cite>The Java
     * Virtual Machine Specification </cite>, if an attempt to resolve a
     * symbolic reference fails because of a linkage error, then subsequent
     * attempts to resolve the reference always fail with the same error that
     * was thrown as a result of the initial resolution attempt.
     *
     * @param  pn
     *         The package name
     * @param  other
     *         The module
     *
     * @return this module
     *
     * @throws IllegalArgumentException
     *         If {@code pn} is {@code null}, or this is a named module and the
     *         package {@code pn} is not a package in this module
     * @throws IllegalCallerException
     *         If this is a named module and the caller's module is not this
     *         module
     *
     * @jvms 5.4.3 Resolution
     * @see #isExported(String,Module)
     */
    @CallerSensitive
    public Module addExports(String pn, Module other) {
        if (pn == null)
            throw new IllegalArgumentException("package is null");
        Objects.requireNonNull(other);

        if (isNamed()) {
            Module caller = getCallerModule(Reflection.getCallerClass());
            if (caller != this) {
                throw new IllegalCallerException(caller + " != " + this);
            }
            implAddExportsOrOpens(pn, other, /*open*/false, /*syncVM*/true);
        }

        return this;
    }

    
If this module has opened a package to at least the caller
module then update this module to open the package to the given module.
Opening a package with this method allows all types in the package,
and all their members, not just public types and their public members,
to be reflected on by the given module when using APIs that support
private access or a way to bypass or suppress default Java language
access control checks.

 This method has no effect if the package is already open
to the given module. 


Params:
  • pn – 
        The package name
  • other – 
        The module
Throws:
  • IllegalArgumentException –  If pn is null, or this is a named module and the package pn is not a package in this module
  • IllegalCallerException – 
        If this is a named module and this module has not opened the
        package to at least the caller's module
See Also:
API Note:This method can be used for cases where a consumer
module uses a qualified opens to open a package to an API
module but where the reflective access to the members of classes in
the consumer module is delegated to code in another module. Code in the
API module can use this method to open the package in the consumer module
to the other module.
Returns:this module
/**
     * If this module has <em>opened</em> a package to at least the caller
     * module then update this module to open the package to the given module.
     * Opening a package with this method allows all types in the package,
     * and all their members, not just public types and their public members,
     * to be reflected on by the given module when using APIs that support
     * private access or a way to bypass or suppress default Java language
     * access control checks.
     *
     * <p> This method has no effect if the package is already <em>open</em>
     * to the given module. </p>
     *
     * @apiNote This method can be used for cases where a <em>consumer
     * module</em> uses a qualified opens to open a package to an <em>API
     * module</em> but where the reflective access to the members of classes in
     * the consumer module is delegated to code in another module. Code in the
     * API module can use this method to open the package in the consumer module
     * to the other module.
     *
     * @param  pn
     *         The package name
     * @param  other
     *         The module
     *
     * @return this module
     *
     * @throws IllegalArgumentException
     *         If {@code pn} is {@code null}, or this is a named module and the
     *         package {@code pn} is not a package in this module
     * @throws IllegalCallerException
     *         If this is a named module and this module has not opened the
     *         package to at least the caller's module
     *
     * @see #isOpen(String,Module)
     * @see java.lang.reflect.AccessibleObject#setAccessible(boolean)
     * @see java.lang.invoke.MethodHandles#privateLookupIn
     */
    @CallerSensitive
    public Module addOpens(String pn, Module other) {
        if (pn == null)
            throw new IllegalArgumentException("package is null");
        Objects.requireNonNull(other);

        if (isNamed()) {
            Module caller = getCallerModule(Reflection.getCallerClass());
            if (caller != this && (caller == null || !isOpen(pn, caller)))
                throw new IllegalCallerException(pn + " is not open to " + caller);
            implAddExportsOrOpens(pn, other, /*open*/true, /*syncVM*/true);
        }

        return this;
    }


    
Updates this module to export a package unconditionally.

API Note:This method is for JDK tests only.
/**
     * Updates this module to export a package unconditionally.
     *
     * @apiNote This method is for JDK tests only.
     */
    void implAddExports(String pn) {
        implAddExportsOrOpens(pn, Module.EVERYONE_MODULE, false, true);
    }

    
Updates this module to export a package to another module.

API Note:Used by Instrumentation::redefineModule and --add-exports
/**
     * Updates this module to export a package to another module.
     *
     * @apiNote Used by Instrumentation::redefineModule and --add-exports
     */
    void implAddExports(String pn, Module other) {
        implAddExportsOrOpens(pn, other, false, true);
    }

    
Updates this module to export a package to all unnamed modules.

