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1. Spring can be imported into Bean through annotations in four ways. We mainly talk about the following two implementation methods of Import:

1. Implement the ImportSerlector interface to load Bean:

Public class TestServiceImpl {public void testImpl () {System.out.println ("I am the service imported through importSelector");}} public class TestService implements ImportSelector {@ Override public String [] selectImports (AnnotationMetadata annotationMetadata) {return new String [] {"com.ycdhz.service.TestServiceImpl"};}} @ Configuration@Import (value = {TestService.class}) public class TestConfig {} public class TestController {@ Autowired private TestServiceImpl testServiceImpl; @ RequestMapping ("testImpl") public String testTuling () {testServiceImpl.testImpl (); return "Ok" }}

2. By implementing the ImportSerlector interface, Bean loading is realized:

Public class TestService {public TestService () {System.out.println ("I am the component imported through ImportBeanDefinitionRegistrar");}} public class TestImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {@ Override public void registerBeanDefinitions (AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {/ / define a BeanDefinition RootBeanDefinition beanDefinition = new RootBeanDefinition (TestService.class); / / Import the custom bean definition into the container registry.registerBeanDefinition ("testService", beanDefinition) } @ Configuration@Import (TestImportBeanDefinitionRegistrar.class) public class TestConfig {} II. Springboot will be automatically assembled during startup

We searched for the configuration of Tomcat under spring-boot-autoconfigure-2.0.6.RELEASE.jar and found that there were two auto-assembly classes, each containing three customizers (object-oriented single responsibility principle) and a factory class.

TomcatWebServerFactoryCustomizer: customize the Tomcat-specific features common to Servlet and Reactive servers.

Public class TomcatWebServerFactoryCustomizer implements WebServerFactoryCustomizer, Ordered {@ Override public void customize (ConfigurableTomcatWebServerFactory factory) {ServerProperties properties = this.serverProperties; ServerProperties.Tomcat tomcatProperties = properties.getTomcat (); PropertyMapper propertyMapper = PropertyMapper.get (); propertyMapper.from (tomcatProperties::getBasedir). WhenNonNull () .to (factory::setBaseDirectory); propertyMapper.from (tomcatProperties::getBackgroundProcessorDelay). WhenNonNull () .as (Long::intValue) .to (factory::setBackgroundProcessorDelay); customizeRemoteIpValve (factory) PropertyMapper.from (tomcatProperties::getMaxThreads) .when (this::isPositive) .to ((maxThreads)-> customizeMaxThreads (factory, tomcatProperties.getMaxThreads ()); propertyMapper.from (tomcatProperties::getMinSpareThreads) .when (this::isPositive) .to ((minSpareThreads)-> customizeMinThreads (factory, minSpareThreads)); propertyMapper.from (()-> determineMaxHttpHeaderSize ()) .when (this::isPositive) .to ((maxHttpHeaderSize)-> customizeMaxHttpHeaderSize (factory, maxHttpHeaderSize)) PropertyMapper.from (tomcatProperties::getMaxHttpPostSize) .when ((maxHttpPostSize)-> maxHttpPostSize! = 0) .to ((maxHttpPostSize)-> customizeMaxHttpPostSize (factory, maxHttpPostSize)); propertyMapper.from (tomcatProperties::getAccesslog) .when (ServerProperties.Tomcat.Accesslog::isEnabled) .to ((enabled)-> customizeAccessLog (factory)); propertyMapper.from (tomcatProperties::getUriEncoding) .whenNonNull () .to (factory::setUriEncoding) PropertyMapper.from (properties::getConnectionTimeout). WhenNonNull () .to ((connectionTimeout)-> customizeConnectionTimeout (factory, connectionTimeout)); propertyMapper.from (tomcatProperties::getMaxConnections) .when (this::isPositive) .to ((maxConnections)-> customizeMaxConnections (factory, maxConnections)); propertyMapper.from (tomcatProperties::getAcceptCount) .when (this::isPositive) .to ((acceptCount)-> customizeAcceptCount (factory, acceptCount)); customizeStaticResources (factory); customizeErrorReportValve (properties.getError (), factory);}}

ServletWebServerFactoryCustomizer:WebServerFactoryCustomizer applies the ServerProperties attribute to the Tomcat web server.

Public class ServletWebServerFactoryCustomizer implements WebServerFactoryCustomizer, Ordered {private final ServerProperties serverProperties; public ServletWebServerFactoryCustomizer (ServerProperties serverProperties) {this.serverProperties = serverProperties;} @ Override public int getOrder () {return 0;} @ Override public void customize (ConfigurableServletWebServerFactory factory) {PropertyMapper map = PropertyMapper.get () .alwaysApplyingWhenNonNull (); map.from (this.serverProperties::getPort) .to (factory::setPort); map.from (this.serverProperties::getAddress) .to (factory::setAddress) Map.from (this.serverProperties.getServlet ():: getContextPath) .to (factory::setContextPath); map.from (this.serverProperties.getServlet ():: getApplicationDisplayName) .to (factory::setDisplayName); map.from (this.serverProperties.getServlet ():: getSession) .to (factory::setSession); map.from (this.serverProperties::getSsl) .to (factory::setSsl); map.from (this.serverProperties.getServlet ():: getJsp) .to (factory::setJsp) Map.from (this.serverProperties::getCompression) .to (factory::setCompression); map.from (this.serverProperties::getHttp2) .to (factory::setHttp2); map.from (this.serverProperties::getServerHeader) .to (factory::setServerHeader); map.from (this.serverProperties.getServlet ():: getContextParameters) .to (factory::setInitParameters);}}

ServletWebServerFactoryCustomizer: WebServerFactoryCustomizer applies the ServerProperties attribute to the Tomcat web server.

