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 * Copyright (c) 2012, 2019 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.jersey.server.internal.inject;

import java.lang.reflect.ParameterizedType;
import java.util.function.Function;

import javax.inject.Singleton;

import org.glassfish.jersey.internal.inject.Binding;
import org.glassfish.jersey.internal.inject.Bindings;
import org.glassfish.jersey.internal.inject.ContextInjectionResolver;
import org.glassfish.jersey.internal.inject.ForeignDescriptor;
import org.glassfish.jersey.internal.inject.Injectee;
import org.glassfish.jersey.internal.inject.InjecteeImpl;
import org.glassfish.jersey.internal.util.collection.Cache;
import org.glassfish.jersey.internal.util.collection.LazyValue;
import org.glassfish.jersey.process.internal.RequestScoped;
import org.glassfish.jersey.server.ContainerRequest;
import org.glassfish.jersey.server.model.Parameter;
import org.glassfish.jersey.model.Parameter.Source;
import org.glassfish.jersey.server.spi.internal.ValueParamProvider;

Value factory provider that delegates the injection target lookup to the underlying injection provider.
Author:
Marek Potociar, Jakub Podlesak/**
 * Value factory provider that delegates the injection target lookup to the underlying injection provider.
 *
 * @author Marek Potociar
 * @author Jakub Podlesak
 */
@Singleton
class DelegatedInjectionValueParamProvider implements ValueParamProvider {

    private final LazyValue<ContextInjectionResolver> resolver;

    private final Function<Binding, ForeignDescriptor> foreignDescriptorFactory;

    
Injection constructor.
Params:
resolver –                 context injection resolver.
foreignDescriptorFactory – function that is able to create a new foreign descriptor./**
     * Injection constructor.
     *
     * @param resolver                 context injection resolver.
     * @param foreignDescriptorFactory function that is able to create a new foreign descriptor.
     */
    public DelegatedInjectionValueParamProvider(LazyValue<ContextInjectionResolver> resolver,
            Function<Binding, ForeignDescriptor> foreignDescriptorFactory) {
        this.resolver = resolver;
        this.foreignDescriptorFactory = foreignDescriptorFactory;
    }

    @Override
    public Function<ContainerRequest, ?> getValueProvider(final Parameter parameter) {
        Source paramSource = parameter.getSource();
        if (paramSource == Parameter.Source.CONTEXT) {
            return containerRequest -> resolver.get().resolve(getInjectee(parameter));
        }
        return null;
    }

    @Override
    public PriorityType getPriority() {
        return Priority.LOW;
    }

    
Creates a new object Injectee corresponding to the injecting point. The injectee contains basic information about the injection point types and ForeignDescriptor of the underlying DI provider to make delegated injection resolver as simple as possible. 
Params:
parameter – jersey-like parameter corresponding to one resource-method's parameter.
Returns:
injectee instance as a source of the information about the injecting point./**
     * Creates a new object {@link Injectee} corresponding to the injecting point. The injectee contains basic information
     * about the injection point types and {@link ForeignDescriptor} of the underlying DI provider to make delegated injection
     * resolver as simple as possible.
     *
     * @param parameter jersey-like parameter corresponding to one resource-method's parameter.
     * @return injectee instance as a source of the information about the injecting point.
     */
    private Injectee getInjectee(Parameter parameter) {
        InjecteeImpl injectee = new InjecteeImpl();
        injectee.setRequiredType(parameter.getType());
        injectee.setInjecteeClass(parameter.getRawType());
        ForeignDescriptor proxyDescriptor = descriptorCache.apply(parameter);
        if (proxyDescriptor != null) {
            injectee.setInjecteeDescriptor(proxyDescriptor);
        }
        return injectee;
    }

    
We do not want to create a new descriptor instance for every and each method invocation. If the underlying DI descriptor ForeignDescriptor is already created for the given Parameter then used the already created descriptor. /**
     * We do not want to create a new descriptor instance for every and each method invocation.
     * If the underlying DI descriptor {@link ForeignDescriptor} is already created for the given {@link Parameter} then
     * used the already created descriptor.
     */
    private final Cache<Parameter, ForeignDescriptor> descriptorCache =
            new Cache<>(parameter -> {
                Class<?> rawType = parameter.getRawType();
                if (rawType.isInterface() && !(parameter.getType() instanceof ParameterizedType)) {
                    return createDescriptor(rawType);
                }
                return null;
            });

    
Method is able to create form incoming class and jersey descriptor a ForeignDescriptor which is provided by underlying DI provider. 
Params:
clazz – class from which jersey-like descriptor is created.
Returns:
foreign descriptor of the underlying DI provider./**
     * Method is able to create form incoming class and {@link Binding jersey descriptor} a {@link ForeignDescriptor} which is
     * provided by underlying DI provider.
     *
     * @param clazz class from which jersey-like descriptor is created.
     * @return foreign descriptor of the underlying DI provider.
     */
    private ForeignDescriptor createDescriptor(Class<?> clazz) {
        return foreignDescriptorFactory.apply(Bindings.serviceAsContract(clazz).in(RequestScoped.class));
    }
}