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    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.0</version>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

Configuration information yml

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mp_db?characterEncoding=utf-8&serverTimezone=UTC
    username: root
    password: root
    driver-class-name: com.mysql.cj.jdbc.Driver

Start class

@SpringBootApplication
@MapperScan("com.mapper")
public class SGApplication {

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

mapping problem

The rules Table name

You can add... To the class name of the entity class @TableName Note to identify

If the table name is tb_user, The entity class name is User You can use the following expression .

@TableName("tb_user")
public class User {
	//....
}

The rules Primary key

for example ：

If you want to set the automatic growth of the primary key, you can set it as follows

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    @TableId(type = IdType.AUTO)
    private Long id;
	//.....
}

AUTO

database ID Self increasing , Database dependent . Please make sure that the database is set with ID Self increasing Otherwise it will not work

NONE

The primary key type is not set . If the primary key is not set manually in the code , It will be automatically generated according to the global policy of the primary key （ The default global primary key policy is self incrementing based on snowflake algorithm ID）

INPUT

You need to set the primary key manually , If we do not set up . Insert operation generates SQL When the sentence is , The value of the primary key column will be null.

ASSIGN_ID

When the primary key is not set manually , That is, when the primary key attribute in the entity class is empty , Will automatically fill , Use snowflake algorithm

ASSIGN_UUID

When the primary key attribute of the entity class is empty , Will automatically fill , Use UUID

Set the field mapping relationship

If a column in the table is called address and The attribute in the entity class is named addressStr You can use the following methods to configure .

    @TableField("address")
    private String addressStr;

MP in Default hump naming ,userName --- user_name（ In the database ）

Based on using

Basic query No, Conditions

XXXXXMapper.selectList(null)

add to

Domain domain =new domain();
domain.set Field ("");
XXmapper.insert(domain)

Delete

1  direct   according to id  Delete 
XXmapper.deteteByid(X);
2   establish   Array   Delete   
   List<Integer> ids = new ArrayList<>();
        ids.add(5);
        ids.add(6);
        ids.add(7);
        int i = userMapper.deleteBatchIds(ids);
        System.out.println(i);


    Map<String, Object> map = new HashMap<>();
        map.put("name"," Tim ");
        map.put("age",22);
        int i = userMapper.deleteByMap(map);
        System.out.println(i);
    }

modify

domain do  = new domaim(); 

do.setid();
do.set Field ();

  mapper.update(do)

Condition selector

QueryWrapper

Common conditions

eq：equals, be equal to 
gt：greater than , Greater than  >
ge：greater than or equals, Greater than or equal to ≥
lt：less than, Less than <
le：less than or equals, Less than or equal to ≤
between： amount to SQL Medium BETWEEN
like： Fuzzy matching .like(“name”,“ yellow ”), amount to SQL Of name like ‘% yellow %’
likeRight： Fuzzy match right half .likeRight(“name”,“ yellow ”), amount to SQL Of name like ‘ yellow %’
likeLeft： Fuzzy match left half .likeLeft(“name”,“ yellow ”), amount to SQL Of name like ‘% yellow ’
notLike：notLike(“name”,“ yellow ”), amount to SQL Of name not like ‘% yellow %’
isNull
isNotNull
and：SQL Connector AND
or：SQL Connector OR

in: in(“age",{1,2,3}) amount to  age in(1,2,3)

groupBy: groupBy(“id”,“name”) amount to  group by id,name

orderByAsc :orderByAsc(“id”,“name”) amount to  order by id ASC,name ASC

orderByDesc :orderByDesc (“id”,“name”) amount to  order by id DESC,name DESC

Basic use

 
        QueryWrapper wrapper = new QueryWrapper();
        wrapper.gt("XXX",XX);
        wrapper.eq("address"," Fox mountain ");
        List<XXX> XXXX = XXXMapper.selectList(wrapper);

UpdateWrapper

Basic use

   UpdateWrapper<XXX> updateWrapper = new UpdateWrapper<>();
        updateWrapper.gt("id",1);   Updated scope 
        updateWrapper.set("age",99);   Modified data 
        XXXXMapper.update(null,updateWrapper);

