详细SpringBoot教程之启动配置原理

忘是亡心i 2023-07-09 03:25 152阅读 0赞

## 写在前面 ##

鉴于有人留言说想要学习SpringBoot相关的知识，我这里打算写一个SpringBoot系列的相关博文，目标呢是想让看了这一系列博文的同学呢，能够对SpringBoot略窥门径，这一系列的博文初步都定下来包括SpringBoot介绍、入门、配置、日志相关、web开发、数据访问、结合docker、缓存、消息队列、检索、任务安全、分布式等等一系列的博文，工作量很大，是个漫长的过程，每一步我都尽量详细，配上截图说明，也希望对看的同学真的有用。  
**单纯就是想分享技术博文，还想说一句就是，如果觉得有用，请点个关注、给个赞吧，也算对我来说是个宽慰，毕竟也得掉不少头发，嘿嘿嘿**

## 系列文章传送条 ##

[详细SpringBoot教程之入门（一）][SpringBoot]  
[详细SpringBoot教程之入门（二）][SpringBoot 1]  
[详细SpringBoot教程之配置文件（一）][SpringBoot 2]  
[详细SpringBoot教程之配置文件（二）][SpringBoot 3]  
[详细SpringBoot教程之日志框架][SpringBoot 4]  
[详细SpringBoot教程之Web开发（一）][SpringBoot_Web]  
[详细SpringBoot教程之Web开发（二）][SpringBoot_Web 1]  
[详细SpringBoot教程之Web开发（三）][SpringBoot_Web 2]  
[详细SpringBoot教程之数据访问][SpringBoot 5]  
[详细SpringBoot教程之启动配置原理][SpringBoot 6]  
[详细SpringBoot教程之缓存开发][SpringBoot 7]

## 启动配置原理 ##

到这里，我们讲解的只是其实已经够我们开发一些比较小的SpringBoot应用了，但是我们随着在使用的过程中，可以对SpringBoot进行底层原理分析，这样我们才能真正将SpringBoot使用的得心应手，然后我们还可以自己开发自己的starter场景启动器，是不是很刺激，后面我们会将，而我这里首先要几个重要的事件回调机制

我们之前也提到过，一般我们的配置核心是在各个配置的META-INF/spring.factories中，而我们SpringBoot的启动相关是

*  ApplicationContextInitializer
 *  SpringApplicationRunListener

只需要放在ioc容器中

*  ApplicationRunner
 *  CommandLineRunner

### 启动流程 ###

#### 创建SpringApplication对象 ####

initialize(sources);
    private void initialize(Object[] sources) { 
        //保存主配置类
        if (sources != null && sources.length > 0) { 
            this.sources.addAll(Arrays.asList(sources));
        }
        //判断当前是否一个web应用
        this.webEnvironment = deduceWebEnvironment();
        //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();
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0RCQ18xMjE_size_16_color_FFFFFF_t_70_pic_center]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0RCQ18xMjE_size_16_color_FFFFFF_t_70_pic_center 1]

#### 运行run方法 ####

public ConfigurableApplicationContext run(String... args) { 
       StopWatch stopWatch = new StopWatch();
       stopWatch.start();
       ConfigurableApplicationContext context = null;
       FailureAnalyzers analyzers = null;
       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
          context = createApplicationContext();
           
          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（）；
           
           //s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);
       }
    }

## 事件监听机制 ##

配置在META-INF/spring.factories

**ApplicationContextInitializer**

public class HelloApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> { 
        @Override
        public void initialize(ConfigurableApplicationContext applicationContext) { 
            System.out.println("ApplicationContextInitializer...initialize..."+applicationContext);
        }
    }

**SpringApplicationRunListener**

public class HelloSpringApplicationRunListener implements SpringApplicationRunListener { 
    
        //必须有的构造器
        public HelloSpringApplicationRunListener(SpringApplication application, String[] args){ 
    
        }
    
        @Override
        public void starting() { 
            System.out.println("SpringApplicationRunListener...starting...");
        }
    
        @Override
        public void environmentPrepared(ConfigurableEnvironment environment) { 
            Object o = environment.getSystemProperties().get("os.name");
            System.out.println("SpringApplicationRunListener...environmentPrepared.."+o);
        }
    
        @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 finished(ConfigurableApplicationContext context, Throwable exception) { 
            System.out.println("SpringApplicationRunListener...finished...");
        }
    }

配置（META-INF/spring.factories）

org.springframework.context.ApplicationContextInitializer=\
    com.atguigu.springboot.listener.HelloApplicationContextInitializer
    
    org.springframework.boot.SpringApplicationRunListener=\
    com.atguigu.springboot.listener.HelloSpringApplicationRunListener

只需要放在ioc容器中

**ApplicationRunner**

@Component
    public class HelloApplicationRunner implements ApplicationRunner { 
        @Override
        public void run(ApplicationArguments args) throws Exception { 
            System.out.println("ApplicationRunner...run....");
        }
    }

**CommandLineRunner**

@Component
    public class HelloCommandLineRunner implements CommandLineRunner { 
        @Override
        public void run(String... args) throws Exception { 
            System.out.println("CommandLineRunner...run..."+ Arrays.asList(args));
        }
    }

