io.jmnarloch.spring.cloud.discovery.DiscoveryClientPropertySourceConfigurer.java Source code

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Here is the source code for io.jmnarloch.spring.cloud.discovery.DiscoveryClientPropertySourceConfigurer.java

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/**
 * Copyright (c) 2015 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
 *
 * 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 io.jmnarloch.spring.cloud.discovery;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
import org.springframework.boot.context.event.ApplicationPreparedEvent;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.Ordered;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.PropertySource;
import org.springframework.core.env.StandardEnvironment;

/**
 * An custom {@link ApplicationEvent} listener that plugs in into Spring Boot
 * {@link org.springframework.core.env.Environment} initialization phase and register custom
 * {@link DiscoveryClientPropertySource}.
 *
 * @author Jakub Narloch
 * @see DiscoveryClientPropertySource
 */
public class DiscoveryClientPropertySourceConfigurer implements ApplicationListener<ApplicationEvent>, Ordered {

    /**
     * {@inheritDoc}
     */
    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof ApplicationEnvironmentPreparedEvent) {
            configurePropertySources(((ApplicationEnvironmentPreparedEvent) event).getEnvironment());
        } else if (event instanceof ApplicationPreparedEvent) {
            registerPostProcessors(((ApplicationPreparedEvent) event).getApplicationContext());
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int getOrder() {
        return HIGHEST_PRECEDENCE + 100;
    }

    /**
     * Configures the property sources
     *
     * @param environment the application environment
     */
    protected void configurePropertySources(ConfigurableEnvironment environment) {
        environment.getPropertySources().addAfter(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,
                new DiscoveryClientPropertySource("discoveryClient"));
    }

    /**
     * Registers bean post processors.
     *
     * @param applicationContext the application context
     */
    protected void registerPostProcessors(ConfigurableApplicationContext applicationContext) {
        applicationContext.addBeanFactoryPostProcessor(new DiscoveryPropertySourceInitializer(applicationContext));
    }

    /**
     * Initializes the {@link DiscoveryClientPropertySource} by injecting into them
     * {@link org.springframework.context.ApplicationContext}.
     *
     * @author Jakub Narloch
     */
    private class DiscoveryPropertySourceInitializer implements BeanFactoryPostProcessor, Ordered {

        /**
         * The application context.
         */
        private ConfigurableApplicationContext applicationContext;

        /**
         * Creates new instance of {@link DiscoveryClientPropertySourceConfigurer}.
         *
         * @param applicationContext the application context
         */
        public DiscoveryPropertySourceInitializer(ConfigurableApplicationContext applicationContext) {
            this.applicationContext = applicationContext;
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
            initialize(applicationContext.getEnvironment());
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public int getOrder() {
            return HIGHEST_PRECEDENCE;
        }

        /**
         * Initializes the {@link DiscoveryClientPropertySource}.
         *
         * @param environment the environment
         */
        protected void initialize(ConfigurableEnvironment environment) {
            for (PropertySource<?> propertySource : environment.getPropertySources()) {
                if (propertySource instanceof DiscoveryClientPropertySource) {
                    ((DiscoveryClientPropertySource) propertySource).setApplicationContext(applicationContext);
                }
            }
        }
    }
}