API Note:Used by the --add-exports command line option.
/**
     * Updates this module to export a package to all unnamed modules.
     *
     * @apiNote Used by the --add-exports command line option.
     */
    void implAddExportsToAllUnnamed(String pn) {
        implAddExportsOrOpens(pn, Module.ALL_UNNAMED_MODULE, false, true);
    }

    
Updates this export to export a package unconditionally without
notifying the VM.

API Note:This method is for VM white-box testing.
/**
     * Updates this export to export a package unconditionally without
     * notifying the VM.
     *
     * @apiNote This method is for VM white-box testing.
     */
    void implAddExportsNoSync(String pn) {
        implAddExportsOrOpens(pn.replace('/', '.'), Module.EVERYONE_MODULE, false, false);
    }

    
Updates a module to export a package to another module without
notifying the VM.

API Note:This method is for VM white-box testing.
/**
     * Updates a module to export a package to another module without
     * notifying the VM.
     *
     * @apiNote This method is for VM white-box testing.
     */
    void implAddExportsNoSync(String pn, Module other) {
        implAddExportsOrOpens(pn.replace('/', '.'), other, false, false);
    }

    
Updates this module to open a package unconditionally.

API Note:This method is for JDK tests only.
/**
     * Updates this module to open a package unconditionally.
     *
     * @apiNote This method is for JDK tests only.
     */
    void implAddOpens(String pn) {
        implAddExportsOrOpens(pn, Module.EVERYONE_MODULE, true, true);
    }

    
Updates this module to open a package to another module.

API Note:Used by Instrumentation::redefineModule and --add-opens
/**
     * Updates this module to open a package to another module.
     *
     * @apiNote Used by Instrumentation::redefineModule and --add-opens
     */
    void implAddOpens(String pn, Module other) {
        implAddExportsOrOpens(pn, other, true, true);
    }

    
Updates this module to open a package to all unnamed modules.

API Note:Used by the --add-opens command line option.
/**
     * Updates this module to open a package to all unnamed modules.
     *
     * @apiNote Used by the --add-opens command line option.
     */
    void implAddOpensToAllUnnamed(String pn) {
        implAddExportsOrOpens(pn, Module.ALL_UNNAMED_MODULE, true, true);
    }

    
Updates a module to export or open a module to another module. If syncVM is true then the VM is notified. 
/**
     * Updates a module to export or open a module to another module.
     *
     * If {@code syncVM} is {@code true} then the VM is notified.
     */
    private void implAddExportsOrOpens(String pn,
                                       Module other,
                                       boolean open,
                                       boolean syncVM) {
        Objects.requireNonNull(other);
        Objects.requireNonNull(pn);

        // all packages are open in unnamed, open, and automatic modules
        if (!isNamed() || descriptor.isOpen() || descriptor.isAutomatic())
            return;

        // check if the package is already exported/open to other
        if (implIsExportedOrOpen(pn, other, open))
            return;

        // can only export a package in the module
        if (!descriptor.packages().contains(pn)) {
            throw new IllegalArgumentException("package " + pn
                                               + " not in contents");
        }

        // update VM first, just in case it fails
        if (syncVM) {
            if (other == EVERYONE_MODULE) {
                addExportsToAll0(this, pn);
            } else if (other == ALL_UNNAMED_MODULE) {
                addExportsToAllUnnamed0(this, pn);
            } else {
                addExports0(this, pn, other);
            }
        }

        // add package name to exports if absent
        Map<String, Boolean> map = ReflectionData.exports
            .computeIfAbsent(this, other,
                             (m1, m2) -> new ConcurrentHashMap<>());
        if (open) {
            map.put(pn, Boolean.TRUE);  // may need to promote from FALSE to TRUE
        } else {
            map.putIfAbsent(pn, Boolean.FALSE);
        }
    }

    
Updates a module to open all packages in the given sets to all unnamed
modules.

