MyBatis Plus基本用法-SpringBoot框架

依赖

使用 Mybatis Plus 框架时，需要添加以下依赖：

<dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>latest-version</version>
</dependency>

其中，latest-version 为最新版本号，可以在官网或 Maven 仓库中查看。

此外，还需要添加与所使用的数据库连接相关的依赖。例如，如果使用 MySQL 数据库，需要添加以下依赖：

<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.26</version>
</dependency>

如果使用 Oracle 数据库，需要添加以下依赖：

<dependency><groupId>com.oracle.database.jdbc</groupId><artifactId>ojdbc8</artifactId><version>19.3.0.0</version>
</dependency>

如果使用 PostgreSQL 数据库，需要添加以下依赖：

<dependency><groupId>org.postgresql</groupId><artifactId>postgresql</artifactId><version>42.2.23</version>
</dependency>

如果使用 SQL Server 数据库，需要添加以下依赖：

<dependency><groupId>com.microsoft.sqlserver</groupId><artifactId>mssql-jdbc</artifactId><version>9.4.0.jre11</version>
</dependency>

这些依赖可以根据实际需要进行选择和配置。

1. XML文件代码注释说明

数据库表生成

首先需要在数据库中创建一个user表，表结构如下：

CREATE TABLE `user` (`id` bigint(20) NOT NULL AUTO_INCREMENT,`name` varchar(20) NOT NULL,`age` int(11) NOT NULL,PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

Mybatis Plus的增删改查

下面是使用XML文件进行增删改查操作的示例代码：

<!-- UserMapper.xml --><mapper namespace="com.example.mapper.UserMapper"><!-- 新增数据 --><insert id="insertUser" parameterType="com.example.entity.User">INSERT INTO user(name, age) VALUES (#{name}, #{age})</insert><!-- 根据id查询数据 --><select id="selectUserById" resultType="com.example.entity.User">SELECT * FROM user WHERE id = #{id}</select><!-- 更新数据 --><update id="updateUser" parameterType="com.example.entity.User">UPDATE user SET name = #{name}, age = #{age} WHERE id = #{id}</update><!-- 根据id删除数据 --><delete id="deleteUserById">DELETE FROM user WHERE id = #{id}</delete><!-- 多表关联分组查询 --><select id="selectUserOrderCount" resultType="com.example.entity.UserOrderCount">SELECT u.name, u.age, COUNT(o.id) as order_count FROM user uLEFT JOIN `order` o ON u.id = o.user_idGROUP BY u.id</select><!-- 视图查询 --><select id="selectUserViewList" resultType="com.example.entity.UserView">SELECT * FROM user_view</select><!-- 存储过程查询 --><select id="callGetUserCount" statementType="CALLABLE" parameterType="java.util.Map">{CALL getUserCount(#{age, mode=IN, jdbcType=INTEGER}, #{count, mode=OUT, jdbcType=INTEGER})}</select></mapper>

2. Mapper文件代码注释

下面是使用Mapper文件调用上述方法的示例代码：

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;import java.util.List;
import java.util.Map;@Mapper
public interface UserMapper {// 新增数据void insertUser(User user);// 根据id查询数据User selectUserById(Long id);// 更新数据void updateUser(User user);// 根据id删除数据void deleteUserById(Long id);// 多表关联分组查询List<UserOrderCount> selectUserOrderCount();// 视图查询List<UserView> selectUserViewList();// 调用存储过程查询void callGetUserCount(Map<String, Object> paramMap);
}

