style: 添加 FlexTransactionAutoConfiguration 注释。

mybatis-flex-spring-boot-starter/src/main/java/com/mybatisflex/spring/boot/FlexTransactionAutoConfiguration.java

@@ -1,4 +1,4 @@
-/**
+/*
  *  Copyright (c) 2022-2023, Mybatis-Flex (fuhai999@gmail.com).
  *  <p>
  *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -26,16 +26,27 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.annotation.TransactionManagementConfigurer;
 
+/**
+ * MyBatis-Flex 事务自动配置。
+ */
 @ConditionalOnClass(Db.class)
 @Configuration(proxyBeanMethods = false)
 @AutoConfigureAfter({MybatisFlexAutoConfiguration.class})
 @AutoConfigureBefore({TransactionAutoConfiguration.class})
 public class FlexTransactionAutoConfiguration implements TransactionManagementConfigurer {
 
+    /**
+     * 这里使用 final 修饰属性是因为：<br>
+     * <p>
+     * 1、调用 {@link #annotationDrivenTransactionManager} 方法会返回 TransactionManager 对象<br>
+     * 2、{@code @Bean} 注入又会返回 TransactionManager 对象<br>
+     * <p>
+     * 需要保证两个对象的一致性。
+     */
     private final FlexTransactionManager flexTransactionManager = new FlexTransactionManager();
 
-    @Override
     @Bean
+    @Override
     public PlatformTransactionManager annotationDrivenTransactionManager() {
         return flexTransactionManager;
     }