MyBatis-Plus

简介

MyBatis-Plus（简称 MP）是一个MyBatis的增强工具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。

特性

  • 无侵入：只做增强不做改变，引入它不会对现有工程产生影响，如丝般顺滑
  • 损耗小：启动即会自动注入基本 CURD，性能基本无损耗，直接面向对象操作
  • 强大的 CRUD 操作：内置通用 Mapper、通用 Service，仅仅通过少量配置即可实现单表大部分 CRUD 操作，更有强大的条件构造器，满足各类使用需求
  • 支持 Lambda 形式调用：通过 Lambda 表达式，方便的编写各类查询条件，无需再担心字段写错
  • 支持主键自动生成：支持多达 4 种主键策略（内含分布式唯一 ID 生成器 - Sequence），可自由配置，完美解决主键问题
  • 支持 ActiveRecord 模式：支持 ActiveRecord 形式调用，实体类只需继承 Model 类即可进行强大的 CRUD 操作
  • 支持自定义全局通用操作：支持全局通用方法注入（ Write once, use anywhere ）
  • 内置代码生成器：采用代码或者 Maven 插件可快速生成 Mapper 、 Model 、 Service 、 Controller 层代码，支持模板引擎，更有超多自定义配置等您来使用
  • 内置分页插件：基于 MyBatis 物理分页，开发者无需关心具体操作，配置好插件之后，写分页等同于普通 List 查询
  • 分页插件支持多种数据库：支持 MySQL、MariaDB、Oracle、DB2、H2、HSQL、SQLite、Postgre、SQLServer 等多种数据库
  • 内置性能分析插件：可输出 SQL 语句以及其执行时间，建议开发测试时启用该功能，能快速揪出慢查询
  • 内置全局拦截插件：提供全表 delete 、 update 操作智能分析阻断，也可自定义拦截规则，预防误操作

基于SpringBoot使用MyBatisPlus

数据库设计

image-20220704195430412

新建项目

image-20220703221600684

image-20220703221718341

image-20220703221735710

image-20220703221754550

导入依赖

image-20220704194517877

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.2.11</version>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.4.1</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
</dependencies>

编辑配置

image-20220704194831358

1
2
3
4
5
6
7
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mybatisplus_db?serverTimezone=UTC
    username: root
    password: 13851176590++

添加启动类

image-20220704201230606

1
2
3
4
5
6
@SpringBootApplication
public class MyBatisPlusApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyBatisPlusApplication.class, args);
    }
}

创建实体类

image-20220704195648242

1
2
3
4
5
6
7
8
@Data
public class User {
    private Long id;
    private String name;
    private String password;
    private Integer age;
    private String tel;
}

创建Dao接口

image-20220704195842852

1
2
3
4
@Mapper
public interface UserMapper extends BaseMapper<User> {

}

创建测试类

image-20220704201317232

1
2
3
4
5
6
7
8
9
10
11
12
@SpringBootTest
public class MyBatisPlusApplicationTest {
    @Resource
    private UserMapper userMapper;
    private static final Logger logger = LoggerFactory.getLogger(MyBatisPlusApplicationTest.class);
    // 查询列表	
    @Test
    void getAll(){
        List<User> users = userMapper.selectList(null);
        logger.info("用户列表：" + users);
    }
}

简化日志输出

新建logback.xml配置文件

image-20220704210131509

编辑配置

image-20220704210209383

1
2
3
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
</configuration>

关闭Banner

image-20220704210523918

启动测试

image-20220704201439508

标准数据层开发

image-20220704202159031

新增操作

image-20220704202540481

1
2
3
4
5
@Test
void saveUser() {
    User user = new User().setName("xiaohong").setAge(21).setPassword("123456").setTel("123456");
    Integer count = userMapper.insert(user);
}

image-20220704202602872

删除操作

image-20220704202734472

image-20220704202937068

修改操作

image-20220704203046171

1
2
3
4
5
@Test
void updateUser() {
    User user = new User().setId(1L).setAge(50);
    userMapper.updateById(user);
}

image-20220704203202535

分页查询

配置分页拦截器

image-20220704204825107

编辑测试类

image-20220704203919463

image-20220704204928225

添加日志输出

image-20220704205216716

image-20220704205339781

DQL

条件查询

查看Wrapper抽象类

image-20220704210847732

image-20220704213548048

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
    // 条件查询
    // 方法一：常规格式
    @Test
    void getByQueryWrapper() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
        queryWrapper.gt("age", 20).lt("age", 40);
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(user -> logger.info("用户：" + user));
    }
    // 方法二：lambda格式
    @Test
    void getByQueryWrapperForLambda() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
        queryWrapper.lambda().gt(User::getAge, 20).lt(User::getAge, 40);
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(user -> logger.info("用户：" + user));
    }
    // 方法三：lambda
    @Test
    void getByLambdaQueryWrapper() {
        LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<User>();
        // 条件：age > 20 and age < 40
        lambdaQueryWrapper.gt(User::getAge, 20).lt(User::getAge, 40);
        // 条件: age < 20 or age > 40
//        lambdaQueryWrapper.gt(User::getAge, 40).or().lt(User::getAge, 20);
        List<User> users = userMapper.selectList(lambdaQueryWrapper);
        users.forEach(user -> logger.info("用户：" + user));
    }

