https://openjdk.java.net/ 
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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
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 *
 * 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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package jdk.nashorn.internal.runtime.linker;

import static jdk.nashorn.internal.lookup.Lookup.MH;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.invoke.MethodType;
import java.lang.reflect.Modifier;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.CodeSigner;
import java.security.CodeSource;
import java.security.Permissions;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import jdk.dynalink.CallSiteDescriptor;
import jdk.dynalink.StandardOperation;
import jdk.dynalink.beans.StaticClass;
import jdk.dynalink.linker.support.SimpleLinkRequest;
import jdk.nashorn.internal.runtime.Context;
import jdk.nashorn.internal.runtime.ECMAException;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.ScriptObject;
import jdk.nashorn.internal.runtime.linker.AdaptationResult.Outcome;


A factory class that generates adapter classes. Adapter classes allow
implementation of Java interfaces and extending of Java classes from
JavaScript. For every combination of a superclass to extend and interfaces to
implement (collectively: "original types"), exactly one adapter class is
generated that extends the specified superclass and implements the specified
interfaces. (But see the discussion of class-based overrides for exceptions.)

 The adapter class is generated in a new secure class loader that inherits Nashorn's protection domain, and has either one of the original types' class loader or the Nashorn's class loader as its parent - the parent class loader is chosen so that all the original types and the Nashorn core classes are visible from it (as the adapter will have constant pool references to ScriptObject and ScriptFunction classes). In case none of the candidate class loaders has visibility of all the required types, an error is thrown. The class uses JavaAdapterBytecodeGenerator to generate the adapter class itself; see its documentation for details about the generated class. 
 You normally don't use this class directly, but rather either create adapters from script using NativeJava.extend(Object, Object...), using the new operator on abstract classes and interfaces (see NativeJava.type(Object, Object)), or implicitly when passing script functions to Java methods expecting SAM types. 
/**
 * A factory class that generates adapter classes. Adapter classes allow
 * implementation of Java interfaces and extending of Java classes from
 * JavaScript. For every combination of a superclass to extend and interfaces to
 * implement (collectively: "original types"), exactly one adapter class is
 * generated that extends the specified superclass and implements the specified
 * interfaces. (But see the discussion of class-based overrides for exceptions.)
 * <p>
 * The adapter class is generated in a new secure class loader that inherits
 * Nashorn's protection domain, and has either one of the original types' class
 * loader or the Nashorn's class loader as its parent - the parent class loader
 * is chosen so that all the original types and the Nashorn core classes are
 * visible from it (as the adapter will have constant pool references to
 * ScriptObject and ScriptFunction classes). In case none of the candidate class
 * loaders has visibility of all the required types, an error is thrown. The
 * class uses {@link JavaAdapterBytecodeGenerator} to generate the adapter class
 * itself; see its documentation for details about the generated class.
 * <p>
 * You normally don't use this class directly, but rather either create adapters
 * from script using {@link jdk.nashorn.internal.objects.NativeJava#extend(Object, Object...)},
 * using the {@code new} operator on abstract classes and interfaces (see
 * {@link jdk.nashorn.internal.objects.NativeJava#type(Object, Object)}), or
 * implicitly when passing script functions to Java methods expecting SAM types.
 */

@SuppressWarnings("javadoc")
public final class JavaAdapterFactory {
    private static final ProtectionDomain MINIMAL_PERMISSION_DOMAIN = createMinimalPermissionDomain();

    // context with permissions needs for AdapterInfo creation
    private static final AccessControlContext CREATE_ADAPTER_INFO_ACC_CTXT =
        ClassAndLoader.createPermAccCtxt("createClassLoader", "getClassLoader",
            "accessDeclaredMembers", "accessClassInPackage.jdk.nashorn.internal.runtime");

    
A mapping from an original Class object to AdapterInfo representing the adapter for the class it represents.

