mybatis-plus整合springboot入门

1、mybatis-plus快速入门

https://mp.baomidou.com/

2、springboot整合mybatis-plus

（1）、映入maven依赖

<!--mybaitsi-plus-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.1.tmp</version>
        </dependency>

备注：springboot版本：2.2.6.RELEASE

（2）、yml文件数据库和mybatis-plus配置

#数据库配置
spring:
  datasource:
   username: root
   password: 123456
   url: jdbc:mysql://localhost:3306/mybaits-plus?useUnicode=true&characterEncoding=UTF-8&useSSL=false&nullCatalogMeansCurrent=true&serverTimezone=Asia/Shanghai

#mybatis-plus配置
logging:
   level:
    com:
      example:
       demo:
         mapper: debug
mybatis-plus:
  mapper-locations: classpath*:mappers/*.xml
  # 实体扫描，多个package用逗号或者分号分隔
  type-aliases-package: com.example.demo.model
  configuration:
    # 驼峰下划线转换
    map-underscore-to-camel-case: true
    cache-enabled: false
    call-setters-on-nulls: true
  global-config:
    # 刷新mapper 调试神器
    refresh: true
    banner: false
    #数据库大写下划线转换
    #capital-mode: true
    #序列接口实现类配置
    #key-generator: com.baomidou.springboot.xxx
    # 数据库相关配置
    db-config:
      db-type: mysql
      # 主键类型  AUTO:"数据库ID自增", INPUT:"用户输入ID",ID_WORKER:"全局唯一ID (数字类型唯一ID)", UUID:"全局唯一ID UUID";
      id-type: AUTO
      # 字段策略 IGNORED:"忽略判断",NOT_NULL:"非 NULL 判断"),NOT_EMPTY:"非空判断"
      field-strategy: not_empty
      capital-mode: true
      #逻辑删除配置
      logic-delete-value: 1
      logic-not-delete-value: 0

（3）、数据准备

CREATE TABLE `user` (
  `id` bigint(11) NOT NULL COMMENT '主键ID',
  `name` varchar(30) NOT NULL COMMENT '姓名',
  `age` int(11) NOT NULL COMMENT '年龄',
  `email` varchar(50) NOT NULL COMMENT '邮箱',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `mybaits-plus`.`user` (`id`, `name`, `age`, `email`) VALUES ('1', 'Jone', '18', 'test1@baomidou.com');
INSERT INTO `mybaits-plus`.`user` (`id`, `name`, `age`, `email`) VALUES ('2', 'Jack', '20', 'test2@baomidou.com');
INSERT INTO `mybaits-plus`.`user` (`id`, `name`, `age`, `email`) VALUES ('3', 'Tom', '28', 'test3@baomidou.com');
INSERT INTO `mybaits-plus`.`user` (`id`, `name`, `age`, `email`) VALUES ('4', 'Sandy', '21', 'test4@baomidou.com');
INSERT INTO `mybaits-plus`.`user` (`id`, `name`, `age`, `email`) VALUES ('5', 'Billie', '24', 'test5@baomidou.com');

CREATE TABLE `course` (
  `id` bigint(20) NOT NULL,
  `course` varchar(10) NOT NULL,
  `user_id` bigint(20) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `mybaits-plus`.`course` (`id`, `course`, `user_id`) VALUES ('1', '语文', '2');

（4）、创建实体类

@Data
public class User implements Serializable {

    private static final long serialVersionUID = -5817579076869802231L;

    private Long id;
    private String name;
    private Integer age;
    private String email;
}

（5）、service层和dao层

public interface UserService extends IService<User> {
    PageInfo<User> selectPage(int pageNo, int pageSize, User user);

    PageInfo<User> selectPageCustom(int pageNo, int pageSize, User user);

    PageInfo<Map<String, Object>> selectPageCustomMap(int pageNo, int pageSize);
}

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper,User> implements UserService {

    @Resource
    private UserMapper userMapper;

    @Override
    public PageInfo<User> selectPage(int pageNo, int pageSize, User user) {
        Page<User> page = new Page<>(pageNo,pageSize,false);
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.like("name",user.getName());
        wrapper.orderByAsc("id");
        page = userMapper.selectPage(page, wrapper);
        return new PageInfo<>(page);
    }

    @Override
    public PageInfo<User> selectPageCustom(int pageNo, int pageSize, User user) {
        Page<User> page = new Page<>(pageNo,pageSize);
        userMapper.pageMyQuery(page,user.getName());
        return new PageInfo<>(page);
    }

