前言:
现时大家对“java怎么键盘输入字符串存入数组”大体比较看重,朋友们都想要剖析一些“java怎么键盘输入字符串存入数组”的相关文章。那么小编在网络上搜集了一些对于“java怎么键盘输入字符串存入数组””的相关文章,希望咱们能喜欢,大家一起来学习一下吧!阅读目录
一、前言二、容器启动2.1 @SpringBootApplication注解2.2 SpringApplication.run()静态方法如上图,容器启动流程可以分为5个主要步骤:1.getRunListeners获取监听器(SpringApplicationRunListeners )载入工厂名称(loadFactoryNames)创建spring工厂实例(createSpringFactoriesInstances)2.准备好环境3.准备上下文4.刷新上下文5.刷新完上下文后三、总结
正文
回到顶部
一、前言
spring cloud大行其道的当下,如果不了解基本原理那么是很纠结的(看见的都是约定大于配置,但是原理呢?为什么要这么做?如何串联起来的?)。spring cloud是基于spring boot快速搭建的,今天咱们就看看spring boot容器启动流程(全文基于1.5.9版本,springboot2基本一致)。(本文不讲解如何快速启动spring boot,那些直接官方看即可,官网文档飞机票)
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二、容器启动
spring boot一般是指定容器启动main方法,然后以命令行方式启动Jar包,如下图:
1 @SpringBootApplication2 public class Application {3 public static void main(String[] args) {4 SpringApplication.run(Application.class, args);5 }6 }
这里核心关注2个东西:
1.@SpringBootApplication注解
2.SpringApplication.run()静态方法
下面我们就分别探究这两块内容。
2.1@SpringBootApplication注解
源码如下:
1 @Target(ElementType.TYPE) 2 @Retention(RetentionPolicy.RUNTIME) 3 @Documented 4 @Inherited 5 @SpringBootConfiguration 6 @EnableAutoConfiguration 7 @ComponentScan(excludeFilters = { 8 @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class), 9 @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })10 public @interface SpringBootApplication {
核心注解:
@SpringBootConfiguration(实际就是个@Configuration):表示这是一个JavaConfig配置类,可以在这个类中自定义bean,依赖关系等。-》这个是spring-boot特有的注解,常用到。@EnableAutoConfiguration:借助@Import的帮助,将所有符合自动配置条件的bean定义加载到IoC容器(建议放在根包路径下,这样可以扫描子包和类)。-》这个需要详细深挖!@ComponentScan:spring的自动扫描注解,可定义扫描范围,加载到IOC容器。-》这个不多说,spring的注解大家肯定眼熟其中@EnableAutoConfiguration这个注解的源码:
1 @SuppressWarnings("deprecation")2 @Target(ElementType.TYPE)3 @Retention(RetentionPolicy.RUNTIME)4 @Documented5 @Inherited6 @AutoConfigurationPackage7 @Import(EnableAutoConfigurationImportSelector.class)8 public @interface EnableAutoConfiguration {
核心是一个EnableAutoConfigurationImportSelector类图如下:
核心方法在顶级接口ImportSelector的selectImports(),源码如下:
1 @Override 2 public String[] selectImports(AnnotationMetadata annotationMetadata) { 3 if (!isEnabled(annotationMetadata)) { 4 return NO_IMPORTS; 5 } 6 try { //1.从META-INF/spring-autoconfigure-metadata.properties文件中载入483条配置属性(有一些有默认值), 7 AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader 8 .loadMetadata(this.beanClassLoader); 9 AnnotationAttributes attributes = getAttributes(annotationMetadata);//2.获取注解属性10 List<String> configurations = getCandidateConfigurations(annotationMetadata,//3.获取97个自动配置类11 attributes);12 configurations = removeDuplicates(configurations);//4.移除重复的13 configurations = sort(configurations, autoConfigurationMetadata);//5.排序14 Set<String> exclusions = getExclusions(annotationMetadata, attributes);//6.获取需要排除的15 checkExcludedClasses(configurations, exclusions);//7.校验排除类16 configurations.removeAll(exclusions);//8.删除所有需要排除的17 configurations = filter(configurations, autoConfigurationMetadata);//9.过滤器OnClassCondition(注解中配置的当存在某类才生效)18 fireAutoConfigurationImportEvents(configurations, exclusions);//10.触发自动配置导入监听事件19 return configurations.toArray(new String[configurations.size()]);20 }21 catch (IOException ex) {22 throw new IllegalStateException(ex);23 }24 }
这里注意3个核心方法:
1)loadMetadata 加载配置
其实就是用类加载器去加载:META-INF/spring-autoconfigure-metadata.properties(spring-boot-autoconfigure-1.5.9.RELEASE-sources.jar)文件中定义的配置,返回PropertiesAutoConfigurationMetadata(实现了AutoConfigurationMetadata接口,封装了属性的get set方法)
2)getCandidateConfigurations获取默认支持的自动配置类名列表
自动配置灵魂方法,SpringFactoriesLoader.loadFactoryNames 从META-INF/spring.factories(spring-boot-autoconfigure-1.5.9.RELEASE-sources.jar)文件中获取自动配置类key=EnableAutoConfiguration.class的配置。
1 protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, 2 AnnotationAttributes attributes) {//话说这里2个入参没啥用啊...谁来给我解释一下... 3 List<String> configurations = SpringFactoriesLoader.loadFactoryNames( 4 getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader()); 5 Assert.notEmpty(configurations, 6 "No auto configuration classes found in META-INF/spring.factories. If you " 7 + "are using a custom packaging, make sure that file is correct."); 8 return configurations; 9 }10 //返回的是EnableAutoConfiguration类11 protected Class<?> getSpringFactoriesLoaderFactoryClass() {12 return EnableAutoConfiguration.class;13 }
实际获取了什么?spring.factories文件如下,实际获取了# Auto Configure自动配置模块的所有类。