image-20220704213630003

空值判定

新建用户查询条件类

image-20220704214625224

空值测试

image-20220704215213584

image-20220704215230612

空值判定方法

方法一：if条件语句控制

image-20220704220102139

1
2
3
4
5
6
7
8
9
10
11
12
13
14
![image-20220704220336783](C:\Users\YuanJW\AppData\Roaming\Typora\typora-user-images\image-20220704220336783.png)    @Test
    void getByIfNull() {
        UserQuery userQuery = new UserQuery();
        userQuery.setLowerAge(20).setUpperAge(40);
        LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<User>();
        if (userQuery.getLowerAge() != null) {
            lambdaQueryWrapper.gt(User::getAge, userQuery.getLowerAge());
        }
        if (userQuery.getUpperAge()![image-20220704220336783](C:\Users\YuanJW\AppData\Roaming\Typora\typora-user-images\image-20220704220336783.png) != null) {
            lambdaQueryWrapper.lt(User::getAge, userQuery.getUpperAge());
        }
        List<User> users = userMapper.selectList(lambdaQueryWrapper);
        users.forEach(user -> logger.info("用户：" + user));
    }
方法二：条件参数控制

image-20220704220338824

1
2
3
4
5
6
7
8
9
10
@Test
void getByCondition() {
    UserQuery userQuery = new UserQuery();
    userQuery.setLowerAge(20).setUpperAge(40);
    LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<User>();
    lambdaQueryWrapper.gt(userQuery.getLowerAge() !=null, User::getAge, userQuery.getLowerAge())
            .lt(userQuery.getUpperAge() != null, User::getAge, userQuery.getUpperAge());
    List<User> users = userMapper.selectList(lambdaQueryWrapper);
    users.forEach(user -> logger.info("用户：" + user));
}

查询投影

情况一：LambdaQueryWrapper

image-20220704223005342

情况二：QueryWrapper

image-20220704223342994

测试

image-20220704223443857

image-20220704224013893

1
2
3
4
5
6
7
8
9
10
11
// 统计映射
@Test
void getTotal(){
    QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
    // 统计
    queryWrapper.select("count(*) as total", "age");
    // 分组
    queryWrapper.groupBy("age");
    List<Map<String, Object>> map = userMapper.selectMaps(queryWrapper);
    System.out.println(map);
}

image-20220704224108616

查询条件设置

API查询地址：https://baomidou.com/pages/10c804/#nested

等值查询

image-20220705143514861

1
2
3
4
5
6
7
8
9
// 登录验证
@Test
void login() {
    // 等值设置
    LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<User>();
    lambdaQueryWrapper.eq(User::getName, "xiaomi").eq(User::getPassword, "123456");
    User user = userMapper.selectOne(lambdaQueryWrapper);
    System.out.println(user);
}

image-20220705143605575

范围查询

image-20220705144336093

1
2
3
4
5
6
7
8
9
10
// 范围查询
@Test
void between() {
    LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<User>();
    lambdaQueryWrapper.between(User::getAge, 20, 40);
    List<User> users = userMapper.selectList(lambdaQueryWrapper);
    users.forEach(user -> {
        System.out.println(user);
    });
}

image-20220705144401989

模糊匹配

image-20220705150836409

1
2
3
4
5
6
7
8
// 模糊匹配
@Test
void like() {
    LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<User>();
    lambdaQueryWrapper.like(User::getName, "xiao");
    List<User> users = userMapper.selectList(lambdaQueryWrapper);
    users.forEach(System.out::println);
}

image-20220705150855577

映射匹配

数据库

image-20220705161614345

实体类映射

image-20220705153154091

测试

image-20220705153059547

DML

Insert

id生成策略控制

场景分析

image-20220705153402857

image-20220705162607843

@TableId()注释

image-20220705162205585

测试

image-20220705162417709

全局配置

image-20220705163327730

1
2
3
4
5
6
7
8
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl # MybatisPlus日志输出
  global-config:
    banner: false  # 关闭MybatisPlus的banner
    db-config:
      id-type: assign_id # id生成算法全局配置
      table-prefix: ums_ # 表名前缀

image-20220705163517590

Delete

批量删除

image-20220705164213057

1
2
3
4
5
6
7
@Test
void batchDelete() {
    // 数组转List
    List<Long> ids = Arrays.asList(new Long[]{1544234982638149633L, 1544235553495506945L});
    // 批量删除
    Integer count = userMapper.deleteBatchIds(ids);
}

image-20220705164313573

逻辑删除

数据库添加逻辑删除字段

image-20220705164959329

实体类添加字段并设定逻辑删除标记字段

image-20220705165955206

测试

image-20220705165752771

1
2
3
4
5
// 逻辑删除
@Test
void deleteByLogic() {
    Integer count = userMapper.deleteById(1L);
}

