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

package com.example.scaffold.mapper;

import com.example.scaffold.entity.User;
import org.apache.ibatis.annotations.*;
import org.apache.ibatis.cache.impl.PerpetualCache;

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
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);
}