API Note:Used during startup to open packages for illegal access.
/**
     * Updates a module to open all packages in the given sets to all unnamed
     * modules.
     *
     * @apiNote Used during startup to open packages for illegal access.
     */
    void implAddOpensToAllUnnamed(Set<String> concealedPkgs, Set<String> exportedPkgs) {
        if (jdk.internal.misc.VM.isModuleSystemInited()) {
            throw new IllegalStateException("Module system already initialized");
        }

        // replace this module's openPackages map with a new map that opens
        // the packages to all unnamed modules.
        Map<String, Set<Module>> openPackages = this.openPackages;
        if (openPackages == null) {
            openPackages = new HashMap<>((4 * (concealedPkgs.size() + exportedPkgs.size()) / 3) + 1);
        } else {
            openPackages = new HashMap<>(openPackages);
        }
        implAddOpensToAllUnnamed(concealedPkgs, openPackages);
        implAddOpensToAllUnnamed(exportedPkgs, openPackages);
        this.openPackages = openPackages;
    }

    private void implAddOpensToAllUnnamed(Set<String> pkgs, Map<String, Set<Module>> openPackages) {
        for (String pn : pkgs) {
            Set<Module> prev = openPackages.putIfAbsent(pn, ALL_UNNAMED_MODULE_SET);
            if (prev != null) {
                prev.add(ALL_UNNAMED_MODULE);
            }

            // update VM to export the package
            addExportsToAllUnnamed0(this, pn);
        }
    }

    // -- services --

    
If the caller's module is this module then update this module to add a service dependence on the given service type. This method is intended for use by frameworks that invoke 
ServiceLoader on behalf of other modules or where the framework is passed a reference to the service type by other code. This method is a no-op when invoked on an unnamed module or an automatic module. 
 This method does not cause 
resolveAndBind to be re-run. 


Params:
  • service – 
        The service type
Throws:
See Also:
Returns:this module
/**
     * If the caller's module is this module then update this module to add a
     * service dependence on the given service type. This method is intended
     * for use by frameworks that invoke {@link java.util.ServiceLoader
     * ServiceLoader} on behalf of other modules or where the framework is
     * passed a reference to the service type by other code. This method is
     * a no-op when invoked on an unnamed module or an automatic module.
     *
     * <p> This method does not cause {@link Configuration#resolveAndBind
     * resolveAndBind} to be re-run. </p>
     *
     * @param  service
     *         The service type
     *
     * @return this module
     *
     * @throws IllegalCallerException
     *         If this is a named module and the caller's module is not this
     *         module
     *
     * @see #canUse(Class)
     * @see ModuleDescriptor#uses()
     */
    @CallerSensitive
    public Module addUses(Class<?> service) {
        Objects.requireNonNull(service);

        if (isNamed() && !descriptor.isAutomatic()) {
            Module caller = getCallerModule(Reflection.getCallerClass());
            if (caller != this) {
                throw new IllegalCallerException(caller + " != " + this);
            }
            implAddUses(service);
        }

        return this;
    }

    
Update this module to add a service dependence on the given service
type.

/**
     * Update this module to add a service dependence on the given service
     * type.
     */
    void implAddUses(Class<?> service) {
        if (!canUse(service)) {
            ReflectionData.uses.putIfAbsent(this, service, Boolean.TRUE);
        }
    }


    
Indicates if this module has a service dependence on the given service type. This method always returns true when invoked on an unnamed module or an automatic module. 
Params:
  • service – 
        The service type
See Also:
Returns:true if this module uses service type st
/**
     * Indicates if this module has a service dependence on the given service
     * type. This method always returns {@code true} when invoked on an unnamed
     * module or an automatic module.
     *
     * @param  service
     *         The service type
     *
     * @return {@code true} if this module uses service type {@code st}
     *
     * @see #addUses(Class)
     */
    public boolean canUse(Class<?> service) {
        Objects.requireNonNull(service);

        if (!isNamed())
            return true;

        if (descriptor.isAutomatic())
            return true;

        // uses was declared
        if (descriptor.uses().contains(service.getName()))
            return true;

        // uses added via addUses
        return ReflectionData.uses.containsKeyPair(this, service);
    }



    // -- packages --

    
Returns the set of package names for the packages in this module.

 For named modules, the returned set contains an element for each
package in the module. 


 For unnamed modules, the returned set contains an element for each package that has been defined in the unnamed module.


Returns:the set of the package names of the packages in this module
/**
     * Returns the set of package names for the packages in this module.
     *
     * <p> For named modules, the returned set contains an element for each
     * package in the module. </p>
     *
     * <p> For unnamed modules, the returned set contains an element for
     * each package that {@link ClassLoader#getDefinedPackages() has been defined}
     * in the unnamed module.</p>
     *
     * @return the set of the package names of the packages in this module
     */
    public Set<String> getPackages() {
        if (isNamed()) {
            return descriptor.packages();
        } else {
            // unnamed module
            Stream<Package> packages;
            if (loader == null) {
                packages = BootLoader.packages();
            } else {
                packages = loader.packages();
            }
            return packages.filter(p -> p.module() == this)
                           .map(Package::getName).collect(Collectors.toSet());
        }
    }

    // -- creating Module objects --

    
Defines all module in a configuration to the runtime.

