Mybatis plus

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mybatisplus

MyBatis Plus

国产的开源框架、基于Mybatis、简化Mybatis开发、提高效率

spirng boot 整合 MyBatis

  • pom
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<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.3.1.tmp</version>
</dependency>
  • pojo
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@Data
@TableName(value = "user")
public class User {

    @TableId(value = "id",type = IdType.AUTO)
    private Long id;

    @TableField(value = "name")
    private String name;

    private Integer sex;

    private Integer age;

    @TableField(value = "create_time", fill = FieldFill.INSERT)
    private Date createTime;

    @TableField(value = "update_time", fill = FieldFill.INSERT_UPDATE)
    private Date updateTime;

}
  • Mapper
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public interface UserMapper extends BaseMapper<User> {

}
  • 启动类
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@SpringBootApplication
@MapperScan("com.dream.xiaobo.mapping")
public class MybatisplusApplication {

    public static void main(String[] args) {
        SpringApplication.run(MybatisplusApplication.class, args);
    }

}
  • test
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@SpringBootTest
class UserMapperTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    void test(){
        userMapper.selectList(null).forEach(System.out::println);
    }

    @Test
    void save(){
        User user = new User();

        user.setName("小博");
        user.setSex(0);
        user.setAge(21);

        userMapper.insert(user);

    }

    @Test
    void update(){
        User user = userMapper.selectById(17);
        System.out.println(user);
        user.setName("wangyibo");
        user.setSex(1);
        user.setAge(22);
        userMapper.updateById(user);
    }
}

注解剖析

  • @TableName

映射数据库表名

  • @TableId
    主键映射
  • value属性

映射字段名

  • type属性

设置主键类型

值 描述
AUTO 数据库自增
NONE set一个主键值、用雪花算法实现的
INPUT 需要开发者手动赋值
ASSIGN_ID 自动分配ID、Long、Integer、String
ASSIGN_UUID 分配UUID、数据类型必须是String类型
  • @TableField

映射非主键字段

  • exist属性

设置是否为数据库字段名、true OR false

  • select属性

表示是否查询该字段

  • fill属性

表示是否自动填充
值：
INSERT
INSRT_UPDATE
UPDATE
DEFAULT

创建时间和更新时间自动填充演示

  • Handler
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@Component
public class MyMetaObjectHandler implements MetaObjectHandler {

    @Override
    public void insertFill(MetaObject metaObject) {
        this.setFieldValByName("createTime",new Date(),metaObject);
        this.setFieldValByName("updateTime",new Date(),metaObject);
    }

    @Override
    public void updateFill(MetaObject metaObject) {
        this.setFieldValByName("updateTime",new Date(),metaObject);
    }
}
  • @Version

标记乐观锁、通过数据库添加version字段、设置个默认值来保护数据安全性、当修改数据时、用version作为条件、当条件成立时方可修改

  • pojo
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@TableField(value = "version")
@Version
private Integer version;
  • config
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@Configuration
public class MyBatisPlusConfig {

    @Bean
    public OptimisticLockerInterceptor optimisticLockerInterceptor(){

        return new OptimisticLockerInterceptor();
    }
}
  • test
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@Test
void update(){
    User user = userMapper.selectById(17);
    user.setName("wangxiaobo");
    user.setSex(0);
    user.setAge(22);

    User user1 = userMapper.selectById(17);

    user1.setName("hhh");

    userMapper.updateById(user1);

    userMapper.updateById(user);

}

@EnumValue实现显示数据转换

通过枚举注解方式

  • enum
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public enum StatusEnum {

    工作(1,"工作"),
    休息(0,"休息");

    StatusEnum(Integer code,String msg){
        this.code = code;
        this.msg = msg;
    }

    @EnumValue
    private Integer code;

    private String msg;

}
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public enum SexEnum {

    男(1,"男"),
    女(0,"女");

    @EnumValue
    private Integer code;
    private String msg;

    SexEnum(Integer code, String msg){
        this.code = code;
        this.msg = msg;
    }

}
  • pojo
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@TableField(value = "sex")
private SexEnum sex;

@TableField(value = "status")
private StatusEnum status;
  • application.yml
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mybatis-plus:
# 扫描enum
  type-enums-package: com.dream.xiaobo.enums

实现接口方式

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public enum SexEnum implements IEnum<Integer> {

    男(1,"男"),
    女(0,"女");

    private Integer code;
    private String msg;

    SexEnum(Integer code, String msg){
        this.code = code;
        this.msg = msg;
    }

    @Override
    public Integer getValue() {
        return this.code;
    }
}

Mybatis Plus 增删改查

SELECT

基本查询

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@Test
    void select(){

        //查询全部
        userMapper.selectList(null).forEach(System.out::println);

        //创建操作对象
        QueryWrapper queryWrapper = new QueryWrapper();

        //创建Map集合
        Map<String,Object> map = new HashMap<>();
        map.put("age",21);
        map.put("name","xiaobo");
        //将Map放入操作对象中
        queryWrapper.allEq(map);
        //模糊查询
        queryWrapper.likeLeft("name","x");
        //模糊查询
        queryWrapper.likeRight("name","x");
        //等值查询
        queryWrapper.eq("age",21);

        //子查询
        queryWrapper.inSql("id","SELECT id FROM user WHERE id < 12");
        queryWrapper.inSql("age","SELECT age FROM user WHERE age < 30");

