Springboot启动配置原理

科技2022-07-13 120

Springboot启动配置原理

启动配置原理

核心启动配置参数

配置在META-INF/spring.factories中 ApplicationContextInitializer SpringApplicationRunListener 需要放在IOC容器中 ApplicationRunner CommandLineRunner

主要步骤

准备环境执行ApplicationContextInitializer.initialize()监听器SpringApplicationRunListener回调contextPrepared加载主配置类定义信息监听器SpringApplicationRunListener回调contextLoaded 刷新启动IOC容器扫描加载所有容器中的组件包括从MEAT-INF/spring.factories中获取所有的EnableAutoConfiguration组件回调容器中所有的ApplicationRunner和CommandLineRunner的run方法监听器SpringApplicationRunListener回调finished

具体流程步骤

首先对启动流程打上断点然后以Dubug模式运行

点击Step Into向下运行，可以看到以下一个方法

public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) { return (new SpringApplication(primarySources)).run(args); }

这个方法主要有两部分，第一部分创建SpringApplication对象，第二部分执行run方法

创建SpringApplication对象

Step Over到new SpringApplication(primarySources))可以看到创建SpringApplication对象的过程

public SpringApplication(Class<?>... primarySources) { this((ResourceLoader)null, primarySources); } public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) { this.sources = new LinkedHashSet(); this.bannerMode = Mode.CONSOLE; this.logStartupInfo = true; this.addCommandLineProperties = true; this.addConversionService = true; this.headless = true; this.registerShutdownHook = true; this.additionalProfiles = new HashSet(); this.isCustomEnvironment = false; 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。 this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class)); // 从类路径下找到META-INF/spring.factories配置的所有ApplicationListener this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class)); //从多个配置类中找到有main方法的主配置类,就是Springboot的启动类 this.mainApplicationClass = this.deduceMainApplicationClass(); }

执行run方法

public ConfigurableApplicationContext run(String... args) { StopWatch stopWatch = new StopWatch(); stopWatch.start(); ConfigurableApplicationContext context = null; Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList(); this.configureHeadlessProperty(); // 获取SpringApplicationRunListener; 从类路径下META-INF/spring.factories获取 SpringApplicationRunListeners listeners = this.getRunListeners(args); // 回调所有的获取SpringApplicationRunListener.starting()方法 listeners.starting(); Collection exceptionReporters; try { // 封装命令行参数 ApplicationArguments applicationArguments = new DefaultApplicationArguments(args); // 准备环境,创建环境完成后回调SpringApplicationRunListener.environmentPrepared();表示环境准备完成 ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments); this.configureIgnoreBeanInfo(environment); //打印Springboot的启动标志logo Banner printedBanner = this.printBanner(environment); // 创建ApplicationContext；决定创建web的IOC还是普通的IOC context = this.createApplicationContext(); exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context); // 准备上下文环境；将environment保存到IOC中，而且执行applyInitializers(); // applyInitializers():回调之前保存的所有ApplicationContextInitializer的initialize方法 // 回调所有的SpringApplicationRunListener的contextPrepared(); this.prepareContext(context, environment, listeners, applicationArguments, printedBanner); // prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded(); // 扫描容器；IOC容器初始化（如果是web应用还会创建嵌入的Tomcat）； // 扫描，创建，加载所有组件的地方(配置类，组件，自动配置) this.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 this.afterRefresh(context, applicationArguments); stopWatch.stop(); if (this.logStartupInfo) { (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch); } listeners.started(context); this.callRunners(context, applicationArguments); } catch (Throwable var10) { this.handleRunFailure(context, var10, exceptionReporters, listeners); throw new IllegalStateException(var10); } try { listeners.running(context); // 整个SpringBoot应用启动完成以后返回启动的IOC容器 return context; } catch (Throwable var9) { this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null); throw new IllegalStateException(var9); } }

事件监听机制

模拟事件监听机制，主要是以下几个类：

配置在META-INF/spring.factories中 ApplicationContextInitializer SpringApplicationRunListener 需要放在IOC容器中 ApplicationRunner CommandLineRunner

ApplicationContextInitializer

配置在META-INF/spring.factories中

package com.hui.listeners; import org.springframework.context.ApplicationContextInitializer; import org.springframework.context.ConfigurableApplicationContext; public class CustomApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> { @Override public void initialize(ConfigurableApplicationContext configurableApplicationContext) { System.out.println("ApplicationContextInitializer.....initialize"); } }