/**
     * A mapping from an original Class object to AdapterInfo representing the adapter for the class it represents.
     */
    private static final ClassValue<Map<List<Class<?>>, AdapterInfo>> ADAPTER_INFO_MAPS = new ClassValue<Map<List<Class<?>>, AdapterInfo>>() {
        @Override
        protected Map<List<Class<?>>, AdapterInfo> computeValue(final Class<?> type) {
            return new HashMap<>();
        }
    };

    
Returns an adapter class for the specified original types. The adapter
class extends/implements the original class/interfaces.

Params:
  • types – the original types. The caller must pass at least one Java type representing either a public interface or a non-final public class with at least one public or protected constructor. If more than one type is specified, at most one can be a class and the rest have to be interfaces. The class can be in any position in the array. Invoking the method twice with exactly the same types in the same order will return the same adapter class, any reordering of types or even addition or removal of redundant types (i.e., interfaces that other types in the list already implement/extend, or java.lang.Object in a list of types consisting purely of interfaces) will result in a different adapter class, even though those adapter classes are functionally identical; we deliberately don't want to incur the additional processing cost of canonicalizing type lists.
  • classOverrides – a JavaScript object with functions serving as the
       class-level overrides and implementations. These overrides are
       defined for all instances of the class, and can be further
       overridden on a per-instance basis by passing additional objects
       in the constructor.
  • lookup – the lookup object identifying the caller class. The
       generated adapter class will have the protection domain of the
       caller class iff the lookup object is full-strength, otherwise it
       will be completely unprivileged.
Throws:
  • ECMAException – with a TypeError if the adapter class can not be
        generated because the original class is final, non-public, or has
        no public or protected constructors.
Returns:an adapter class. See this class' documentation for details on
        the generated adapter class.
/**
     * Returns an adapter class for the specified original types. The adapter
     * class extends/implements the original class/interfaces.
     *
     * @param types the original types. The caller must pass at least one Java
     *        type representing either a public interface or a non-final public
     *        class with at least one public or protected constructor. If more
     *        than one type is specified, at most one can be a class and the
     *        rest have to be interfaces. The class can be in any position in
     *        the array. Invoking the method twice with exactly the same types
     *        in the same order will return the same adapter class, any
     *        reordering of types or even addition or removal of redundant types
     *        (i.e., interfaces that other types in the list already
     *        implement/extend, or {@code java.lang.Object} in a list of types
     *        consisting purely of interfaces) will result in a different
     *        adapter class, even though those adapter classes are functionally
     *        identical; we deliberately don't want to incur the additional
     *        processing cost of canonicalizing type lists.
     * @param classOverrides a JavaScript object with functions serving as the
     *        class-level overrides and implementations. These overrides are
     *        defined for all instances of the class, and can be further
     *        overridden on a per-instance basis by passing additional objects
     *        in the constructor.
     * @param lookup the lookup object identifying the caller class. The
     *        generated adapter class will have the protection domain of the
     *        caller class iff the lookup object is full-strength, otherwise it
     *        will be completely unprivileged.
     *
     * @return an adapter class. See this class' documentation for details on
     *         the generated adapter class.
     *
     * @throws ECMAException with a TypeError if the adapter class can not be
     *         generated because the original class is final, non-public, or has
     *         no public or protected constructors.
     */
    public static StaticClass getAdapterClassFor(final Class<?>[] types, final ScriptObject classOverrides, final MethodHandles.Lookup lookup) {
        return getAdapterClassFor(types, classOverrides, getProtectionDomain(lookup));
    }

    private static StaticClass getAdapterClassFor(final Class<?>[] types, final ScriptObject classOverrides, final ProtectionDomain protectionDomain) {
        assert types != null && types.length > 0;
        final SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            for (final Class<?> type : types) {
                // check for restricted package access
                Context.checkPackageAccess(type);
                // check for classes, interfaces in reflection
                ReflectionCheckLinker.checkReflectionAccess(type, true);
            }
        }
        return getAdapterInfo(types).getAdapterClass(classOverrides, protectionDomain);
    }

    private static ProtectionDomain getProtectionDomain(final MethodHandles.Lookup lookup) {
        if((lookup.lookupModes() & Lookup.PRIVATE) == 0) {
            return MINIMAL_PERMISSION_DOMAIN;
        }
        return getProtectionDomain(lookup.lookupClass());
    }

    private static ProtectionDomain getProtectionDomain(final Class<?> clazz) {
        return AccessController.doPrivileged(new PrivilegedAction<ProtectionDomain>() {
            @Override
            public ProtectionDomain run() {
                return clazz.getProtectionDomain();
            }
        });
    }

