死磕源码系列【ContextIdApplicationContextInitializer源码解析】-蒲公英云

死磕源码系列【ContextIdApplicationContextInitializer源码解析】

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;
        }
    }
}