SpringApplicationRunListener

配置在META-INF/spring.factories中

package com.hui.listeners; import org.springframework.boot.SpringApplication; import org.springframework.boot.SpringApplicationRunListener; import org.springframework.context.ConfigurableApplicationContext; import org.springframework.core.env.ConfigurableEnvironment; public class CustomSpringApplicationRunListener implements SpringApplicationRunListener { // 必须有的构造器 public CustomSpringApplicationRunListener(SpringApplication application, String[] args){ } @Override public void starting() { System.out.println("SpringApplicationRunListener...starting...."); } @Override public void environmentPrepared(ConfigurableEnvironment environment) { Map<String, Object> systemEnvironment = environment.getSystemEnvironment(); for (Map.Entry<String, Object> key_value : systemEnvironment.entrySet()) { System.out.println(key_value.getKey()+"==="+key_value.getValue()); } } @Override public void contextPrepared(ConfigurableApplicationContext context) { System.out.println("SpringApplicationRunListener..contextPrepared"); } @Override public void contextLoaded(ConfigurableApplicationContext context) { System.out.println("SpringApplicationRunListener..contextLoaded"); } @Override public void started(ConfigurableApplicationContext context) { System.out.println("SpringApplicationRunListener..started"); } @Override public void running(ConfigurableApplicationContext context) { System.out.println("SpringApplicationRunListener..running"); } @Override public void failed(ConfigurableApplicationContext context, Throwable exception) { System.out.println("SpringApplicationRunListener..failed"); } }

添加META-INF/spring.factories配置

在resources下创建包META-INF，在包下创建文件spring.factories，然后将CustomApplicationContextInitializer和CustomSrpingApplicationRunListener配置进去

# Initializers org.springframework.context.ApplicationContextInitializer=\ com.hui.listeners.CustomApplicationContextInitializer # SpringApplicationRunListener Listeners org.springframework.boot.SpringApplicationRunListener=\ com.hui.listeners.CustomSpringApplicationRunListener

ApplicationRunner

需要放在IOC容器中

package com.hui.listeners; import org.springframework.boot.ApplicationArguments; import org.springframework.boot.ApplicationRunner; import org.springframework.stereotype.Component; @Component public class CustomApplicationRunner implements ApplicationRunner { @Override public void run(ApplicationArguments args) throws Exception { System.out.println("applicationRunner ... run ..."); } }

CommandLineRunner

需要放在IOC容器中

package com.hui.listeners; import org.springframework.boot.CommandLineRunner; import org.springframework.stereotype.Component; @Component public class CustomCommandLineRunner implements CommandLineRunner { @Override public void run(String... args) throws Exception { System.out.println("commandLineRunner ... run ..."); } }

