SpringBoot应用启动流程源码解析
作者:TomDu 时间:2023-11-25 00:03:24
前言
Springboot应用在启动的时候分为两步:首先生成 SpringApplication 对象 ,运行 SpringApplication 的 run 方法,下面一一看一下每一步具体都干了什么
public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
return new SpringApplication(primarySources).run(args);
}
创建 SpringApplication 对象
public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
this.resourceLoader = resourceLoader;
Assert.notNull(primarySources, "PrimarySources must not be null");
//保存主配置类
this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
//判断当前是否一个web应用
this.webApplicationType = WebApplicationType.deduceFromClasspath();
//从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer;然后保存起来
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
//从类路径下找到ETA-INF/spring.factories配置的所有ApplicationListener
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
//从多个配置类中找到有main方法的主配置类
this.mainApplicationClass = deduceMainApplicationClass();
}
其中从类路径下获取到META-INF/spring.factories配置的所有ApplicationContextInitializer和ApplicationListener的具体代码如下
public final class SpringFactoriesLoader {
/**spring.factories的位置*/
public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";
private static final Log logger = LogFactory.getLog(SpringFactoriesLoader.class);
/**
* 缓存扫描后的结果, 注意这个cache是static修饰的,说明是多个实例共享的
* 其中MultiValueMap的key就是spring.factories中的key(比如org.springframework.boot.autoconfigure.EnableAutoConfiguration),
* 其值就是key对应的value以逗号分隔后得到的List集合(这里用到了MultiValueMap,他是guava的一键多值map, 类似Map<String, List<String>>)
*/
private static final Map<ClassLoader, MultiValueMap<String, String>> cache = new ConcurrentReferenceHashMap<>();
private SpringFactoriesLoader() {
}
/**
* AutoConfigurationImportSelector及应用的初始化器和 * 里最终调用的就是这个方法,
* 这里的factoryType是EnableAutoConfiguration.class、ApplicationContextInitializer.class、或ApplicationListener.class
* classLoader是AutoConfigurationImportSelector、ApplicationContextInitializer、或ApplicationListener里的beanClassLoader
*/
public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) {
String factoryTypeName = factoryType.getName();
return loadSpringFactories(classLoader).getOrDefault(factoryTypeName, Collections.emptyList());
}
/**
* 加载 spring.factories文件的核心实现
*/
private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {
// 先从缓存获取,如果获取到了说明之前已经被加载过
MultiValueMap<String, String> result = cache.get(classLoader);
if (result != null) {
return result;
}
try {
// 找到所有jar中的spring.factories文件的地址
Enumeration<URL> urls = (classLoader != null ?
classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
result = new LinkedMultiValueMap<>();
// 循环处理每一个spring.factories文件
while (urls.hasMoreElements()) {
URL url = urls.nextElement();
UrlResource resource = new UrlResource(url);
// 加载spring.factories文件中的内容到Properties对象中
Properties properties = PropertiesLoaderUtils.loadProperties(resource);
// 遍历spring.factories内容中的所有的键值对
for (Map.Entry<?, ?> entry : properties.entrySet()) {
// 获得spring.factories内容中的key(比如org.springframework.boot.autoconfigure.EnableAutoConfiguratio)
String factoryTypeName = ((String) entry.getKey()).trim();
// 获取value, 然后按英文逗号(,)分割得到value数组并遍历
for (String factoryImplementationName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) {
// 存储结果到上面的多值Map中(MultiValueMap<String, String>)
result.add(factoryTypeName, factoryImplementationName.trim());
}
}
}
cache.put(classLoader, result);
return result;
}
catch (IOException ex) {
throw new IllegalArgumentException("Unable to load factories from location [" +
