add spring refresh source code analysis introduction in readme file

Author: ipipman

springboot-source-code-analysis/(12)框架Refresh方法解析一.md

@@ -0,0 +1,276 @@
+
+
+### 框架Refresh方法解析一
+
+
+
+#### 1.Refresh方法简介
+
+- Bean配置读取加载入口
+- Spring框架的启动流程
+
+
+
+#### 2.Refresh方法的执行步骤
+
+<img src="https://tva1.sinaimg.cn/large/008i3skNly1gvib55enehj61eg0u041602.jpg" alt="image-20211017144834689" align="left" width="800" />
+
+```java
+	@Override
+	public void refresh() throws BeansException, IllegalStateException {
+		synchronized (this.startupShutdownMonitor) {
+			// Prepare this context for refreshing.
+      // 准备此上下文
+			prepareRefresh();
+
+			// Tell the subclass to refresh the internal bean factory.
+      // 获取BeanFacotry
+			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
+
+			// Prepare the bean factory for use in this context.
+      // 准备此类上下文中使用的Bean工厂
+			prepareBeanFactory(beanFactory);
+
+			try {
+				// Allows post-processing of the bean factory in context subclasses.
+        // 允许在上下文子类中对Bean工厂进行后处理
+				postProcessBeanFactory(beanFactory);
+
+				// Invoke factory processors registered as beans in the context.
+        // 调用在上下文中注册为Bean的工厂处理器
+				invokeBeanFactoryPostProcessors(beanFactory);
+
+				// Register bean processors that intercept bean creation.
+        // 注册拦截Bean创建的Bean处理器
+				registerBeanPostProcessors(beanFactory);
+
+				// Initialize message source for this context.
+        // 为此上下文初始化消息源
+				initMessageSource();
+
+				// Initialize event multicaster for this context.
+        // 为此上下文初始化事件广播器
+				initApplicationEventMulticaster();
+
+				// Initialize other special beans in specific context subclasses.
+        // 初始化特定上下文子类中的其他特殊Bean
+				onRefresh();
+
+				// Check for listener beans and register them.
+        // 检查监听器，并注册
+				registerListeners();
+
+				// Instantiate all remaining (non-lazy-init) singletons.
+        // 实例化所有剩余的（非延迟初始化）单例。
+				finishBeanFactoryInitialization(beanFactory);
+
+				// Last step: publish corresponding event.
+        // 最后一步：发布相应的事件
+				finishRefresh();
+			}
+
+			catch (BeansException ex) {
+				if (logger.isWarnEnabled()) {
+					logger.warn("Exception encountered during context initialization - " +
+							"cancelling refresh attempt: " + ex);
+				}
+
+				// Destroy already created singletons to avoid dangling resources.
+        // 销毁已经创建的单例以避免浪费资源
+				destroyBeans();
+
+				// Reset 'active' flag.
+        // 重置active标志
+				cancelRefresh(ex);
+
+				// Propagate exception to caller.
+				throw ex;
+			}
+
+			finally {
+				// Reset common introspection caches in Spring's core, since we
+				// might not ever need metadata for singleton beans anymore...
+       	// 重置 Spring 核心中的常见内省缓存，因为我们可能不再需要单例 bean 的元数据...
+				resetCommonCaches();
+			}
+		}
+	}
+```
+
+
+
+#### 3.准备上下文：prepareRefersh#方法
+
+- prepareRefersh#方法简介
+  - 清除本地元数据缓存
+  - 准备框架上下文
+    - 设置框架启动时间
+    - 设置框架 active 启动状态为true
+    - 如果是Debug模式打印Debug日志
+    - 初始化环境配置
+      - 获取当前环境配置
+      - 如果是Web环境，配置ServletContext 和 ServletConfig
+    - 检查环境配置中的必备属性是否存在
+    - 如果没有早期的事件监听器，就注册应用监听器：applicationListeners
+
+-  prepareRefresh#方法
+
+```java
+	@Override
+	protected void prepareRefresh() {
+    // 清除元数据缓存
+		this.scanner.clearCache();
+    // 准备上下文
+		super.prepareRefresh();
+	}
+```
+
+- clearCache#方法
+
+```java
+	/**
+	 * Clear the local metadata cache, if any, removing all cached class metadata.
+	 * 清除本地元数据缓存（如果有），删除所有缓存的类元数据。
+	 */
+	public void clearCache() {
+		if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
+			// Clear cache in externally provided MetadataReaderFactory; this is a no-op
+			// for a shared cache since it'll be cleared by the ApplicationContext.
+      // 清除外部提供的 MetadataReaderFactory 中的缓存；这是一个无操作用于共享缓存，因为它将被 ApplicationContext 清除。
+			((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
+		}
+	}
+```
+
+-  super.prepareRefresh方法
+
+```java
+	/**
+	 * Prepare this context for refreshing, setting its startup date and
+	 * active flag as well as performing any initialization of property sources.
+	 * 准备此上下文以进行刷新、设置其启动日期和* active 标志以及执行属性源的任何初始化
+	 */
+	protected void prepareRefresh() {
+		// Switch to active.
+    // 设置启动时间
+		this.startupDate = System.currentTimeMillis();
