feat: Spring Boot 学习脚手架 v2.0

- 新增 IoC 容器学习模块
- 新增 AOP 切面编程学习模块
- 新增 MyBatis 集成学习模块
- 新增事务管理学习模块
- 新增用户/产品/订单 CRUD
- 新增 7 个交互式学习页面
- 集成性能监控切面

src/main/java/com/example/scaffold/mapper/UserMapper.java

@@ -0,0 +1,78 @@
+package com.example.scaffold.mapper;
+
+import com.example.scaffold.entity.User;
+import org.apache.ibatis.annotations.*;
+import org.apache.ibatis.cache.decorators.LruCache;
+
+import java.util.List;
+
+/**
+ * User MyBatis Mapper - 演示 MyBatis 注解方式
+ * 
+ * 学习要点：
+ * 1. @Mapper - 标记为 MyBatis Mapper 接口
+ * 2. @Select/@Insert/@Update/@Delete - SQL 注解
+ * 3. @Options - 额外选项（如返回自增ID）
+ * 4. @ResultMap - 结果映射
+ * 5. @CacheNamespace - 二级缓存
+ */
+@Mapper
+@CacheNamespace(implementation = LruCache.class, size = 1024)
+public interface UserMapper {
+    
+    /**
+     * 查询所有用户
+     */
+    @Select("SELECT * FROM users ORDER BY created_at DESC")
+    List<User> findAll();
+    
+    /**
+     * 根据ID查询 - 使用一级缓存
+     */
+    @Select("SELECT * FROM users WHERE id = #{id}")
+    User findById(@Param("id") Long id);
+    
+    /**
+     * 根据用户名模糊查询 - 动态SQL演示
+     */
+    @Select("SELECT * FROM users WHERE username LIKE CONCAT('%', #{username}, '%')")
+    List<User> findByUsernameLike(@Param("username") String username);
+    
+    /**
+     * 插入用户 - 返回自增ID
+     */
+    @Insert("INSERT INTO users(username, email, phone, bio, active, created_at, updated_at) " +
+            "VALUES(#{username}, #{email}, #{phone}, #{bio}, #{active}, NOW(), NOW())")
+    @Options(useGeneratedKeys = true, keyProperty = "id")
+    int insert(User user);
+    
+    /**
+     * 更新用户
+     */
+    @Update("UPDATE users SET username=#{username}, email=#{email}, phone=#{phone}, " +
+            "bio=#{bio}, active=#{active}, updated_at=NOW() WHERE id=#{id}")
+    int update(User user);
+    
+    /**
+     * 删除用户
+     */
+    @Delete("DELETE FROM users WHERE id = #{id}")
+    int deleteById(@Param("id") Long id);
+    
+    /**
+     * 统计用户数量
+     */
+    @Select("SELECT COUNT(*) FROM users")
+    long count();
+    
+    /**
+     * 批量插入 - 演示脚本SQL
+     */
+    @Insert("<script>" +
+            "INSERT INTO users(username, email, phone, active, created_at, updated_at) VALUES " +
+            "<foreach collection='users' item='u' separator=','>" +
+            "(#{u.username}, #{u.email}, #{u.phone}, #{u.active}, NOW(), NOW())" +
+            "</foreach>" +
+            "</script>")
+    int batchInsert(@Param("users") List<User> users);
+}