Public class TomcatServletWebServerFactoryCustomizer implements WebServerFactoryCustomizer, Ordered {private final ServerProperties serverProperties; public TomcatServletWebServerFactoryCustomizer (ServerProperties serverProperties) {this.serverProperties = serverProperties;} @ Override public void customize (TomcatServletWebServerFactory factory) {ServerProperties.Tomcat tomcatProperties = this.serverProperties.getTomcat (); if (! ObjectUtils.isEmpty (tomcatProperties.getAdditionalTldSkipPatterns () {factory.getTldSkipPatterns () .addAll (tomcatProperties.getAdditionalTldSkipPatterns ());} if (tomcatProperties.getRedirectContextRoot ()! = null) {customizeRedirectContextRoot (factory, tomcatProperties.getRedirectContextRoot ()) } if (tomcatProperties.getUseRelativeRedirects ()! = null) {customizeUseRelativeRedirects (factory, tomcatProperties.getUseRelativeRedirects ());} 3. With TomcatServletWebServerFactory, it is equivalent to having the entrance for Spring loading.

Start tomcat with AbstractApplicationContext#onReFresh () in the IOC container, and then follow up on the other steps of the ioc container.

Through breakpoints, we can observe the entire life cycle of Tomcat loading, as well as the loading process of the three customizers.

@ Overridepublic WebServer getWebServer (ServletContextInitializer... Initializers) {Tomcat tomcat = new Tomcat (); File baseDir = (this.baseDirectory! = null)? This.baseDirectory: createTempDir ("tomcat"); tomcat.setBaseDir (baseDir.getAbsolutePath ()); Connector connector = new Connector (this.protocol); tomcat.getService (). AddConnector (connector); customizeConnector (connector); tomcat.setConnector (connector); / / set whether tomcat.getHost (). SetAutoDeploy (false); / / create Tomcat engine configureEngine (tomcat.getEngine ()); for (Connector additionalConnector: this.additionalTomcatConnectors) {tomcat.getService () .addConnector (additionalConnector) } / / refresh context prepareContext (tomcat.getHost (), initializers); / / prepare to launch return getTomcatWebServer (tomcat);} private void initialize () throws WebServerException {TomcatWebServer.logger .info ("Tomcat initialized with port (s):" + getPortsDescription (false)); synchronized (this.monitor) {try {addInstanceIdToEngineName (); Context context = findContext () Context.addLifecycleListener ((event)-> {if (context.equals (event.getSource ()) & Lifecycle.START_EVENT.equals (event.getType () {/ / Remove service connectors so that protocol binding doesn't / / happen when the service is started. RemoveServiceConnectors ();}}); / / Start the server to trigger initialization listeners this.tomcat.start (); / / We can re-throw failure exception directly in the main thread rethrowDeferredStartupExceptions (); try {ContextBindings.bindClassLoader (context, context.getNamingToken (), getClass (). GetClassLoader ());} catch (NamingException ex) {/ / Naming is not enabled. Continue} / / Unlike Jetty, all Tomcat threads are daemon threads. We create a / / blocking non-daemon to stop immediate shutdown startDaemonAwaitThread ();} catch (Exception ex) {stopSilently (); throw new WebServerException ("Unable to start embedded Tomcat", ex);}

Note: in this process, we need to understand the life cycle of Bean. All three customizers of Tomcat are loaded in the BeanPostProcessorsRegistrar (Bean post processor) process.

Construction method-- > Bean post processor Before-- > InitializingBean-- > init-method-- > Bean post processor After

Org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#initializeBeanprotected Object doCreateBean (final String beanName, final RootBeanDefinition mbd, final @ Nullable Object [] args) throws BeanCreationException {/ / Instantiate the bean. BeanWrapper instanceWrapper = null; if (mbd.isSingleton ()) {instanceWrapper = this.factoryBeanInstanceCache.remove (beanName);} if (instanceWrapper = = null) {/ / Construction method instanceWrapper = createBeanInstance (beanName, mbd, args);} final Object bean = instanceWrapper.getWrappedInstance (); Class beanType = instanceWrapper.getWrappedClass (); if (beanType! = NullBean.class) {mbd.resolvedTargetType = beanType;} / / Initialize the bean instance. . Return exposedObject;} protected Object initializeBean (final String beanName, final Object bean, @ Nullable RootBeanDefinition mbd) {if (System.getSecurityManager ()! = null) {AccessController.doPrivileged ((PrivilegedAction) ()-> {invokeAwareMethods (beanName, bean); return null;}, getAccessControlContext ());} else {invokeAwareMethods (beanName, bean);} Object wrappedBean = bean; if (mbd = = null | |! mbd.isSynthetic ()) {/ / Bean post processor Before wrappedBean = applyBeanPostProcessorsBeforeInitialization (wrappedBean, beanName) } try {invokeInitMethods (beanName, wrappedBean, mbd);} catch (Throwable ex) {throw new BeanCreationException ((mbd! = null?) Mbd.getResourceDescription (): null), beanName, "Invocation of init method failed", ex);} if (mbd = = null | |! mbd.isSynthetic ()) {/ / Bean post processor After wrappedBean = applyBeanPostProcessorsAfterInitialization (wrappedBean, beanName);} return wrappedBean } the above is about the article "how to realize self-startup with Tomcat container in springboot". I believe you all have some understanding. I hope the content shared by the editor will be helpful to you. If you want to learn more about related knowledge, please follow the industry information channel.

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