image-20220705170207379

image-20220705170231137

image-20220705170936129

image-20220705170909635

全局配置

image-20220705170536943

Update

乐观锁

当更新一条记录时，希望这条记录没有被别人更新

乐观锁的实现方式：

  • 取出记录时，获取当前version
  • 更新时，带上这个version
  • 执行更新时，set version = newVersion where version = oldVersion
  • 如果version不对，更新失败
数据库添加字段

image-20220705173918160

实体类添加字段

image-20220705174101440

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
@Accessors(chain = true)/*对象链式赋值*/
@EqualsAndHashCode(callSuper = false)
//@TableName("ums_user")/*表名映射*/
public class User {
//    @TableId(type = IdType.ASSIGN_ID)/*id生成策略*/
    private Long id;
    private String name;
    @TableField(value = "pwd", select = false)/*表名映射*/
    private String password;
    private Integer age;
    private String tel;
    @TableField(exist = false)
    private Integer online;
    @TableField(value = "is_delete")
    @TableLogic(value = "0", delval = "1")
    private Integer deleted;
    @Version
    private Integer version;/*乐观锁Version*/
}
添加配置

image-20220705174204504

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
/**
 * MyBatisPlus配置类
 * Created by YuanJW on 2022/7/4.
 */
@Configuration
public class MyBatisPlusConfig {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        // 定义MyBatisPlus拦截器
        MybatisPlusInterceptor mybatisPlusInterceptor = new MybatisPlusInterceptor();
        // 添加分页拦截器
        mybatisPlusInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
        // 添加乐观锁拦截器
        mybatisPlusInterceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
        return mybatisPlusInterceptor;
    }
}

测试

image-20220705175322928

1
2
3
4
5
6
7
// 乐观锁
@Test
void update() {
    User user = new User().setId(3L).setName("aa")
            .setVersion(1); // setVersion()开启锁机制
    Integer count = userMapper.updateById(user);
}

image-20220705175127188

并发测试

image-20220705180306328

1
2
3
4
5
6
7
8
9
10
// 并发测试
@Test
void updateByConcurrency() {
    User user1 = userMapper.selectById(3L);
    User user2 = userMapper.selectById(3L);
    user1.setName("aa");
    Integer count1 = userMapper.updateById(user1);
    user2.setName("bb");
    Integer count2 = userMapper.updateById(user2);
}

image-20220705180403752

image-20220705180423160

代码生成器

导入依赖

image-20220705211930870

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.2.11</version>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.4.1</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
    </dependency>
    <!-- MP代码生成器 -->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-generator</artifactId>
        <version>3.4.1</version>
    </dependency>
    <!-- velocity模板引擎 -->
    <dependency>
        <groupId>org.apache.velocity</groupId>
        <artifactId>velocity-engine-core</artifactId>
        <version>2.3</version>
    </dependency>
</dependencies>

添加代码自动生成器类

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
/**
 * 代码自动生成器
 * Created by YuanJW on 2022/7/5.
 */
public class Generator {
    public static void main(String[] args) {
        // 代码生成器对象
        AutoGenerator autoGenerator = new AutoGenerator();
        // 数据源配置
        DataSourceConfig dataSourceConfig = new DataSourceConfig();
        dataSourceConfig.setDriverName("com.mysql.cj.jdbc.Driver");
        dataSourceConfig.setUrl("jdbc:mysql://localhost:3306/mybatisplus_db?serverTimezone=UTC");
        dataSourceConfig.setUsername("root");
        dataSourceConfig.setPassword("13851176590++");
        autoGenerator.setDataSource(dataSourceConfig);
        // 设置全局配置
        GlobalConfig globalConfig = new GlobalConfig();
        globalConfig.setOutputDir("D:\\Users\\YuanJW\\Desktop\\Java Learn\\MyBatis-Plus\\MyBatisPlusGenerator\\src\\main\\java")  //文件输出位置
                .setOpen(false)
                .setAuthor("xiaoyuanjw")
                .setFileOverride(true)
                .setMapperName("%sMapper")
                .setIdType(IdType.ASSIGN_ID);
        autoGenerator.setGlobalConfig(globalConfig);
        // 设置包名相关配置
        PackageConfig packageConfig = new PackageConfig();
        packageConfig.setParent("com.example.demo")
                .setEntity("domain")
                .setMapper("dao");
        autoGenerator.setPackageInfo(packageConfig);
        // 策略设置
        StrategyConfig strategyConfig = new StrategyConfig();
        strategyConfig.setInclude("ums_user")
                .setTablePrefix("ums_")
                .setRestControllerStyle(true)
                .setVersionFieldName("version")
                .setLogicDeleteFieldName("deleted")
                .setEntityLombokModel(true);
        autoGenerator.setStrategy(strategyConfig);
        // 执行代码生成器
        autoGenerator.execute();
    }
}

生成结构

image-20220705214654400