3. SQL脚本

下面是提供相关建表、建视图、建存储过程和数据插入的SQL脚本：

-- 创建user表
CREATE TABLE `user` (`id` bigint(20) NOT NULL AUTO_INCREMENT,`name` varchar(20) NOT NULL,`age` int(11) NOT NULL,PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;-- 创建order表
CREATE TABLE `order` (`id` bigint(20) NOT NULL AUTO_INCREMENT,`order_no` varchar(50) NOT NULL,`user_id` bigint(20) NOT NULL,PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;-- 创建user_view视图
CREATE VIEW `user_view` AS 
SELECT u.name, u.age, COUNT(o.id) as order_count FROM user u 
LEFT JOIN `order` o ON u.id = o.user_id 
GROUP BY u.id;-- 创建存储过程getUserCount
CREATE PROCEDURE `getUserCount`(IN age INT, OUT count INT)
BEGINSELECT COUNT(*)INTO countFROM userWHERE age = age;
END;-- 插入测试数据
INSERT INTO user(name, age) VALUES ('张三', 18);
INSERT INTO user(name, age) VALUES ('李四', 20);
INSERT INTO user(name, age) VALUES ('王五', 22);INSERT INTO `order`(order_no, user_id) VALUES ('202201010001', 1);
INSERT INTO `order`(order_no, user_id) VALUES ('202201010002', 1);
INSERT INTO `order`(order_no, user_id) VALUES ('202201010003', 2);
INSERT INTO `order`(order_no, user_id) VALUES ('202201010004', 3);

4. YML文件代码注释说明

下面是使用YML文件进行Mybatis Plus的详细全面的配置的示例代码：

mybatis-plus:# mapper文件的路径mapper-locations: classpath:/mapper/*.xml# 实体类的包路径typeAliasesPackage: com.example.entityconfiguration:# 配置驼峰命名规则map-underscore-to-camel-case: true# 配置缓存cache-enabled: true# 配置多数据源# dataSource: com.baomidou.mybatisplus.spring.boot.starter.jdbc.MybatisPlusProperties$Druidglobal-config:# 配置逻辑删除字段db-config:logic-delete-field: deletedlogic-delete-value: 1logic-not-delete-value: 0# 配置分页插件page-helper:auto-dialect: truereasonable: truesupport-methods-arguments: true

5. Java文件代码注释

下面是使用Java文件进行实体类的示例代码：

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;@Data
@TableName("user")
public class User {@TableId(value = "id", type = IdType.AUTO)private Long id;@TableField("name")private String name;@TableField("age")private Integer age;}

import lombok.Data;@Data
public class UserOrderCount {private String name;private Integer age;private Integer orderCount;}

import com.baomidou.mybatisplus.annotation.TableField;
import lombok.Data;@Data
public class UserView {@TableField("name")private String name;@TableField("age")private Integer age;@TableField("order_count")private Integer orderCount;}

下面是使用Java文件进行Service和Controller的示例代码：

import com.baomidou.mybatisplus.extension.service.IService;public interface UserService extends IService<User> {void addUser(User user);User getUserById(Long id);void updateUser(User user);void deleteUserById(Long id);List<UserOrderCount> getUserOrderCount();List<UserView> getUserViewList();Integer getUserCountByAge(Integer age);}

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {@Overridepublic void addUser(User user) {baseMapper.insertUser(user);}@Overridepublic User getUserById(Long id) {return baseMapper.selectUserById(id);}@Overridepublic void updateUser(User user) {baseMapper.updateUser(user);}@Overridepublic void deleteUserById(Long id) {baseMapper.deleteUserById(id);}@Overridepublic List<UserOrderCount> getUserOrderCount() {return baseMapper.selectUserOrderCount();}@Overridepublic List<UserView> getUserViewList() {return baseMapper.selectUserViewList();}@Overridepublic Integer getUserCountByAge(Integer age) {Map<String, Object> paramMap = new HashMap<>();paramMap.put("age", age);paramMap.put("count", null);baseMapper.callGetUserCount(paramMap);return (Integer) paramMap.get("count");}}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;@RestController
@RequestMapping("/user")
public class UserController {@Autowiredprivate UserService userService;@PostMapping("/add")public String addUser(@RequestBody User user) {userService.addUser(user);return "添加成功";}@GetMapping("/{id}")public User getUserById(@PathVariable Long id) {return userService.getUserById(id);}@PutMapping("/update")public String updateUser(@RequestBody User user) {userService.updateUser(user);return "更新成功";}@DeleteMapping("/{id}")public String deleteUserById(@PathVariable Long id) {userService.deleteUserById(id);return "删除成功";}@GetMapping("/orderCount")public List<UserOrderCount> getUserOrderCount() {return userService.getUserOrderCount();}@GetMapping("/viewList")public List<UserView> getUserViewList() {return userService.getUserViewList();}@GetMapping("/countByAge")public Integer getUserCountByAge(@RequestParam Integer age) {return userService.getUserCountByAge(age);}}