java - 在 spring-mvc 应用程序开始时运行一个类

Question

在spring mvc中是否可以在应用启动时运行一个类我想在那个类中初始化一个线程？？

或者有什么办法..？

                public class MyServletContextListener implements Runnable {



            public void run() {

                while (true) {

                try {
                    System.out.println("Inside run()");
                    Thread.sleep(10000);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                }


            }

            }

我在添加 ApplicationListener 接口(interface)后得到的输出

            NFO: HHH000206: hibernate.properties not found
            Jul 24, 2017 8:42:33 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
            INFO: HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
            Jul 24, 2017 8:42:35 PM org.hibernate.dialect.Dialect <init>
            INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQL5Dialect
            Jul 24, 2017 8:42:36 PM org.hibernate.engine.jdbc.env.internal.LobCreatorBuilderImpl useContextualLobCreation
            INFO: HHH000423: Disabling contextual LOB creation as JDBC driver reported JDBC version [3] less than 4

            Thread Started
            getApplicationName() : /Hibernate_webservice
            getId() : org.springframework.web.context.WebApplicationContext:/Hibernate_webservice
            getParent() : null
            getDisplayName() : Root WebApplicationContext


            Jul 24, 2017 8:42:38 PM org.springframework.web.context.ContextLoader initWebApplicationContext
            INFO: Root WebApplicationContext: initialization completed in 8880 ms
            Jul 24, 2017 8:42:38 PM org.apache.catalina.core.ApplicationContext log
            INFO: Initializing Spring FrameworkServlet 'appServlet'
            Jul 24, 2017 8:42:38 PM org.springframework.web.servlet.DispatcherServlet initServletBean
            INFO: FrameworkServlet 'appServlet': initialization started
            Jul 24, 2017 8:42:38 PM org.springframework.web.context.support.XmlWebApplicationContext prepareRefresh
            INFO: Refreshing WebApplicationContext for namespace 'appServlet-servlet': startup date [Mon Jul 24 20:42:38 IST 2017]; parent: Root WebApplicationContext
            Jul 24, 2017 8:42:38 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
            INFO: Loading XML bean definitions from ServletContext resource [/WEB-INF/spring-config.xml]
            Jul 24, 2017 8:42:38 PM org.springframework.context.support.PropertySourcesPlaceholderConfigurer loadProperties
            INFO: Loading properties file from class path resource [application.properties]
            Jul 24, 2017 8:42:38 PM org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor <init>
            INFO: JSR-330 'javax.inject.Inject' annotation found and supported for autowiring
            Jul 24, 2017 8:42:38 PM org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping registerHandlerMethod
            INFO: Mapped "{[/form],methods=[],params=[],headers=[],consumes=[],produces=[],custom=[]}" onto public org.springframework.web.servlet.ModelAndView sample.test.TestController.method()
            Jul 24, 2017 8:42:39 PM org.hibernate.dialect.Dialect <init>
            INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQL5Dialect
            Jul 24, 2017 8:42:39 PM org.hibernate.engine.jdbc.env.internal.LobCreatorBuilderImpl useContextualLobCreation
            INFO: HHH000423: Disabling contextual LOB creation as JDBC driver reported JDBC version [3] less than 4

            Thread Started
            getApplicationName() : /Hibernate_webservice
            getId() : org.springframework.web.context.WebApplicationContext:/Hibernate_webservice/appServlet
            getParent() : Root WebApplicationContext: startup date [Mon Jul 24 20:42:30 IST 2017]; root of context hierarchy
            getDisplayName() : WebApplicationContext for namespace 'appServlet-servlet'



            Thread Started
            getApplicationName() : /Hibernate_webservice
            getId() : org.springframework.web.context.WebApplicationContext:/Hibernate_webservice/appServlet
            getParent() : Root WebApplicationContext: startup date [Mon Jul 24 20:42:30 IST 2017]; root of context hierarchy
            getDisplayName() : WebApplicationContext for namespace 'appServlet-servlet'


            Jul 24, 2017 8:42:39 PM org.springframework.web.servlet.DispatcherServlet initServletBean
            INFO: FrameworkServlet 'appServlet': initialization completed in 1365 ms
            Jul 24, 2017 8:42:40 PM org.apache.coyote.AbstractProtocol start
            INFO: Starting ProtocolHandler ["http-nio-8082"]
            Jul 24, 2017 8:42:40 PM org.apache.coyote.AbstractProtocol start
            INFO: Starting ProtocolHandler ["ajp-nio-8011"]
            Jul 24, 2017 8:42:40 PM org.apache.catalina.startup.Catalina start
            INFO: Server startup in 19807 ms

Answer 1

Spring 提供了 ApplicationListener<ContextRefreshedEvent>界面及其onApplicationEvent(ContextRefreshedEvent event)钩。

例如:

@Component
public class MyServiceCreationListener implements ApplicationListener<ContextRefreshedEvent> {

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
      // do something on container startup
    }
}

无论你在 onApplicationEvent 中写什么方法将在创建 Spring 上下文时执行一次且仅执行一次。

如果您发现此方法被多次调用，那么您必须有多个 ApplicationContext在玩。如果你检查 event.getApplicationContext()您可能会看到它们中的每一个都有不同的 id 和 displayName 并且您可以找出它们的来源。如果您的应用程序是 Spring MVC 应用程序，那么您可能同时拥有 ContextLoaderListener和 DispatcherServlet , 这两个都创建了自己的 ApplicationContext每个都会触发 ContextRefreshedEvent .

如果您想确定哪个是父上下文，您可以尝试 event.getApplicationContext().getParent() != null或者您可以在 ApplicationListener 中切换一个类 boolean 值，例如alreadyInitialised .

还有 Spring 4 的 SmartInitializingSingleton这可能允许您在不同级别 Hook 上下文创建。