Throws:
  • IllegalArgumentException – 
        If the function maps a module to the null or platform class loader
  • IllegalStateException – 
        If the module cannot be defined to the VM or its packages overlap
        with another module mapped to the same class loader
Returns:a map of module name to runtime Module
/**
     * Defines all module in a configuration to the runtime.
     *
     * @return a map of module name to runtime {@code Module}
     *
     * @throws IllegalArgumentException
     *         If the function maps a module to the null or platform class loader
     * @throws IllegalStateException
     *         If the module cannot be defined to the VM or its packages overlap
     *         with another module mapped to the same class loader
     */
    static Map<String, Module> defineModules(Configuration cf,
                                             Function<String, ClassLoader> clf,
                                             ModuleLayer layer)
    {
        boolean isBootLayer = (ModuleLayer.boot() == null);

        int numModules = cf.modules().size();
        int cap = (int)(numModules / 0.75f + 1.0f);
        Map<String, Module> nameToModule = new HashMap<>(cap);

        // to avoid repeated lookups and reduce iteration overhead, we create
        // arrays holding correlated information about each module.
        ResolvedModule[] resolvedModules = new ResolvedModule[numModules];
        Module[] modules = new Module[numModules];
        ClassLoader[] classLoaders = new ClassLoader[numModules];

        resolvedModules = cf.modules().toArray(resolvedModules);

        // record that we want to bind the layer to non-boot and non-platform
        // module loaders as a final step
        HashSet<ClassLoader> toBindLoaders = new HashSet<>(4);
        boolean hasPlatformModules = false;

        // map each module to a class loader
        ClassLoader pcl = ClassLoaders.platformClassLoader();
        boolean isModuleLoaderMapper = ModuleLoaderMap.isBuiltinMapper(clf);

        for (int index = 0; index < numModules; index++) {
            String name = resolvedModules[index].name();
            ClassLoader loader = clf.apply(name);

            if (loader == null || loader == pcl) {
                if (!isModuleLoaderMapper) {
                    throw new IllegalArgumentException("loader can't be 'null'"
                            + " or the platform class loader");
                }
                hasPlatformModules = true;
            } else {
                toBindLoaders.add(loader);
            }

            classLoaders[index] = loader;
        }

        // define each module in the configuration to the VM
        for (int index = 0; index < numModules; index++) {
            ModuleReference mref = resolvedModules[index].reference();
            ModuleDescriptor descriptor = mref.descriptor();
            String name = descriptor.name();
            ClassLoader loader = classLoaders[index];
            Module m;
            if (loader == null && name.equals("java.base")) {
                // java.base is already defined to the VM
                m = Object.class.getModule();
            } else {
                URI uri = mref.location().orElse(null);
                m = new Module(layer, loader, descriptor, uri);
            }
            nameToModule.put(name, m);
            modules[index] = m;
        }

        // setup readability and exports/opens
        for (int index = 0; index < numModules; index++) {
            ResolvedModule resolvedModule = resolvedModules[index];
            ModuleReference mref = resolvedModule.reference();
            ModuleDescriptor descriptor = mref.descriptor();
            Module m = modules[index];

            // reads
            Set<Module> reads = new HashSet<>();

            // name -> source Module when in parent layer
            Map<String, Module> nameToSource = Map.of();

            for (ResolvedModule other : resolvedModule.reads()) {
                Module m2 = null;
                if (other.configuration() == cf) {
                    // this configuration
                    m2 = nameToModule.get(other.name());
                    assert m2 != null;
                } else {
                    // parent layer
                    for (ModuleLayer parent: layer.parents()) {
                        m2 = findModule(parent, other);
                        if (m2 != null)
                            break;
                    }
                    assert m2 != null;
                    if (nameToSource.isEmpty())
                        nameToSource = new HashMap<>();
                    nameToSource.put(other.name(), m2);
                }
                reads.add(m2);

                // update VM view
                addReads0(m, m2);
            }
            m.reads = reads;

            // automatic modules read all unnamed modules
            if (descriptor.isAutomatic()) {
                m.implAddReads(ALL_UNNAMED_MODULE, true);
            }

