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在 Spring Boot整合MyBatis连接数据库这篇文章中，我们已经可以使用Spring Boot整合MyBatis来连接数据库，但随着使用，我们发现，MyBatis还是稍微有点复杂，那有没有更加简单的方式来操作数据库呢，我们惊奇的发现了MyBatis Plus。

0 开发环境

JDK：1.8
Spring Boot：2.1.1.RELEASE
MySQL：5.7.13

1 引入依赖

<dependency>  <groupId>com.baomidou</groupId>  <artifactId>mybatis-plus-boot-starter</artifactId>  <version>3.5.4</version></dependency><dependency>  <groupId>mysql</groupId>  <artifactId>mysql-connector-java</artifactId>  <scope>runtime</scope></dependency><!--lombok--><dependency>  <groupId>org.projectlombok</groupId>  <artifactId>lombok</artifactId>  <version>1.18.30</version>  <scope>provided</scope></dependency>

2 引入数据源

application.yml 增加如下配置信息

spring:  datasource:   url: jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf8&serverTimezone=GMT%2B8   username: root   password: root   driver-class-name: com.mysql.cj.jdbc.Driver#mybatis-plus:  mapper-locations: classpath:mapper/*.xml        #对应mapper映射xml文件所在路径  type-aliases-package: cn.wbnull.springbootdemo.entity  #对应实体类路径

3 测试

3.1 新建数据库表

CREATE SCHEMA `test` DEFAULT CHARACTER SET utf8mb4 ;CREATE TABLE `test`.`user` (  `id` INT NOT NULL AUTO_INCREMENT,  `name` VARCHAR(45) NOT NULL,  PRIMARY KEY (`id`));INSERT INTO `test`.`user` (`name`) VALUES ('张三');INSERT INTO `test`.`user` (`name`) VALUES ('李四');INSERT INTO `test`.`user` (`name`) VALUES ('王五');INSERT INTO `test`.`user` (`name`) VALUES ('周六');

3.2 创建实体类

package cn.wbnull.springbootdemo.entity;import lombok.Data;@Datapublic class User {  private int id;  private String name;}

3.3 创建Mapper

package cn.wbnull.springbootdemo.mapper;import cn.wbnull.springbootdemo.entity.User;import com.baomidou.mybatisplus.core.mapper.BaseMapper;import org.springframework.stereotype.Repository;@Repositorypublic interface UserMapper extends BaseMapper<User> {}

3.4 创建映射文件

在 resources 目录下新建 mapper 文件夹，用于存放MyBatis Plus映射文件

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="cn.wbnull.springbootdemo.mapper.UserMapper">  <!-- 通用查询映射结果 -->  <resultMap id="BaseResultMap" type="cn.wbnull.springbootdemo.entity.User">    <id column="id" property="id"/>    <result column="name" property="name"/>  </resultMap>  <!-- 通用查询结果列 -->  <sql id="Base_Column_List">     id, name  </sql></mapper>

3.5 创建Service

package cn.wbnull.springbootdemo.service;import cn.wbnull.springbootdemo.entity.User;import cn.wbnull.springbootdemo.mapper.UserMapper;import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;import com.baomidou.mybatisplus.core.conditions.update.LambdaUpdateWrapper;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import java.util.List;@Servicepublic class UserService {  @Autowired  private UserMapper userMapper;  public String add(String name) {    User user = new User();    user.setName(name);    userMapper.insert(user);    return "操作成功";   }  public List<User> query() {    LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();    return userMapper.selectList(queryWrapper);   }  public String update(int id, String name) {    LambdaUpdateWrapper<User> updateWrapper = new LambdaUpdateWrapper<>();    updateWrapper.set(User::getName, name);    updateWrapper.eq(User::getId, id);    userMapper.update(updateWrapper);    return "操作成功";   }  public String delete(int id) {    LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();    queryWrapper.eq(User::getId, id);    userMapper.delete(queryWrapper);    return "操作成功";   }}

