Chapter 2 MybatisPlus general CRUD

1. Overview

Recall that if we have a User table and have created the corresponding entity class, what do we need to do to implement the CRUD operation of the User table?

Steps for Mybatis universal CRUD

First, we need to write the UserMapper mapping interface and manually define the CRUD method in the UserMapper interface

Then we need to create usermapper XML Mapping file, and manually write the SQL statement corresponding to each method

Steps for MybatisPlus universal CRUD

Just create the UserMapper interface and inherit the BaseMapper interface. This is all the operations that need to be completed to use MP. We can make the Mapper interface we create have the most basic CRUD method without even creating an SQL mapping file

2. Insert operation

0,Insert API

// Insert a record
int insert(T entity);

Parameter description

type	Parameter name	describe
T	entity	Entity object

1. Insert: insert a record (int);

@Test
public void insert() {
    User userOneby = new User();
    userOneby.setName("Oneby");
    userOneby.setAge(21);
    userOneby.setEmail("Oneby@baomidou.com");
    int result = userMapper.insert(userOneby);
    System.out.println("Number of affected rows:" + result);
    System.out.println(userOneby);

    User userHeygo = new User();
    userHeygo.setName("Heygo");
    userHeygo.setAge(21);
    userHeygo.setEmail(null);
    result = userMapper.insert(userHeygo);
    System.out.println("Number of affected rows:" + result);
    System.out.println(userHeygo);
}

When inserting data, the insert() method will make non empty judgment according to each attribute of the entity class, and only the field corresponding to the non empty attribute will appear in the SQL statement

The id field of the printout user object is not null, which indicates that the primary key is automatically backfilled by default. However, there is a problem: the primary key does not seem to be self incremented. Please refer to the @ TableId annotation to solve this problem, which will be discussed later

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@51e0301d] was not registered for synchronization because synchronization is not active
2021-04-22 21:45:52.571  INFO 8228 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:45:52.696  INFO 8228 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@2097614581 wrapping com.mysql.cj.jdbc.ConnectionImpl@7a55f148] will not be managed by Spring
==>  Preparing: INSERT INTO user ( id, name, age, email ) VALUES ( ?, ?, ?, ? )
==> Parameters: 1385228362414358529(Long), Oneby(String), 21(Integer), Oneby@baomidou.com(String)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@51e0301d]
Number of affected rows: 1
User(id=1385228362414358529, name=Oneby, age=21, email=Oneby@baomidou.com)
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@bd1111a] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@501650218 wrapping com.mysql.cj.jdbc.ConnectionImpl@7a55f148] will not be managed by Spring
==>  Preparing: INSERT INTO user ( id, name, age ) VALUES ( ?, ?, ? )
==> Parameters: 1385228363135778818(Long), Heygo(String), 21(Integer)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@bd1111a]
Number of affected rows: 1
User(id=1385228363135778818, name=Heygo, age=21, email=null)

3. Update operation

0,Update API

// Update the record according to the whereWrapper condition
int update(@Param(Constants.ENTITY) T updateEntity, @Param(Constants.WRAPPER) Wrapper<T> whereWrapper);
// Modify according to ID
int updateById(@Param(Constants.ENTITY) T entity);

Parameter description

type	Parameter name	describe
T	entity	Entity object (set condition value, nullable)
Wrapper	updateWrapper	Entity object encapsulates operation class (null able, and entity in it is used to generate where statement)

1. Modify according to the primary key: int updateById(@Param(Constants.ENTITY) T entity);

@Test
public void updateById() {
    User user = new User();
    user.setId(1L);
    user.setName("Heygo");
    user.setAge(21);
    user.setEmail(null);
    int result = userMapper.updateById(user);
    System.out.println("Number of affected rows:" + result);

    User retUser = userMapper.selectById(1);
    System.out.println(retUser);
}

When updateById() method updates data, the update condition of SQL statement is WHERE id =?, Non null judgment will be made according to each attribute of the entity class, and only the field corresponding to the non null attribute will appear in the SQL statement

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5f303ecd] was not registered for synchronization because synchronization is not active
2021-04-22 21:46:10.286  INFO 18636 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:46:10.411  INFO 18636 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1066656936 wrapping com.mysql.cj.jdbc.ConnectionImpl@12b5454f] will not be managed by Spring
==>  Preparing: UPDATE user SET name=?, age=? WHERE id=?
==> Parameters: Heygo(String), 21(Integer), 1(Long)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5f303ecd]
Number of affected rows: 1
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5d01ea21] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@596905862 wrapping com.mysql.cj.jdbc.ConnectionImpl@12b5454f] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE id=?
==> Parameters: 1(Integer)
<==    Columns: id, name, age, email
<==        Row: 1, Heygo, 21, test1@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5d01ea21]
User(id=1, name=Heygo, age=21, email=test1@baomidou.com)