            // exports and opens, skipped for open and automatic
            if (!descriptor.isOpen() && !descriptor.isAutomatic()) {
                if (isBootLayer && descriptor.opens().isEmpty()) {
                    // no open packages, no qualified exports to modules in parent layers
                    initExports(m, nameToModule);
                } else {
                    initExportsAndOpens(m, nameToSource, nameToModule, layer.parents());
                }
            }
        }

        // if there are modules defined to the boot or platform class loaders
        // then register the modules in the class loader's services catalog
        if (hasPlatformModules) {
            ServicesCatalog bootCatalog = BootLoader.getServicesCatalog();
            ServicesCatalog pclCatalog = ServicesCatalog.getServicesCatalog(pcl);
            for (int index = 0; index < numModules; index++) {
                ResolvedModule resolvedModule = resolvedModules[index];
                ModuleReference mref = resolvedModule.reference();
                ModuleDescriptor descriptor = mref.descriptor();
                if (!descriptor.provides().isEmpty()) {
                    Module m = modules[index];
                    ClassLoader loader = classLoaders[index];
                    if (loader == null) {
                        bootCatalog.register(m);
                    } else if (loader == pcl) {
                        pclCatalog.register(m);
                    }
                }
            }
        }

        // record that there is a layer with modules defined to the class loader
        for (ClassLoader loader : toBindLoaders) {
            layer.bindToLoader(loader);
        }

        return nameToModule;
    }

    
Find the runtime Module corresponding to the given ResolvedModule
in the given parent layer (or its parents).

/**
     * Find the runtime Module corresponding to the given ResolvedModule
     * in the given parent layer (or its parents).
     */
    private static Module findModule(ModuleLayer parent,
                                     ResolvedModule resolvedModule) {
        Configuration cf = resolvedModule.configuration();
        String dn = resolvedModule.name();
        return parent.layers()
                .filter(l -> l.configuration() == cf)
                .findAny()
                .map(layer -> {
                    Optional<Module> om = layer.findModule(dn);
                    assert om.isPresent() : dn + " not found in layer";
                    Module m = om.get();
                    assert m.getLayer() == layer : m + " not in expected layer";
                    return m;
                })
                .orElse(null);
    }

    
Initialize/setup a module's exports.

Params:
  • m – the module
  • nameToModule – map of module name to Module (for qualified exports)
/**
     * Initialize/setup a module's exports.
     *
     * @param m the module
     * @param nameToModule map of module name to Module (for qualified exports)
     */
    private static void initExports(Module m, Map<String, Module> nameToModule) {
        Map<String, Set<Module>> exportedPackages = new HashMap<>();

        for (Exports exports : m.getDescriptor().exports()) {
            String source = exports.source();
            if (exports.isQualified()) {
                // qualified exports
                Set<Module> targets = new HashSet<>();
                for (String target : exports.targets()) {
                    Module m2 = nameToModule.get(target);
                    if (m2 != null) {
                        addExports0(m, source, m2);
                        targets.add(m2);
                    }
                }
                if (!targets.isEmpty()) {
                    exportedPackages.put(source, targets);
                }
            } else {
                // unqualified exports
                addExportsToAll0(m, source);
                exportedPackages.put(source, EVERYONE_SET);
            }
        }

        if (!exportedPackages.isEmpty())
            m.exportedPackages = exportedPackages;
    }

    
Initialize/setup a module's exports.

Params:
  • m – the module
  • nameToSource – map of module name to Module for modules that m reads
  • nameToModule – map of module name to Module for modules in the layer
                    under construction
  • parents – the parent layers
/**
     * Initialize/setup a module's exports.
     *
     * @param m the module
     * @param nameToSource map of module name to Module for modules that m reads
     * @param nameToModule map of module name to Module for modules in the layer
     *                     under construction
     * @param parents the parent layers
     */
    private static void initExportsAndOpens(Module m,
                                            Map<String, Module> nameToSource,
                                            Map<String, Module> nameToModule,
                                            List<ModuleLayer> parents) {
        ModuleDescriptor descriptor = m.getDescriptor();
        Map<String, Set<Module>> openPackages = new HashMap<>();
        Map<String, Set<Module>> exportedPackages = new HashMap<>();

        // process the open packages first
        for (Opens opens : descriptor.opens()) {
            String source = opens.source();

            if (opens.isQualified()) {
                // qualified opens
                Set<Module> targets = new HashSet<>();
                for (String target : opens.targets()) {
                    Module m2 = findModule(target, nameToSource, nameToModule, parents);
                    if (m2 != null) {
                        addExports0(m, source, m2);
                        targets.add(m2);
                    }
                }
                if (!targets.isEmpty()) {
                    openPackages.put(source, targets);
                }
            } else {
                // unqualified opens
                addExportsToAll0(m, source);
                openPackages.put(source, EVERYONE_SET);
            }
        }

