instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
+ // 按@Order注解进行排序，值约小的越靠前
+ AnnotationAwareOrderComparator.sort(instances);
+ return instances;
+ }
+```
+
+
+
+##### 6、将初始化器排序好的实例注册到Spring容器中
+
+```java
+ public void setInitializers(Collection> initializers) {
+ this.initializers = new ArrayList<>();
+ // 将初始化器的实例添加到Spring容器中
+ this.initializers.addAll(initializers);
+ }
+```
+
+
+
+#### 总结
+
+- SpringFactoriesLoader作用： SpringBoot框架中从类路径jar包中读取特定的文件（META-INF/spring.factories）实现扩展类的载入
+
+
+
+- LoadFactories流程
+
+
diff --git "a/springboot-source-code-analysis/(4)\347\263\273\347\273\237\345\210\235\345\247\213\345\214\226\345\231\250\350\247\243\346\236\220.md" "b/springboot-source-code-analysis/(4)\347\263\273\347\273\237\345\210\235\345\247\213\345\214\226\345\231\250\350\247\243\346\236\220.md"
new file mode 100644
index 0000000..b293a0e
--- /dev/null
+++ "b/springboot-source-code-analysis/(4)\347\263\273\347\273\237\345\210\235\345\247\213\345\214\226\345\231\250\350\247\243\346\236\220.md"
@@ -0,0 +1,215 @@
+### 系统初始化器解析
+
+#### 1、ApplicationContextInitializer作用
+
+```java
+/**
+ * Callback interface for initializing a Spring {@link ConfigurableApplicationContext}
+ * prior to being {@linkplain ConfigurableApplicationContext#refresh() refreshed}.
+ *
+ * Typically used within web applications that require some programmatic initialization
+ * of the application context. For example, registering property sources or activating
+ * profiles against the {@linkplain ConfigurableApplicationContext#getEnvironment()
+ * context's environment}. See {@code ContextLoader} and {@code FrameworkServlet} support
+ * for declaring a "contextInitializerClasses" context-param and init-param, respectively.
+ *
+ *
{@code ApplicationContextInitializer} processors are encouraged to detect
+ * whether Spring's {@link org.springframework.core.Ordered Ordered} interface has been
+ * implemented or if the @{@link org.springframework.core.annotation.Order Order}
+ * annotation is present and to sort instances accordingly if so prior to invocation.
+ *
+ * @author Chris Beams
+ * @since 3.1
+ * @param the application context type
+ * @see org.springframework.web.context.ContextLoader#customizeContext
+ * @see org.springframework.web.context.ContextLoader#CONTEXT_INITIALIZER_CLASSES_PARAM
+ * @see org.springframework.web.servlet.FrameworkServlet#setContextInitializerClasses
+ * @see org.springframework.web.servlet.FrameworkServlet#applyInitializers
+ */
+public interface ApplicationContextInitializer {
+
+ /**
+ * Initialize the given application context.
+ * @param applicationContext the application to configure
+ */
+ void initialize(C applicationContext);
+}
+
+```
+
+- 上下文刷新即refersh方法前调用；
+- 用来编码设置一些属性变量，通常用在web环境中；
+- 可以通过order接口进行排序；
+
+
+
+#### 2、ApplicationContextInitializer调用点，通过SpringFactoriesLoder中的this.initializers进行初始化
+
+
+
+- 步骤一：在刷新上下文前，调用prepareContext#()准备上下文的方法
+
+```java
+public ConfigurableApplicationContext run(String... args) {
+ StopWatch stopWatch = new StopWatch();
+ stopWatch.start();
+ ConfigurableApplicationContext context = null;
+ Collection exceptionReporters = new ArrayList<>();
+ configureHeadlessProperty();
+ SpringApplicationRunListeners listeners = getRunListeners(args);
+ listeners.starting();
+ try {
+ ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
+ ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
+ configureIgnoreBeanInfo(environment);
+ Banner printedBanner = printBanner(environment);
+ context = createApplicationContext();
+ exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
+ new Class[] { ConfigurableApplicationContext.class }, context);
+ // 准备上下文
+ prepareContext(context, environment, listeners, applicationArguments, printedBanner);
+ // 刷新上下文
+ refreshContext(context);
+ afterRefresh(context, applicationArguments);
+ stopWatch.stop();
+ if (this.logStartupInfo) {
+ new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
+ }
+ listeners.started(context);
+ 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);
+ }
+ return context;
+ }
+```
+
+- 步骤二：调用初始化器 applyInitializers(context) 方法
+
+```java
+ private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
+ SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
+ context.setEnvironment(environment);
+ postProcessApplicationContext(context);
+ // 调用初始化器方法
+ 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);
+ }
+ // Load the sources
+ Set
+
+
+
+
+
+#### 在SpringBoot工程中引入Freemarker依赖
+
+```java
+
+
+
+
+##### Netty并不是只支持过NIO，但是不建议（depercate）阻塞I/O（BIO/OIO）
+
+- 连接数高的情况下：阻塞 -> 消耗源、效率低
+
+##### Netty也不建议（depercate）使用AIO
+
+- AIO在Windows 下比较成熟，但是很少用来做服务器
+- Linux 常用来做服务器，但是AIO实现不够成熟
+- Linux 的AIO相比NIO的性能没有显著的提升，反而会为开发者带来高额的维护成本
+
+##### Netty和JDK NIO在Linux下，都是基于epoll实现，为什么要用Netty？
+
+- Netty 暴露了更多的可用参数，如：
+ - JDK 的 NIO 默认实现是水平触发
+ - Netty 是边缘触发（默认）和水平触发可以切换
+- Netty 实现的垃圾回收更少、性能更好
+
+
+
+#### 2.Netty NIO 中的Reactor 开发模式
+
+Netty 三种开发模式版本
+
+BIO 下是 Thread-Per-Connection
+
+
+
+
+
+***Thread-Per-Connection：对应每个连接都有1个线程处理，1个线程同时处理：读取、解码、计算、编码、发送***
+
+
+
+NIO 下是 Reactor
+
+
+
+
+
+***Reactor 多线程模式，由多个线程负责：读取、发送，由线程池负责处理：解码、计算、编码***
+
+***Reactor 主从多线程模式，由单独mainReactor 单线程负责接收请求，subReactor和 Reactor 多线程模式一致***
+
+
+
+AIO 下是 Proactor
+
+Reactor 是一种开发模式，模式的核心流程：
+
+> 注册感兴趣的事件 -> 扫描是否有感兴趣的事件发生 -> 事件发生后做出相应的处理
+
+
+
+##### Netty下使用 NIO 示范例
+
+- Reactor 单线程模式
+
+```java
+//线程数1
+EventLoopGroup eventGroup = new NioEventLoopGroup(1);
+
+ServerBootStrap serverBootStrap = new ServerBootStrap();
+serverBootStrap.group(eventGroup);
+```
+
+- Reactor 多线程模式
+
+```java
+//多线程，不传具体的线程数时，Netty会根据CPU核心数分配
+EventLoopGroup eventGroup = new NioEventLoopGroup();
+
+ServerBootStrap serverBootStrap = new ServerBootStrap();
+serverBootStrap.group(serverBootStrap);
+```
+
+- Reactor 主从多线程模式
+
+```java
+// 主线程负责接收请求 acceptor，是单线程
+EventLoopGroup bossGroup = new NioEventLoopGroup();
+// 从线程负责：读取、解码、计算、编码、发送，是多线程
+EventLoopGroup workerGroup = new NioEventLoopGroup();
+
+SeverBootStrap serverBootStrap = new ServerBootStrap();
+serverBootStrap.group(bossGroup, workerGroup);
+```
+
+
+
+##### Netty 支持主从 Reactor 源码分析
+
+1.初始化 Main EventLoopGroup
+
+```java
+public abstract class AbstractBootstrap, C extends Channel> implements Cloneable {
+
+ // main Event Loop Group
+ volatile EventLoopGroup group;
+
+ ....
+
+ // 初始化 mian Event Loop Group 方法
+ public B group(EventLoopGroup group) {
+ ObjectUtil.checkNotNull(group, "group");
+ if (this.group != null) {
+ throw new IllegalStateException("group set already");
+ }
+ this.group = group;
+ return self();
+ }
+
+ ....
+}
+```
+
+2. 初始化 Worker EventLoopGroup
+
+```java
+public class ServerBootstrap extends AbstractBootstrap