springboot几种优雅关闭服务的方式

通过kill pid命令可触发的关闭服务资源的几种方式，kill -9 pid 无法触发！

1.JVM自带的shutdownHook

Runtime.getRuntime().addShutdownHook(new Thread(() -> log.info("shutdown！！！")));

比如在启动函数中添加：

@SpringBootApplication
@Slf4j
public class WebApplication {
    public static void main(String[] args) {
        java.lang.Runtime.getRuntime().addShutdownHook(new Thread(()->{
            log.info("程序退出啦!");
        }));
        SpringApplication.run(WebApplication.class, args);
    }
}

2.实现DisposableBean接口

/*
 * Copyright 2002-2018 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.beans.factory;

/**
 * Interface to be implemented by beans that want to release resources on destruction.
 * A {@link BeanFactory} will invoke the destroy method on individual destruction of a
 * scoped bean. An {@link org.springframework.context.ApplicationContext} is supposed
 * to dispose all of its singletons on shutdown, driven by the application lifecycle.
 *
 * <p>A Spring-managed bean may also implement Java's {@link AutoCloseable} interface
 * for the same purpose. An alternative to implementing an interface is specifying a
 * custom destroy method, for example in an XML bean definition. For a list of all
 * bean lifecycle methods, see the {@link BeanFactory BeanFactory javadocs}.
 * 
 * @author Juergen Hoeller
 * @since 12.08.2003
 * @see InitializingBean
 * @see org.springframework.beans.factory.support.RootBeanDefinition#getDestroyMethodName()
 * @see org.springframework.beans.factory.config.ConfigurableBeanFactory#destroySingletons()
 * @see org.springframework.context.ConfigurableApplicationContext#close()
 */
//由想要在销毁时释放资源的 Bean 实现的接口。BeanFactory 将在单个销毁作用域内的 Bean 时调用 destroy 方法。一个组织 springframework。上下文。ApplicationContext 应该在关闭时释放其所有单例，由应用程序生命周期驱动。Spring 管理的 bean 也可以出于相同的目的实现 Java 的 AutoCloseable 接口。实现接口的替代方法是指定自定义销毁方法，例如在 XML Bean 定义中。有关所有 Bean 生命周期方法的列表，请参阅 BeanFactory javadocs。
public interface DisposableBean {

    /**
     * Invoked by the containing {@code BeanFactory} on destruction of a bean.
     * @throws Exception in case of shutdown errors. Exceptions will get logged
     * but not rethrown to allow other beans to release their resources as well.
     */
  //由包含的 BeanFactory 在销毁 Bean 时调用。抛出：异常 – 在发生关机错误的情况下。异常将被记录，但不会被重新抛出，以允许其他 Bean 也释放其资源。
    void destroy() throws Exception;
}

3.监听spring的ContextClosedEvent

spring提供了各种监听事件，可以参照以下示例（内容来自Spring官网)

实现ApplicationListener接口，监听ContextClosedEvent

@Component
@Slf4j
public class ShutdownListener implements ApplicationListener<ContextClosedEvent> {
    @Override
    public void onApplicationEvent(ContextClosedEvent event) {
        log.info("shutdown!!! ");  
    }
}

4.使用注解@PreDestroy

javax.annotation.PreDestroy,

/**
 * The PreDestroy annotation is used on methods as a callback notification to
 * signal that the instance is in the process of being removed by the
 * container. The method annotated with PreDestroy is typically used to
 * release resources that it has been holding. This annotation MUST be
 * supported by all container managed objects that support PostConstruct
 * except the application client container in Java EE 5. The method on which
 * the PreDestroy annotation is applied MUST fulfill all of the following
 * criteria:
 * <p>
 * <ul>
 * <li>The method MUST NOT have any parameters except in the case of
 * interceptors in which case it takes an InvocationContext object as
 * defined by the Interceptors specification.</li>
 * <li>The method defined on an interceptor class MUST HAVE one of the
 * following signatures:
 * <p>
 * void &#060;METHOD&#062;(InvocationContext)
 * <p>
 * Object &#060;METHOD&#062;(InvocationContext) throws Exception
 * <p>
 * <i>Note: A PreDestroy interceptor method must not throw application
 * exceptions, but it may be declared to throw checked exceptions including
 * the java.lang.Exception if the same interceptor method interposes on
 * business or timeout methods in addition to lifecycle events. If a
 * PreDestroy interceptor method returns a value, it is ignored by
 * the container.</i>
 * </li>
 * <li>The method defined on a non-interceptor class MUST HAVE the
 * following signature:
 * <p>
 * void &#060;METHOD&#062;()
 * </li>
 * <li>The method on which PreDestroy is applied MAY be public, protected,
 * package private or private.</li>
 * <li>The method MUST NOT be static.</li>
 * <li>The method MAY be final.</li>
 * <li>If the method throws an unchecked exception it is ignored except in the
 * case of EJBs where the EJB can handle exceptions.</li>
 * </ul>
 *
 * @see javax.annotation.PostConstruct
 * @see javax.annotation.Resource
 * @since Common Annotations 1.0
 */

@Documented
@Retention (RUNTIME)
@Target(METHOD)
public @interface PreDestroy {
}

PreDestroy 注释在方法上用作回调通知，以指示实例正在被容器删除。使用 PreDestroy 批注的方法通常用于释放它一直持有的资源。除 Java EE 5 中的应用程序客户机容器外，所有支持 PostConstruct 的容器托管对象都必须支持此注释。

使用如下：

    @PreDestroy
    public void destroy() {
        log.info("Pre destroy shutdown!!! ");
    }

对于@PreDestroy会存在一个不生效的情况，对于Scope为prototype的bean，Spring不会调用@PreDestory标记的方法。