spring-加载源码解析

最新推荐文章于 2025-04-21 23:12:36 发布

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#spring boot 相关知识

MANIFEST.MF 文件

Manifest-Version: 1.0
Archiver-Version: Plexus Archiver
Built-By: jin
Start-Class: com.nbd.ocp.study.springboot.OcpStudySpringBootApplication
Spring-Boot-Classes: BOOT-INF/classes/
Spring-Boot-Lib: BOOT-INF/lib/
Spring-Boot-Version: 2.1.3.RELEASE
Created-By: Apache Maven 3.5.4
Build-Jdk: 1.8.0_202
Main-Class: org.springframework.boot.loader.JarLauncher

spring boot基础加载类：

org.springframework.boot.loader.Launcher
org.springframework.boot.loader.ExecutableArchiveLauncher：基于jar
org.springframework.boot.loader.archive.JarFileArchive ：基于文件系统
org.springframework.boot.loader.JarLauncher
org.springframework.boot.loader.WarLauncher

spring boot 加载顺序

以下拆分较细，spring定义的阶段详见org.springframework.boot.SpringApplicationRunListener

入口：Main-Class:(org.springframework.boot.loader.JarLauncher/WarLauncher)
- org.springframework.boot.loader.JarLauncher.main() launch(args) //开始加载
- org.springframework.boot.loader.Launcher.launch() JarFile.registerUrlProtocolHandler();//在系统属性中设置注册了自定义的URL处理器
- org.springframework.boot.loader.Launcher.launch() ClassLoader classLoader = createClassLoader(getClassPathArchives());//Spring-Boot-* 创建类加载器
- org.springframework.boot.loader.Launcher.launch() launch(args, getMainClass(), classLoader);//Start-Class 执行初始化逻辑
执行Start-Class对应的main函数
org.springframework.boot.SpringApplication.run(Class<?> primarySource, String… args):
- new SpringApplication(primarySources): 初始化包信息，
org.springframework.boot.SpringApplication.run(String… args)
- 启动时间控制，记录启动时间：StopWatch stopWatch = new StopWatch();
- 初始化监听器：SpringApplicationRunListeners listeners = this.getRunListeners(args);
- 发布ApplicationStartedEvent事件：listeners.starting();
- 装配参数和环境：ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
- 打印banner：Banner printedBanner = this.printBanner(environment);
- 创建ApplicationContext：context = this.createApplicationContext();
- 装配Context：this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
- 刷新上下文：this.refreshContext(context);
- 刷新后：this.afterRefresh(context, applicationArguments);
- 调用所有监听器的started(ctx)：listeners.started(context);
- 调用实现了 ApplicationRunner、CommandLineRunner 的对象的 run 方法：callRunners(context, applicationArguments);
- 调用所有监听器的running()：listeners.running(context);
- 返回上下文

spring boot 加载默认实现

详见:org.springframework.boot.spring-boot包内的spring.factories。各个实现的作用详见类注解。

    # PropertySource Loaders
    org.springframework.boot.env.PropertySourceLoader=\
    org.springframework.boot.env.PropertiesPropertySourceLoader,\
    org.springframework.boot.env.YamlPropertySourceLoader
    
    # Run Listeners
    org.springframework.boot.SpringApplicationRunListener=\
    org.springframework.boot.context.event.EventPublishingRunListener
    
    # Application Context Initializers
    org.springframework.context.ApplicationContextInitializer=\
    org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\
    org.springframework.boot.context.ContextIdApplicationContextInitializer,\
    org.springframework.boot.context.config.DelegatingApplicationContextInitializer,\
    org.springframework.boot.context.web.ServerPortInfoApplicationContextInitializer
    
    # Application Listeners
    org.springframework.context.ApplicationListener=\
    org.springframework.boot.builder.ParentContextCloserApplicationListener,\
    org.springframework.boot.context.FileEncodingApplicationListener,\
    org.springframework.boot.context.config.AnsiOutputApplicationListener,\
    org.springframework.boot.context.config.ConfigFileApplicationListener,\
    org.springframework.boot.context.config.DelegatingApplicationListener,\
    org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener,\
    org.springframework.boot.logging.ClasspathLoggingApplicationListener,\
    org.springframework.boot.logging.LoggingApplicationListener
    
    # Environment Post Processors
    org.springframework.boot.env.EnvironmentPostProcessor=\
    org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\
    org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor

spring boot扩展点

ApplicationContextInitializer

说明

主要用来在ConfigurableApplicationContext#refresh()之前对ConfigurableApplicationContext进行一些初始化的操作。一般来说主要做一些程序化的操作，比如注册配置源，根据配置激活某个profile等
* org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer：检查一些错误的configuration
* org.springframework.boot.context.ContextIdApplicationContextInitializer：主要用来设置contextId
* org.springframework.boot.context.config.DelegatingApplicationContextInitializer：主要用来委派执行ConfigurableEnvironment中定义的那些ApplicationContextInitializer
* org.springframework.boot.context.web.ServerPortInfoApplicationContextInitializer：设置server的端口至Environment properties

自定义

一、添加实现类
添加类实现ApplicationContextInitializer接口

public class MyApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
    @Override
    public void initialize(ConfigurableApplicationContext configurableApplicationContext) {
        System.out.println("=======“);
    }
}

二、注册到spring boot
方法1：

@SpringBootApplication
public class BlogApplication {
    public static void main(String[] args) {
        SpringApplication springApplication = new SpringApplication(BlogApplication.class);
        //关键一步：将一个或多个initializer加入至spring容器中
        springApplication.addInitializers(new MyApplicationContextInitializer());
        springApplication.run(args).close();
    }
}

方法2：
在application.properties中以context.initializer.classes为key配置一个或多个自定义Initializer

context.initializer.classes=com.MyApplicationContextInitializer

SpringApplicationRunListener

SpringApplication.run()的生命周期广播各个事件，实现类如：EventPublishingRunListener。此监听可以监听的时间详见接口：org.springframework.boot.SpringApplicationRunListener
使用：
* 创建CustomSpringApplicationRunListener继承org.springframework.boot.SpringApplicationRunListener。构造方法需要两个参数：org.springframework.boot.SpringApplication，String[]
* META-INF/spring.fatories 内添加 org.springframework.boot.SpringApplicationRunListener=com.CustomSpringApplicationRunListener