    
Returns a method handle representing a constructor that takes a single argument of the source type (which, really, should be one of ScriptObject, ScriptFunction, or Object, and returns an instance of the adapter for the target type. Used to implement the function autoconverters as well as the Nashorn JSR-223 script engine's getInterface() method. 
Params:
  • sourceType – the source type; should be either ScriptObject, ScriptFunction, or Object. In case of Object, it will return a method handle that dispatches to either the script object or function constructor at invocation based on the actual argument.
  • targetType – the target type, for which adapter instances will be created
  • lookup – method handle lookup to use
Throws:
Returns:the constructor method handle.
/**
     * Returns a method handle representing a constructor that takes a single
     * argument of the source type (which, really, should be one of {@link ScriptObject},
     * {@link ScriptFunction}, or {@link Object}, and returns an instance of the
     * adapter for the target type. Used to implement the function autoconverters
     * as well as the Nashorn JSR-223 script engine's {@code getInterface()}
     * method.
     *
     * @param sourceType the source type; should be either {@link ScriptObject},
     *        {@link ScriptFunction}, or {@link Object}. In case of {@code Object},
     *        it will return a method handle that dispatches to either the script
     *        object or function constructor at invocation based on the actual
     *        argument.
     * @param targetType the target type, for which adapter instances will be created
     * @param lookup method handle lookup to use
     *
     * @return the constructor method handle.
     *
     * @throws Exception if anything goes wrong
     */
    public static MethodHandle getConstructor(final Class<?> sourceType, final Class<?> targetType, final MethodHandles.Lookup lookup) throws Exception {
        final StaticClass adapterClass = getAdapterClassFor(new Class<?>[] { targetType }, null, lookup);
        return MH.bindTo(Bootstrap.getLinkerServices().getGuardedInvocation(new SimpleLinkRequest(
                new CallSiteDescriptor(lookup, StandardOperation.NEW,
                        MethodType.methodType(targetType, StaticClass.class, sourceType)), false,
                        adapterClass, null)).getInvocation(), adapterClass);
    }

    
Returns whether an instance of the specified class/interface can be generated from a ScriptFunction. Returns true iff: the adapter for the class/interface can be created, it is abstract (this includes interfaces), it has at least one abstract method, all the abstract methods share the same name, and it has a public or protected default constructor. Note that invoking this class will most likely result in the adapter class being defined in the JVM if it hasn't been already. 
Params:
  • clazz – the inspected class
Returns:true iff an instance of the specified class/interface can be generated from a ScriptFunction.
/**
     * Returns whether an instance of the specified class/interface can be
     * generated from a ScriptFunction. Returns {@code true} iff: the adapter
     * for the class/interface can be created, it is abstract (this includes
     * interfaces), it has at least one abstract method, all the abstract
     * methods share the same name, and it has a public or protected default
     * constructor. Note that invoking this class will most likely result in the
     * adapter class being defined in the JVM if it hasn't been already.
     *
     * @param clazz the inspected class
     *
     * @return {@code true} iff an instance of the specified class/interface can
     *         be generated from a ScriptFunction.
     */
    static boolean isAutoConvertibleFromFunction(final Class<?> clazz) {
        return getAdapterInfo(new Class<?>[] { clazz }).isAutoConvertibleFromFunction();
    }

    private static AdapterInfo getAdapterInfo(final Class<?>[] types) {
        final ClassAndLoader definingClassAndLoader = ClassAndLoader.getDefiningClassAndLoader(types);

        final Map<List<Class<?>>, AdapterInfo> adapterInfoMap = ADAPTER_INFO_MAPS.get(definingClassAndLoader.getRepresentativeClass());
        final List<Class<?>> typeList = types.length == 1 ? Collections.<Class<?>>singletonList(types[0]) : Arrays.asList(types.clone());
        AdapterInfo adapterInfo;
        synchronized(adapterInfoMap) {
            adapterInfo = adapterInfoMap.get(typeList);
            if(adapterInfo == null) {
                adapterInfo = createAdapterInfo(types, definingClassAndLoader);
                adapterInfoMap.put(typeList, adapterInfo);
            }
        }
        return adapterInfo;
    }

   
For a given class, create its adapter class and associated info.

