dynalink/beans/BeansLinker.java

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/*
 * This file is available under and governed by the GNU General Public
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 * However, the following notice accompanied the original version of this
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/*
   Copyright 2009-2013 Attila Szegedi

   Licensed under both the Apache License, Version 2.0 (the "Apache License")
   and the BSD License (the "BSD License"), with licensee being free to
   choose either of the two at their discretion.

   You may not use this file except in compliance with either the Apache
   License or the BSD License.

   If you choose to use this file in compliance with the Apache License, the
   following notice applies to you:

       You may obtain a copy of the Apache License at

           http://www.apache.org/licenses/LICENSE-2.0

       Unless required by applicable law or agreed to in writing, software
       distributed under the License is distributed on an "AS IS" BASIS,
       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
       implied. See the License for the specific language governing
       permissions and limitations under the License.

   If you choose to use this file in compliance with the BSD License, the
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       modification, are permitted provided that the following conditions are
       met:
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         notice, this list of conditions and the following disclaimer.
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*/

package jdk.dynalink.beans;

import java.lang.invoke.MethodHandles.Lookup;
import java.util.Collections;
import java.util.Set;
import jdk.dynalink.DynamicLinkerFactory;
import jdk.dynalink.StandardNamespace;
import jdk.dynalink.StandardOperation;
import jdk.dynalink.linker.GuardedInvocation;
import jdk.dynalink.linker.GuardingDynamicLinker;
import jdk.dynalink.linker.LinkRequest;
import jdk.dynalink.linker.LinkerServices;
import jdk.dynalink.linker.TypeBasedGuardingDynamicLinker;

/**
 * A linker for ordinary Java objects. Normally used as the ultimate fallback
 * linker by the {@link DynamicLinkerFactory} so it is given the chance to link
 * calls to all objects that no other linker recognized. Specifically, this
 * linker will:
 * <ul>
 * <li>expose all public methods of form {@code setXxx()}, {@code getXxx()},
 * and {@code isXxx()} as property setters and getters for
 * {@link StandardOperation#SET} and {@link StandardOperation#GET} operations in the
 * {@link StandardNamespace#PROPERTY} namespace;</li>
 * <li>expose all public methods for retrieval for
 * {@link StandardOperation#GET} operation in the {@link StandardNamespace#METHOD} namespace;
 * the methods thus retrieved can then be invoked using {@link StandardOperation#CALL}.</li>
 * <li>expose all public fields as properties, unless there are getters or
 * setters for the properties of the same name;</li>
 * <li> expose elements of native Java arrays, {@link java.util.List} and {@link java.util.Map} objects as
 * {@link StandardOperation#GET} and {@link StandardOperation#SET} operations in the
 * {@link StandardNamespace#ELEMENT} namespace;</li>
 * <li>expose a virtual property named {@code length} on Java arrays, {@link java.util.Collection} and
 * {@link java.util.Map} objects;</li>
 * <li>expose {@link StandardOperation#NEW} on instances of {@link StaticClass}
 * as calls to constructors, including those static class objects that represent
 * Java arrays (their constructors take a single {@code int} parameter
 * representing the length of the array to create);</li>
 * <li>expose static methods, fields, and properties of classes in a similar
 * manner to how instance method, fields, and properties are exposed, on
 * {@link StaticClass} objects.</li>
 * <li>expose a virtual property named {@code static} on instances of
 * {@link java.lang.Class} to access their {@link StaticClass}.</li>
 * </ul>
 * <p><strong>Overloaded method resolution</strong> is performed automatically
 * for property setters, methods, and constructors. Additionally, manual
 * overloaded method selection is supported by having a call site specify a name
 * for a method that contains an explicit signature, e.g.
 * {@code StandardOperation.GET.withNamespace(METHOD).named("parseInt(String,int)")}
 * You can use non-qualified class names in such signatures regardless of those
 * classes' packages, they will match any class with the same non-qualified name. You
 * only have to use a fully qualified class name in case non-qualified class
 * names would cause selection ambiguity (that is extremely rare). Overloaded
 * resolution for constructors is not automatic as there is no logical place to
 * attach that functionality to but if a language wishes to provide this
 * functionality, it can use {@link #getConstructorMethod(Class, String)} as a
 * useful building block for it.</p>
 * <p><strong>Variable argument invocation</strong> is handled for both methods
 * and constructors.</p>
 * <p><strong>Caller sensitive methods</strong> can be linked as long as they
 * are otherwise public and link requests have call site descriptors carrying
 * full-strength {@link Lookup} objects and not weakened lookups or the public
 * lookup.</p>
 * <p><strong>The behavior for handling missing members</strong> can be
 * customized by passing a {@link MissingMemberHandlerFactory} to the
 * {@link BeansLinker#BeansLinker(MissingMemberHandlerFactory) constructor}.
 * </p>
 * <p>The class also exposes various methods for discovery of available
 * property and method names on classes and class instances, as well as access
 * to per-class linkers using the {@link #getLinkerForClass(Class)}
 * method.</p>
 */
public class BeansLinker implements GuardingDynamicLinker {
    private static final ClassValue<TypeBasedGuardingDynamicLinker> linkers = new ClassValue<TypeBasedGuardingDynamicLinker>() {
        @Override
        protected TypeBasedGuardingDynamicLinker computeValue(final Class<?> clazz) {
            // If ClassValue.put() were public, we could just pre-populate with these known mappings...
            return
                clazz == Class.class ? new ClassLinker() :
                clazz == StaticClass.class ? new StaticClassLinker() :
                DynamicMethod.class.isAssignableFrom(clazz) ? new DynamicMethodLinker() :
                new BeanLinker(clazz);
        }
    };

