死磕源码系列【ContextIdApplicationContextInitializer源码解析】

拼搏现实的明天。 2022-11-21 03:34 161阅读 0赞

> ContextIdApplicationContextInitializer类是ApplicationContextInitializer初始化器接口实现类，会在应用程序启动的时候初始化应用程序的唯一ID。

ContextIdApplicationContextInitializer设置Spring ApplicationContext上下文ID,如果spring.application.name属性存在，则将其作为ID，否则使用application默认值作为ID，源码如下：

public class ContextIdApplicationContextInitializer
    		implements ApplicationContextInitializer<ConfigurableApplicationContext>, Ordered { 
    
    	private int order = Ordered.LOWEST_PRECEDENCE - 10;
    
    	public void setOrder(int order) { 
    		this.order = order;
    	}
    
    	@Override
    	public int getOrder() { 
    		return this.order;
    	}
    	//初始化器对象回调方法
    	@Override
    	public void initialize(ConfigurableApplicationContext applicationContext) { 
        //获取上下文ID实例
    		ContextId contextId = getContextId(applicationContext);
        //将获取到的ID设置到ApplicationContext上下文中
    		applicationContext.setId(contextId.getId());
        //将上下文ID注入到IOC容器之中
    		applicationContext.getBeanFactory().registerSingleton(ContextId.class.getName(), contextId);
    	}
    	//获取上下文 ID实例对象
    	private ContextId getContextId(ConfigurableApplicationContext applicationContext) { 
    		ApplicationContext parent = applicationContext.getParent();
    		if (parent != null && parent.containsBean(ContextId.class.getName())) { 
    			return parent.getBean(ContextId.class).createChildId();
    		}
    		return new ContextId(getApplicationId(applicationContext.getEnvironment()));
    	}
    	//获取应用程序上下文ID,如果spring.application.name存在，则使用此值，否则使用application
    	private String getApplicationId(ConfigurableEnvironment environment) { 
    		String name = environment.getProperty("spring.application.name");
    		return StringUtils.hasText(name) ? name : "application";
    	}
    
    	/** * 上下文ID */
    	static class ContextId { 
    
    		private final AtomicLong children = new AtomicLong(0);
    
    		private final String id;
    
    		ContextId(String id) { 
    			this.id = id;
    		}
    
    		ContextId createChildId() { 
    			return new ContextId(this.id + "-" + this.children.incrementAndGet());
    		}
    
    		String getId() { 
    			return this.id;
    		}
    
    	}
    
    }

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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