MybatisPlus从入门到精通

一、MyBatis-Plus核心特性

1. 无侵入性
   在MyBatis基础上增强，无需修改原有代码即可使用。
2. 自动化CRUD
   内置通用Mapper和Service，减少80%单表操作代码。
3. Lambda表达式
   支持Lambda形式的条件构造，避免字段名硬编码错误。
4. 主键策略
   支持雪花算法（ASSIGN_ID）、UUID（ASSIGN_UUID）、自增（AUTO）等主键生成方式。

二、快速入门案例

1. 数据库准备

DROP TABLE IF EXISTS sys_user;CREATE TABLE sys_user
(id BIGINT NOT NULL COMMENT '主键ID',name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',age INT NULL DEFAULT NULL COMMENT '年龄',email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',PRIMARY KEY (id)
);
DELETE FROM sys_user;INSERT INTO sys_user (id, name, age, email) VALUES
(1, 'Jone', 18, '[e-mail]'),
(2, 'Jack', 20, '[e-mail]'),
(3, 'Tom', 28, '[e-mail]'),
(4, 'Sandy', 21, '[e-mail]'),
(5, 'Billie', 24, '[e-mail]');

2. Spring Boot配置

pom.xml依赖：

<dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-annotation</artifactId><version>3.5.3.1</version></dependency><dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-core</artifactId><version>3.5.3.1</version></dependency><dependency><groupId>org.mybatis</groupId><artifactId>mybatis-spring</artifactId><version>3.0.3</version></dependency>

application.yml：

spring:datasource:url: jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8username: rootpassword: root

3. 实体类与Mapper

package com.awei.mybatismodel.entity;import lombok.Data;@Data
public class SysUser {private Long id;private String name;private Integer age;private String email;
}

package com.awei.mybatismodel.mapper;import com.awei.mybatismodel.entity.SysUser;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;public interface SysUserMapper extends BaseMapper<SysUser> {}

4.启动类

package com.awei.mybatismodel;import org.springframework.boot.SpringApplication;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication
@MapperScan("com.awei.mybatismodel.mapper")
public class MybatisModelApplication {public static void main(String[] args) {SpringApplication.run(MybatisModelApplication.class, args);}}

5.测试

package com.awei.mybatismodel;import com.awei.mybatismodel.entity.SysUser;
import com.awei.mybatismodel.mapper.SysUserMapper;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.util.List;@SpringBootTest
public class QuickStartTest {@Autowiredprivate SysUserMapper userMapper;@Testpublic void testSelect() {System.out.println(("----- selectAll method test ------"));List<SysUser> userList = userMapper.selectList(null);Assertions.assertEquals(5, userList.size());userList.forEach(System.out::println);}
}

三、核心注解详解

注解	作用	示例
@TableName	指定实体类对应的表名	@TableName("sys_user")
@TableId	标识主键字段	@TableId(type = IdType.AUTO)
@TableField	字段与列映射/自动填充策略	@TableField(value = "email", fill = FieldFill.INSERT_UPDATE)

主键策略示例：

public enum IdType {AUTO,        // 数据库自增ASSIGN_ID,   // 雪花算法（默认）ASSIGN_UUID  // UUID生成
}

---

四、CRUD操作

1. 基础操作

// 插入
User user = new User();
user.setName("Tom");
userMapper.insert(user);// 查询
User user = userMapper.selectById(1L);// 更新
user.setAge(30);
userMapper.updateById(user);// 删除
userMapper.deleteById(2L);

2. 条件构造器（Wrapper）

LambdaQueryWrapper<User> wrapper = new LambdaQueryWrapper<>();
wrapper.like(User::getName, "J")      // 模糊查询.ge(User::getAge, 18)          // 年龄>=18.orderByDesc(User::getCreateTime);List<User> users = userMapper.selectList(wrapper);

生成SQL：

SELECT * FROM user WHERE name LIKE '%J%' AND age >= 18 ORDER BY create_time DESC

---

五、分页查询

1. 配置分页插件

@Configuration
public class MybatisPlusConfig {@Beanpublic MybatisPlusInterceptor mybatisPlusInterceptor() {MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));return interceptor;}
}

2. 分页查询代码

Page<User> page = new Page<>(1, 10);  // 第1页，每页10条
LambdaQueryWrapper<User> wrapper = new LambdaQueryWrapper<>();
wrapper.eq(User::getAge, 20);IPage<User> userPage = userMapper.selectPage(page, wrapper);
System.out.println("总记录数：" + userPage.getTotal());

---

六、高级功能

1. 逻辑删除

表字段：

ALTER TABLE user ADD is_deleted TINYINT(1) DEFAULT 0 COMMENT '逻辑删除标记';

配置：

mybatis-plus:global-config:db-config:logic-delete-field: isDeleted  # 逻辑删除字段名logic-delete-value: 1          # 删除标记值logic-not-delete-value: 0      # 未删除标记值

2. 自动填充

public class MetaObjectHandler implements MetaObjectHandler {@Overridepublic void insertFill(MetaObject metaObject) {this.strictInsertFill(metaObject, "createTime", LocalDateTime.class, LocalDateTime.now());}
}

更新中----