3.6 创建Controller

package cn.wbnull.springbootdemo.controller;import cn.wbnull.springbootdemo.entity.User;import cn.wbnull.springbootdemo.service.UserService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.PostMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.RestController;import java.util.List;@RestController@RequestMapping("user")public class UserController {  @Autowired  public UserService userService;  @PostMapping(value = "add")  public String add(@RequestParam(value = "name") String name) {    return userService.add(name);   }  @PostMapping(value = "query")  public List<User> query() {    return userService.query();   }  @PostMapping(value = "update")  public String update(@RequestParam(value = "id") int id, @RequestParam(value = "name") String name) {    return userService.update(id, name);   }  @PostMapping(value = "delete")  public String delete(@RequestParam(value = "id") int id) {    return userService.delete(id);   }}

3.7 项目启动类

增加@MapperScan，扫描mapper

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

3.8 测试

使用Postman进行测试，输出结果如下

3.8.1 select

3.8.2 insert

我们查下数据库，并再用postman请求

3.8.3 update

数据库中成功更新

3.8.4 delete

数据库中成功删除

截至这里，Spring Boot已经成功整合MyBatis Plus并连接上了数据库，且测试正常。

对比发现，我们使用LambdaQueryWrapper来操作数据库会特别方便，

并且，在我们实际开发中，如果存在大量数据库表，我们依旧可以使用Generator来自动生成代码

4 条件构造器 QueryWrapper

上面 3.5 中，我们创建的Service类中，使用了QueryWrapper简化SQL，其基本用法可参考官方文档：https://baomidou.com/pages/10c804/

以下简单整理可供参考

函数名	说明	例子
allEq	全部eq(或个别isNull)	allEq({id:1,name:"老王",age:null})`--->`id = 1 and name = '老王' and age is nullallEq({id:1,name:"老王",age:null}, false)`--->`id = 1 and name = '老王'
eq	等于 =	eq("name", "老王")`--->`name = '老王'
ne	不等于 <>	ne("name", "老王")`--->`name <> '老王'
gt	大于 >	gt("age", 18)`--->`age > 18
ge	大于等于 >=	ge("age", 18)`--->`age >= 18
lt	小于 <	lt("age", 18)`--->`age < 18
le	小于等于 <=	le("age", 18)`--->`age <= 18
between	BETWEEN 值1 AND 值2	between("age", 18, 30)`--->`age between 18 and 30
notBetween	NOT BETWEEN 值1 AND 值2	notBetween("age", 18, 30)`--->`age not between 18 and 30
like	LIKE '%值%'	like("name", "王")`--->`name like '%王%'
notLike	NOT LIKE '%值%'	notLike("name", "王")`--->`name not like '%王%'
likeLeft	LIKE '%值'	likeLeft("name", "王")`--->`name like '%王'
likeRight	LIKE '值%'	likeRight("name", "王")`--->`name like '王%'
notLikeLeft	NOT LIKE '%值'	notLikeLeft("name", "王")`--->`name not like '%王'
