org.springframework.boot.builder.ParentContextApplicationContextInitializer.java Source code

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Here is the source code for org.springframework.boot.builder.ParentContextApplicationContextInitializer.java

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/*
 * Copyright 2012-2019 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.boot.builder;

import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.core.Ordered;

/**
 * {@link ApplicationContextInitializer} for setting the parent context. Also publishes
 * {@link ParentContextAvailableEvent} when the context is refreshed to signal to other
 * listeners that the context is available and has a parent.
 *
 * @author Dave Syer
 * @since 1.0.0
 */
public class ParentContextApplicationContextInitializer
        implements ApplicationContextInitializer<ConfigurableApplicationContext>, Ordered {

    private int order = Ordered.HIGHEST_PRECEDENCE;

    private final ApplicationContext parent;

    public ParentContextApplicationContextInitializer(ApplicationContext parent) {
        this.parent = parent;
    }

    public void setOrder(int order) {
        this.order = order;
    }

    @Override
    public int getOrder() {
        return this.order;
    }

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        if (applicationContext != this.parent) {
            applicationContext.setParent(this.parent);
            applicationContext.addApplicationListener(EventPublisher.INSTANCE);
        }
    }

    private static class EventPublisher implements ApplicationListener<ContextRefreshedEvent>, Ordered {

        private static final EventPublisher INSTANCE = new EventPublisher();

        @Override
        public int getOrder() {
            return Ordered.HIGHEST_PRECEDENCE;
        }

        @Override
        public void onApplicationEvent(ContextRefreshedEvent event) {
            ApplicationContext context = event.getApplicationContext();
            if (context instanceof ConfigurableApplicationContext && context == event.getSource()) {
                context.publishEvent(new ParentContextAvailableEvent((ConfigurableApplicationContext) context));
            }
        }

    }

    /**
     * {@link ApplicationEvent} fired when a parent context is available.
     */
    @SuppressWarnings("serial")
    public static class ParentContextAvailableEvent extends ApplicationEvent {

        public ParentContextAvailableEvent(ConfigurableApplicationContext applicationContext) {
            super(applicationContext);
        }

        public ConfigurableApplicationContext getApplicationContext() {
            return (ConfigurableApplicationContext) getSource();
        }

    }

}