    private final MissingMemberHandlerFactory missingMemberHandlerFactory;

    /**
     * Creates a new beans linker. Equivalent to
     * {@link BeansLinker#BeansLinker(MissingMemberHandlerFactory)} with
     * {@code null} passed as the missing member handler factory, resulting in
     * the default behavior for linking and evaluating missing members.
     */
    public BeansLinker() {
        this(null);
    }

    /**
     * Creates a new beans linker with the specified factory for creating
     * missing member handlers. The passed factory can be null if the default
     * behavior is adequate. See {@link MissingMemberHandlerFactory} for details.
     * @param missingMemberHandlerFactory a factory for creating handlers for
     * operations on missing members.
     */
    public BeansLinker(final MissingMemberHandlerFactory missingMemberHandlerFactory) {
        this.missingMemberHandlerFactory = missingMemberHandlerFactory;
    }

    /**
     * Returns a bean linker for a particular single class. Useful when you need
     * to override or extend the behavior of linking for some classes in your
     * language runtime's linker, but still want to delegate to the default
     * behavior in some cases.
     * @param clazz the class
     * @return a bean linker for that class
     */
    public TypeBasedGuardingDynamicLinker getLinkerForClass(final Class<?> clazz) {
        final TypeBasedGuardingDynamicLinker staticLinker = getStaticLinkerForClass(clazz);
        if (missingMemberHandlerFactory == null) {
            return staticLinker;
        }
        return new NoSuchMemberHandlerBindingLinker(staticLinker, missingMemberHandlerFactory);
    }

    private static class NoSuchMemberHandlerBindingLinker implements TypeBasedGuardingDynamicLinker {
        private final TypeBasedGuardingDynamicLinker linker;
        private final MissingMemberHandlerFactory missingMemberHandlerFactory;

        NoSuchMemberHandlerBindingLinker(final TypeBasedGuardingDynamicLinker linker, final MissingMemberHandlerFactory missingMemberHandlerFactory) {
            this.linker = linker;
            this.missingMemberHandlerFactory = missingMemberHandlerFactory;
        }

        @Override
        public boolean canLinkType(final Class<?> type) {
            return linker.canLinkType(type);
        }

        @Override
        public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices) throws Exception {
            return linker.getGuardedInvocation(linkRequest,
                    LinkerServicesWithMissingMemberHandlerFactory.get(
                            linkerServices, missingMemberHandlerFactory));
        }
    }

    static TypeBasedGuardingDynamicLinker getStaticLinkerForClass(final Class<?> clazz) {
        return linkers.get(clazz);
    }

    /**
     * Returns true if the object is a Java dynamic method (e.g., one
     * obtained through a {@code GET:METHOD} operation on a Java object or
     * {@link StaticClass} or through
     * {@link #getConstructorMethod(Class, String)}.
     *
     * @param obj the object we want to test for being a Java dynamic method.
     * @return true if it is a dynamic method, false otherwise.
     */
    public static boolean isDynamicMethod(final Object obj) {
        return obj instanceof DynamicMethod;
    }