+		this.closed.set(false);
+    // 设置 active 标志状态为 true
+		this.active.set(true);
+    
+    // 如果当前日志状态是Debug模式的话，会打印一段话
+		if (logger.isDebugEnabled()) {
+			if (logger.isTraceEnabled()) {
+				logger.trace("Refreshing " + this);
+			}
+			else {
+				logger.debug("Refreshing " + getDisplayName());
+			}
+		}
+
+		// Initialize any placeholder property sources in the context environment.
+    // 初始化环境配置
+		initPropertySources();
+
+		// Validate that all properties marked as required are resolvable:
+		// see ConfigurablePropertyResolver#setRequiredProperties
+    // 检查环境属性中必备的环境数据，如果没有就 throw MissingRequiredPropertiesException 异常
+		getEnvironment().validateRequiredProperties();
+
+		// Store pre-refresh ApplicationListeners...
+    // 将系统的事件监听器进行注册
+		if (this.earlyApplicationListeners == null) {
+			this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
+		}
+		else {
+			// Reset local application listeners to pre-refresh state.
+			this.applicationListeners.clear();
+			this.applicationListeners.addAll(this.earlyApplicationListeners);
+		}
+
+    // Allow for the collection of early ApplicationEvents,
+		// to be published once the multicaster is available...
+		this.earlyApplicationEvents = new LinkedHashSet<>();
+	}
+
+```
+
+- initPropertySources#方法
+
+```java
+    protected void initPropertySources() {
+        // 获取环境配置上下文
+        ConfigurableEnvironment env = this.getEnvironment();
+     		// 如果当前环境是Web环境，将servletContext 和 ServletConfig 加载到环境配置上下文中
+        if (env instanceof ConfigurableWebEnvironment) {
+            ((ConfigurableWebEnvironment)env).initPropertySources(this.servletContext, (ServletConfig)null);
+        }
+    }
+```
+
+
+
+
+
+#### 获取新的Bean工厂：obtainFreshBeanFacotry#方法
+
+- obtainFreshBeanFacotry#方法简介
+  - 设置当前上下文刷新状态为true
+  - 这是BeanFactory序列化ID（默认是application）
+  - 返回BeanFacotry
+
+- obtainFreshBeanFactory#方法
+
+```java
+	/**
+	 * Tell the subclass to refresh the internal bean factory.
+	 * 告诉子类刷新内部 bean 工厂
+	 * @return the fresh BeanFactory instance
+	 * @see #refreshBeanFactory()
+	 * @see #getBeanFactory()
+	 */
+	protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
+    // 设置上下文刷新状态和Beanfacotory的序列化ID
+		refreshBeanFactory();
+    // 获取BeanFactory（默认是DefaultListableBeanFacotry）
+		return getBeanFactory();
+	}
+
+```
+
+- refreshBeanFacoty#方法
+
+```java
+	/**
+	 * Do nothing: We hold a single internal BeanFactory and rely on callers
+	 * to register beans through our public methods (or the BeanFactory's).
+	 * @see #registerBeanDefinition
+	 */
+	@Override
+	protected final void refreshBeanFactory() throws IllegalStateException {
+    // 设置当前上下文刷新状态：true
+		if (!this.refreshed.compareAndSet(false, true)) {
+			throw new IllegalStateException(
+					"GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
+		}
+    // 设置BeanFacotry序列化ID：默认是application
+		this.beanFactory.setSerializationId(getId());
+	}
+```
+
+- getBeanFacotory#方法
+
+```java
+/**
+	 * Return the single internal BeanFactory held by this context
+	 * (as ConfigurableListableBeanFactory).
+	 */
+	@Override
+	public final ConfigurableListableBeanFactory getBeanFactory() {
+    // 返回默认的 DefaultListableBeanFacotry
+		return this.beanFactory;
+	}
+```
+
+
+

springboot-source-code-analysis/src/main/java/com/example/springboot/source/code/analysis/initializer/FirstInitializer.java

@@ -30,6 +30,9 @@ public void initialize(ConfigurableApplicationContext configurableApplicationCon
         ConfigurableEnvironment environment =
                 configurableApplicationContext.getEnvironment();
 
+        // 设置必填属性
+        environment.setRequiredProperties("app.enviroment");
+
         // 设置自定义属性
         Map<String, Object> attributeMap = new HashMap<>();
         attributeMap.put("firstKey", "firstValue");

springboot-source-code-analysis/src/main/resources/application.properties

@@ -5,4 +5,8 @@ context.initializer.classes=\
 # 通过系统事件监听器，监听事件
 context.listener.classes=\
   com.example.springboot.source.code.analysis.listener.ThirdListener,\
-  com.example.springboot.source.code.analysis.listener.FourthListener
+  com.example.springboot.source.code.analysis.listener.FourthListener
+
+
+# 通过ConfigurableEnviroment.requiredProperty()方法设置的必填属性
+app.enviroment=ipman