notLikeRight	NOT LIKE '值%'	notLikeRight("name", "王")`--->`name not like '王%'
isNull	字段 IS NULL	isNull("name")`--->`name is null
isNotNull	字段 IS NOT NULL	isNotNull("name")`--->`name is not null
in	字段 IN (value.get(0), value.get(1), ...)字段 IN (v0, v1, ...)	in("age",{1,2,3})`--->`age in (1,2,3)in("age", 1, 2, 3)`--->`age in (1,2,3)
notIn	字段 NOT IN (value.get(0), value.get(1), ...)NOT IN (v0, v1, ...)	notIn("age",{1,2,3})`--->`age not in (1,2,3)notIn("age", 1, 2, 3)`--->`age not in (1,2,3)
inSql	字段 IN ( sql语句 )	inSql("age", "1,2,3,4,5,6")`--->`age in (1,2,3,4,5,6)inSql("id", "select id from table where id < 3")`--->`id in (select id from table where id < 3)
notInSql	字段 NOT IN ( sql语句 )	notInSql("age", "1,2,3,4,5,6")`--->`age not in (1,2,3,4,5,6)notInSql("id", "select id from table where id < 3")`--->`id not in (select id from table where id < 3)
groupBy	分组：GROUP BY 字段, ...	groupBy("id", "name")`--->`group by id,name
orderByAsc	排序：ORDER BY 字段, ... ASC	orderByAsc("id", "name")`--->`order by id ASC,name ASC
orderByDesc	排序：ORDER BY 字段, ... DESC	orderByDesc("id", "name")`--->`order by id DESC,name DESC
orderBy	排序：ORDER BY 字段, ...	orderBy(true, true, "id", "name")`--->`order by id ASC,name ASC
having	HAVING ( sql语句 )	having("sum(age) > 10")`--->`having sum(age) > 10having("sum(age) > {0}", 11)`--->`having sum(age) > 11
func	func 方法(主要方便在出现if...else下调用不同方法能不断链)	func(i -> if(true) {i.eq("id", 1)} else {i.ne("id", 1)})
or	拼接 OR	eq("id",1).or().eq("name","老王")`--->`id = 1 or name = '老王'or(i -> i.eq("name", "李白").ne("status", "活着"))`--->`or (name = '李白' and status <> '活着')
and	AND 嵌套	and(i -> i.eq("name", "李白").ne("status", "活着"))`--->`and (name = '李白' and status <> '活着')
nested	正常嵌套不带 AND 或者 OR	nested(i -> i.eq("name", "李白").ne("status", "活着"))`--->`(name = '李白' and status <> '活着')
apply	拼接 sql	apply("id = 1")`--->`id = 1apply("date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")`--->`date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'") apply("date_format(dateColumn,'%Y-%m-%d') = {0}", "2008-08-08")`--->`date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")
last	无视优化规则直接拼接到 sql 的最后	last("limit 1")
exists	拼接 EXISTS ( sql语句 )	exists("select id from table where age = 1")`--->`exists (select id from table where age = 1)
notExists	拼接 NOT EXISTS ( sql语句 )	notExists("select id from table where age = 1")`--->`not exists (select id from table where age = 1)