        // next the exports, skipping exports when the package is open
        for (Exports exports : descriptor.exports()) {
            String source = exports.source();

            // skip export if package is already open to everyone
            Set<Module> openToTargets = openPackages.get(source);
            if (openToTargets != null && openToTargets.contains(EVERYONE_MODULE))
                continue;

            if (exports.isQualified()) {
                // qualified exports
                Set<Module> targets = new HashSet<>();
                for (String target : exports.targets()) {
                    Module m2 = findModule(target, nameToSource, nameToModule, parents);
                    if (m2 != null) {
                        // skip qualified export if already open to m2
                        if (openToTargets == null || !openToTargets.contains(m2)) {
                            addExports0(m, source, m2);
                            targets.add(m2);
                        }
                    }
                }
                if (!targets.isEmpty()) {
                    exportedPackages.put(source, targets);
                }
            } else {
                // unqualified exports
                addExportsToAll0(m, source);
                exportedPackages.put(source, EVERYONE_SET);
            }
        }

        if (!openPackages.isEmpty())
            m.openPackages = openPackages;
        if (!exportedPackages.isEmpty())
            m.exportedPackages = exportedPackages;
    }

    
Find the runtime Module with the given name. The module name is the
name of a target module in a qualified exports or opens directive.

Params:
  • target – The target module to find
  • nameToSource – The modules in parent layers that are read
  • nameToModule – The modules in the layer under construction
  • parents – The parent layers
/**
     * Find the runtime Module with the given name. The module name is the
     * name of a target module in a qualified exports or opens directive.
     *
     * @param target The target module to find
     * @param nameToSource The modules in parent layers that are read
     * @param nameToModule The modules in the layer under construction
     * @param parents The parent layers
     */
    private static Module findModule(String target,
                                     Map<String, Module> nameToSource,
                                     Map<String, Module> nameToModule,
                                     List<ModuleLayer> parents) {
        Module m = nameToSource.get(target);
        if (m == null) {
            m = nameToModule.get(target);
            if (m == null) {
                for (ModuleLayer parent : parents) {
                    m = parent.findModule(target).orElse(null);
                    if (m != null) break;
                }
            }
        }
        return m;
    }


    // -- annotations --

    
{@inheritDoc} This method returns null when invoked on an unnamed module. 
 Note that any annotation returned by this method is a
declaration annotation.

/**
     * {@inheritDoc}
     * This method returns {@code null} when invoked on an unnamed module.
     *
     * <p> Note that any annotation returned by this method is a
     * declaration annotation.
     */
    @Override
    public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
        return moduleInfoClass().getDeclaredAnnotation(annotationClass);
    }

    
{@inheritDoc}
This method returns an empty array when invoked on an unnamed module.

 Note that any annotations returned by this method are
declaration annotations.

/**
     * {@inheritDoc}
     * This method returns an empty array when invoked on an unnamed module.
     *
     * <p> Note that any annotations returned by this method are
     * declaration annotations.
     */
    @Override
    public Annotation[] getAnnotations() {
        return moduleInfoClass().getAnnotations();
    }

    
{@inheritDoc}
This method returns an empty array when invoked on an unnamed module.

 Note that any annotations returned by this method are
declaration annotations.

/**
     * {@inheritDoc}
     * This method returns an empty array when invoked on an unnamed module.
     *
     * <p> Note that any annotations returned by this method are
     * declaration annotations.
     */
    @Override
    public Annotation[] getDeclaredAnnotations() {
        return moduleInfoClass().getDeclaredAnnotations();
    }

    // cached class file with annotations
    private volatile Class<?> moduleInfoClass;

    @SuppressWarnings("removal")
    private Class<?> moduleInfoClass() {
        Class<?> clazz = this.moduleInfoClass;
        if (clazz != null)
            return clazz;

        synchronized (this) {
            clazz = this.moduleInfoClass;
            if (clazz == null) {
                if (isNamed()) {
                    PrivilegedAction<Class<?>> pa = this::loadModuleInfoClass;
                    clazz = AccessController.doPrivileged(pa);
                }
                if (clazz == null) {
                    class DummyModuleInfo { }
                    clazz = DummyModuleInfo.class;
                }
                this.moduleInfoClass = clazz;
            }
            return clazz;
        }
    }

    private Class<?> loadModuleInfoClass() {
        Class<?> clazz = null;
        try (InputStream in = getResourceAsStream("module-info.class")) {
            if (in != null)
                clazz = loadModuleInfoClass(in);
        } catch (Exception ignore) { }
        return clazz;
    }

    
Loads module-info.class as a package-private interface in a class loader
that is a child of this module's class loader.