2. Modify according to the condition constructor: int update (@ param (constants. Entity) t entity, @ param (constants. Wrapper) wrapper < T > updatewrapper);

@Test
public void update() {
    User user = new User();
    user.setName("NiuNiu");
    user.setAge(18);
    user.setEmail(null);
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.eq("id", 2);
    wrapper.eq("age", 20);
    int result = userMapper.update(user, wrapper);
    System.out.println("Number of affected rows:" + result);

    User retUser = userMapper.selectById(2);
    System.out.println(retUser);
}

When updating data, the update() method will dynamically splice the conditions of the WHERE clause in the SQL statement according to the wrapper object, and make non empty judgment according to each attribute of the entity class. Only the fields corresponding to non empty attributes will appear in the SQL statement

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3b08f438] was not registered for synchronization because synchronization is not active
2021-04-22 21:46:25.325  INFO 20524 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:46:25.450  INFO 20524 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@203401172 wrapping com.mysql.cj.jdbc.ConnectionImpl@7a93b263] will not be managed by Spring
==>  Preparing: UPDATE user SET name=?, age=? WHERE (id = ? AND age = ?)
==> Parameters: NiuNiu(String), 18(Integer), 2(Integer), 20(Integer)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3b08f438]
Number of affected rows: 1
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6d5037a9] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1412612727 wrapping com.mysql.cj.jdbc.ConnectionImpl@7a93b263] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE id=?
==> Parameters: 2(Integer)
<==    Columns: id, name, age, email
<==        Row: 2, NiuNiu, 18, test2@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6d5037a9]
User(id=2, name=NiuNiu, age=18, email=test2@baomidou.com)

4. Query operation

0,Select API

// Query by ID
T selectById(Serializable id);
// Query a record according to the entity condition
T selectOne(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

// Query (batch query by ID)
List<T> selectBatchIds(@Param(Constants.COLLECTION) Collection<? extends Serializable> idList);
// Query all records according to the entity condition
List<T> selectList(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// Query (based on columnMap criteria)
List<T> selectByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);
// Query all records according to Wrapper conditions
List<Map<String, Object>> selectMaps(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// Query all records according to Wrapper conditions. Note: only the value of the first field is returned
List<Object> selectObjs(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

// Query all records (and turn the page) according to the entity condition
IPage<T> selectPage(IPage<T> page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// Query all records (and turn pages) according to Wrapper conditions
IPage<Map<String, Object>> selectMapsPage(IPage<T> page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// Query the total number of records according to Wrapper conditions
Integer selectCount(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

Parameter description

type	Parameter name	describe
Serializable	id	Primary key ID
Wrapper	queryWrapper	Entity object encapsulates operation class (null able)
Collection<? extends Serializable>	idList	List of primary key ID S (cannot be null and empty)
Map<String, Object>	columnMap	Table field map object
IPage	page	Paging query criteria (can be rowboundaries. Default)

1. Query a record according to the primary key: T selectById(Serializable id);

@Test
public void selectById() {
    User user = userMapper.selectById(1);
    System.out.println(user);
}

The selectById() method will query all fields in the table. The filter condition of the SQL statement is WHERE id =?

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@62e6a3ec] was not registered for synchronization because synchronization is not active
2021-04-22 21:46:38.630  INFO 20528 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:46:38.763  INFO 20528 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1289834245 wrapping com.mysql.cj.jdbc.ConnectionImpl@71dfcf21] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE id=?
==> Parameters: 1(Integer)
<==    Columns: id, name, age, email
<==        Row: 1, Heygo, 21, test1@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@62e6a3ec]
User(id=1, name=Heygo, age=21, email=test1@baomidou.com)

2. Batch query according to the primary key list: List < T > selectbatchids (@ param (constants. Collection) collection <? extends Serializable> idList);

@Test
public void selectBatchIds() {
    List<User> users = userMapper.selectBatchIds(Arrays.asList(1, 2));
    users.forEach(System.out::println);
}

The selectBatchIds() method will query all fields in the table. The filter criteria of the SQL statement is WHERE id IN (?,?)