Custom method （mapper Interface ）

public interface UserMapper extends BaseMapper<User> {

    User findMyUser(Long id);
}

XML Corresponding

<?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.sangeng.mapper.UserMapper">

    <select id="findMyUser" resultType="com.sangeng.domian.User">
       select * from user where id = #{id} 
    </select>
</mapper>

Paging query

Get ready Pagination plug-in unit

@Configuration
public class PageConfig {

    /**
     * 3.4.0 Previous version 
     * @return
     */
   /* @Bean
    public PaginationInterceptor paginationInterceptor(){
        return  new PaginationInterceptor();
    }*/

    /**
     * 3.4.0 After the version 
     * @return
     */
   @Bean
   public MybatisPlusInterceptor mybatisPlusInterceptor(){
       MybatisPlusInterceptor mybatisPlusInterceptor = new MybatisPlusInterceptor();
       mybatisPlusInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
       return mybatisPlusInterceptor;
   }
}

Single table query


    public void testPage(){
        IPage<XXX> page = new Page<>();
        // Set number of entries per page 
        page.setSize(2);
        // Set the page number of the query 
        page.setCurrent(1);
        userMapper.selectPage(page, null);
        System.out.println(page.getRecords());// Gets the data of the current page 
        System.out.println(page.getTotal());// Get the total number of records 
        System.out.println(page.getCurrent());// The current page number 
    }

Multi-table query

Inquire about A B Two form Of When

Add up Use mapper in Corresponding Entity class

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Orders  {
	// Omit irrelevant code 
    private String userName;
}

 IPage<XXX> findAllOrders(Page<XXXX> XXXX);

    public void testOrdersPage(){
        Page<Orders> page = new Page<>();
        // Set the size of each page 
        page.setSize(2);
        // Set the current page number 
        page.setCurrent(2);
        ordersMapper.findAllOrders(page);
        System.out.println(page.getRecords());
        System.out.println(page.getTotal());
    }

Service

Before transformation

public interface UserService {
    List<User> list();
}

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserMapper userMapper;

    @Override
    public List<User> list() {
        return userMapper.selectList(null);
    }
}

After transformation

Compared with before Interface Will bring some methods , Basic query addition, deletion, modification and query can be completed by directly calling the interface .

public interface UserService extends IService<User> {

}

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

    @Autowired
    private UserService userService;


    @Test
    public void testSeervice(){
        List<User> list = userService.list();
        System.out.println(list);
    }

Custom method

Comparison mapper Interface , There's no difference

public interface UserService extends IService<User> {


    User test();
}

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

    @Autowired
    private OrdersMapper ordersMapper;

    @Override
    public User test() {
        UserMapper userMapper = getBaseMapper();
        List<Orders> orders = ordersMapper.selectList(null);
        User user = userMapper.selectById(3);
        // Query the user's order 
        QueryWrapper<Orders> wrapper = new QueryWrapper<>();
        wrapper.eq("user_id",3);
        List<Orders> ordersList = ordersMapper.selectList(wrapper);
        return user;
    }
}

Auto fill

Use tablefield（fill = fiedfill.insert_update）

 /**
     *  Update time 
     */
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private LocalDateTime updateTime;

    /**
     *  Creation time 
     */
    @TableField(fill = FieldFill.INSERT)
    private LocalDateTime createTime;

Custom fill processor MetaObjectHandler

@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
    @Override
    public void insertFill(MetaObject metaObject) {
        this.setFieldValByName("createTime", LocalDateTime.now(), metaObject);
        this.setFieldValByName("updateTime", LocalDateTime.now(), metaObject);
        //                            " Field ", data type ,value
    }

    @Override
    public void updateFill(MetaObject metaObject) {
        this.setFieldValByName("updateTime", LocalDateTime.now(), metaObject);
    }
}

Logical deletion

To configure

yml
mybatis-plus:
  global-config:
    db-config:
      logic-delete-field: delFlag  #  The name of the entity field for global logical deletion (since 3.3.0, After configuration, you can ignore the non configuration steps 2)
      logic-delete-value: 1 #  Logical deleted value ( The default is  1)
      logic-not-delete-value: 0 #  Logical undeleted value ( The default is  0)

After deleting delflag Of The default value is Will change

result