/**
     * Loads module-info.class as a package-private interface in a class loader
     * that is a child of this module's class loader.
     */
    private Class<?> loadModuleInfoClass(InputStream in) throws IOException {
        final String MODULE_INFO = "module-info";

        ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS
                                         + ClassWriter.COMPUTE_FRAMES);

        ClassVisitor cv = new ClassVisitor(Opcodes.ASM7, cw) {
            @Override
            public void visit(int version,
                              int access,
                              String name,
                              String signature,
                              String superName,
                              String[] interfaces) {
                cw.visit(version,
                        Opcodes.ACC_INTERFACE
                            + Opcodes.ACC_ABSTRACT
                            + Opcodes.ACC_SYNTHETIC,
                        MODULE_INFO,
                        null,
                        "java/lang/Object",
                        null);
            }
            @Override
            public AnnotationVisitor visitAnnotation(String desc, boolean visible) {
                // keep annotations
                return super.visitAnnotation(desc, visible);
            }
            @Override
            public void visitAttribute(Attribute attr) {
                // drop non-annotation attributes
            }
            @Override
            public ModuleVisitor visitModule(String name, int flags, String version) {
                // drop Module attribute
                return null;
            }
        };

        ClassReader cr = new ClassReader(in);
        cr.accept(cv, 0);
        byte[] bytes = cw.toByteArray();

        ClassLoader cl = new ClassLoader(loader) {
            @Override
            protected Class<?> findClass(String cn)throws ClassNotFoundException {
                if (cn.equals(MODULE_INFO)) {
                    return super.defineClass(cn, bytes, 0, bytes.length);
                } else {
                    throw new ClassNotFoundException(cn);
                }
            }
            @Override
            protected Class<?> loadClass(String cn, boolean resolve)
                throws ClassNotFoundException
            {
                synchronized (getClassLoadingLock(cn)) {
                    Class<?> c = findLoadedClass(cn);
                    if (c == null) {
                        if (cn.equals(MODULE_INFO)) {
                            c = findClass(cn);
                        } else {
                            c = super.loadClass(cn, resolve);
                        }
                    }
                    if (resolve)
                        resolveClass(c);
                    return c;
                }
            }
        };

        try {
            return cl.loadClass(MODULE_INFO);
        } catch (ClassNotFoundException e) {
            throw new InternalError(e);
        }
    }


    // -- misc --


    
Returns an input stream for reading a resource in this module. The name parameter is a '/'-separated path name that identifies the resource. As with 
Class.getResourceAsStream, this method delegates to the module's class loader 
findResource(String,String) method, invoking it with the module name (or null when the module is unnamed) and the name of the resource. If the resource name has a leading slash then it is dropped before delegation. 
 A resource in a named module may be encapsulated so that
it cannot be located by code in other modules. Whether a resource can be
located or not is determined as follows: 


    
    
  •  If the resource name ends with ".class" then it is not encapsulated. 
    • 
    
  •  A package name is derived from the resource name. If the package name is a package in the module then the resource can only be located by the caller of this method when the package is open to at least the caller's module. If the resource is not in a package in the module then the resource is not encapsulated. 
    • 



 In the above, the package name for a resource is derived from the subsequence of characters that precedes the last '/' in the name and then replacing each '/' character in the subsequence with '.'. A leading slash is ignored when deriving the package name. As an example, the package name derived for a resource named "a/b/c/foo.properties" is "a.b.c". A resource name with the name "META-INF/MANIFEST.MF" is never encapsulated because "META-INF" is not a legal package name. 


 This method returns null if the resource is not in this module, the resource is encapsulated and cannot be located by the caller, or access to the resource is denied by the security manager. 


