@PostConstruct注解的使用

@PostConstruct注解的使用

定义：

@PostContruct是spring框架的注解，在方法上加该注解会在项目启动的时候执行该方法，也可以理解为在spring容器初始化的时候执行该方法。

@PostConstruct 和 @PreDestroy，这两个注解被用来修饰一个非静态的void（）方法。

1.@PostConstruct说明

被@PostConstruct修饰的方法会在服务器加载Servlet的时候运行，并且只会被服务器调用一次，类似于Serclet的inti()方法。被@PostConstruct修饰的方法会在构造函数之后，init()方法之前运行。

2.@PreConstruct说明

被@PreConstruct修饰的方法会在服务器卸载Servlet的时候运行，并且只会被服务器调用一次，类似于Servlet的destroy()方法。被@PreConstruct修饰的方法会在destroy()方法之后运行，在Servlet被彻底卸载之前。

执行顺序：

通常我们会是在Spring框架中使用到@PostConstruct注解 该注解的方法在整个Bean初始化中的执行顺序：

Constructor(构造方法) -> @Autowired(依赖注入) -> @PostConstruct(注释 的方法)

@PostConstruct注解的方法在项目启动的时候执行这个方法，也可以理解为在spring容器启动的时候执行，可作为一些数据的常规化加载，比如数据字典之类的。只有在该方法在执行完成后项目才会启动完成。

用法示例：

测试service类

@Service
public class TestService {
     


    @PostConstruct
    public void init(){
     
        System.out.println("1111111111111111111111111111");
        try {
     
            Thread.sleep(10000);
        } catch (InterruptedException e) {
     
            e.printStackTrace();
        }
        System.out.println("执行结束");
    }

}

项目启动结果：

2020-07-30 17:39:58,146 main INFO Log4j appears to be running in a Servlet environment, but there's no log4j-web module available. If you want better web container support, please add the log4j-web JAR to your web archive or server lib directory.
[17:39:58:325] [INFO] - org.springframework.context.support.AbstractApplicationContext.prepareRefresh(AbstractApplicationContext.java:590) - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@82de64a: startup date [Thu Jul 30 17:39:58 CST 2020]; root of context hierarchy
[17:39:58:456] [INFO] - org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.(AutowiredAnnotationBeanPostProcessor.java:154) - JSR-330 'javax.inject.Inject' annotation found and supported for autowiring
[17:39:58:476] [INFO] - org.springframework.context.support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker.postProcessAfterInitialization(PostProcessorRegistrationDelegate.java:328) - Bean 'configurationPropertiesRebinderAutoConfiguration' of type [org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration$$EnhancerBySpringCGLIB$$395ea18e] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2020-07-30 17:39:59,250 main INFO Log4j appears to be running in a Servlet environment, but there's no log4j-web module available. If you want better web container support, please add the log4j-web JAR to your web archive or server lib directory.

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.0.3.RELEASE)