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3be4f71] was not registered for synchronization because synchronization is not active
2021-04-22 21:46:51.438  INFO 8972 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:46:51.563  INFO 8972 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@338765435 wrapping com.mysql.cj.jdbc.ConnectionImpl@342726f1] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE id IN ( ? , ? )
==> Parameters: 1(Integer), 2(Integer)
<==    Columns: id, name, age, email
<==        Row: 1, Heygo, 21, test1@baomidou.com
<==        Row: 2, NiuNiu, 18, test2@baomidou.com
<==      Total: 2
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3be4f71]
User(id=1, name=Heygo, age=21, email=test1@baomidou.com)
User(id=2, name=NiuNiu, age=18, email=test2@baomidou.com)

3. Batch query according to columnMap conditions: List < T > selectbymap (@ param (constants. Column_map) map < string, Object > columnMap);

@Test
public void selectByMap() {
    Map<String, Object> params = new HashMap<>() ;
    params.put("name", "NiuNiu");
    params.put("age", 18);
    List<User> users = userMapper.selectByMap(params);
    users.forEach(System.out::println);
}

All fields in the query table will be queried by the select method; The filter conditions of WHERE clause in SQL statement will be spliced dynamically according to the Map object

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3be4f71] was not registered for synchronization because synchronization is not active
2021-04-22 21:47:26.111  INFO 9296 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:47:26.252  INFO 9296 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1061806694 wrapping com.mysql.cj.jdbc.ConnectionImpl@5f18f9d2] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE name = ? AND age = ?
==> Parameters: NiuNiu(String), 18(Integer)
<==    Columns: id, name, age, email
<==        Row: 2, NiuNiu, 18, test2@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3be4f71]
User(id=2, name=NiuNiu, age=18, email=test2@baomidou.com)

4. Query a record according to the condition constructor: t selectone (@ param (constants. Wrapper) wrapper < T > querywrapper);

@Test
public void selectOne() {
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.eq("name", "Oneby");
    User user = userMapper.selectOne(wrapper);
    System.out.println(user);

    wrapper.clear();
    wrapper.eq("age", 21);
    user = userMapper.selectOne(wrapper);
    System.out.println(user);
}

The selectOne() method will query all fields in the table; The filter conditions of WHERE clause in SQL statement will be spliced dynamically according to wrapper object. If more than one result is obtained from the query, TooManyResultsException will be thrown

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7a344b65] was not registered for synchronization because synchronization is not active
2021-04-22 21:47:41.497  INFO 13692 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:47:41.628  INFO 13692 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1689723487 wrapping com.mysql.cj.jdbc.ConnectionImpl@33db72bd] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE (name = ?)
==> Parameters: Oneby(String)
<==    Columns: id, name, age, email
<==        Row: 1385228362414358529, Oneby, 21, Oneby@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7a344b65]
User(id=1385228362414358529, name=Oneby, age=21, email=Oneby@baomidou.com)
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@72d0f2b4] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1831717330 wrapping com.mysql.cj.jdbc.ConnectionImpl@33db72bd] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE (age = ?)
==> Parameters: 21(Integer)
<==    Columns: id, name, age, email
<==        Row: 1, Heygo, 21, test1@baomidou.com
<==        Row: 4, Sandy, 21, test4@baomidou.com
<==        Row: 1385228362414358529, Oneby, 21, Oneby@baomidou.com
<==        Row: 1385228363135778818, Heygo, 21, null
<==      Total: 4
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@72d0f2b4]

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 4

5. Query the total number of records according to the condition constructor: integer selectcount (@ param (constants. Wrapper) wrapper < T > querywrapper);

@Test
public void selectCount() {
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.eq("age", 21);
    Integer count = userMapper.selectCount(wrapper);
    System.out.println(count);
}

The selectCount() method will query all fields in the table; The filter conditions of the WHERE clause in the SQL statement will be spliced dynamically according to the wrapper object

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6b474074] was not registered for synchronization because synchronization is not active
2021-04-22 21:50:12.402  INFO 15376 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:50:12.527  INFO 15376 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@2140322192 wrapping com.mysql.cj.jdbc.ConnectionImpl@31e04b13] will not be managed by Spring
==>  Preparing: SELECT COUNT( * ) FROM user WHERE (age = ?)
==> Parameters: 21(Integer)
<==    Columns: COUNT( * )
<==        Row: 4
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6b474074]
4

6. Query all records according to the condition constructor: List < T > selectlist (@ param (constants. Wrapper) wrapper < T > querywrapper);

@Test
public void selectList() {
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.eq("age", 21);
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}

The selectList() method will query all fields in the table; The filter conditions of the WHERE clause in the SQL statement will be spliced dynamically according to the wrapper object

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@108531c2] was not registered for synchronization because synchronization is not active
2021-04-22 21:50:49.681  INFO 1432 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:50:49.816  INFO 1432 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@870019773 wrapping com.mysql.cj.jdbc.ConnectionImpl@7f92b990] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE (age = ?)
==> Parameters: 21(Integer)
<==    Columns: id, name, age, email
<==        Row: 1, Heygo, 21, test1@baomidou.com
<==        Row: 4, Sandy, 21, test4@baomidou.com
<==        Row: 1385228362414358529, Oneby, 21, Oneby@baomidou.com
<==        Row: 1385228363135778818, Heygo, 21, null
<==      Total: 4
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@108531c2]
User(id=1, name=Heygo, age=21, email=test1@baomidou.com)
User(id=4, name=Sandy, age=21, email=test4@baomidou.com)
User(id=1385228362414358529, name=Oneby, age=21, email=Oneby@baomidou.com)
User(id=1385228363135778818, name=Heygo, age=21, email=null)