Params:
  • name – 
        The resource name
Throws:
See Also:
Returns:An input stream for reading the resource or null
/**
     * Returns an input stream for reading a resource in this module.
     * The {@code name} parameter is a {@code '/'}-separated path name that
     * identifies the resource. As with {@link Class#getResourceAsStream
     * Class.getResourceAsStream}, this method delegates to the module's class
     * loader {@link ClassLoader#findResource(String,String)
     * findResource(String,String)} method, invoking it with the module name
     * (or {@code null} when the module is unnamed) and the name of the
     * resource. If the resource name has a leading slash then it is dropped
     * before delegation.
     *
     * <p> A resource in a named module may be <em>encapsulated</em> so that
     * it cannot be located by code in other modules. Whether a resource can be
     * located or not is determined as follows: </p>
     *
     * <ul>
     *     <li> If the resource name ends with  "{@code .class}" then it is not
     *     encapsulated. </li>
     *
     *     <li> A <em>package name</em> is derived from the resource name. If
     *     the package name is a {@linkplain #getPackages() package} in the
     *     module then the resource can only be located by the caller of this
     *     method when the package is {@linkplain #isOpen(String,Module) open}
     *     to at least the caller's module. If the resource is not in a
     *     package in the module then the resource is not encapsulated. </li>
     * </ul>
     *
     * <p> In the above, the <em>package name</em> for a resource is derived
     * from the subsequence of characters that precedes the last {@code '/'} in
     * the name and then replacing each {@code '/'} character in the subsequence
     * with {@code '.'}. A leading slash is ignored when deriving the package
     * name. As an example, the package name derived for a resource named
     * "{@code a/b/c/foo.properties}" is "{@code a.b.c}". A resource name
     * with the name "{@code META-INF/MANIFEST.MF}" is never encapsulated
     * because "{@code META-INF}" is not a legal package name. </p>
     *
     * <p> This method returns {@code null} if the resource is not in this
     * module, the resource is encapsulated and cannot be located by the caller,
     * or access to the resource is denied by the security manager. </p>
     *
     * @param  name
     *         The resource name
     *
     * @return An input stream for reading the resource or {@code null}
     *
     * @throws IOException
     *         If an I/O error occurs
     *
     * @see Class#getResourceAsStream(String)
     */
    @CallerSensitive
    public InputStream getResourceAsStream(String name) throws IOException {
        if (name.startsWith("/")) {
            name = name.substring(1);
        }

        if (isNamed() && Resources.canEncapsulate(name)) {
            Module caller = getCallerModule(Reflection.getCallerClass());
            if (caller != this && caller != Object.class.getModule()) {
                String pn = Resources.toPackageName(name);
                if (getPackages().contains(pn)) {
                    if (caller == null && !isOpen(pn)) {
                        // no caller, package not open
                        return null;
                    }
                    if (!isOpen(pn, caller)) {
                        // package not open to caller
                        return null;
                    }
                }
            }
        }

        String mn = this.name;

        // special-case built-in class loaders to avoid URL connection
        if (loader == null) {
            return BootLoader.findResourceAsStream(mn, name);
        } else if (loader instanceof BuiltinClassLoader) {
            return ((BuiltinClassLoader) loader).findResourceAsStream(mn, name);
        }

        // locate resource in module
        URL url = loader.findResource(mn, name);
        if (url != null) {
            try {
                return url.openStream();
            } catch (SecurityException e) { }
        }

        return null;
    }

    
Returns the string representation of this module. For a named module, the representation is the string "module", followed by a space, and then the module name. For an unnamed module, the representation is the string "unnamed module", followed by a space, and then an implementation specific string that identifies the unnamed module. 
Returns:The string representation of this module
/**
     * Returns the string representation of this module. For a named module,
     * the representation is the string {@code "module"}, followed by a space,
     * and then the module name. For an unnamed module, the representation is
     * the string {@code "unnamed module"}, followed by a space, and then an
     * implementation specific string that identifies the unnamed module.
     *
     * @return The string representation of this module
     */
    @Override
    public String toString() {
        if (isNamed()) {
            return "module " + name;
        } else {
            String id = Integer.toHexString(System.identityHashCode(this));
            return "unnamed module @" + id;
        }
    }

    
Returns the module that a given caller class is a member of. Returns null if the caller is null. 
/**
     * Returns the module that a given caller class is a member of. Returns
     * {@code null} if the caller is {@code null}.
     */
    private Module getCallerModule(Class<?> caller) {
        return (caller != null) ? caller.getModule() : null;
    }


    // -- native methods --

    // JVM_DefineModule
    private static native void defineModule0(Module module,
                                             boolean isOpen,
                                             String version,
                                             String location,
                                             Object[] pns);

    // JVM_AddReadsModule
    private static native void addReads0(Module from, Module to);

    // JVM_AddModuleExports
    private static native void addExports0(Module from, String pn, Module to);

    // JVM_AddModuleExportsToAll
    private static native void addExportsToAll0(Module from, String pn);

    // JVM_AddModuleExportsToAllUnnamed
    private static native void addExportsToAllUnnamed0(Module from, String pn);
}