Spring boot自定义starter

1. 原理分析

1.1 spring.factories 如何被加载

首先启动一个简单的springboot项目，后面依次是断点位置

  1. 启动类WebApplication.java

    @SpringBootApplication
public class WebApplication {
    public static void main(String[] args) {
        SpringApplication.run(WebApplication.class, args);
    }
}

  2. Spring应用类SpringApplication.java

    public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
    return new SpringApplication(primarySources)//这里是用来加载META-INF/spring.factories
        .run(args); //这里将加载的结果交给spring容器管理
}
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();
    //这里就是从spring.factories加载数据了，继续跟进去
    setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
    setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
    this.mainApplicationClass = deduceMainApplicationClass();
}

  3. SpringFactoriesLoader.java 加载META-INF/spring.factories的所有配置

    public static List loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) {
    String factoryTypeName = factoryType.getName();
    return (List)loadSpringFactories(classLoader).getOrDefault(factoryTypeName, Collections.emptyList());
}
private static Map> loadSpringFactories(@Nullable ClassLoader classLoader) {
		MultiValueMap result = cache.get(classLoader);
		if (result != null) {
			return result;
		}
		try {
			Enumeration urls = (classLoader != null ?
					classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
					ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
			result = new LinkedMultiValueMap<>();
			while (urls.hasMoreElements()) {
				URL url = urls.nextElement();
				UrlResource resource = new UrlResource(url);
				Properties properties = PropertiesLoaderUtils.loadProperties(resource);
				for (Map.Entry<?, ?> entry : properties.entrySet()) {
					String factoryClassName = ((String) entry.getKey()).trim();
					for (String factoryName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) {
						result.add(factoryClassName, factoryName.trim());
					}
				}
			}
			cache.put(classLoader, result);
			return result;
		}
		catch (IOException ex) {
			throw new IllegalArgumentException("Unable to load factories from location [" +
					FACTORIES_RESOURCE_LOCATION + "]", ex);
		}
	}

    这里我们可以测试一下ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION)) 这个方法，会将META-INF/spring.factories所有的配置属性都找出

    @SpringBootApplication
public class WebApplication {
    public static void main(String[] args) throws IOException {
        //测试直接加载的结果
        String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";
        Enumeration urls = (
                ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
        while (urls.hasMoreElements()) {
            URL url = urls.nextElement();
            UrlResource resource = new UrlResource(url);
            Properties properties = PropertiesLoaderUtils.loadProperties(resource);
            for (Map.Entry objectObjectEntry : properties.entrySet()) {
                System.out.println(objectObjectEntry.getKey() + ":" +objectObjectEntry.getValue());
            }
        }
        //原springboot启动
        SpringApplication.run(WebApplication.class, args);
    }
}

1.2 加载完之后，如何交给Spring容器管理

  1. 进入run方法 SpringApplication.java

    public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
    return new SpringApplication(primarySources)//这里是用来加载META-INF/spring.factories
        .run(args); //这里将加载的结果交给spring容器管理
}
public ConfigurableApplicationContext run(String... args) {
    StopWatch stopWatch = new StopWatch();
    stopWatch.start();
    ConfigurableApplicationContext context = null;
    Collection exceptionReporters = new ArrayList<>();
    configureHeadlessProperty();
    //从类路径下META-INF/spring.factories获取SpringApplicationRunListeners
    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
        configureIgnoreBeanInfo(environment);
        //打印Banner图
        Banner printedBanner = printBanner(environment);
        //创建ApplicationContext,决定创建web的ioc还是普通的ioc 
        context = createApplicationContext();
         //异常分析报告
        exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
                                                         new Class[] { ConfigurableApplicationContext.class }, context);
        //prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded() 
        prepareContext(context, environment, listeners, applicationArguments, printedBanner);
        //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)//扫描，创建，加载所有组件的地方,(配置类，组件，自动配置) 
        refreshContext(context);
        afterRefresh(context, applicationArguments);
        stopWatch.stop();
        if (this.logStartupInfo) {
            new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
        }
        //所有的SpringApplicationRunListener回调started方法  
        listeners.started(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
        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);
    }
    //整个SpringBoot应用启动完成以后返回启动的ioc容器
    return context;
}

  2. 最主要的prepareContext()方法，这里就是将bean交给IOC容器管理

    private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
			SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
    context.setEnvironment(environment);
    postProcessApplicationContext(context);
    //回调之前保存的所有的ApplicationContextInitializer的initialize方法
    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 sources = getAllSources();
    Assert.notEmpty(sources, "Sources must not be empty");
    load(context, sources.toArray(new Object[0]));
    listeners.contextLoaded(context);
}




    2.自定义starter
    

    2.1 建立自己的starter项目 hsm-spring-boot-starter
    

      

    1. 目录结构
      2. 

    

    

      

    1. 

      pom.xml
      

      <?xml version="1.0" encoding="UTF-8"?>

    4.0.0
    
        org.springframework.boot
        spring-boot-starter-parent
        2.2.6.RELEASE
    
    com.hsm
    hsm-spring-boot-starter
    0.0.1-RELEASE

    
        8
        8
        1.8
    

    
        
            org.springframework.boot
            spring-boot-configuration-processor
            true
        

        
            org.springframework.boot
            spring-boot-starter
        

        
            org.projectlombok
            lombok
            1.18.8
            true
        
    



      

      2. 

    2. 

      DemoConfig.java
      

      @EnableConfigurationProperties(DemoProperties.class)
@ConditionalOnProperty(prefix = "demo",name = "isopen",havingValue = "true")
public class DemoConfig {
    @Resource
    private DemoProperties demoProperties;

    @Bean(name = "demo")
    public DemoService demoService(){
        return new DemoService(demoProperties.getSayWhat(), demoProperties.getToWho());
    }
}

      

      3. 

    3. 

      DemoProperties.java
      

      @ConfigurationProperties(prefix = "demo")
@Data
public class DemoProperties {

    private String sayWhat;
    private String toWho;
}

      

      4. 

    4. 

      DemoService.java
      

      public class DemoService {
    public String sayWhat;
    public String toWho;
    public DemoService(String sayWhat, String toWho){
        this.sayWhat = sayWhat;
        this.toWho = toWho;
    }
    public String say(){
        return this.sayWhat + "!  " + toWho;
    }
}

      

      5. 

    5. 

      spring.factories
      

      org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.hsm.config.DemoConfig

      

      6. 

    

    3. 使用starter
    

      

    1. 

      pom.xml
      

      
    
        com.hsm
        hsm-spring-boot-starter
        0.0.1-RELEASE
    
    
        org.springframework.boot
        spring-boot-starter-web
        2.2.6.RELEASE
    


      

      2. 

    2. 

      启动类
      

      @SpringBootApplication
public class WebApplication {
    public static void main(String[] args) throws IOException {
        SpringApplication.run(WebApplication.class, args);
    }
}

      

      3. 

    3. 

      控制类
      

      @RestController
public class DemoController {
    @Resource(name = "demo")
    private DemoService demoService;

    @GetMapping("/say")
    public String sayWhat() {
        return demoService.say();
    }
}


      

      4. 

    4. 

      配置文件 application.properties
      

      demo.isopen=true
demo.say-what=hello
demo.to-who=shf

      

      5. 

    5. 

      访问
      

      localhost:8080/say

      

      6. 

    
						  
					  
						
							
    

						
    
							
							
			Springspringbootstarter自定义							
						



						
    
						
						
    

						

						
					
					
    
					
					
    
						
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