Spring Boot起步依赖源码分析(一)

 2019-10-17 21:58  阅读(749)
文章分类:Spring boot

这里我们搭建一个简单的spring boot web应用
maven依赖
pom.xml

<parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.4.2.RELEASE</version>
        </parent>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
        </dependencies>

下面是一个简单的spring boot的启动配置类,需要关注的有只有两点@EnableAutoConfiguration注解和SpringApplication类
(如果你还没有使用过搭建过spring boot的开发环境,请先查阅我的上篇博客3分钟快速搭建Spring Boot开发环境

@EnableAutoConfiguration
    public class MainInit {

        public static void main(String[] args) throws Exception {
            SpringApplication.run(MainInit.class, args);
        }

    }

1、程序入口

public static ConfigurableApplicationContext run(Object[] sources, String[] args) {
            return new SpringApplication(sources).run(args);
        }

这是一个静态方法创建了一个SpringApplication对象,注入了入口函数的Class(作用:获取@EnableAutoConfiguration注解)和args,并调用了SpringApplication对象的run()方法
2、构造初始化

public SpringApplication(Object... sources) {
            initialize(sources);
        }

        @SuppressWarnings({ "unchecked", "rawtypes" })
        private void initialize(Object[] sources) {
            if (sources != null && sources.length > 0) {
                this.sources.addAll(Arrays.asList(sources));
            }
            this.webEnvironment = deduceWebEnvironment(); //推测当前是否是web环境
            setInitializers((Collection) getSpringFactoriesInstances(
                    ApplicationContextInitializer.class));
            setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
            this.mainApplicationClass = deduceMainApplicationClass();
        }

这里的mainApplicationClass就是我们自己写的MainInit类
3、SpringApplication.run()

public ConfigurableApplicationContext run(String... args) {
            StopWatch stopWatch = new StopWatch();
            stopWatch.start();
            ConfigurableApplicationContext context = null;
            FailureAnalyzers analyzers = null;
            configureHeadlessProperty();
            SpringApplicationRunListeners listeners = getRunListeners(args);
            listeners.started();
            try {
                ApplicationArguments applicationArguments = new DefaultApplicationArguments(
                        args);
                ConfigurableEnvironment environment = prepareEnvironment(listeners,
                        applicationArguments);
                Banner printedBanner = printBanner(environment);
                context = createApplicationContext();
                analyzers = new FailureAnalyzers(context);
                prepareContext(context, environment, listeners, applicationArguments,
                        printedBanner);
                refreshContext(context);
                afterRefresh(context, applicationArguments);
                listeners.finished(context, null);
                stopWatch.stop();
                if (this.logStartupInfo) {
                    new StartupInfoLogger(this.mainApplicationClass)
                            .logStarted(getApplicationLog(), stopWatch);
                }
                return context;
            }
            catch (Throwable ex) {
                handleRunFailure(context, listeners, analyzers, ex);
                throw new IllegalStateException(ex);
            }
        }

看到这里,如果追过spring源码的老司机应该就很熟悉,这里初始化了spring,afterRefresh(context, applicationArguments)最终会调用AbstractApplicationContext.refresh()方法中,在这里会构建spring的ioc容器
4、构建ioc容器

@Override
        public void refresh() throws BeansException, IllegalStateException {
            synchronized (this.startupShutdownMonitor) {
                // Prepare this context for refreshing.
                prepareRefresh();

                // Tell the subclass to refresh the internal bean factory.
                ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

                // Prepare the bean factory for use in this context.
                prepareBeanFactory(beanFactory);

                try {
                    // Allows post-processing of the bean factory in context subclasses.
                    postProcessBeanFactory(beanFactory);

                    // Invoke factory processors registered as beans in the context.
                    invokeBeanFactoryPostProcessors(beanFactory);

                    // Register bean processors that intercept bean creation.
                    registerBeanPostProcessors(beanFactory);

                    // Initialize message source for this context.
                    initMessageSource();

                    // Initialize event multicaster for this context.
                    initApplicationEventMulticaster();

                    // Initialize other special beans in specific context subclasses.
                    onRefresh();

                    // Check for listener beans and register them.
                    registerListeners();

                    // Instantiate all remaining (non-lazy-init) singletons.
                    finishBeanFactoryInitialization(beanFactory);

                    // Last step: publish corresponding event.
                    finishRefresh();
                }

                catch (BeansException ex) {
                    if (logger.isWarnEnabled()) {
                        logger.warn("Exception encountered during context initialization - " +
                                "cancelling refresh attempt: " + ex);
                    }

                    // Destroy already created singletons to avoid dangling resources.
                    destroyBeans();

                    // Reset 'active' flag.
                    cancelRefresh(ex);

                    // Propagate exception to caller.
                    throw ex;
                }

                finally {
                    // Reset common introspection caches in Spring's core, since we
                    // might not ever need metadata for singleton beans anymore...
                    resetCommonCaches();
                }
            }
        }

这里构建了IOC容器,因为在pom.xml中我们加入了spring mvc的依赖,这里spring boot会自动把spring mvc所需要的bean注册到IOC容器中,这里我们不看IOC容器是如果构建的,只关心spring boot 是如何自动把spring mvc所需要的bean注册到IOC容器中的。还记得@EnableAutoConfiguration注解吗?(如果忘了,请翻到博客头部回忆一下)下面是EnableAutoConfiguration注解的源码

@Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    @Inherited
    @AutoConfigurationPackage
    @Import(EnableAutoConfigurationImportSelector.class)
    public @interface EnableAutoConfiguration {

        String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";

        /** * Exclude specific auto-configuration classes such that they will never be applied. * @return the classes to exclude */
        Class<?>[] exclude() default {};

        /** * Exclude specific auto-configuration class names such that they will never be * applied. * @return the class names to exclude * @since 1.3.0 */
        String[] excludeName() default {};

    }

主要看EnableAutoConfigurationImportSelector这个类,这个类会导入spring boot中的一个配置文件,方法如下:

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata,
                AnnotationAttributes attributes) {
            List<String> configurations = SpringFactoriesLoader.loadFactoryNames(
                    getSpringFactoriesLoaderFactoryClass(), 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;
        }

这个方法会导入spring-boot-autoconfigure包下META-INF/spring.factories配置文件
spring.factories

# Initializers
    org.springframework.context.ApplicationContextInitializer=\
    org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer,\
    org.springframework.boot.autoconfigure.logging.AutoConfigurationReportLoggingInitializer

    # Application Listeners
    org.springframework.context.ApplicationListener=\
    org.springframework.boot.autoconfigure.BackgroundPreinitializer

    # Auto Configure
    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.MessageSourceAutoConfiguration,\
    org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration,\
    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.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.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.jms.hornetq.HornetQAutoConfiguration,\
    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.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.velocity.VelocityAutoConfiguration,\
    org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\
    org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,\
    org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,\
    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

    # Failure analyzers
    org.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 providers
    org.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.velocity.VelocityTemplateAvailabilityProvider,\
    org.springframework.boot.autoconfigure.web.JspTemplateAvailabilityProvider

通过getCandidateConfigurations方法,会把配置文件中org.springframework.boot.autoconfigure.EnableAutoConfiguration=后的所有配置类的全类名信息读取到一个List集合中,这里看到一个比较亲切的名字org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration看类名就能猜到这应该就是我们需要找东西了。2016年12月21日23:43:06 时间不早,(~﹃~)~zZ 下次再战,预知后事如何,请听下回分解


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