# Initializersorg.springframework.context.ApplicationContextInitializer=\org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer,\org.springframework.boot.autoconfigure.logging.AutoConfigurationReportLoggingInitializer# Application Listenersorg.springframework.context.ApplicationListener=\org.springframework.boot.autoconfigure.BackgroundPreinitializer# Auto Configuration Import Listenersorg.springframework.boot.autoconfigure.AutoConfigurationImportListener=\org.springframework.boot.autoconfigure.condition.ConditionEvaluationReportAutoConfigurationImportListener# Auto Configuration Import Filtersorg.springframework.boot.autoconfigure.AutoConfigurationImportFilter=\org.springframework.boot.autoconfigure.condition.OnClassCondition# Auto Configure ===========这里就是全部的自动配置类===============================org.springframework.boot.autoconfigure.EnableAutoConfiguration=\org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,\org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration,\org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration,\org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration,\org.springframework.boot.autoconfigure.cloud.CloudAutoConfiguration,\org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,\org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration,\org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,\org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration,\org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration,\org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchAutoConfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.ldap.LdapDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.neo4j.Neo4jRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.solr.SolrRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration,\org.springframework.boot.autoconfigure.data.web.SpringDataWebAutoConfiguration,\org.springframework.boot.autoconfigure.elasticsearch.jest.JestAutoConfiguration,\org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,\org.springframework.boot.autoconfigure.h2.H2ConsoleAutoConfiguration,\org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,\org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,\org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration,\org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration,\org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration,\org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration,\org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration,\org.springframework.boot.autoconfigure.jms.JmsAutoConfiguration,\org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration,\org.springframework.boot.autoconfigure.jms.JndiConnectionFactoryAutoConfiguration,\org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration,\org.springframework.boot.autoconfigure.jms.artemis.ArtemisAutoConfiguration,\org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,\org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,\org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration,\org.springframework.boot.autoconfigure.ldap.LdapAutoConfiguration,\org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,\org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,\org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,\org.springframework.boot.autoconfigure.mobile.DeviceResolverAutoConfiguration,\org.springframework.boot.autoconfigure.mobile.DeviceDelegatingViewResolverAutoConfiguration,\org.springframework.boot.autoconfigure.mobile.SitePreferenceAutoConfiguration,\org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,\org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\org.springframework.boot.autoconfigure.reactor.ReactorAutoConfiguration,\org.springframework.boot.autoconfigure.security.SecurityAutoConfiguration,\org.springframework.boot.autoconfigure.security.SecurityFilterAutoConfiguration,\org.springframework.boot.autoconfigure.security.FallbackWebSecurityAutoConfiguration,\org.springframework.boot.autoconfigure.security.oauth2.OAuth2AutoConfiguration,\org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\org.springframework.boot.autoconfigure.social.SocialWebAutoConfiguration,\org.springframework.boot.autoconfigure.social.FacebookAutoConfiguration,\org.springframework.boot.autoconfigure.social.LinkedInAutoConfiguration,\org.springframework.boot.autoconfigure.social.TwitterAutoConfiguration,\org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,\org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,\org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration