springboot源码解析-管中窥豹系列之总体结构（一）
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。
目录
springboot源码解析-管中窥豹系列之总体结构（一）
springboot源码解析-管中窥豹系列之项目类型（二）
springboot源码解析-管中窥豹系列之Runner（三）
springboot源码解析-管中窥豹系列之Initializer（四）
springboot源码解析-管中窥豹系列之排序（五）
springboot源码解析-管中窥豹系列之aware（六）
springboot源码解析-管中窥豹系列之web服务器（七）
springboot源码解析-管中窥豹系列之BeanDefinition（八）
springboot源码解析-管中窥豹系列之自动装配（九）
springboot源码解析-管中窥豹系列之EnableXXX（十）
springboot源码解析-管中窥豹系列之BeanFactoryPostProcessor（十一）
springboot源码解析-管中窥豹系列之BeanPostProcessor（十二）
springboot源码解析-管中窥豹系列之BeanDefine如何加载（十三）
springboot源码解析-管中窥豹系列之bean如何生成？（十四）
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