    @Override
    public PageInfo<Map<String, Object>> selectPageCustomMap(int pageNo, int pageSize) {
        Page<Map<String, Object>> page = new Page<>(pageNo,pageSize);
        page = userMapper.pageMyMapQuery(page);
        return new PageInfo<>(page);
    }

public interface UserMapper extends BaseMapper<User> {

    Page<User> pageMyQuery(Page<User> pageInfo, @Param("name") String name);

    Page<Map<String,Object>> pageMyMapQuery(Page pageInfo);
}

mapper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="com.example.demo.mapper.UserMapper">

    <select id="pageMyQuery" parameterType="User" resultType="User">
        select id,name,age from user where name = #{name}
    </select>
    <select id="pageMyMapQuery" resultType="map">
        SELECT * FROM course c
        LEFT JOIN `user` u on c.id = u.id
    </select>
</mapper>

（6）、单元测试

@SpringBootTest
@RunWith(SpringRunner.class)
public class MybatisPlusTest {

    @Autowired
    private UserService userService;
    /**
     * 全局id生成器
     */
    @Autowired
    private DefaultIdentifierGenerator defaultIdentifierGenerator;

    /**
     * list查询
     */
    @Test
    public  void selectList(){
        List<User> list = userService.list();
        Assert.assertEquals(6, list.size());
        list.forEach(System.out::println);
    }

    /**
     *单条插入
     */
    @Test
    public void inset(){
        User user = new User();
        user.setName("张三");
        user.setAge(20);
        user.setEmail("1165523762@qq.com");
        user.setId(defaultIdentifierGenerator.nextId(user));
        userService.save(user);
    }

    /**
     * 批量插入
     */
    @Test
    public void saveBatch(){
        List<User> list = new ArrayList<>();
        User user1 = new User();
        user1.setName("王五");
        user1.setAge(20);
        user1.setEmail("1234567@qq.com");
        user1.setId(defaultIdentifierGenerator.nextId(user1));
        list.add(user1);

        User user2 = new User();
        user2.setName("李四");
        user2.setAge(20);
        user2.setEmail("7654321@qq.com");
        user2.setId(defaultIdentifierGenerator.nextId(user1));
        list.add(user2);

        userService.saveBatch(list);

    }

    /**
     * 按照id集合删除
     */
    @Test
    public void delBatch(){
        List<Long> ids = new ArrayList<>();
        ids.add(1259742998092120066L);
        ids.add(1259749231041806337L);
        userService.removeByIds(ids);
    }

    /**
     * 分页查询
     */
    @Test
    public void queryPage(){
        User user = new User();
        user.setName("李四");
        PageInfo<User> userPageInfo =  userService.selectPage(1,3,user);
        System.err.println(userPageInfo);
    }

    /**
     * 自定义分页查询返回T
     */
    @Test
    public void queryPageCustom(){
        User user = new User();
        user.setName("李四");
        PageInfo<User> userPageInfo =  userService.selectPageCustom(1,3,user);
        System.err.println(userPageInfo);
    }

    /**
     * 自定义分页查询返回map
     */
    @Test
    public void queryPageCustomMap(){
        PageInfo<Map<String,Object>> userPageInfo =  userService.selectPageCustomMap(1,3);
        System.err.println(userPageInfo);
    }

补充：PageInfo源码（自定义分页实体类）

@Data
public class PageInfo<T> {

    /**
     * 当前页
     */
    private Long pageNo;

    /**
     * 每页显示条数
     */
    private Long PageSize;

    /**
     * 总条数
     */
    private Long total;

    /**
     * 结果集
     */
    private List<T> result;

    public PageInfo(Page<T> page) {
        this.pageNo = page.getCurrent();
        this.PageSize = page.getSize();
        this.total = page.getTotal();
        this.result = page.getRecords();
    }
}

 mybatis-plus配置类

@Configuration
public class MybatisPlusConfig {

    /**
     * 全局id生成器
     * @return
     */
    @Bean
    public DefaultIdentifierGenerator identifierGenerator(){
        return new DefaultIdentifierGenerator();
    }

    /**
     * 分页插件
     * @return
     */
    @Bean
    public PaginationInterceptor paginationInterceptor(){
        PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
        // 设置请求的页面大于最大页后操作， true调回到首页，false 继续请求  默认false
        // paginationInterceptor.setOverflow(false);
        // 设置最大单页限制数量，默认 500 条，-1 不受限制
        // paginationInterceptor.setLimit(500);
        // 开启 count 的 join 优化,只针对部分 left join
        paginationInterceptor.setCountSqlParser(new JsqlParserCountOptimize(true));
        return paginationInterceptor;
    }
}