7. Query records according to paging conditions: < e extensions iPage < T > > e selectpage (e page, @ param (constants. Wrapper) wrapper < T > querywrapper);

@Test
public void selectPage() {
    Page<User> page = new Page<>();
    page.setCurrent(1);
    page.setSize(2);
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.eq("age", 21);
    Page<User> userPage = userMapper.selectPage(page, wrapper);
    userPage.getRecords().forEach(System.out::println);
}

The selectList() method will query all fields in the table; The filter conditions of WHERE clause in SQL statement will be spliced dynamically according to the wrapper object; The LIMIT OFFSET clause of the SQL statement will be spliced dynamically according to the page object

It can be seen from the log that there is no LIMIT OFFSET clause in the SQL statement, which indicates that the parameters set by the page object do not take effect, because we do not turn on the function of the paging plug-in, which will be described later

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7b7b3edb] was not registered for synchronization because synchronization is not active
2021-04-22 21:51:34.960  INFO 13584 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:51:35.069  INFO 13584 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@870019773 wrapping com.mysql.cj.jdbc.ConnectionImpl@7f92b990] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE (age = ?)
==> Parameters: 21(Integer)
<==    Columns: id, name, age, email
<==        Row: 1, Heygo, 21, test1@baomidou.com
<==        Row: 4, Sandy, 21, test4@baomidou.com
<==        Row: 1385228362414358529, Oneby, 21, Oneby@baomidou.com
<==        Row: 1385228363135778818, Heygo, 21, null
<==      Total: 4
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7b7b3edb]
User(id=1, name=Heygo, age=21, email=test1@baomidou.com)
User(id=4, name=Sandy, age=21, email=test4@baomidou.com)
User(id=1385228362414358529, name=Oneby, age=21, email=Oneby@baomidou.com)
User(id=1385228363135778818, name=Heygo, age=21, email=null)

5. Delete operation

0,Delete API

// Delete the record according to the entity condition
int delete(@Param(Constants.WRAPPER) Wrapper<T> wrapper);
// Delete (batch delete according to ID)
int deleteBatchIds(@Param(Constants.COLLECTION) Collection<? extends Serializable> idList);
// Delete by ID
int deleteById(Serializable id);
// Delete the record according to the columnMap condition
int deleteByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);

Parameter description

type	Parameter name	describe
Wrapper	wrapper	Entity object encapsulates operation class (null able)
Collection<? extends Serializable>	idList	List of primary key ID S (cannot be null and empty)
Serializable	id	Primary key ID
Map<String, Object>	columnMap	Table field map object

1. Delete by primary key: int deleteById(Serializable id);

@Test
public void deleteById() {
    int result = userMapper.deleteById(1);
    System.out.println("Number of affected rows:" + result);
}

When the deleteById() method is executed, the deletion filter condition of the SQL statement is WHERE id =?

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@50d3bf39] was not registered for synchronization because synchronization is not active
2021-04-22 21:59:34.538  INFO 9312 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:59:34.668  INFO 9312 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1289834245 wrapping com.mysql.cj.jdbc.ConnectionImpl@71dfcf21] will not be managed by Spring
==>  Preparing: DELETE FROM user WHERE id=?
==> Parameters: 1(Integer)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@50d3bf39]
Number of affected rows: 1

2. Batch delete according to the primary key list: int deletebatchids (@ parameter (constants. Collection) collection <? extends Serializable> idList);

@Test
public void deleteBatchIds() {
    int result = userMapper.deleteBatchIds(Arrays.asList(2, 3));
    System.out.println("Number of affected rows:" + result);
}

When the deleteBatchIds() method is executed, the deletion filter condition of the SQL statement is WHERE id IN (?,?)