*QueryWrapper*
select	设置查询字段	select("id", "name", "age")select(i -> i.getProperty().startsWith("test"))

*UpdateWrapper*
set	SQL SET 字段	set("name", "老李头")set("name", "")`--->`数据库字段值变为空字符串set("name", null)`--->`数据库字段值变为null
setSql	设置 SET 部分 SQL	setSql("name = '老李头'")

5 代码生成器

5.1 引入依赖

<!-- 代码生成器 --><dependency>  <groupId>com.baomidou</groupId>  <artifactId>mybatis-plus-generator</artifactId>  <version>3.5.4</version></dependency><!-- 模板引擎 --><dependency>  <groupId>org.apache.velocity</groupId>  <artifactId>velocity-engine-core</artifactId>  <version>2.3</version></dependency>

5.2 新建代码生成器类

代码生成器所有配置可参考官方文档：https://baomidou.com/pages/981406/

package cn.wbnull.springbootdemo.mybatis;import com.baomidou.mybatisplus.core.exceptions.MybatisPlusException;import com.baomidou.mybatisplus.generator.AutoGenerator;import com.baomidou.mybatisplus.generator.config.*;import com.baomidou.mybatisplus.generator.config.rules.DateType;import java.util.Collections;import java.util.Scanner;public class MybatisPlusGenerator {  private static final String URL = "jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf8&serverTimezone=GMT%2B8";  private static final String USERNAME = "root";  private static final String PASSWORD = "root";  private static final String PACKAGE_PATH = System.getProperty("user.dir") + "/spring-boot-mybatis-plus/src/main/java";  private static final String RESOURCES_MAPPER_PATH = System.getProperty("user.dir") + "/spring-boot-mybatis-plus/src/main/resources/mapper/";  public static void main(String[] args) {    DataSourceConfig dataSourceConfig = new DataSourceConfig.Builder(URL, USERNAME, PASSWORD)         .build();    AutoGenerator autoGenerator = new AutoGenerator(dataSourceConfig);    autoGenerator.global(globalConfig());    autoGenerator.packageInfo(packageConfig());    autoGenerator.strategy(strategyConfig());    autoGenerator.execute();   }  private static GlobalConfig globalConfig() {    return new GlobalConfig.Builder()         .outputDir(PACKAGE_PATH)         .author("null")         .dateType(DateType.TIME_PACK)         .commentDate("yyyy-MM-dd")         .disableOpenDir()         .build();   }  private static PackageConfig packageConfig() {    return new PackageConfig.Builder()         .parent("cn.wbnull.springbootdemo")         .pathInfo(Collections.singletonMap(OutputFile.xml, RESOURCES_MAPPER_PATH))         .build();   }  private static StrategyConfig strategyConfig() {    return new StrategyConfig.Builder()         .addInclude(scanner().split(","))         .mapperBuilder()         .enableBaseResultMap()         .enableBaseColumnList()         .build();   }  public static String scanner() {    Scanner scanner = new Scanner(System.in);    String hint = "请输入数据库表名，多个表名使用英文逗号分隔：";    System.out.println(hint);    if (scanner.hasNext()) {      String ipt = scanner.next();      if (ipt != null && ipt.length() > 0) {        return ipt;       }     }    throw new MybatisPlusException("请输入正确的数据库表名");   }}

5.3 测试

5.3.1 新建数据库表

我们先新建一个数据库表，便于一会测试自动生成代码

CREATE TABLE `test`.`user_info` (  `id` INT NOT NULL AUTO_INCREMENT,  `userCode` VARCHAR(20) NOT NULL,  `userName` VARCHAR(45) NULL,  `password` VARCHAR(40) NOT NULL,  PRIMARY KEY (`id`));

5.3.2 测试

运行MybatisPlusGenerator，输入需要生成的表名

文件生成完成

生成文件如下

这样，对于大量的数据库表，我们就可以使用Generator来生成基本的代码，然后自己再添加其他所需要的代码即可。

CSDN：https://blog.csdn.net/dkbnull/article/details/136331111

本篇文章来源于微信公众号: 程序员null

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雪影轻语·静谧之间

Spring Boot整合MyBatis Plus连接数据库

如果文章中代码不便于阅读，请使用电脑查看或点击阅读原文。

1 引入依赖

2 引入数据源

3 测试

3.1 新建数据库表

3.2 创建实体类

3.3 创建Mapper

3.4 创建映射文件

3.5 创建Service

3.6 创建Controller

3.7 项目启动类

3.8 测试

3.8.1 select

3.8.2 insert

3.8.3 update

3.8.4 delete

4 条件构造器 QueryWrapper

5 代码生成器

5.1 引入依赖

5.2 新建代码生成器类

5.3 测试

5.3.1 新建数据库表

5.3.2 测试

JVM 21 的调优指南：如何进行JVM调优，JVM调优参数

吃透Redis系列：琳琅满目的数据类型（上篇）

Comments NOTHING

取消回复

雪影轻语·静谧之间

如果文章中代码不便于阅读，请使用电脑查看或点击阅读原文。

1 引入依赖

2 引入数据源

3 测试

3.1 新建数据库表

3.2 创建实体类

3.3 创建Mapper

3.4 创建映射文件

3.5 创建Service

3.6 创建Controller

3.7 项目启动类

3.8 测试

3.8.1 select

3.8.2 insert

3.8.3 update

3.8.4 delete

4 条件构造器 QueryWrapper

5 代码生成器

5.1 引入依赖

5.2 新建代码生成器类

5.3 测试

5.3.1 新建数据库表

5.3.2 测试

​JVM 21 的调优指南：如何进行JVM调优，JVM调优参数

吃透Redis系列：琳琅满目的数据类型（上篇）

Comments NOTHING

取消回复

JVM 21 的调优指南：如何进行JVM调优，JVM调优参数