org.springframework.cloud.context.scope.refresh.RefreshScope Maven / Gradle / Ivy

/*
 * 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.cloud.context.scope.refresh;

import java.io.Serializable;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.cloud.context.scope.GenericScope;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.core.Ordered;
import org.springframework.jmx.export.annotation.ManagedOperation;
import org.springframework.jmx.export.annotation.ManagedResource;

/**
 * 
 * A Scope implementation that allows for beans to be refreshed dynamically at runtime
 * (see {@link #refresh(String)} and {@link #refreshAll()}). If a bean is refreshed then
 * the next time the bean is accessed (i.e. a method is executed) a new instance is
 * created. All lifecycle methods are applied to the bean instances, so any destruction
 * callbacks that were registered in the bean factory are called when it is refreshed, and
 * then the initialization callbacks are invoked as normal when the new instance is
 * created. A new bean instance is created from the original bean definition, so any
 * externalized content (property placeholders or expressions in string literals) is
 * re-evaluated when it is created.
 * 
 *
 * 
 * Note that all beans in this scope are only initialized when first accessed, so
 * the scope forces lazy initialization semantics.
 * 
 *
 * 
 * The scoped proxy approach adopted here has a side benefit that bean instances are
 * automatically {@link Serializable}, and can be sent across the wire as long as the
 * receiver has an identical application context on the other side. To ensure that the two
 * contexts agree that they are identical, they have to have the same serialization ID.
 * One will be generated automatically by default from the bean names, so two contexts
 * with the same bean names are by default able to exchange beans by name. If you need to
 * override the default ID, then provide an explicit {@link #setId(String) id} when the
 * Scope is declared.
 * 
 *
 * @author Dave Syer
 * @since 3.1
 *
 */
@ManagedResource
public class RefreshScope extends GenericScope implements ApplicationContextAware,
		ApplicationListener, Ordered {

	private ApplicationContext context;

	private BeanDefinitionRegistry registry;

	private boolean eager = true;

	private int order = Ordered.LOWEST_PRECEDENCE - 100;

	/**
	 * Creates a scope instance and gives it the default name: "refresh".
	 */
	public RefreshScope() {
		super.setName("refresh");
	}

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

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

	/**
	 * Flag to determine whether all beans in refresh scope should be instantiated eagerly
	 * on startup. Default true.
	 * @param eager The flag to set.
	 */
	public void setEager(boolean eager) {
		this.eager = eager;
	}

	@Override
	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
			throws BeansException {
		this.registry = registry;
		super.postProcessBeanDefinitionRegistry(registry);
	}

	@Override
	public void onApplicationEvent(ContextRefreshedEvent event) {
		start(event);
	}

	public void start(ContextRefreshedEvent event) {
		if (event.getApplicationContext() == this.context && this.eager
				&& this.registry != null) {
			eagerlyInitialize();
		}
	}

	private void eagerlyInitialize() {
		for (String name : this.context.getBeanDefinitionNames()) {
			BeanDefinition definition = this.registry.getBeanDefinition(name);
			if (this.getName().equals(definition.getScope())
					&& !definition.isLazyInit()) {
				Object bean = this.context.getBean(name);
				if (bean != null) {
					bean.getClass();
				}
			}
		}
	}

	@ManagedOperation(description = "Dispose of the current instance of bean name "
			+ "provided and force a refresh on next method execution.")
	public boolean refresh(String name) {
		if (!name.startsWith(SCOPED_TARGET_PREFIX)) {
			// User wants to refresh the bean with this name but that isn't the one in the
			// cache...
			name = SCOPED_TARGET_PREFIX + name;
		}
		// Ensure lifecycle is finished if bean was disposable
		if (super.destroy(name)) {
			this.context.publishEvent(new RefreshScopeRefreshedEvent(name));
			return true;
		}
		return false;
	}

	@ManagedOperation(description = "Dispose of the current instance of all beans "
			+ "in this scope and force a refresh on next method execution.")
	public void refreshAll() {
		super.destroy();
		this.context.publishEvent(new RefreshScopeRefreshedEvent());
	}

	@Override
	public void setApplicationContext(ApplicationContext context) throws BeansException {
		this.context = context;
	}

}