        //升降序
        queryWrapper.orderByAsc("age");
        queryWrapper.orderByDesc("id");

        //打印查询结果
        userMapper.selectList(queryWrapper).forEach(System.out::println);

        根据Id查询
        userMapper.selectBatchIds(Arrays.asList(1,2,3,4)).forEach(System.out::println);

        Map<String,Object> map = new HashMap<>();
        map.put("name","xiaobo");
        //Map 只能做等值判断、逻辑判断需要使用 queryWrapper 来处理
        userMapper.selectByMap(map).forEach(System.out::println);

        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.eq("age",21);
        //查询结果数量
        System.out.println(userMapper.selectCount(queryWrapper));


        //分页查询
        Page<User> page = new Page<>(1,3);
        Page<User> result = userMapper.selectPage(page, null);
        System.out.println(result.getSize());
        System.out.println(result.getTotal());
        System.out.println(result.getCurrent());

        result.getRecords().forEach(System.out::println);


        //将map放在Page里面
        Page<Map<String,Object>> page = new Page<>(1,4);
        userMapper.selectMapsPage(page,null).getRecords().forEach(System.out::println);
        userMapper.selectObjs(null).forEach(System.out::println);

    }

自定义查询

  • pojo
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@Data
public class UserVO {

    private String name;
    private Integer age;
    private String username;
    private String password;

}
  • mapper
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public interface UserMapper extends BaseMapper<User> {

    @Select("SELECT u.id,username,password,name,age FROM user u,login l " +
            "WHERE u.login_id = l.id AND u.id = #{id }")
    List<UserVO> userVoList(Integer id);

}

INSERT

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@Test
void save(){
    User user = new User();

    user.setName("小博");
    user.setSex(SexEnum.男);
    user.setAge(21);

    userMapper.insert(user);
}

DELETE

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@Test
    void delete(){
//        userMapper.deleteById(17);
        Map<String,Object> map = new HashMap<>();
        map.put("id",2);
        userMapper.deleteByMap(map);
    }

UPDATE

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@Test
    void update(){
//        User user = userMapper.selectById(17);
//        user.setName("wangxiaobo");
//        user.setSex(SexEnum.女);
//        user.setAge(21);
//        User user1 = userMapper.selectById(17);
//        user1.setName("hhh");
//        userMapper.updateById(user1);
//        userMapper.updateById(user);


        User user = userMapper.selectById(17);
        user.setName("wangxiaobo");
        user.setSex(SexEnum.男);

        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.eq("id",17);
        userMapper.update(user,queryWrapper);
    }

Mybatis Plus 自动生成

  • pom
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<!--        Mybatis Plus 自动生成-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-generator</artifactId>
            <version>3.3.1.tmp</version>
        </dependency>
        <dependency>
            <groupId>org.apache.velocity</groupId>
            <artifactId>velocity</artifactId>
            <version>1.7</version>
        </dependency>
  • 生成类
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public class Main {

    public static void main(String[] args) {
        //创建generator对象
        AutoGenerator autoGenerator = new AutoGenerator();
        //数据源
        DataSourceConfig dataSourceConfig = new DataSourceConfig();
        dataSourceConfig.setDbType(DbType.MYSQL);
        dataSourceConfig.setUrl("jdbc:mysql://localhost:3306/db_springboot?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC");
        dataSourceConfig.setUsername("root");
        dataSourceConfig.setPassword("xiaobo");
        dataSourceConfig.setDriverName("com.mysql.cj.jdbc.Driver");
        autoGenerator.setDataSource(dataSourceConfig);
        //全局配置
        GlobalConfig globalConfig = new GlobalConfig();
        globalConfig.setOutputDir(System.getProperty("user.dir")+"/src/main/java");
        globalConfig.setOpen(false);
        globalConfig.setAuthor("dream.xiaobo");
        globalConfig.setServiceName("%sService");
        autoGenerator.setGlobalConfig(globalConfig);
        //包信息
        PackageConfig packageConfig = new PackageConfig();
        packageConfig.setParent("com.dream.xiaobo.mybatisplus");
        packageConfig.setModuleName("generator");
        packageConfig.setController("controller");
        packageConfig.setService("service");
        packageConfig.setServiceImpl("service.impl");
        packageConfig.setMapper("mapper");
        packageConfig.setEntity("entity");
        autoGenerator.setPackageInfo(packageConfig);
        //配置策略
        StrategyConfig strategyConfig = new StrategyConfig();
        strategyConfig.setEntityLombokModel(true);
        strategyConfig.setNaming(NamingStrategy.underline_to_camel);
        strategyConfig.setColumnNaming(NamingStrategy.underline_to_camel);
        autoGenerator.setStrategy(strategyConfig);

        autoGenerator.execute();
    }
}

正确的开始、微小的长进、然后持续、嘿、我是小博、带你一起看我目之所及的世界……

-------------本文结束 感谢您的阅读-------------

本文标题:Mybatis plus

文章作者:小博

发布时间:2021年07月29日 - 09:38

最后更新:2021年07月29日 - 09:41

原始链接:https://codexiaobo.github.io/posts/92906615/

许可协议: 署名-非商业性使用-禁止演绎 4.0 国际 转载请保留原文链接及作者。