Java利用ShutDownHook关闭系统资源

客官°小女子只卖身不卖艺 2022-06-17 01:09 252阅读 0赞

## Java关闭钩子 ##

在Java程序中可以通过添加关闭钩子，实现在程序退出时关闭资源的功能。   
使用Runtime.addShutdownHook(Thread hook)向JVM添加关闭钩子

public void addShutdownHook(Thread hook) {
            SecurityManager sm = System.getSecurityManager();
            if (sm != null) {
                sm.checkPermission(new RuntimePermission("shutdownHooks"));
            }
            ApplicationShutdownHooks.add(hook);
        }
     
      
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ShutdownHook(Thread hook)方法，可以注册一个JVM关闭的钩子，这个钩子可以在以下几种场景被调用：   
1）程序正常退出   
2）使用System.exit()   
3）终端使用Ctrl+C触发的中断   
4）系统关闭   
5）使用Kill pid命令干掉进程

## 在Eclipse中使用关闭钩子 ##

在Eclipse中直接点击Terminate关闭程序时不会触发关闭钩子的。在Linux下使用kill -9也是不会触发钩子的

如果想在Eclipse中实现关闭钩子的功能，需要另起一个线程监听控制台，在控制台输入Enter时关闭系统

/** * 类描述： 输入Enter键关闭系统 * 创建人：王成委 * 创建时间：2015年6月8日 下午5:23:31 */
 public class ExitThread extends Thread { 
 private Log logger = LogFactory.getLog(getClass());
 
 public void run() {
 logger.info("press ENTER to call System.exit(0) "); 
 try {
 System.in.read();
 } catch (IOException e) { 
 e.printStackTrace();
 } 
 System.exit(0); 
 }
 
 }
 
 
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## Spring中关闭资源的配置 ##

在使用Spring时，可以在Bean中配置destroy-method来实现系统关闭时对Bean的一些处理。

<bean id="simpleHandler" class="com.tiamaes.gjds.socket.server.SimpleHanlder" destroy-method="destroy">
 <property name="annotationSocketServiceFactory" ref="annotationSocketServiceFactory" />
 </bean>
 
 
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//此方法需要声明void，并且没有任何参数
        public void destroy(){
            logger.info("Stop socket handler.");
        }
     
      
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## Java+Spring实现在程序退出时关闭Spring ##

/** * 类描述： 系统关闭钩子，用于关闭Spring资源 * 创建人：王成委 * 创建时间：2015年6月8日 下午5:06:46 */
 public class ShutDownHook extends Thread { 
 
 private Log logger = LogFactory.getLog(getClass());
 
 private ConfigurableApplicationContext applicationContext;
 
 public ShutDownHook(ConfigurableApplicationContext applicationContext ){
 super();
 this.applicationContext = applicationContext;
 }
 
 @Override 
 public void run() {
 logger.info("Start clean the login info.");
 //在系统关闭时，清理所有用户的登录状态
 TbDxpUserLoginStatusRepository repository = applicationContext.getBean(TbDxpUserLoginStatusRepository.class);
 repository.deleteAll();
 applicationContext.close();
 logger.info("Socket server shutdown");
 }
 }
 
 
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在ShutdownHook实例化时需要传入Spring上下文，在系统关闭时调用ApplicationContext的Close方法。

public static void main(String[] args) {
            ClassPathXmlApplicationContext ct = 
                    new ClassPathXmlApplicationContext("applicationContext.xml");
    
            Runtime.getRuntime().addShutdownHook(new ShutDownHook(ct));
    
            //在正式部署时不需要下面的代码，这段代码仅供调试时使用
            Thread thread = new ExitThread();
            thread.start();
        }
     