[17:39:59:275] [INFO] - org.springframework.boot.SpringApplication.logStartupProfileInfo(SpringApplication.java:663) - The following profiles are active: dev
[17:39:59:311] [INFO] - org.springframework.context.support.AbstractApplicationContext.prepareRefresh(AbstractApplicationContext.java:590) - Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@7b84fcf8: startup date [Thu Jul 30 17:39:59 CST 2020]; parent: org.springframework.context.annotation.AnnotationConfigApplicationContext@82de64a
[17:39:59:838] [INFO] - org.springframework.cloud.context.scope.GenericScope.setSerializationId(GenericScope.java:294) - BeanFactory id=628559bc-c8fb-37b4-b809-0ec50dd3151d
[17:39:59:851] [INFO] - org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.(AutowiredAnnotationBeanPostProcessor.java:154) - JSR-330 'javax.inject.Inject' annotation found and supported for autowiring
[17:39:59:916] [INFO] - org.springframework.context.support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker.postProcessAfterInitialization(PostProcessorRegistrationDelegate.java:328) - Bean 'org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration' of type [org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration$$EnhancerBySpringCGLIB$$395ea18e] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
[17:40:00:060] [INFO] - org.xnio.Xnio.(Xnio.java:104) - XNIO version 3.3.8.Final
[17:40:00:069] [INFO] - org.xnio.nio.NioXnio.(NioXnio.java:55) - XNIO NIO Implementation Version 3.3.8.Final
[17:40:00:090] [WARN] - io.undertow.websockets.jsr.Bootstrap.handleDeployment(Bootstrap.java:67) - UT026009: XNIO worker was not set on WebSocketDeploymentInfo, the default worker will be used
[17:40:00:091] [WARN] - io.undertow.websockets.jsr.Bootstrap.handleDeployment(Bootstrap.java:76) - UT026010: Buffer pool was not set on WebSocketDeploymentInfo, the default pool will be used
[17:40:00:106] [INFO] - io.undertow.servlet.spec.ServletContextImpl.log(ServletContextImpl.java:360) - Initializing Spring embedded WebApplicationContext
[17:40:00:107] [INFO] - org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.prepareWebApplicationContext(ServletWebServerApplicationContext.java:285) - Root WebApplicationContext: initialization completed in 796 ms
[17:40:00:234] [WARN] - com.netflix.config.sources.URLConfigurationSource.(URLConfigurationSource.java:121) - No URLs will be polled as dynamic configuration sources.
[17:40:00:234] [INFO] - com.netflix.config.sources.URLConfigurationSource.(URLConfigurationSource.java:122) - To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
[17:40:00:243] [INFO] - com.netflix.config.DynamicPropertyFactory.getInstance(DynamicPropertyFactory.java:281) - DynamicPropertyFactory is initialized with configuration sources: com.netflix.config.ConcurrentCompositeConfiguration@45bf6f39
[17:40:00:587] [INFO] - org.springframework.boot.web.servlet.ServletRegistrationBean.addRegistration(ServletRegistrationBean.java:186) - Servlet dispatcherServlet mapped to [/]
[17:40:00:590] [INFO] - org.springframework.boot.web.servlet.AbstractFilterRegistrationBean.configure(AbstractFilterRegistrationBean.java:245) - Mapping filter: 'characterEncodingFilter' to: [/*]
[17:40:00:590] [INFO] - org.springframework.boot.web.servlet.AbstractFilterRegistrationBean.configure(AbstractFilterRegistrationBean.java:245) - Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
[17:40:00:590] [INFO] - org.springframework.boot.web.servlet.AbstractFilterRegistrationBean.configure(AbstractFilterRegistrationBean.java:245) - Mapping filter: 'httpPutFormContentFilter' to: [/*]
[17:40:00:590] [INFO] - org.springframework.boot.web.servlet.AbstractFilterRegistrationBean.configure(AbstractFilterRegistrationBean.java:245) - Mapping filter: 'requestContextFilter' to: [/*]
[17:40:00:591] [INFO] - org.springframework.boot.web.servlet.AbstractFilterRegistrationBean.configure(AbstractFilterRegistrationBean.java:245) - Mapping filter: 'httpTraceFilter' to: [/*]
[17:40:00:591] [INFO] - org.springframework.boot.web.servlet.AbstractFilterRegistrationBean.configure(AbstractFilterRegistrationBean.java:245) - Mapping filter: 'webMvcMetricsFilter' to: [/*]
1111111111111111111111111111
执行结束
[17:40:10:672] [WARN] - org.springframework.cloud.netflix.archaius.ArchaiusAutoConfiguration.configureArchaius(ArchaiusAutoConfiguration.java:151) - No spring.application.name found, defaulting to 'application'
[17:40:10:673] [WARN] - com.netflix.config.sources.URLConfigurationSource.(URLConfigurationSource.java:121) - No URLs will be polled as dynamic configuration sources.
[17:40:10:673] [INFO] - com.netflix.config.sources.URLConfigurationSource.(URLConfigurationSource.java:122) - To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