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@771db12c] was not registered for synchronization because synchronization is not active
2021-04-22 21:59:48.184  INFO 15280 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:59:48.314  INFO 15280 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@253380088 wrapping com.mysql.cj.jdbc.ConnectionImpl@5edf2821] will not be managed by Spring
==>  Preparing: DELETE FROM user WHERE id IN ( ? , ? )
==> Parameters: 2(Integer), 3(Integer)
<==    Updates: 2
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@771db12c]
Number of affected lines: 2

3. Batch deletion according to columnMap conditions: int deletebymap (@ parameter (constants. Column_map) map < string, Object > columnMap);

@Test
public void deleteByMap() {
    Map<String, Object> params = new HashMap<>();
    params.put("name", "Billie");
    params.put("age", 24);
    int result = userMapper.deleteByMap(params);
    System.out.println("Number of affected rows:" + result);
}

When the deleteByMap method is executed, it will dynamically splice the filter conditions of the WHERE clause in the SQL statement according to the map object

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1eb6e1c] was not registered for synchronization because synchronization is not active
2021-04-22 22:00:00.418  INFO 15056 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 22:00:00.548  INFO 15056 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1066656936 wrapping com.mysql.cj.jdbc.ConnectionImpl@12b5454f] will not be managed by Spring
==>  Preparing: DELETE FROM user WHERE name = ? AND age = ?
==> Parameters: Billie(String), 24(Integer)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1eb6e1c]
Number of affected rows: 1

4. Batch deletion by condition constructor: int delete (@ param (constants. Wrapper) wrapper < T > querywrapper);

@Test
public void delete() {
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.eq("age", 21);
    int result = userMapper.delete(wrapper);
    System.out.println("Number of affected rows:" + result);
}

When the delete method is executed, it will dynamically splice the filter conditions of the WHERE clause in the SQL statement according to the wrapper object

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3104351d] was not registered for synchronization because synchronization is not active
2021-04-22 22:00:13.593  INFO 8676 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 22:00:13.723  INFO 8676 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1077464378 wrapping com.mysql.cj.jdbc.ConnectionImpl@14ac77b9] will not be managed by Spring
==>  Preparing: DELETE FROM user WHERE (age = ?)
==> Parameters: 21(Integer)
<==    Updates: 3
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3104351d]
Number of affected lines: 3

6. Full column operation

mapper layer option

The options are located on COM baomidou. mybatisplus. extension. injector. Cooperation is required under the methods package Sql injector use, case See for details Source code comments

The most commonly used option should be AlwaysUpdateSomeColumnById. As mentioned earlier, the API will first judge whether the field is empty. If it is empty, it will not be updated, but AlwaysUpdateSomeColumnById will update the fixed fields according to the ID (but logical deletion is not included)

7. Common notes

@TableName

We change the table name of the database from user to t_user, execute the selectById() method again and find that the program throws an exception: BadSqlGrammarException

The specific information of the exception is: cause: Java sql. SQLSyntaxErrorException: Table 'mybatis_plus.user 'doesn't exist, saying that mybatis cannot be found_ plus. Use this form

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@652ab8d9] was not registered for synchronization because synchronization is not active
2021-04-20 08:22:38.576  INFO 3304 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-20 08:22:38.700  INFO 3304 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@665317128 wrapping com.mysql.cj.jdbc.ConnectionImpl@280e8a1a] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user WHERE id=?
==> Parameters: 1(Integer)
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@652ab8d9]

org.springframework.jdbc.BadSqlGrammarException: 
### Error querying database.  Cause: java.sql.SQLSyntaxErrorException: Table 'mybatis_plus.user' doesn't exist
### The error may exist in com/oneby/mapper/UserMapper.java (best guess)
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: SELECT id,name,age,email FROM user WHERE id=?
### Cause: java.sql.SQLSyntaxErrorException: Table 'mybatis_plus.user' doesn't exist
; bad SQL grammar []; nested exception is java.sql.SQLSyntaxErrorException: Table 'mybatis_plus.user' doesn't exist

MybatisPlus will use the class name of the entity class to find the corresponding table in the database by default, but if the class name of the entity class is inconsistent with the database, you need to use the @ TableName annotation to mark the database table name corresponding to the entity class

/**
 * @Author Oneby
 * @Date 2021/4/18 17:53
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
@TableName("t_user")
public class User {

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

}

We execute the query again, and the table name in the sent SQL statement becomes t_user

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@50d3bf39] was not registered for synchronization because synchronization is not active
2021-04-20 08:25:25.826  INFO 2428 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-20 08:25:25.951  INFO 2428 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1688526221 wrapping com.mysql.cj.jdbc.ConnectionImpl@2dddc1b9] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM t_user WHERE id=?
==> Parameters: 1(Integer)
<==    Columns: id, name, age, email
<==        Row: 1, Jone, 18, test1@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@50d3bf39]
User(id=1, name=Jone, age=18, email=test1@baomidou.com)

@TableName annotation

/**
 * Database table correlation
 *
 * @author hubin, hanchunlin
 * @since 2016-01-23
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.ANNOTATION_TYPE})
public @interface TableName {

    /**
     * Table name corresponding to entity
     */
    String value() default "";

    /**
     * schema
     * <p>
     * Configuring this value overrides the globally configured schema
     *
     * @since 3.1.1
     */
    String schema() default "";