FACTORIES_RESOURCE_LOCATION + "]", ex);
}
}
}
运行run方法
public ConfigurableApplicationContext run(String... args) {
//开始停止的监听
StopWatch stopWatch = new StopWatch();
stopWatch.start();
//声明一个可配置的ioc容器
ConfigurableApplicationContext context = null;
FailureAnalyzers analyzers = null;
//配置awt相关的东西
configureHeadlessProperty();
//获取SpringApplicationRunListeners;从类路径下META-INF/spring.factories
SpringApplicationRunListeners listeners = getRunListeners(args);
//回调所有的获取SpringApplicationRunListener.starting()方法
listeners.starting();
try {
//封装命令行参数
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
//准备环境
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
//创建环境完成后回调SpringApplicationRunListener.environmentPrepared();表示环境准备完成
Banner printedBanner = printBanner(environment);
//创建ApplicationContext;决定创建web的ioc还是普通的ioc,
//通过反射创建ioc容器((ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);)
context = createApplicationContext();
//出现异常之后做异常分析报告
analyzers = new FailureAnalyzers(context);
//准备上下文环境;将environment保存到ioc中;而且applyInitializers();
//applyInitializers():回调之前保存的所有的ApplicationContextInitializer的initialize方法
//回调所有的SpringApplicationRunListener的contextPrepared();
//
prepareContext(context, environment, listeners, applicationArguments,
printedBanner);
//prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded();
//刷新容器;ioc容器初始化(如果是web应用还会创建嵌入式的Tomcat);Spring注解版
//扫描,创建,加载所有组件的地方;(配置类,组件,自动配置)
refreshContext(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
afterRefresh(context, applicationArguments);
//所有的SpringApplicationRunListener回调finished方法
listeners.finished(context, null);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
//整个SpringBoot应用启动完成以后返回启动的ioc容器;
return context;
}
catch (Throwable ex) {
handleRunFailure(context, listeners, analyzers, ex);
throw new IllegalStateException(ex);
}
}
几个重要的事件回调机制
配置在META-INF/spring.factories
ApplicationContextInitializer
SpringApplicationRunListener
只需要放在ioc容器中
ApplicationRunner
CommandLineRunner
来源:https://www.cnblogs.com/tombky/p/12600191.html
标签:Spring,Boot,启动,流程
![](/images/zang.png)
![](/images/jiucuo.png)
猜你喜欢
Android空心圆及层叠效果实现代码
2021-07-04 13:10:51
Java注释代码执行方法解析
2023-09-28 00:16:01
猜数游戏java实现代码
2023-01-05 18:39:28
![](https://img.aspxhome.com/file/2023/6/96036_0s.jpg)
从try-with-resources到ThreadLocal,优化你的代码编写方式
2023-11-11 03:19:52
Winform实现抓取web页面内容的方法
2022-03-07 21:15:53
Android长按imageview把图片保存到本地的实例代码
2021-07-23 14:20:38
详解@ConfigurationProperties实现原理与实战
2023-11-24 05:19:26
![](https://img.aspxhome.com/file/2023/7/58997_0s.png)
Android内核源码 在Ubuntu上下载,编译,安装
2023-02-21 19:43:39
C#难点逐个击破(3):params数组参数
2022-01-17 14:40:22
![](https://img.aspxhome.com/file/2023/7/102197_0s.png)
MyBatis 动态SQL和缓存机制实例详解
2022-01-14 16:47:33
Opencv实现读取摄像头和视频数据
2023-07-16 15:19:58
spring 自定义让@Value被解析到
2022-12-21 13:27:49
SpringIOC容器Bean的作用域及生命周期实例
2023-10-01 11:21:34
![](https://img.aspxhome.com/file/2023/1/76611_0s.png)
Android RecycleView添加head配置封装的实例
2021-09-14 00:05:58
Android如何实现一个DocumentProvider示例详解
2022-12-30 20:10:13
![](https://img.aspxhome.com/file/2023/5/102595_0s.jpg)
.NET实现父窗体关闭而不影响子窗体的方法
2022-10-06 20:56:04
![](https://img.aspxhome.com/file/2023/4/104264_0s.jpg)
LeetCode程序员面试题之无重复字符的最长子串
2021-09-12 05:26:36
5个主流的Java开源IDE工具详解
2021-10-13 06:06:50
![](https://img.aspxhome.com/file/2023/6/63306_0s.jpg)
mybatis错误之in查询 <foreach>循环问题
2023-11-17 01:10:09
Android 顶部标题栏随滑动时的渐变隐藏和渐变显示效果
2023-11-26 07:48:39
![](https://img.aspxhome.com/file/2023/4/102574_0s.gif)