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/*
 *    DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 *    Copyright (c) [2019] Payara Foundation and/or its affiliates. All rights reserved.
 *
 *    The contents of this file are subject to the terms of either the GNU
 *    General Public License Version 2 only ("GPL") or the Common Development
 *    and Distribution License("CDDL") (collectively, the "License").  You
 *    may not use this file except in compliance with the License.  You can
 *    obtain a copy of the License at
 *    https://github.com/payara/Payara/blob/master/LICENSE.txt
 *    See the License for the specific
 *    language governing permissions and limitations under the License.
 *
 *    When distributing the software, include this License Header Notice in each
 *    file and include the License file at glassfish/legal/LICENSE.txt.
 *
 *    GPL Classpath Exception:
 *    The Payara Foundation designates this particular file as subject to the "Classpath"
 *    exception as provided by the Payara Foundation in the GPL Version 2 section of the License
 *    file that accompanied this code.
 *
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 */

package fish.payara.ejb.http.client.adapter;

import javax.naming.Context;
import javax.naming.NamingException;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;

/**
 * Adapter that allows composing multiple adapter implementations. {@Ccode CompositeClientAdapter}
 * invokes all registered adapters in order in which they were registered, and returns first non-empty match for a name.
 * 
Downstream adapters are registered by constructing a new {@link Builder}, or method {@link #newBuilder()}

 * 
Downstream adapters can also be customized by decorators provided by {@link ClientAdapterCustomizer}, which
 * allows separating name matching from proxy construction in adapters' implementations.

 * @see ClientAdapterCustomizer
 */
public final class CompositeClientAdapter implements ClientAdapter {
    private final List adapters;

    private CompositeClientAdapter(Builder builder) {
        this.adapters = new ArrayList<>(builder.adapters);
    }

    /**
     * Find a client adapter for handling specific {@code jndiName}. Composite client adapter will attempt invoking
     * {@link ClientAdapter#makeLocalProxy(String, Context)} for all registered adapters in order they were
     * registered in. The iteration ends when
     * 
    
     *     
  1. A registered adapter returns non-empty value; or
    2. 
     *     
  2. A registered adapter throws {@code NamingException}
    3. 
     *     
  3. All adapters are tried and return empty value
    4. 
     * 

     *
     * @param jndiName JNDI name that is being looked up
     * @param remoteContext EJB HTTP Client naming context for delegating the calls
     * @return adapter object if any of registered client adapters returns one, {@code Optional.empty()} otherwise
     * @throws NamingException if any of attempted client adapters throws one
     */
    @Override
    public Optional makeLocalProxy(String jndiName, Context remoteContext) throws NamingException {
        for (ClientAdapter adapter : adapters) {
            Optional result = adapter.makeLocalProxy(jndiName, remoteContext);
            if (result.isPresent()) {
                return result;
            }
        }
        return Optional.empty();
    }

    /**
     * Convenience method for constructing a {@link Builder}
     * @return new builder instance
     */
    public static Builder newBuilder() {
        return new Builder();
    }

    /**
     * Builder for composite Client Adapter.
     * 
Adapters can be registered in three ways:

     * 
    
     *     
  • {@link #register(ClientAdapter...)} : providing an instance
    • 
     *     
  • {@link #register(Class[])} : providing a class name. Class will be immediately instantiated via default constructor. 
    • 
     * 

     * Further customization of client adapter is possible by means of {@link ClientAdapterCustomizer}
     */
    public static final class Builder {
        private List adapters = new ArrayList<>();

        /**
         * Build resulting adapter.
         * @return new instance of CompositeClientAdapter
         */
        public CompositeClientAdapter build() {
            return new CompositeClientAdapter(this);
        }

        /**
         * Register new adapter by means of class name(s). Each class will be instantiated using default constructor.
         * @param adapterClasses adapter classes to register
         * @return this builder
         */
        public Builder register(Class... adapterClasses) {
            for (Class adapterClass : adapterClasses) {
                ClientAdapter instance = instantiate(adapterClass);
                register(instance);
            }
            return this;
        }

        /**
         * Register new adapter by means of instance(s).
         * @param adapterInstances adapter instances to register
         * @return this builder
         */
        public Builder register(ClientAdapter... adapterInstances) {
            Stream.of(adapterInstances).forEach(this::register);
            return this;
        }

        private void register(ClientAdapter adapterSupplier) {
            adapters.add(adapterSupplier);
        }

        static ClientAdapter instantiate(Class adapterClass) {
            try {
                return adapterClass.newInstance();
            } catch (InstantiationException | IllegalAccessException e) {
                throw new IllegalArgumentException("Cannot instantiate " + adapterClass.getName(), e);
            }
        }
    }

}
 















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