,\org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration,\org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration,\org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration,\org.springframework.boot.autoconfigure.web.HttpEncodingAutoConfiguration,\org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration,\org.springframework.boot.autoconfigure.web.MultipartAutoConfiguration,\org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration,\org.springframework.boot.autoconfigure.web.WebClientAutoConfiguration,\org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration,\org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration,\org.springframework.boot.autoconfigure.websocket.WebSocketMessagingAutoConfiguration,\org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration============================================end================================================# Failure analyzersorg.springframework.boot.diagnostics.FailureAnalyzer=\org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer,\org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer,\org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer# Template availability providersorg.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider=\org.springframework.boot.autoconfigure.freemarker.FreeMarkerTemplateAvailabilityProvider,\org.springframework.boot.autoconfigure.mustache.MustacheTemplateAvailabilityProvider,\org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAvailabilityProvider,\org.springframework.boot.autoconfigure.thymeleaf.ThymeleafTemplateAvailabilityProvider,\org.springframework.boot.autoconfigure.web.JspTemplateAvailabilityProvider
3)filter过滤器 根据OnClassCondition注解把不满足条件的过滤掉
1 private List<String> filter(List<String> configurations, 2 AutoConfigurationMetadata autoConfigurationMetadata) { 3 long startTime = System.nanoTime(); 4 String[] candidates = configurations.toArray(new String[configurations.size()]); 5 boolean[] skip = new boolean[candidates.length]; 6 boolean skipped = false; //获取需要过滤的自动配置导入拦截器,spring.factories配置中就一个:org.springframework.boot.autoconfigure.condition.OnClassCondition 7 for (AutoConfigurationImportFilter filter : getAutoConfigurationImportFilters()) { 8 invokeAwareMethods(filter); 9 boolean[] match = filter.match(candidates, autoConfigurationMetadata);10 for (int i = 0; i < match.length; i++) {11 if (!match[i]) {12 skip[i] = true;13 skipped = true;14 }15 }16 }17 if (!skipped) {//多条件只要有一个不匹配->skipped = true,全部匹配-》skipped = false->直接返回18 return configurations;19 }20 List<String> result = new ArrayList<String>(candidates.length);21 for (int i = 0; i < candidates.length; i++) {22 if (!skip[i]) {//匹配-》不跳过-》添加进result23 result.add(candidates[i]);24 }25 }26 if (logger.isTraceEnabled()) {27 int numberFiltered = configurations.size() - result.size();28 logger.trace("Filtered " + numberFiltered + " auto configuration class in "29 + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTime)30 + " ms");31 }32 return new ArrayList<String>(result);33 }2.2SpringApplication.run()静态方法
SpringApplication.run
1 public ConfigurableApplicationContext run(String... args) { 2 StopWatch stopWatch = new StopWatch(); 3 stopWatch.start(); 4 ConfigurableApplicationContext context = null; 5 FailureAnalyzers analyzers = null; 6 configureHeadlessProperty(); 7 SpringApplicationRunListeners listeners = getRunListeners(args);//1.获取监听器 8 listeners.starting();-->启动! 9 try {10 ApplicationArguments applicationArguments = new DefaultApplicationArguments(11 args);12 ConfigurableEnvironment environment = prepareEnvironment(listeners,//2.准备好环境,触发ApplicationEnvironmentPreparedEvent事件13 applicationArguments);14 Banner printedBanner = printBanner(environment);//打印启动提示字符,默认spring的字符图15 context = createApplicationContext();//实例化一个可配置应用上下文16 analyzers = new FailureAnalyzers(context);17 prepareContext(context, environment, listeners, applicationArguments,//3.准备上下文18 printedBanner);19 refreshContext(context);//4.刷新上下文20 afterRefresh(context, applicationArguments);//5.刷新上下文后21 listeners.finished(context, null);--关闭!22 stopWatch.stop();23 if (this.logStartupInfo) {24 new StartupInfoLogger(this.mainApplicationClass)25 .logStarted(getApplicationLog(), stopWatch);26 }27 return context;28 }29 catch (Throwable ex) {30 handleRunFailure(context, listeners, analyzers, ex);31 throw new IllegalStateException(ex);32 }33 }如上图,容器启动流程可以分为5个主要步骤:1.getRunListeners获取监听器(SpringApplicationRunListeners)