      
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最终效果如下

2015-06-09 09:43:51,233 INFO ClassPathXmlApplicationContext  - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@2e52cdcc: startup date [Tue Jun 09 09:43:51 CST 2015]; root of context hierarchy 2015-06-09 09:43:52,263 INFO XmlBeanDefinitionReader - Loading XML bean definitions from class path resource [applicationContext.xml] 2015-06-09 09:43:55,559 INFO XmlBeanDefinitionReader - Loading XML bean definitions from class path resource [applicationContext-service.xml] 2015-06-09 09:43:55,724 INFO XmlBeanDefinitionReader - Loading XML bean definitions from class path resource [applicationContext-db.xml] 2015-06-09 09:44:01,358 INFO PropertyPlaceholderConfigurer - Loading properties file from class path resource [jdbc.properties] 2015-06-09 09:44:02,687 INFO MLog - MLog clients using slf4j logging. 2015-06-09 09:44:06,563 INFO C3P0Registry - Initializing c3p0-0.9.5-pre9 [built 08-October-2014 03:06:08 -0700; debug? true; trace: 10] 2015-06-09 09:44:08,930 INFO LocalContainerEntityManagerFactoryBean - Building JPA container EntityManagerFactory for persistence unit 'Oracle' 2015-06-09 09:44:09,251 INFO LogHelper - HHH000204: Processing PersistenceUnitInfo [
        name: Oracle
        ...] 2015-06-09 09:44:13,400 INFO Version - HHH000412: Hibernate Core {4.3.7.Final} 2015-06-09 09:44:13,404 INFO Environment - HHH000206: hibernate.properties not found 2015-06-09 09:44:13,439 INFO Environment - HHH000021: Bytecode provider name : javassist 2015-06-09 09:44:15,016 INFO Version - HCANN000001: Hibernate Commons Annotations {4.0.5.Final} 2015-06-09 09:44:15,660 INFO Dialect - HHH000400: Using dialect: org.hibernate.dialect.Oracle10gDialect 2015-06-09 09:44:15,739 INFO LobCreatorBuilder - HHH000422: Disabling contextual LOB creation as connection was null 2015-06-09 09:44:16,056 INFO ASTQueryTranslatorFactory - HHH000397: Using ASTQueryTranslatorFactory 2015-06-09 09:44:21,032 INFO EhCacheManagerFactoryBean - Initializing EhCache CacheManager 2015-06-09 09:44:21,977 INFO ExitThread - press ENTER to call System.exit(0) 2015-06-09 09:54:23,694 INFO ShutDownHook - Start clean the login info. 2015-06-09 09:54:23,787 INFO AbstractPoolBackedDataSource - Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 5, acquireRetryAttempts -> 0, acquireRetryDelay -> 1000, autoCommitOnClose -> true, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 5000, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, contextClassLoaderSource -> caller, dataSourceName -> 1hge7dt991ndh1jygiycad|7402fff0, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> oracle.jdbc.OracleDriver, extensions -> {}, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, forceUseNamedDriverClass -> false, identityToken -> 1hge7dt991ndh1jygiycad|7402fff0, idleConnectionTestPeriod -> 0, initialPoolSize -> 5, jdbcUrl -> jdbc:oracle:thin:@192.168.57.62:1521:orcl, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 36000, maxIdleTimeExcessConnections -> 1800, maxPoolSize -> 20, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 5, numHelperThreads -> 3, preferredTestQuery -> null, privilegeSpawnedThreads -> false, properties -> {user=******, password=******}, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, userOverrides -> {}, usesTraditionalReflectiveProxies -> false ] Hibernate: select tbdxpuserl0_.SESSION_ID as SESSION_ID1_1_, tbdxpuserl0_.CREATE_TIME as CREATE_TIME2_1_, tbdxpuserl0_.IP_ADDR as IP_ADDR3_1_, tbdxpuserl0_.LOGIN_TIME as LOGIN_TIME4_1_, tbdxpuserl0_.status as status5_1_, tbdxpuserl0_.USER_ID as USER_ID6_1_, tbdxpuserl0_.username as username7_1_ from TB_DXP_USER_LOGIN_STATUS tbdxpuserl0_ 2015-06-09 09:54:25,555 INFO ClassPathXmlApplicationContext - Closing org.springframework.context.support.ClassPathXmlApplicationContext@2e52cdcc: startup date [Tue Jun 09 09:43:51 CST 2015]; root of context hierarchy 2015-06-09 09:54:25,556 INFO EhCacheManagerFactoryBean - Shutting down EhCache CacheManager 2015-06-09 09:54:25,574 INFO SimpleHanlder - Stop socket handler. 2015-06-09 09:54:25,576 INFO LocalContainerEntityManagerFactoryBean - Closing JPA EntityManagerFactory for persistence unit 'Oracle' 2015-06-09 09:54:25,579 INFO ShutDownHook - Socket server shutdown 
     
      
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此方法可以实现在系统退出时对资源的关闭及缓存数据清理等功能，是一个非常使用的功能。