[17:40:10:726] [INFO] - org.springframework.web.servlet.handler.AbstractUrlHandlerMapping.registerHandler(AbstractUrlHandlerMapping.java:373) - Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
[17:40:10:855] [INFO] - org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.initControllerAdviceCache(RequestMappingHandlerAdapter.java:574) - Looking for @ControllerAdvice: org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@7b84fcf8: startup date [Thu Jul 30 17:39:59 CST 2020]; parent: org.springframework.context.annotation.AnnotationConfigApplicationContext@82de64a
[17:40:10:896] [INFO] - org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.register(AbstractHandlerMethodMapping.java:547) - Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity> org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
[17:40:10:897] [INFO] - org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.register(AbstractHandlerMethodMapping.java:547) - Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
[17:40:10:918] [INFO] - org.springframework.web.servlet.handler.AbstractUrlHandlerMapping.registerHandler(AbstractUrlHandlerMapping.java:373) - Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
[17:40:10:918] [INFO] - org.springframework.web.servlet.handler.AbstractUrlHandlerMapping.registerHandler(AbstractUrlHandlerMapping.java:373) - Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
[17:40:12:563] [INFO] - org.springframework.boot.actuate.endpoint.web.EndpointLinksResolver.(EndpointLinksResolver.java:59) - Exposing 2 endpoint(s) beneath base path '/actuator'
[17:40:12:572] [INFO] - org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.register(AbstractHandlerMethodMapping.java:547) - Mapped "{[/actuator/health],methods=[GET],produces=[application/vnd.spring-boot.actuator.v2+json || application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.web.servlet.AbstractWebMvcEndpointHandlerMapping$OperationHandler.handle(javax.servlet.http.HttpServletRequest,java.util.Map)
[17:40:12:573] [INFO] - org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.register(AbstractHandlerMethodMapping.java:547) - Mapped "{[/actuator/info],methods=[GET],produces=[application/vnd.spring-boot.actuator.v2+json || application/json]}" onto public java.lang.Object org.springframework.boot.actuate.endpoint.web.servlet.AbstractWebMvcEndpointHandlerMapping$OperationHandler.handle(javax.servlet.http.HttpServletRequest,java.util.Map)
[17:40:12:573] [INFO] - org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.register(AbstractHandlerMethodMapping.java:547) - Mapped "{[/actuator],methods=[GET],produces=[application/vnd.spring-boot.actuator.v2+json || application/json]}" onto protected java.util.Map> org.springframework.boot.actuate.endpoint.web.servlet.WebMvcEndpointHandlerMapping.links(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
[17:40:12:613] [INFO] - org.springframework.jmx.export.MBeanExporter.afterSingletonsInstantiated(MBeanExporter.java:433) - Registering beans for JMX exposure on startup
[17:40:12:620] [INFO] - org.springframework.jmx.export.MBeanExporter.autodetect(MBeanExporter.java:895) - Bean with name 'environmentManager' has been autodetected for JMX exposure
[17:40:12:621] [INFO] - org.springframework.jmx.export.MBeanExporter.autodetect(MBeanExporter.java:895) - Bean with name 'configurationPropertiesRebinder' has been autodetected for JMX exposure
[17:40:12:622] [INFO] - org.springframework.jmx.export.MBeanExporter.autodetect(MBeanExporter.java:895) - Bean with name 'refreshScope' has been autodetected for JMX exposure
[17:40:12:624] [INFO] - org.springframework.jmx.export.MBeanExporter.registerBeanInstance(MBeanExporter.java:675) - Located managed bean 'environmentManager': registering with JMX server as MBean [org.springframework.cloud.context.environment:name=environmentManager,type=EnvironmentManager]
[17:40:12:629] [INFO] - org.springframework.jmx.export.MBeanExporter.registerBeanInstance(MBeanExporter.java:675) - Located managed bean 'refreshScope': registering with JMX server as MBean [org.springframework.cloud.context.scope.refresh:name=refreshScope,type=RefreshScope]
[17:40:12:647] [INFO] - org.springframework.jmx.export.MBeanExporter.registerBeanInstance(MBeanExporter.java:675) - Located managed bean 'configurationPropertiesRebinder': registering with JMX server as MBean [org.springframework.cloud.context.properties:name=configurationPropertiesRebinder,context=7b84fcf8,type=ConfigurationPropertiesRebinder]
[17:40:12:745] [INFO] - org.springframework.boot.web.embedded.undertow.UndertowServletWebServer.start(UndertowServletWebServer.java:148) - Undertow started on port(s) 8800 (http) with context path ''
[17:40:12:747] [INFO] - org.springframework.boot.StartupInfoLogger.logStarted(StartupInfoLogger.java:59) - Started ScTestApplication in 15.577 seconds (JVM running for 17.38)