1.第一个步骤进入SpringApplication构造函数
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();//这个type是SERVLET
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));//设置初始化
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));//设置监听器
this.mainApplicationClass = deduceMainApplicationClass();
}
1.1 看一下 setInitializers 方法做了些什么事情
// type 是 ApplicationContextInitializer.class
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = getClassLoader();//
// Use names and ensure unique to protect against duplicates
Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));//返回ApplicationContextInitializer对应的类路径
List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);//
AnnotationAwareOrderComparator.sort(instances);
return instances;
}
返回ApplicationContextInitializer对应的类路径
public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) {
String factoryTypeName = factoryType.getName();//ApplicationContextInitializer
//加载/META-INF/spring.factories下面的文件，并获取ApplicationContextInitializer为key对应的值
return (List)loadSpringFactories(classLoader).getOrDefault(factoryTypeName, Collections.emptyList());
}
根据类路径反射生成类的实例
private <T> List<T> createSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes,
ClassLoader classLoader, Object[] args, Set<String> names) {
List<T> instances = new ArrayList<>(names.size());
for (String name : names) {
try {
Class<?> instanceClass = ClassUtils.forName(name, classLoader);
Assert.isAssignable(type, instanceClass);
Constructor<?> constructor = instanceClass.getDeclaredConstructor(parameterTypes);
T instance = (T) BeanUtils.instantiateClass(constructor, args);
instances.add(instance);
}
catch (Throwable ex) {
throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, ex);
}
}
return instances;
}
1.2 setListeners做了什么
//type = ApplicationListener.class 和上面一样获取ApplicationListener的类实例
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = getClassLoader();
// Use names and ensure unique to protect against duplicates
Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
AnnotationAwareOrderComparator.sort(instances);
return instances;
}
1.3 获取主类
private Class<?> deduceMainApplicationClass() {
try {
StackTraceElement[] stackTrace = new RuntimeException().getStackTrace();
for (StackTraceElement stackTraceElement : stackTrace) {
if ("main".equals(stackTraceElement.getMethodName())) {
return Class.forName(stackTraceElement.getClassName());
}
}
}
catch (ClassNotFoundException ex) {
// Swallow and continue
}
return null;
}
2.第二个步骤调用run方法
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
configureHeadlessProperty();//配置handless参数
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;
}
2.1 设置系统handless参数
private static final String SYSTEM_PROPERTY_JAVA_AWT_HEADLESS = "java.awt.headless";
private void configureHeadlessProperty() {
System.setProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS,
System.getProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS, Boolean.toString(this.headless)));
}
2.2 获取SpringApplicationRunListeners的实例
private SpringApplicationRunListeners getRunListeners(String[] args) {
Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };
return new SpringApplicationRunListeners(logger,
getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));
}
2.3 准备环境
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
// Create and configure the environment
ConfigurableEnvironment environment = getOrCreateEnvironment();// new StandardServletEnvironment() 创建Servlet环境
configureEnvironment(environment, applicationArguments.getSourceArgs());
ConfigurationPropertySources.attach(environment);
listeners.environmentPrepared(environment);
bindToSpringApplication(environment);
if (!this.isCustomEnvironment) {
environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
deduceEnvironmentClass());
}
ConfigurationPropertySources.attach(environment);
return environment;
}
2.4 console开启banner
图片配置路径：spring.banner.image.location
图片配置名称：banner.{ "gif", "jpg", "png" }
文本配置路径：spring.banner.location
默认数据resource下的：banner.txt
2.5 创建上下文类
public static final String DEFAULT_SERVLET_WEB_CONTEXT_CLASS = "org.springframework.boot."
+ "web.servlet.context.AnnotationConfigServletWebServerApplicationContext";
protected ConfigurableApplicationContext createApplicationContext() {
contextClass = Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);
return (ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);
}
2.6 准备上下文
private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
context.setEnvironment(environment);
postProcessApplicationContext(context);
applyInitializers(context);
listeners.contextPrepared(context);
if (this.logStartupInfo) {
logStartupInfo(context.getParent() == null);
logStartupProfileInfo(context);
}
// Add boot specific singleton beans
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
if (printedBanner != null) {
beanFactory.registerSingleton("springBootBanner", printedBanner);
}
if (beanFactory instanceof DefaultListableBeanFactory) {
((DefaultListableBeanFactory) beanFactory)
.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
if (this.lazyInitialization) {
context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
}
// Load the sources
Set<Object> sources = getAllSources();
Assert.notEmpty(sources, "Sources must not be empty");
load(context, sources.toArray(new Object[0]));
listeners.contextLoaded(context);
}