Params:
  • types – the class and interfaces for which the adapter is created
Returns:the adapter info for the class.
/**
     * For a given class, create its adapter class and associated info.
     *
     * @param types the class and interfaces for which the adapter is created
     *
     * @return the adapter info for the class.
     */
    private static AdapterInfo createAdapterInfo(final Class<?>[] types, final ClassAndLoader definingClassAndLoader) {
        Class<?> superClass = null;
        final List<Class<?>> interfaces = new ArrayList<>(types.length);
        for(final Class<?> t: types) {
            final int mod = t.getModifiers();
            if(!t.isInterface()) {
                if(superClass != null) {
                    return new AdapterInfo(AdaptationResult.Outcome.ERROR_MULTIPLE_SUPERCLASSES, t.getCanonicalName() + " and " + superClass.getCanonicalName());
                }
                if (Modifier.isFinal(mod)) {
                    return new AdapterInfo(AdaptationResult.Outcome.ERROR_FINAL_CLASS, t.getCanonicalName());
                }
                superClass = t;
            } else {
                if (interfaces.size() > 65535) {
                    throw new IllegalArgumentException("interface limit exceeded");
                }

                interfaces.add(t);
            }

            if(!Modifier.isPublic(mod)) {
                return new AdapterInfo(AdaptationResult.Outcome.ERROR_NON_PUBLIC_CLASS, t.getCanonicalName());
            }
        }


        final Class<?> effectiveSuperClass = superClass == null ? Object.class : superClass;
        return AccessController.doPrivileged(new PrivilegedAction<AdapterInfo>() {
            @Override
            public AdapterInfo run() {
                try {
                    return new AdapterInfo(effectiveSuperClass, interfaces, definingClassAndLoader);
                } catch (final AdaptationException e) {
                    return new AdapterInfo(e.getAdaptationResult());
                } catch (final RuntimeException e) {
                    return new AdapterInfo(new AdaptationResult(Outcome.ERROR_OTHER, e, Arrays.toString(types), e.toString()));
                }
            }
        }, CREATE_ADAPTER_INFO_ACC_CTXT);
    }

    private static class AdapterInfo {
        private static final ClassAndLoader SCRIPT_OBJECT_LOADER = new ClassAndLoader(ScriptFunction.class, true);

        private final ClassLoader commonLoader;
        // TODO: soft reference the JavaAdapterClassLoader objects. They can be recreated when needed.
        private final JavaAdapterClassLoader classAdapterGenerator;
        private final JavaAdapterClassLoader instanceAdapterGenerator;
        private final Map<CodeSource, StaticClass> instanceAdapters = new ConcurrentHashMap<>();
        final boolean autoConvertibleFromFunction;
        final AdaptationResult adaptationResult;

        AdapterInfo(final Class<?> superClass, final List<Class<?>> interfaces, final ClassAndLoader definingLoader) throws AdaptationException {
            this.commonLoader = findCommonLoader(definingLoader);
            final JavaAdapterBytecodeGenerator gen = new JavaAdapterBytecodeGenerator(superClass, interfaces, commonLoader, false);
            this.autoConvertibleFromFunction = gen.isAutoConvertibleFromFunction();
            instanceAdapterGenerator = gen.createAdapterClassLoader();
            this.classAdapterGenerator = new JavaAdapterBytecodeGenerator(superClass, interfaces, commonLoader, true).createAdapterClassLoader();
            this.adaptationResult = AdaptationResult.SUCCESSFUL_RESULT;
        }

        AdapterInfo(final AdaptationResult.Outcome outcome, final String classList) {
            this(new AdaptationResult(outcome, classList));
        }