启动项目

启动项目，在控制台可以看到监听器的执行顺序

SpringApplicationRunListener...starting.... ACTEL_FOR_ALTIUM_OVERRIDE=== USERDOMAIN_ROAMINGPROFILE===DESKTOP-COC7777 PROCESSOR_LEVEL===6 SESSIONNAME===Console ALLUSERSPROFILE===C:\ProgramData PROCESSOR_ARCHITECTURE===AMD64 GIT_INSTALL_ROOT===C:\Users\wanghui\scoop\apps\git\current PSModulePath===C:\Program Files\WindowsPowerShell\Modules;C:\Windows\system32\WindowsPowerShell\v1.0\Modules SystemDrive===C: MOZ_PLUGIN_PATH===C:\Users\wanghui\scoop\apps\foxit-reader\current\plugins\ USERNAME===wanghui ProgramFiles(x86)===C:\Program Files (x86) FPS_BROWSER_USER_PROFILE_STRING===Default PATHEXT===.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC Cmder===C:\Tools\cmder DriverData===C:\Windows\System32\Drivers\DriverData ProgramData===C:\ProgramData ProgramW6432===C:\Program Files HOMEPATH===\Users\wanghui PROCESSOR_IDENTIFIER===Intel64 Family 6 Model 158 Stepping 10, GenuineIntel ProgramFiles===C:\Program Files PUBLIC===C:\Users\Public windir===C:\Windows =::===::\ OneDriveCommercial===C:\Users\wanghui\OneDrive - students.solano.edu LOCALAPPDATA===C:\Users\wanghui\AppData\Local IntelliJ IDEA===C:\tools\JetBrains\IntelliJ IDEA 2019.3.3\bin; USERDOMAIN===DESKTOP-COC7777 FPS_BROWSER_APP_PROFILE_STRING===Internet Explorer LOGONSERVER===\\DESKTOP-COC7777 JAVA_HOME===C:\Users\wanghui\scoop\apps\ojdkbuild8-full\current ALTERA_FOR_ALTIUM_OVERRIDE=== CATALINA_BASE===C:\Users\wanghui\scoop\apps\tomcat8\current OneDrive===C:\Users\wanghui\OneDrive - students.solano.edu APPDATA===C:\Users\wanghui\AppData\Roaming CommonProgramFiles===C:\Program Files\Common Files Path===C:\Tools\Xshell\;C:\Tools\Xmanager\;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\iCLS\;C:\Program Files\Intel\Intel(R) Management Engine Components\iCLS\;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files\Intel\Intel(R) Management Engine Components\DAL;C:\Tools\Git\cmd;C:\Tools\apache-maven-3.6.3\bin;C:\Tools\java18\jdk1.8.0_161\bin;C:\Users\wanghui\scoop\apps\nodejs12\current\bin;C:\Users\wanghui\scoop\apps\nodejs12\current;C:\Users\wanghui\scoop\apps\maven\current\bin;C:\Users\wanghui\scoop\apps\ojdkbuild8-full\current\bin;C:\Users\wanghui\scoop\shims;C:\Users\wanghui\AppData\Local\Microsoft\WindowsApps;C:\Users\wanghui\AppData\Local\Pandoc\;C:\Tools\bandzip\;C:\tools\JetBrains\IntelliJ IDEA 2019.3.3\bin; OS===Windows_NT COMPUTERNAME===DESKTOP-COC7777 CATALINA_HOME===C:\Users\wanghui\scoop\apps\tomcat8\current PROCESSOR_REVISION===9e0a CommonProgramW6432===C:\Program Files\Common Files ComSpec===C:\Windows\system32\cmd.exe SystemRoot===C:\Windows TEMP===C:\Users\wanghui\AppData\Local\Temp HOMEDRIVE===C: USERPROFILE===C:\Users\wanghui TMP===C:\Users\wanghui\AppData\Local\Temp CommonProgramFiles(x86)===C:\Program Files (x86)\Common Files NUMBER_OF_PROCESSORS===6 IDEA_INITIAL_DIRECTORY===C:\Users\wanghui\Desktop . ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.1.13.RELEASE) ApplicationContextInitializer.....initialize SpringApplicationRunListener..contextPrepared 2020-08-24 02:56:36.255 INFO 4544 --- [ main] com.hui.SpringbootdemoApplication : Starting SpringbootdemoApplication on DESKTOP-COC7777 with PID 4544 (started by wanghui in D:\Hui\Persion\Application\IntelliJ IDEA\springbootdemo) 2020-08-24 02:56:36.257 INFO 4544 --- [ main] com.hui.SpringbootdemoApplication : No active profile set, falling back to default profiles: default SpringApplicationRunListener..contextLoaded 2020-08-24 02:56:36.827 INFO 4544 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http) 2020-08-24 02:56:36.840 INFO 4544 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2020-08-24 02:56:36.841 INFO 4544 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.31] 2020-08-24 02:56:36.897 INFO 4544 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2020-08-24 02:56:36.897 INFO 4544 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 616 ms 2020-08-24 02:56:37.006 INFO 4544 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor' 2020-08-24 02:56:37.107 INFO 4544 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path '' 2020-08-24 02:56:37.109 INFO 4544 --- [ main] com.hui.SpringbootdemoApplication : Started SpringbootdemoApplication in 1.085 seconds (JVM running for 1.567) SpringApplicationRunListener..started applicationRunner ... run ... commandLineRunner ... run ... SpringApplicationRunListener..running

Springboot自定义starter

如何编写自动配置

我们参照@WebMvcAutoConfiguration为例，我们看看们需要准备哪些东西，下面是WebMvcAutoConfiguration的部分代码：

@Configuration @ConditionalOnWebApplication @ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurerAdapter.class}) @ConditionalOnMissingBean({WebMvcConfigurationSupport.class}) @AutoConfigureOrder(-2147483638) @AutoConfigureAfter({DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class}) public class WebMvcAutoConfiguration { @Import({WebMvcAutoConfiguration.EnableWebMvcConfiguration.class}) @EnableConfigurationProperties({WebMvcProperties.class, ResourceProperties.class}) public static class WebMvcAutoConfigurationAdapter extends WebMvcConfigurerAdapter { @Bean @ConditionalOnBean({View.class}) @ConditionalOnMissingBean public BeanNameViewResolver beanNameViewResolver() { BeanNameViewResolver resolver = new BeanNameViewResolver(); resolver.setOrder(2147483637); return resolver; } } }