    /**
     * Whether to keep the value of using global tablePrefix
     * <p> It only takes effect when both the global tablePrefix and the value of {@ link #value()} above are set</p>
     * <li> If false, the global tablePrefix will not take effect</li>
     *
     * @since 3.1.1
     */
    boolean keepGlobalPrefix() default false;

    /**
     * Entity mapping result set,
     * method that only takes effect and is automatically injected by mp
     */
    String resultMap() default "";

    /**
     * Whether to automatically build and use the resultMap,
     * The method that only takes effect and is automatically injected by mp,
     * If the resultMap is set, the resultMap will not be automatically built and injected,
     * It is only applicable when typeHandler or JDBC type is set in individual fields
     *
     * @since 3.1.2
     */
    boolean autoResultMap() default false;

    /**
     * Attribute name to exclude
     *
     * @since 3.3.1
     */
    String[] excludeProperty() default {};
}

@TableField

We will t_ Change the user column of the user table to username, execute the selectById() method again, and find that the program throws an exception: BadSqlGrammarException

The specific information of the exception is: cause: Java sql. Sqlsyntaxerrorexception: unknown column 'name' in 'field list', which means the column name cannot be found

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5f13be1] was not registered for synchronization because synchronization is not active
2021-04-20 08:26:10.119  INFO 8344 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-20 08:26:10.244  INFO 8344 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1609754699 wrapping com.mysql.cj.jdbc.ConnectionImpl@74abbb] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM t_user WHERE id=?
==> Parameters: 1(Integer)
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5f13be1]

org.springframework.jdbc.BadSqlGrammarException: 
### Error querying database.  Cause: java.sql.SQLSyntaxErrorException: Unknown column 'name' in 'field list'
### The error may exist in com/oneby/mapper/UserMapper.java (best guess)
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: SELECT id,name,age,email FROM t_user WHERE id=?
### Cause: java.sql.SQLSyntaxErrorException: Unknown column 'name' in 'field list'
; bad SQL grammar []; nested exception is java.sql.SQLSyntaxErrorException: Unknown column 'name' in 'field list'

MybatisPlus will use the field name of the entity class to find the corresponding column in the database table by default (the hump naming rule is enabled by default), but when the class name of the entity class is inconsistent with the database, the @ TableField annotation needs to be used to mark the database table name corresponding to the entity class

/**
 * @Author Oneby
 * @Date 2021/4/18 17:53
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
@TableName("t_user")
public class User {

    private Long id;
    
    @TableField("username")
    private String name;
    
    private Integer age;
    
    private String email;

}

We execute the query again, and the column name in the sent SQL statement becomes username

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@17814b1c] was not registered for synchronization because synchronization is not active
2021-04-22 22:16:13.980  INFO 19028 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 22:16:14.110  INFO 19028 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1487287849 wrapping com.mysql.cj.jdbc.ConnectionImpl@7de843ef] will not be managed by Spring
==>  Preparing: SELECT id,username AS name,age,email FROM t_user WHERE id=?
==> Parameters: 1(Integer)
<==    Columns: id, name, age, email
<==        Row: 1, Jone, 18, test1@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@17814b1c]
User(id=1, name=Jone, age=18, email=test1@baomidou.com)

@TableField annotation: if some fields in the entity class are not database fields, set exist = false

/**
 * Table field ID
 *
 * @author hubin sjy tantan
 * @since 2016-09-09
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.ANNOTATION_TYPE})
public @interface TableField {

    /**
     * Database field value
     * <p>
     * When this value does not need to be configured:
     * <li> When {@ link com.baomidou.mybatisplus.core.MybatisConfiguration#mapUnderscoreToCamelCase} is true,
     * (mp The default value is. Myfalse in the database replace("_","").toUpperCase() = = entity attribute name toUpperCase() </li>
     * <li> When {@ link com.baomidou.mybatisplus.core.MybatisConfiguration#mapUnderscoreToCamelCase} is false,
     * Database field value Touppercase() = = entity attribute name toUpperCase() </li>
     */
    String value() default "";

    /**
     * Is it a database table field
     * <p>
     * By default, true exists and false does not exist
     */
    boolean exist() default true;

    /**
     * Field where entity query comparison criteria
     * <p>
     * Default {sqllink @ SQL}
     */
    String condition() default "";

    /**
     * The field update set is partially injected. This annotation is better than the el annotation
     * <p>
     * Example 1: @ tablefield (.., update = "% s + 1") where% s will be filled as a field
     * The output SQL is: update table set field = field + 1 where
     * <p>
     * Example 2: @ tablefield (.., update = "now()") uses database time
     * The output SQL is: update table set field = now() where
     */
    String update() default "";

