一、简介

Springboot源码解析是一件大工程，逐行逐句的去研究代码，会很枯燥，也不容易坚持下去。
我们不追求大而全，而是试着每次去研究一个小知识点，最终聚沙成塔，这就是我们的springboot源码管中窥豹系列。

二、框架

我们先把springboot源码的框架了解清楚。

1、新建一个springboot项目

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication

public class MyprojectApplication {

 public static void main(String[] args) {

   SpringApplication.run(MyprojectApplication.class, args);

 }

}

2、分析源码

相比于spring项目或者springmvc项目，springboot的入口很好找，就在main里面的run方法，我们进入run方法

public static ConfigurableApplicationContext run(Class<?> primarySource, String... args) {

  return run(new Class<?>[] { primarySource }, args);

}

public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {

  return new SpringApplication(primarySources).run(args);

}

通过SpringApplication的静态方法，新建了一个SpringApplication类，调用它的run方法，我们先看SpringApplication的构造方法，再看run方法

public SpringApplication(Class<?>... primarySources) {

  this(null, primarySources);

}

@SuppressWarnings({ "unchecked", "rawtypes" })

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {

  this.resourceLoader = resourceLoader;

  Assert.notNull(primarySources, "PrimarySources must not be null");

  this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));

  this.webApplicationType = WebApplicationType.deduceFromClasspath();

  setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));

  setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));

  this.mainApplicationClass = deduceMainApplicationClass();

}

构造方法主要做了这几件事：

确定web类型：webApplicationType
加载ApplicationContextInitializer
加载ApplicationListener
确定applicationcontext的实现类

实现细节我们先不探讨，接着看run方法

public ConfigurableApplicationContext run(String... args) {

  StopWatch stopWatch = new StopWatch();

  stopWatch.start();

  ConfigurableApplicationContext context = null;

  Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();

  configureHeadlessProperty();

  SpringApplicationRunListeners listeners = getRunListeners(args);

  listeners.starting();

  try {

   ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);

    ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);

    configureIgnoreBeanInfo(environment);

    Banner printedBanner = printBanner(environment);

    context = createApplicationContext();

    exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,

        new Class[] { ConfigurableApplicationContext.class }, context);

    prepareContext(context, environment, listeners, applicationArguments, printedBanner);

    refreshContext(context);

    afterRefresh(context, applicationArguments);

    stopWatch.stop();

    if (this.logStartupInfo) {

        new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);

    }

    listeners.started(context);

    callRunners(context, applicationArguments);

  }

  catch (Throwable ex) {

    handleRunFailure(context, ex, exceptionReporters, listeners);

      throw new IllegalStateException(ex);

  }

  try {

    listeners.running(context);

  }

  catch (Throwable ex) {

    handleRunFailure(context, ex, exceptionReporters, null);

    throw new IllegalStateException(ex);

  }

  return context;

}

run方法做了几件事：

stopwatch记录springboot启动耗时
不同阶段触发spring的listen事件
新建applicationcontext实现类
启动spring：refreshContext(context)
启动完成加载runner

最重要的就是refreshContext方法，延用的springframe的fresh方法

private void refreshContext(ConfigurableApplicationContext context) {

  refresh((ApplicationContext) context);

  if (this.registerShutdownHook) {

    try {

        context.registerShutdownHook();

    }

    catch (AccessControlException ex) {

        // Not allowed in some environments.

    }

  }

}

AbstractApplicationContext类的方法

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();

    }

    }

}

先不必深究，看看就好，了解整体的框架，至此springboot项目的源码主框架就是这样了。

核心能力还是spring的refresh方法
通过SpringApplication封装起来提供更多的功能。

这期就这样，从下期开始，我们带着问题去源码里面找实现。

欢迎关注公众号：丰极，更多技术学习分享。

巴特西

springboot源码解析-管中窥豹系列之总体结构（一）

一、简介

二、框架

1、新建一个springboot项目

2、分析源码

最新文章

热门文章