实际是SpringApplicationRunListener类
1 private SpringApplicationRunListeners getRunListeners(String[] args) { 2 Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class }; 3 return new SpringApplicationRunListeners(logger, getSpringFactoriesInstances( 4 SpringApplicationRunListener.class, types, this, args)); 5 } 6 7 private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type) { 8 return getSpringFactoriesInstances(type, new Class<?>[] {}); 9 }10 11 private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type,12 Class<?>[] parameterTypes, Object... args) {13 ClassLoader classLoader = Thread.currentThread().getContextClassLoader();14 // 使用Set确保的字符串的唯一性15 Set<String> names = new LinkedHashSet<String>(16 SpringFactoriesLoader.loadFactoryNames(type, classLoader));// 1.载入工厂名称集合17 List<T> instances = createSpringFactoriesInstances(type, parameterTypes,// 2.创建工厂实例18 classLoader, args, names);19 AnnotationAwareOrderComparator.sort(instances);// 排序20 return instances;21 }载入工厂名称(loadFactoryNames)
当前类的类加载器从META-INF/spring.factories文件中获取SpringApplicationRunListener类的配置
1 public static List<String> loadFactoryNames(Class<?> factoryClass, ClassLoader classLoader) { 2 String factoryClassName = factoryClass.getName(); 3 try { 4 Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) : 5 ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION)); 6 List<String> result = new ArrayList<String>(); 7 while (urls.hasMoreElements()) { 8 URL url = urls.nextElement(); 9 Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));10 String factoryClassNames = properties.getProperty(factoryClassName);11 result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames)));12 }13 return result;14 }15 catch (IOException ex) {16 throw new IllegalArgumentException("Unable to load [" + factoryClass.getName() +17 "] factories from location [" + FACTORIES_RESOURCE_LOCATION + "]", ex);18 }19 }
上图,获取到工厂类名后,下面来看看META-INF/spring.factories中定义了啥:
# PropertySource Loadersorg.springframework.boot.env.PropertySourceLoader=\org.springframework.boot.env.PropertiesPropertySourceLoader,\org.springframework.boot.env.YamlPropertySourceLoader# Run Listeners 这里呢,看这里!!!!org.springframework.boot.SpringApplicationRunListener=\org.springframework.boot.context.event.EventPublishingRunListener# Application Context Initializersorg.springframework.context.ApplicationContextInitializer=\org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\org.springframework.boot.context.ContextIdApplicationContextInitializer,\org.springframework.boot.context.config.DelegatingApplicationContextInitializer,\org.springframework.boot.context.embedded.ServerPortInfoApplicationContextInitializer# Application Listenersorg.springframework.context.ApplicationListener=\org.springframework.boot.ClearCachesApplicationListener,\org.springframework.boot.builder.ParentContextCloserApplicationListener,\org.springframework.boot.context.FileEncodingApplicationListener,\org.springframework.boot.context.config.AnsiOutputApplicationListener,\org.springframework.boot.context.config.ConfigFileApplicationListener,\org.springframework.boot.context.config.DelegatingApplicationListener,\org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener,\org.springframework.boot.logging.ClasspathLoggingApplicationListener,\org.springframework.boot.logging.LoggingApplicationListener# Environment Post Processorsorg.springframework.boot.env.EnvironmentPostProcessor=\org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor# Failure Analyzersorg.springframework.boot.diagnostics.FailureAnalyzer=\org.springframework.boot.diagnostics.analyzer.BeanCurrentlyInCreationFailureAnalyzer,\org.springframework.boot.diagnostics.analyzer.BeanNotOfRequiredTypeFailureAnalyzer,\org.springframework.boot.diagnostics.analyzer.BindFailureAnalyzer,\org.springframework.boot.diagnostics.analyzer.ConnectorStartFailureAnalyzer,\org.springframework.boot.diagnostics.analyzer.NoUniqueBeanDefinitionFailureAnalyzer,\org.springframework.boot.diagnostics.analyzer.PortInUseFailureAnalyzer,\org.springframework.boot.diagnostics.analyzer.ValidationExceptionFailureAnalyzer# FailureAnalysisReportersorg.springframework.boot.diagnostics.FailureAnalysisReporter=\org.springframework.boot.diagnostics.LoggingFailureAnalysisReporter
哇,都是些类全名称,且key都是接口,value都是实现类。我们根据key=“org.springframework.boot.SpringApplicationRunListener”查询得到实现类value="org.springframework.boot.context.event.EventPublishingRunListener"事件发布启动监听器,一猜也知道肯定要用”反射”根据类名获取类实例,下面很快得到验证...
