【Spring框架家族】SpringBoot自动配置原理源码跟进

继承springboot父工程依赖pox.xml

    <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.1.8.RELEASE</version></dependency>

spring-boot-starter-parent继承了spring-boot-dependencies

这个依赖中定义了常用依赖的版本，以及锁定了其版本，所以我们在导入starter时，无需定义版本
若没有在这里定义版本，则需要自己导入相应的版本信息，如mysql的jdbc驱动

starter【web】启动器

    <!-- 导入了web模块正常运行所依赖的组件，DispatcherServlet，内置tomcat容器等等--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>

spring-boot-starter-web：

    <!-- 这是springboot的基础依赖，基本所有的启动器都依赖于spring-boot-starter。其依赖内容包括自动配置，日志，注解，spring核心，yaml等。 导入了相应的starter后，springboot就会自动配置其运行组件springboot官方定义的启动器依赖都是以 spring-boot-starter 开头的。【spring-boot-starter-xxx】如果官方没有定义，其他技术需要集成springboot，则需要自己定义启动器依赖，如 mybatis 【mybatis-spring-boot-starter】--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId><version>2.1.8.RELEASE</version><scope>compile</scope></dependency>

@SpringBootApplication注解

    // 标记当前是一个启动引导类，是springboot应用的入口。// 本身是一个组合注解。@SpringBootConfiguration // 点击@EnableAutoConfiguration // 点击// 包扫描器，不包含excludeFilters以下过滤注解@ComponentScan(excludeFilters = {@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),@Filter(type = FilterType.CUSTOM,classes = AutoConfigurationExcludeFilter.class) })public @interface SpringBootApplication {//...............}

@SpringBootConfiguration

    @Target({ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)@Documented@Configuration //点击public @interface SpringBootConfiguration {}@Target({ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)@Documented@Component // 表示该注解是一个配置类注解，并且自己是容器中的一个组件public @interface Configuration {    @AliasFor(        annotation = Component.class    )    String value() default "";}

@EnableAutoConfiguration

    @Target({ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)@Documented@Inherited@AutoConfigurationPackage // 点击@Import({AutoConfigurationImportSelector.class})public @interface EnableAutoConfiguration {String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";Class<?>[] exclude() default {};String[] excludeName() default {};}

@AutoConfigurationPackage

    @Target({ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)@Documented@Inherited// 自定义化配置包扫描，指定要扫描的包@Import({Registrar.class}) // 点击public @interface AutoConfigurationPackage {}static class Registrar implements ImportBeanDefinitionRegistrar, DeterminableImports {Registrar() {}public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {AutoConfigurationPackages.register(registry, (new AutoConfigurationPackages.PackageImport(metadata)).getPackageName());}public Set<Object> determineImports(AnnotationMetadata metadata) {return Collections.singleton(new AutoConfigurationPackages.PackageImport(metadata));}}private final String packageName;public String getPackageName() {// 包名：就是Spring容器需要去扫描能够识别的注解。其实就是启动引导类所在的包及其子包return this.packageName;}

@AutoConfigurationImportSelector

    public String[] selectImports(AnnotationMetadata annotationMetadata) {if (!this.isEnabled(annotationMetadata)) {return NO_IMPORTS;} else {// 获取自动化配置的元数据AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);// 通过配置的元数据和注解的元数据，得到一个自动化配置的entry键值对AutoConfigurationImportSelector.AutoConfigurationEntry autoConfigurationEntry = this.getAutoConfigurationEntry(autoConfigurationMetadata, annotationMetadata);return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());}}

    protected AutoConfigurationImportSelector.AutoConfigurationEntry getAutoConfigurationEntry(AutoConfigurationMetadata autoConfigurationMetadata, AnnotationMetadata annotationMetadata) {if (!this.isEnabled(annotationMetadata)) {return EMPTY_ENTRY;} else {// 获取注解的属性AnnotationAttributes attributes = this.getAttributes(annotationMetadata);// 通过注解元数据和属性获取真正意义上的集合List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes);configurations = this.removeDuplicates(configurations);Set<String> exclusions = this.getExclusions(annotationMetadata, attributes);this.checkExcludedClasses(configurations, exclusions);configurations.removeAll(exclusions);configurations = this.filter(configurations, autoConfigurationMetadata);this.fireAutoConfigurationImportEvents(configurations, exclusions);return new AutoConfigurationImportSelector.AutoConfigurationEntry(configurations, exclusions);}}