        AdapterInfo(final AdaptationResult adaptationResult) {
            this.commonLoader = null;
            this.classAdapterGenerator = null;
            this.instanceAdapterGenerator = null;
            this.autoConvertibleFromFunction = false;
            this.adaptationResult = adaptationResult;
        }

        StaticClass getAdapterClass(final ScriptObject classOverrides, final ProtectionDomain protectionDomain) {
            if(adaptationResult.getOutcome() != AdaptationResult.Outcome.SUCCESS) {
                throw adaptationResult.typeError();
            }
            return classOverrides == null ? getInstanceAdapterClass(protectionDomain) :
                getClassAdapterClass(classOverrides, protectionDomain);
        }

        boolean isAutoConvertibleFromFunction() {
            if(adaptationResult.getOutcome() == AdaptationResult.Outcome.ERROR_OTHER) {
                throw adaptationResult.typeError();
            }
            return autoConvertibleFromFunction;
        }

        private StaticClass getInstanceAdapterClass(final ProtectionDomain protectionDomain) {
            CodeSource codeSource = protectionDomain.getCodeSource();
            if(codeSource == null) {
                codeSource = MINIMAL_PERMISSION_DOMAIN.getCodeSource();
            }
            StaticClass instanceAdapterClass = instanceAdapters.get(codeSource);
            if(instanceAdapterClass != null) {
                return instanceAdapterClass;
            }
            // Any "unknown source" code source will default to no permission domain.
            final ProtectionDomain effectiveDomain = codeSource.equals(MINIMAL_PERMISSION_DOMAIN.getCodeSource()) ?
                    MINIMAL_PERMISSION_DOMAIN : protectionDomain;

            instanceAdapterClass = instanceAdapterGenerator.generateClass(commonLoader, effectiveDomain);
            final StaticClass existing = instanceAdapters.putIfAbsent(codeSource, instanceAdapterClass);
            return existing == null ? instanceAdapterClass : existing;
        }

        private StaticClass getClassAdapterClass(final ScriptObject classOverrides, final ProtectionDomain protectionDomain) {
            JavaAdapterServices.setClassOverrides(classOverrides);
            try {
                return classAdapterGenerator.generateClass(commonLoader, protectionDomain);
            } finally {
                JavaAdapterServices.setClassOverrides(null);
            }
        }

        
Choose between the passed class loader and the class loader that defines the
ScriptObject class, based on which of the two can see the classes in both.

Params:
  • classAndLoader – the loader and a representative class from it that will
       be used to add the generated adapter to its ADAPTER_INFO_MAPS.
Throws:
Returns:the class loader that sees both the specified class and Nashorn classes.
/**
         * Choose between the passed class loader and the class loader that defines the
         * ScriptObject class, based on which of the two can see the classes in both.
         *
         * @param classAndLoader the loader and a representative class from it that will
         *        be used to add the generated adapter to its ADAPTER_INFO_MAPS.
         *
         * @return the class loader that sees both the specified class and Nashorn classes.
         *
         * @throws IllegalStateException if no such class loader is found.
         */
        private static ClassLoader findCommonLoader(final ClassAndLoader classAndLoader) throws AdaptationException {
            if(classAndLoader.canSee(SCRIPT_OBJECT_LOADER)) {
                return classAndLoader.getLoader();
            }
            if (SCRIPT_OBJECT_LOADER.canSee(classAndLoader)) {
                return SCRIPT_OBJECT_LOADER.getLoader();
            }

            throw new AdaptationException(AdaptationResult.Outcome.ERROR_NO_COMMON_LOADER, classAndLoader.getRepresentativeClass().getCanonicalName());
        }
    }

    private static ProtectionDomain createMinimalPermissionDomain() {
        // Generated classes need to have at least the permission to access Nashorn runtime and runtime.linker packages.
        final Permissions permissions = new Permissions();
        permissions.add(new RuntimePermission("accessClassInPackage.jdk.nashorn.internal.runtime"));
        permissions.add(new RuntimePermission("accessClassInPackage.jdk.nashorn.internal.runtime.linker"));
        return new ProtectionDomain(new CodeSource(null, (CodeSigner[])null), permissions);
    }
}