创建spring工厂实例(createSpringFactoriesInstances)
根据第一步得到的Set<String> names(SpringApplicationRunListener的唯一实现类EventPublishingRunListener)生成"事件发布启动监听器"工厂实例
1 @SuppressWarnings("unchecked") 2 private <T> List<T> createSpringFactoriesInstances(Class<T> type, 3 Class<?>[] parameterTypes, ClassLoader classLoader, Object[] args, 4 Set<String> names) { 5 List<T> instances = new ArrayList<T>(names.size()); 6 for (String name : names) { 7 try { 8 Class<?> instanceClass = ClassUtils.forName(name, classLoader);// 利用反射获取类 9 Assert.isAssignable(type, instanceClass);10 Constructor<?> constructor = instanceClass11 .getDeclaredConstructor(parameterTypes);// 得到构造器12 T instance = (T) BeanUtils.instantiateClass(constructor, args);// 根据构造器和参数构造实例13 instances.add(instance);14 }15 catch (Throwable ex) {16 throw new IllegalArgumentException(17 "Cannot instantiate " + type + " : " + name, ex);18 }19 }20 return instances;21 }2.准备好环境
构造一个ConfigurableEnvironment,这里不多说。3.准备上下文
1 private void prepareContext(ConfigurableApplicationContext context, 2 ConfigurableEnvironment environment, SpringApplicationRunListeners listeners, 3 ApplicationArguments applicationArguments, Banner printedBanner) { 4 context.setEnvironment(environment); 5 postProcessApplicationContext(context);//单例一个BeanNameGenerator,把ResourceLoader设置进应用上下文 6 applyInitializers(context);//执行初始化器 7 listeners.contextPrepared(context);// 监听器执行上下文"已准备好"方法 8 if (this.logStartupInfo) { 9 logStartupInfo(context.getParent() == null);10 logStartupProfileInfo(context);11 }12 13 // 添加spring boot特殊单例bean14 context.getBeanFactory().registerSingleton("springApplicationArguments",15 applicationArguments);16 if (printedBanner != null) {17 context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);18 }19 20 // 载入资源21 Set<Object> sources = getSources();22 Assert.notEmpty(sources, "Sources must not be empty");23 load(context, sources.toArray(new Object[sources.size()]));24 listeners.contextLoaded(context);// 监听器执行"上下文已加载"方法25 }4.刷新上下文
1 private void refreshContext(ConfigurableApplicationContext context) { 2 refresh(context);//核心类 3 if (this.registerShutdownHook) { 4 try { 5 context.registerShutdownHook();//注册关闭钩子,容器关闭时执行 6 } 7 catch (AccessControlException ex) { 8 // Not allowed in some environments. 9 }10 }11 }12 13 protected void refresh(ApplicationContext applicationContext) {14 Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext);15 ((AbstractApplicationContext) applicationContext).refresh();16 }
最终执行的是AbstractApplicationContext抽象类的refresh方法。
1 public void refresh() throws BeansException, IllegalStateException { 2 synchronized (this.startupShutdownMonitor) { 3 //准备刷新的上下文环境,例如对系统属性或者环境变量进行准备及验证。 4 prepareRefresh(); 5 6 //启动子类的refreshBeanFactory方法.解析xml 7 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); 8 9 //为BeanFactory配置容器特性,例如类加载器、事件处理器等.10 prepareBeanFactory(beanFactory);11 12 try {13 //设置BeanFactory的后置处理. 空方法,留给子类拓展用。 14 postProcessBeanFactory(beanFactory);15 16 //调用BeanFactory的后处理器, 这些后处理器是在Bean定义中向容器注册的. 