    /**
     * Insert of field verification strategy: when the insert operation is performed, the strategy when the field splices the insert statement
     * <p>
     * IGNORED: Direct splicing insert into table_a(column) values (#{columnProperty});
     * NOT_NULL: insert into table_a(<if test="columnProperty != null">column</if>) values (<if test="columnProperty != null">#{columnProperty}</if>)
     * NOT_EMPTY: insert into table_a(<if test="columnProperty != null and columnProperty!=''">column</if>) values (<if test="columnProperty != null and columnProperty!=''">#{columnProperty}</if>)
     * NOT_EMPTY If you are targeting a field of non CharSequence type, the effect is equal to NOT_NULL
     *
     * @since 3.1.2
     */
    FieldStrategy insertStrategy() default FieldStrategy.DEFAULT;

    /**
     * update of field validation policy: when updating, the policy when the field splices the set statement
     * <p>
     * IGNORED: Direct splicing update table_a set column=#{columnProperty}, null / empty string will be set in
     * NOT_NULL: update table_a set <if test="columnProperty != null">column=#{columnProperty}</if>
     * NOT_EMPTY: update table_a set <if test="columnProperty != null and columnProperty!=''">column=#{columnProperty}</if>
     * NOT_EMPTY If you are targeting a field of non CharSequence type, the effect is equal to NOT_NULL
     *
     * @since 3.1.2
     */
    FieldStrategy updateStrategy() default FieldStrategy.DEFAULT;

    /**
     * Where of field validation policy: indicates the policy of the field when splicing the where condition
     * <p>
     * IGNORED: Direct splicing column=#{columnProperty}
     * NOT_NULL: <if test="columnProperty != null">column=#{columnProperty}</if>
     * NOT_EMPTY: <if test="columnProperty != null and columnProperty!=''">column=#{columnProperty}</if>
     * NOT_EMPTY If you are targeting a field of non CharSequence type, the effect is equal to NOT_NULL
     *
     * @since 3.1.2
     */
    FieldStrategy whereStrategy() default FieldStrategy.DEFAULT;

    /**
     * Field auto fill policy
     * <p>
     * In the corresponding mode, the configuration of insertStrategy or updatestategy will be ignored, which is equal to asserting that this field must have a value
     */
    FieldFill fill() default FieldFill.DEFAULT;

    /**
     * select query
     * <p>
     * Large fields can be set to false and will not be included in the select query range
     */
    boolean select() default true;

    /**
     * Whether to keep the value of using global columnFormat
     * <p>
     * It only takes effect when both the global columnFormat and the value of {@ link #value()} above are set
     * If false, the global columnFormat will not take effect
     *
     * @since 3.1.1
     */
    boolean keepGlobalFormat() default false;

    /**
     * JDBC Type (this default value does not mean that it will take effect according to this value),
     * The method that only takes effect and is automatically injected by mp,
     * It is recommended to use with {@ link TableName#autoResultMap()}
     * <p>
     * {@link ResultMapping#jdbcType} and {@link ParameterMapping#jdbcType}
     *
     * @since 3.1.2
     */
    JdbcType jdbcType() default JdbcType.UNDEFINED;

    /**
     * Type processor (this default does not mean that it will take effect according to this value),
     * The method that only takes effect and is automatically injected by mp,
     * It is recommended to use with {@ link TableName#autoResultMap()}
     * <p>
     * {@link ResultMapping#typeHandler} and {@link ParameterMapping#typeHandler}
     *
     * @since 3.1.2
     */
    Class<? extends TypeHandler> typeHandler() default UnknownTypeHandler.class;

    /**
     * Only when {@ link #typeHandler()} is used, judge whether to append javaType
     * <p>
     * Generally, it is not recommended
     * {@link ParameterMapping#javaType}
     *
     * @since 3.4.0 @2020-07-23
     */
    boolean javaType() default false;

    /**
     * Specify the number of digits to keep after the decimal point,
     * It only applies to method s automatically injected by mp,
     * It is recommended to use with {@ link TableName#autoResultMap()}
     * <p>
     * {@link ParameterMapping#numericScale}
     *
     * @since 3.1.2
     */
    String numericScale() default "";
}

@TableId

When we executed the insert() method before, we found that the primary key value of automatic backfill is not automatically incremented

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@51e0301d] was not registered for synchronization because synchronization is not active
2021-04-22 21:45:52.571  INFO 8228 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 21:45:52.696  INFO 8228 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@2097614581 wrapping com.mysql.cj.jdbc.ConnectionImpl@7a55f148] will not be managed by Spring
==>  Preparing: INSERT INTO user ( id, name, age, email ) VALUES ( ?, ?, ?, ? )
==> Parameters: 1385228362414358529(Long), Oneby(String), 21(Integer), Oneby@baomidou.com(String)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@51e0301d]
Number of affected rows: 1
User(id=1385228362414358529, name=Oneby, age=21, email=Oneby@baomidou.com)