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {List<String> configurations = SpringFactoriesLoader.loadFactoryNames(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader());Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct.");return configurations;}public static List<String> loadFactoryNames(Class<?> factoryClass, @Nullable ClassLoader classLoader) {String factoryClassName = factoryClass.getName();return (List)loadSpringFactories(classLoader).getOrDefault(factoryClassName, Collections.emptyList());}private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {MultiValueMap<String, String> result = (MultiValueMap)cache.get(classLoader);if (result != null) {return result;} else {try {// 加载配置文件中的信息Enumeration<URL> urls = classLoader != null ? classLoader.getResources("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories");LinkedMultiValueMap result = new LinkedMultiValueMap();while(urls.hasMoreElements()) {URL url = (URL)urls.nextElement();UrlResource resource = new UrlResource(url);// 遍历配置文件中的信息，转换为Properties对象，放入到信息中Properties properties = PropertiesLoaderUtils.loadProperties(resource);Iterator var6 = properties.entrySet().iterator();// 遍历while(var6.hasNext()) {Entry<?, ?> entry = (Entry)var6.next();// 获取工厂类名称String factoryClassName = ((String)entry.getKey()).trim();String[] var9 = StringUtils.commaDelimitedListToStringArray((String)entry.getValue());int var10 = var9.length;for(int var11 = 0; var11 < var10; ++var11) {String factoryName = var9[var11];result.add(factoryClassName, factoryName.trim());}}}// 添加缓存cache.put(classLoader, result);return result;} catch (IOException var13) {throw new IllegalArgumentException("Unable to load factories from location [META-INF/spring.factories]", var13);}}}

META-INF/spring.factories

    @Configuration// 是否自动配置的条件@ConditionalOnWebApplication(type = Type.SERVLET)// 判断是否有下面三个的配置的@ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class})@ConditionalOnMissingBean({WebMvcConfigurationSupport.class})@AutoConfigureOrder(-2147483638)@AutoConfigureAfter({DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class, ValidationAutoConfiguration.class})public class WebMvcAutoConfiguration {

SpringApplication.run(XXX.class, args)

    // public static ConfigurableApplicationContext run()返回一个Spring容器对象public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {return (new SpringApplication(primarySources)).run(args);}

创建SpringApplication对象

    public SpringApplication(Class... primarySources) {this((ResourceLoader)null, primarySources);}

    public SpringApplication(ResourceLoader resourceLoader, Class... primarySources) {this.sources = new LinkedHashSet();this.bannerMode = Mode.CONSOLE;this.logStartupInfo = true;this.addCommandLineProperties = true;this.addConversionService = true;this.headless = true;this.registerShutdownHook = true;this.additionalProfiles = new HashSet();this.isCustomEnvironment = false;this.resourceLoader = resourceLoader;Assert.notNull(primarySources, "PrimarySources must not be null");this.primarySources = new LinkedHashSet(Arrays.asList(primarySources));// 判断当前是否是web环境this.webApplicationType = WebApplicationType.deduceFromClasspath();  // 从类路径下找到META‐INF/spring.factories配置的所有ApplicationContextInitializer；// 然后封装成一个Map，转成Set，遍历Set，通过反射创建对象，// 赋值给SpringApplication的initializers属性this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));// 从类路径下找到META‐INF/spring.factories配置的所有ApplicationListener；// 然后封装成一个Map，转成Set，遍历Set，通过反射创建对象，// 赋值给SpringApplication的listeners属性this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));// 从多个配置类中找到有main方法的主配置类this.mainApplicationClass = this.deduceMainApplicationClass();}

执行run方法

    public ConfigurableApplicationContext run(String... args) {// 创建StopWatch对象，执行start方法，开始计时。StopWatch用来计算run方法的执行时间StopWatch stopWatch = new StopWatch();stopWatch.start();ConfigurableApplicationContext context = null;Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList();this.configureHeadlessProperty();// 从类路径下META‐INF/spring.factories中获取SpringApplicationRunListeners，// 反射创建对象，并回调start方法；SpringApplicationRunListeners listeners = this.getRunListeners(args);listeners.starting();Collection exceptionReporters;try {// 准备命令行参数，就是传入的argsApplicationArguments applicationArguments = new DefaultApplicationArguments(args);// 准备环境，完成后，回调listener的environmentPrepared方法。ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);this.configureIgnoreBeanInfo(environment);// 打印SpringBoot的logoBanner printedBanner = this.printBanner(environment);// 创建Spring容器，通过判断，决定是web的Spring容器还是普通的Spring容器context = this.createApplicationContext();exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);// 准备上下文环境this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);// 刷新容器，加载所有的组件【如果是web环境，会启动tomcat】this.refreshContext(context);this.afterRefresh(context, applicationArguments);// 停止计时，stopWatch.stop();if (this.logStartupInfo) {(new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);}// 回调所有的SpringApplicationRunListener的started()；listeners.started(context);// 从ioc容器中获取所有的ApplicationRunner和CommandLineRunner进行回调// 【ApplicationRunner先回调，CommandLineRunner再回调】this.callRunners(context, applicationArguments);} catch (Throwable var10) {this.handleRunFailure(context, var10, exceptionReporters, listeners);throw new IllegalStateException(var10);}try {listeners.running(context);return context;} catch (Throwable var9) {this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null);throw new IllegalStateException(var9);}}

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【Spring框架家族】SpringBoot自动配置原理源码跟进

继承springboot父工程依赖pox.xml

starter【web】启动器

@SpringBootApplication注解

【Spring框架家族】SpringBoot自动配置原理源码跟进相关推荐

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