死磕源码系列【springboot主配置源类加载the primary source to load】

淡淡的烟草味﹌ 2022-12-13 01:48 103阅读 0赞

通常使用springboot开发是会有一个主方法main方法入口：

import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    public class QuartzBootStrap { 
        public static void main(String[] args) { 
            //参数QuartzBootStrap.class是主配置源类
            SpringApplication.run(QuartzBootStrap.class, args);
        }
    }

进入到SpringApplication\#run方法：

/** * Static helper that can be used to run a {@link SpringApplication} from the * specified sources using default settings and user supplied arguments. * @param primarySources the primary sources to load * @param args the application arguments (usually passed from a Java main method) * @return the running {@link ApplicationContext} */
    	public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) { 
    		return new SpringApplication(primarySources).run(args);
    	}

run方法是一个静态方法，传递主配置源参数，会将主配置源类优先注册到IOC容器，为后续扫描加载项目中的其它bean做准备；上述方法创建类一个SpringApplication对象，构造函数如下：

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) { 
    		this.resourceLoader = resourceLoader;
    		Assert.notNull(primarySources, "PrimarySources must not be null");
        //此处会对主配置源参数做初始化，后续注册到容器时会用到
    		this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
    		this.webApplicationType = WebApplicationType.deduceFromClasspath();
    		setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
    		setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
    		this.mainApplicationClass = deduceMainApplicationClass();
    	}

由SpringApplication\#run进入SpringApplication\#prepareContext方法：

private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
    		...省略
    		// Load the sources 加载主配置源类
    		Set<Object> sources = getAllSources();
    		Assert.notEmpty(sources, "Sources must not be empty");
    		load(context, sources.toArray(new Object[0]));
    		listeners.contextLoaded(context);
    	}

获取主配置源类方法SpringApplication\#getAllSources：

public Set<Object> getAllSources() { 
       Set<Object> allSources = new LinkedHashSet<>();
       if (!CollectionUtils.isEmpty(this.primarySources)) { 
       		//此处获取到的主配置源类就是上述主方法传入的配置源类
          allSources.addAll(this.primarySources);
       }
       if (!CollectionUtils.isEmpty(this.sources)) { 
          allSources.addAll(this.sources);
       }
       return Collections.unmodifiableSet(allSources);
    }

BeanDefinitionLoader\#load()方法加载主配置类并注册到IOC容器：

int load() { 
    		int count = 0;
    		for (Object source : this.sources) { 
    			count += load(source);
    		}
    		return count;
    	}
    
    	private int load(Object source) { 
    		Assert.notNull(source, "Source must not be null");
    		if (source instanceof Class<?>) { 
    			return load((Class<?>) source);
    		}
    		if (source instanceof Resource) { 
    			return load((Resource) source);
    		}
    		if (source instanceof Package) { 
    			return load((Package) source);
    		}
    		if (source instanceof CharSequence) { 
    			return load((CharSequence) source);
    		}
    		throw new IllegalArgumentException("Invalid source type " + source.getClass());
    	}
    
    	private int load(Class<?> source) { 
    		if (isGroovyPresent() && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) { 
    			// Any GroovyLoaders added in beans{} DSL can contribute beans here
    			GroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source, GroovyBeanDefinitionSource.class);
    			load(loader);
    		}
        //检查bean是否符合注册条件
    		if (isEligible(source)) { 
          //将配置类注册到IOC容器之中
    			this.annotatedReader.register(source);
    			return 1;
    		}
    		return 0;
    	}

GitHub地址：[https://github.com/mingyang66/spring-parent][https_github.com_mingyang66_spring-parent]

[https_github.com_mingyang66_spring-parent]: https://github.com/mingyang66/spring-parent