    /**
     * Returns true if the object is a Java constructor (obtained through
     * {@link #getConstructorMethod(Class, String)}}.
     *
     * @param obj the object we want to test for being a Java constructor.
     * @return true if it is a constructor, false otherwise.
     */
    public static boolean isDynamicConstructor(final Object obj) {
        return obj instanceof DynamicMethod && ((DynamicMethod)obj).isConstructor();
    }

    /**
     * Return the dynamic method of constructor of the given class and the given
     * signature. This method is useful for exposing a functionality for
     * selecting an overloaded constructor based on an explicit signature, as
     * this functionality is not otherwise exposed by Dynalink as
     * {@link StaticClass} objects act as overloaded constructors without
     * explicit signature selection. Example usage would be:
     * {@code getConstructorMethod(java.awt.Color.class, "int, int, int")}.
     * @param clazz the class
     * @param signature full signature of the constructor. Note how you can use
     * names of primitive types, array names with normal Java notation (e.g.
     * {@code "int[]"}), and normally you can even use unqualified class names
     * (e.g. {@code "String, List"} instead of
     * {@code "java.lang.String, java.util.List"} as long as they don't cause
     * ambiguity in the specific parameter position.
     * @return dynamic method for the constructor or null if no constructor with
     * the specified signature exists.
     */
    public static Object getConstructorMethod(final Class<?> clazz, final String signature) {
        return StaticClassLinker.getConstructorMethod(clazz, signature);
    }

    /**
     * Returns a set of names of all readable instance properties of a class.
     * @param clazz the class
     * @return a set of names of all readable instance properties of a class.
     */
    public static Set<String> getReadableInstancePropertyNames(final Class<?> clazz) {
        final TypeBasedGuardingDynamicLinker linker = getStaticLinkerForClass(clazz);
        if(linker instanceof BeanLinker) {
            return ((BeanLinker)linker).getReadablePropertyNames();
        }
        return Collections.emptySet();
    }

    /**
     * Returns a set of names of all writable instance properties of a class.
     * @param clazz the class
     * @return a set of names of all writable instance properties of a class.
     */
    public static Set<String> getWritableInstancePropertyNames(final Class<?> clazz) {
        final TypeBasedGuardingDynamicLinker linker = getStaticLinkerForClass(clazz);
        if(linker instanceof BeanLinker) {
            return ((BeanLinker)linker).getWritablePropertyNames();
        }
        return Collections.emptySet();
    }

    /**
     * Returns a set of names of all instance methods of a class.
     * @param clazz the class
     * @return a set of names of all instance methods of a class.
     */
    public static Set<String> getInstanceMethodNames(final Class<?> clazz) {
        final TypeBasedGuardingDynamicLinker linker = getStaticLinkerForClass(clazz);
        if(linker instanceof BeanLinker) {
            return ((BeanLinker)linker).getMethodNames();
        }
        return Collections.emptySet();
    }

    /**
     * Returns a set of names of all readable static properties of a class.
     * @param clazz the class
     * @return a set of names of all readable static properties of a class.
     */
    public static Set<String> getReadableStaticPropertyNames(final Class<?> clazz) {
        return StaticClassLinker.getReadableStaticPropertyNames(clazz);
    }

    /**
     * Returns a set of names of all writable static properties of a class.
     * @param clazz the class
     * @return a set of names of all writable static properties of a class.
     */
    public static Set<String> getWritableStaticPropertyNames(final Class<?> clazz) {
        return StaticClassLinker.getWritableStaticPropertyNames(clazz);
    }

    /**
     * Returns a set of names of all static methods of a class.
     * @param clazz the class
     * @return a set of names of all static methods of a class.
     */
    public static Set<String> getStaticMethodNames(final Class<?> clazz) {
        return StaticClassLinker.getStaticMethodNames(clazz);
    }

    @Override
    public GuardedInvocation getGuardedInvocation(final LinkRequest request, final LinkerServices linkerServices)
            throws Exception {
        final Object receiver = request.getReceiver();
        if(receiver == null) {
            // Can't operate on null
            return null;
        }
        return getLinkerForClass(receiver.getClass()).getGuardedInvocation(request,
                LinkerServicesWithMissingMemberHandlerFactory.get(linkerServices,
                        missingMemberHandlerFactory));
    }
}