我们可以抽取到我们自定义starter时同样需要的一些配置。

@Configuration //指定这个类是一个配置类 @ConditionalOnXXX //指定条件成立的情况下自动配置类生效 @AutoConfigureOrder //指定自动配置类的顺序 @Bean //向容器中添加组件 @ConfigurationProperties //结合相关xxxProperties来绑定相关的配置 @EnableConfigurationProperties //让xxxProperties生效加入到容器中自动配置类要能加载需要将自动配置类，配置在META-INF/spring.factories中 org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\ org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\

模式

我们参照 spring-boot-starter-web 我们发现其中没有代码，但是其下的依赖里是有代码的：我们做自己的自动配置也采用这种模式，就是我们调用的XXX-spring-boot-starter启动器里不写代码，只是一个父依赖，我们要写的自动配置类XXX-spring-boot-autoconfigure里才写我们需要的代码

自定义starter实例

我们需要实现的工程：在主配置文件中配置一些参数，这些参数能生效

我们需要先创建两个工程 hello-spring-boot-starter 和 hello-spring-boot-starter-autoconfigurer

hello-spring-boot-starter：是maven工程，只是一份父依赖工程，pom文件：

hello-spring-boot-starter-autoconfigurer：是一个Springboot工程，pom文件：

删除：启动类、resources下的文件，test文件

在hello-spring-boot-starter-autoconfigurer下写需要的服务和自动配置文件

HelloProperties

package com.hui.starter; import org.springframework.boot.context.properties.ConfigurationProperties; //将配置文件中所有wh.hello的配置映射到HelloProperties配置类中 @ConfigurationProperties(prefix = "wh.hello") public class HelloProperties { private String before; private String after; public String getBefore() { return before; } public void setBefore(String before) { this.before = before; } public String getAfter() { return after; } public void setAfter(String after) { this.after = after; } }

HelloService

package com.hui.starter; public class HelloService { HelloProperties helloProperties; public HelloProperties getHelloProperties() { return helloProperties; } public void setHelloProperties(HelloProperties helloProperties) { this.helloProperties = helloProperties; } public String sayHello(String name ) { return helloProperties.getBefore()+ "-" + name + "-" +helloProperties.getAfter(); } }

HelloServiceAutoConfiguration

package com.hui.starter; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication; import org.springframework.boot.context.properties.EnableConfigurationProperties; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration @ConditionalOnWebApplication //web应用时生效，其实就是工程依赖中引入spring-boot-starter-web @EnableConfigurationProperties(HelloProperties.class) public class HelloServiceAutoConfiguration { @Autowired HelloProperties helloProperties; @Bean public HelloService helloService() { HelloService service = new HelloService(); service.setHelloProperties(helloProperties); return service; } }

spring.factories

在 resources 下创建文件夹 META-INF 并在 META-INF 下创建文件 spring.factories ，内容如下：

# Auto Configure org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ com.gf.service.HelloServiceAutoConfiguration

到这儿，我们的配置自定义的starter就写完了，我们将hello-spring-boot-starter-autoconfigurer、hello-spring-boot-starter 先后安装成本地jar包。

测试自定义starter

随便写一个Springboot的测试项目

pom文件

<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.1.13.RELEASE</version> <relativePath/>  </parent> <groupId>com.hui</groupId> <artifactId>springbootactivemq</artifactId> <version>0.0.1-SNAPSHOT</version> <name>springbootdemo</name> <description>Demo project for Spring Boot</description> <properties> <java.version>1.8</java.version> <targetJavaProject>src/main/java</targetJavaProject>  <targetResourcesProject>src/main/resources</targetResourcesProject> <targetXMLPackage>mapper</targetXMLPackage> <targetMapperPackage>com.hui.dao</targetMapperPackage> <targetModelPackage>com.hui.pojo</targetModelPackage> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency>  <dependency> <groupId>org.hui</groupId> <artifactId>hello-spring-boot-starter</artifactId> <version>1.0-SNAPSHOT</version> </dependency> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.17</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> <exclusions> <exclusion> <groupId>org.junit.vintage</groupId> <artifactId>junit-vintage-engine</artifactId> </exclusion> </exclusions> </dependency> </dependencies> </project>

HelloController

package com.hui.controller; import com.hui.starter.HelloService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RestController; @RestController public class HelloController { @Autowired private HelloService helloService; @GetMapping("/hello/{name}") public String hello(@PathVariable(value = "name") String name) { return helloService.sayHello(name); } }

application.yml

wh: hello: before: wang after: hui

启动项目，运行http://localhost:8080/hello/xiao访问，我的运行结果：

wang-xiao-hui

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