GuiceConfigurer.java

/*
 * Copyright 2015 Petr Bouda
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the 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.
 */
package org.joyrest.guice;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.Set;

import org.joyrest.context.ApplicationContext;
import org.joyrest.context.configurer.AbstractConfigurer;
import org.joyrest.logging.JoyLogger;

import com.google.inject.ConfigurationException;
import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.Module;
import com.google.inject.TypeLiteral;

import static java.util.Objects.requireNonNull;
import static java.util.stream.Collectors.toList;

public class GuiceConfigurer extends AbstractConfigurer<Module> {

    private final static JoyLogger log = new JoyLogger(GuiceConfigurer.class);

    private Injector injector;

    @Override
    public ApplicationContext initialize(Module applicationConfig) {
        requireNonNull(applicationConfig, "Application module must be non-null for configuring Guice.");

        injector = Guice.createInjector(applicationConfig);
        return initializeContext();
    }

    @Override
    public <B> List<B> getBeans(Class<B> clazz) {
        return provide(new TypeLiteral<Set<B>>() {});
    }

    /*
     * dagger provides an unmodifiable nullable set and this method convert this to modifiable list with non-null elements
     */
    private <E> List<E> provide(TypeLiteral<Set<E>> type) {
        List<E> collection;
        try {
            Set<E> retrieved = injector.getInstance(Key.get(type));
            collection = retrieved.stream().filter(Objects::nonNull).collect(toList());

            if (collection.isEmpty()) {
                throw new ConfigurationException(new ArrayList<>());
            }

        } catch (ConfigurationException ce) {
            log.info(() -> "There is no registered instance of the type: ");
            collection = new ArrayList<>();
        }

        return collection;
    }
}