17 invokeBeanFactoryPostProcessors(beanFactory);18 19 //注册Bean的后处理器, 在Bean创建过程中调用. 20 registerBeanPostProcessors(beanFactory);21 22 //初始化上下文中的消息源,即不同语言的消息体进行国际化处理 23 initMessageSource();24 25 //初始化ApplicationEventMulticaster bean,应用事件广播器26 initApplicationEventMulticaster();27 28 //初始化其它特殊的Bean, 空方法,留给子类拓展用。 29 onRefresh();30 31 //检查并向容器注册监听器Bean32 registerListeners();33 34 //实例化所有剩余的(non-lazy-init) 单例Bean.35 finishBeanFactoryInitialization(beanFactory);36 37 //发布容器事件, 结束refresh过程. 38 finishRefresh();39 }40 41 catch (BeansException ex) {42 if (logger.isWarnEnabled()) {43 logger.warn("Exception encountered during context initialization - " +44 "cancelling refresh attempt: " + ex);45 }46 47 //销毁已经创建的单例Bean, 以避免资源占用.48 destroyBeans();49 50 //取消refresh操作, 重置active标志. 51 cancelRefresh(ex);52 53 // Propagate exception to caller.54 throw ex;55 }56 57 finally {58 //重置Spring的核心缓存59 resetCommonCaches();60 }61 }62 }5.刷新完上下文后
spring boot提供的2个供用户自己拓展的接口:ApplicationRunner和CommandLineRunner。可以在容器启动完毕后(上下文刷新后)执行,做一些类似数据初始化的操作。
1 private void callRunners(ApplicationContext context, ApplicationArguments args) { 2 List<Object> runners = new ArrayList<Object>(); 3 runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());//从上下文中获取ApplicationRunner类型的bean 4 runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());//从上下文中获取CommandLineRunner类型的bean 5 AnnotationAwareOrderComparator.sort(runners);//排序 6 for (Object runner : new LinkedHashSet<Object>(runners)) { 7 if (runner instanceof ApplicationRunner) { 8 callRunner((ApplicationRunner) runner, args);//执行 9 }10 if (runner instanceof CommandLineRunner) {11 callRunner((CommandLineRunner) runner, args);12 }13 }14 }
两个区别在于入参不同,根据实际情况自己选择。
1 public interface CommandLineRunner { 8 void run(String... args) throws Exception;10 }11 12 public interface ApplicationRunner {19 void run(ApplicationArguments args) throws Exception;20 21 }
CommandLineRunner中执行参数是原始的java启动类main方法的String[] args字符串数组参数;ApplicationRunner中的参数经过处理提供一些方法例如:
1 List<String> getOptionValues(String name);
根据名称获取值list,java 启动命令中 --foo=bar --foo=baz,则根据foo参数名返回list["bar", "baz"]
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三、总结
按照前面的分析,Spring-boot容器启动流程总体可划分为2部分:
1)执行注解:扫描指定范围下的bean、载入自动配置类对应的bean加载到IOC容器。
2)man方法中具体SpringAppliocation.run(),全流程贯穿SpringApplicationEvent,有6个子类:
ApplicationEnvironmentPreparedEvent
ApplicationFailedEvent.class
ApplicationPreparedEvent.class
ApplicationReadyEvent.class
ApplicationStartedEvent.class
ApplicationStartingEvent.class
这里用到了很经典的spring事件驱动模型,飞机票:Spring事件驱动模型和观察者模式
类图如下:
如上图,就是一个经典spring 事件驱动模型,包含3种角色:事件发布者、事件、监听者。对应到spring-boot中就是:
1.EventPublishingRunListener这个类封装了事件发布,
2.SpringApplicationEvent是spring-boot中定义的事件(上面说的6种事件),继承自ApplicationEvent(spring中定义的)
3.ApplicationListener<E extends ApplicationEvent> 是spring-boot针对上述6种事件的监听者,这里用户也可以自己实现监听者(上述6种事件)来注入spring boot容器启动流程,触发相应的事件。
例如:实现ApplicationListener<ApplicationReadyEvent>这个接口,在容器启动完毕时最后一步listener.finished时,如果启动没有异常,就会执行!可以做一些数据初始化之类的操作。