When we do not set the primary key type, MybatisPlus will help us register the auto fill plug-in for filling. If you want to set primary key auto increment, you need to use @ TableId(type = IdType.AUTO) annotation to identify the primary key field

/**
 * @Author Oneby
 * @Date 2021/4/18 17:53
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
@TableName("t_user")
public class User {

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

    @TableField("name")
    private String name;

    private Integer age;

    private String email;

}

When we execute the insert() method again to insert data, we find a magical thing: there is no id field in the issued SQL statement, but the program throws an exception: dataintegrity violationexception

The body information of the exception is: cause: Java sql. Sqlexception: field 'id' doesn't have a default value, which means t_ The id field in the user table does not have a default value

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@58399d82] was not registered for synchronization because synchronization is not active
2021-04-22 22:26:43.141  INFO 2324 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 22:26:43.258  INFO 2324 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1779219567 wrapping com.mysql.cj.jdbc.ConnectionImpl@67110f71] will not be managed by Spring
==>  Preparing: INSERT INTO t_user ( username, age, email ) VALUES ( ?, ?, ? )
==> Parameters: Oneby(String), 21(Integer), Oneby@baomidou.com(String)
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@58399d82]

org.springframework.dao.DataIntegrityViolationException: 
### Error updating database.  Cause: java.sql.SQLException: Field 'id' doesn't have a default value
### The error may exist in com/oneby/mapper/UserMapper.java (best guess)
### The error may involve com.oneby.mapper.UserMapper.insert-Inline
### The error occurred while setting parameters
### SQL: INSERT INTO t_user  ( username, age, email )  VALUES  ( ?, ?, ? )
### Cause: java.sql.SQLException: Field 'id' doesn't have a default value
; Field 'id' doesn't have a default value; nested exception is java.sql.SQLException: Field 'id' doesn't have a default value

This is because we did not set the id field to self increment in MySQL database. After setting the id field to self increment, we executed the insert() method again: the SQL statement did not carry the id field and its field value. The data was inserted successfully and the value of the self increment primary key was automatically backfilled

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3c017078] was not registered for synchronization because synchronization is not active
2021-04-22 22:29:24.961  INFO 17588 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-04-22 22:29:25.089  INFO 17588 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@313869647 wrapping com.mysql.cj.jdbc.ConnectionImpl@5445f5ba] will not be managed by Spring
==>  Preparing: INSERT INTO t_user ( username, age, email ) VALUES ( ?, ?, ? )
==> Parameters: Oneby(String), 21(Integer), Oneby@baomidou.com(String)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3c017078]
Number of affected rows: 1
User(id=6, name=Oneby, age=21, email=Oneby@baomidou.com)

@TableId annotation

/**
 * Table primary key ID
 *
 * @author hubin
 * @since 2016-01-23
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.ANNOTATION_TYPE})
public @interface TableId {

    /**
     * Field name (this value can be null)
     */
    String value() default "";

    /**
     * Primary key type
     * {@link IdType}
     */
    IdType type() default IdType.NONE;
}

IdType primary key type

@Getter
public enum IdType {
    /**
     * Self increment of database ID
     * <p>For this type, please ensure that the database is set with ID self increment, otherwise it is invalid</p>
     */
    AUTO(0),
    /**
     * This type is not set with primary key (in the annotation, it is equal to follow the global, and the global value is equal to INPUT)
     */
    NONE(1),
    /**
     * User input ID
     * <p>This type can be filled by registering the auto fill plug-in</p>
     */
    INPUT(2),

    /* The following three types are automatically filled only when the inserted object ID is empty. */
    /**
     * Assign ID (the primary key type is number or string),
     * Default implementation class {@ link com. Baomidou. Mybatisplus. Core. Increment. Defaultidentifier generator} (snowflake algorithm)
     *
     * @since 3.3.0
     */
    ASSIGN_ID(3),
    /**
     * Assign UUID (the primary key type is string)
     * Default implementation class {@ link com. Baomidou. Mybatisplus. Core. Increment. Defaultidentifiergenerator} (UUID. Replace ("-", ""))
     */
    ASSIGN_UUID(4),
    /**
     * @deprecated 3.3.0 please use {@link #ASSIGN_ID}
     */
    @Deprecated
    ID_WORKER(3),
    /**
     * @deprecated 3.3.0 please use {@link #ASSIGN_ID}
     */
    @Deprecated
    ID_WORKER_STR(3),
    /**
     * @deprecated 3.3.0 please use {@link #ASSIGN_UUID}
     */
    @Deprecated
    UUID(4);

    private final int key;

    IdType(int key) {
        this.key = key;
    }
}