## 自定义starter ##

我们在之前的SpringBoot中，引入依赖的starter是不是很舒服，那么我们现在来学着怎么开发自己的starter，其实也非常简单，具体操作如下，首先我们使用Idea创建一个空项目  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0RCQ18xMjE_size_16_color_FFFFFF_t_70_pic_center 2]  
然后我们会到这里的界面，在这里，我们可以给空项目创建模块，我们如果要自己的启动器的话，那么最基本需要两个模块，不过是哪两个模块呢？这里我们要来讲讲。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0RCQ18xMjE_size_16_color_FFFFFF_t_70_pic_center 3]

我们需要搞清楚两个问题，如下

*  这个场景需要使用到的依赖是什么？
 *  如何编写自动配置

我们找个starter来进行分析，如下

@Configuration  //指定这个类是一个配置类
    @ConditionalOnXXX  //在指定条件成立的情况下自动配置类生效
    @AutoConfigureAfter  //指定自动配置类的顺序
    @Bean  //给容器中添加组件
    
    @ConfigurationPropertie  //结合相关xxxProperties类来绑定相关的配置
    @EnableConfigurationProperties //让xxxProperties生效加入到容器中
    
    //自动配置类要能加载
    //将需要启动就加载的自动配置类，配置在META-INF/spring.factories
    org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
    org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
    org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\

现在我们

所以我们应该符合以下模式：

*  启动器只用来做依赖导入；
 *  专门来写一个自动配置模块；
 *  启动器依赖自动配置；别人只需要引入启动器（starter）
 *  像mybatis-spring-boot-starter，我们命名应该自定义启动器名-spring-boot-starter

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0RCQ18xMjE_size_16_color_FFFFFF_t_70_pic_center 4]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0RCQ18xMjE_size_16_color_FFFFFF_t_70_pic_center 5]  
又到了我们熟悉的界面，我们要创建两个，一个是啥都不勾选的SpringBoot项目，还有一个只勾选web模块，创建好了之后，在pom.xml中进行如下更改

**启动器模块**

**自动配置模块**

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
       <modelVersion>4.0.0</modelVersion>
    
       <groupId>com.atguigu.starter</groupId>
       <artifactId>atguigu-spring-boot-starter-autoconfigurer</artifactId>
       <version>0.0.1-SNAPSHOT</version>
       <packaging>jar</packaging>
    
       <name>atguigu-spring-boot-starter-autoconfigurer</name>
       <description>Demo project for Spring Boot</description>
    
       <parent>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-parent</artifactId>
          <version>1.5.10.RELEASE</version>
          <relativePath/> 
       </parent>
    
       <properties>
          <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
          <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
          <java.version>1.8</java.version>
       </properties>
    
       <dependencies>
    
          
          <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter</artifactId>
          </dependency>
    
       </dependencies>
    
    
    
    </project>

package com.atguigu.starter;
    
    import org.springframework.boot.context.properties.ConfigurationProperties;
    
    @ConfigurationProperties(prefix = "atguigu.hello")
    public class HelloProperties { 
    
        private String prefix;
        private String suffix;
    
        public String getPrefix() { 
            return prefix;
        }
    
        public void setPrefix(String prefix) { 
            this.prefix = prefix;
        }
    
        public String getSuffix() { 
            return suffix;
        }
    
        public void setSuffix(String suffix) { 
            this.suffix = suffix;
        }
    }

package com.atguigu.starter;
    
    public class HelloService { 
    
        HelloProperties helloProperties;
    
        public HelloProperties getHelloProperties() { 
            return helloProperties;
        }
    
        public void setHelloProperties(HelloProperties helloProperties) { 
            this.helloProperties = helloProperties;
        }
    
        public String sayHellAtguigu(String name){ 
            return helloProperties.getPrefix()+"-" +name + helloProperties.getSuffix();
        }
    }

package com.atguigu.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应用才生效
    @EnableConfigurationProperties(HelloProperties.class)
    public class HelloServiceAutoConfiguration { 
    
        @Autowired
        HelloProperties helloProperties;
        @Bean
        public HelloService helloService(){ 
            HelloService service = new HelloService();
            service.setHelloProperties(helloProperties);
            return service;
        }
    }

## 下一篇 ##

SpringBoot官网其实给了很多案例给我们参考，集成了很多模块的示例代码，SpringBoot放在[GitHub上][GitHub]可以下载运行然后研究，下一遍对缓存进行讲解。

[SpringBoot]: https://blog.csdn.net/DBC_121/article/details/104383089
[SpringBoot 1]: https://blog.csdn.net/DBC_121/article/details/104429074
[SpringBoot 2]: https://blog.csdn.net/DBC_121/article/details/104446690
[SpringBoot 3]: https://blog.csdn.net/DBC_121/article/details/104448353
[SpringBoot 4]: https://dengbocong.blog.csdn.net/article/details/104456941
[SpringBoot_Web]: https://dengbocong.blog.csdn.net/article/details/104473765
[SpringBoot_Web 1]: https://blog.csdn.net/DBC_121/article/details/104503158
[SpringBoot_Web 2]: https://blog.csdn.net/DBC_121/article/details/104503231
[SpringBoot 5]: https://blog.csdn.net/DBC_121/article/details/104527730
[SpringBoot 6]: https://blog.csdn.net/DBC_121/article/details/104541113
[SpringBoot 7]: https://blog.csdn.net/DBC_121/article/details/104559440
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[GitHub]: https://github.com/spring-projects/spring-boot/tree/master/spring-boot-samples