1. Use mybatis-plus in springboot

1. Add MyBatis Plus dependency in Maven.

For Maven users, pom.xmladd the following dependencies to the file:

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>{你的版本}</version>
</dependency>

2. Configure the data source

Configure data source information in ( application.propertiesor application.yml) file:

spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false
spring.datasource.username=root
spring.datasource.password=123456

3. Create entity classes

Create a Java class that represents a row of records in a database table, and use @TableNameannotations to specify the table name associated with it. For example:

@Data
@TableName("user")
public class User {
    @TableId(type = IdType.AUTO)
    private Long id;
    private String name;
    private Integer age;
}

Lombok is used to simplify the code, and the annotation provided by MyBatis Plus is used @TableIdto identify the primary key, and the primary key generation strategy is specified as auto-increment.

4. Create Mapper interface

Create a Java interface, inherit from it BaseMapper, and specify the generic type as your entity class. For example:

public interface UserMapper extends BaseMapper<User> {
}

The base class provided by MyBatis Plus is used BaseMapper, which provides many common CRUD operation methods.

5. Perform query operations

Inject the instance in your Java code UserMapper, and use it for queries. For example:

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;

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

The method provided by MyBatis Plus is used selectListto query all user records.

2. Common CRUD encapsulation methods for BaseMappe in Mybatis-plus

insert method

// 插入一条记录
int insert(T entity);

// 批量插入多条记录
int insertBatch(List<T> entityList);

// 插入一条记录并返回主键值
int insertAndGetId(T entity);

update method

// 根据主键更新记录
int updateById(T entity);

// 根据主键批量更新记录
int updateBatchById(List<T> entityList);

// 根据条件更新记录
int update(@Param("entity") T entity, @Param("updateWrapper") UpdateWrapper<T> updateWrapper);

delete method

// 根据主键删除记录
int deleteById(Serializable id);

// 根据主键批量删除记录
int deleteBatchIds(Collection<? extends Serializable> idList);

// 根据条件删除记录
int delete(@Param("queryWrapper") QueryWrapper<T> queryWrapper);

query method

// 根据主键查询记录
T selectById(Serializable id);

// 根据主键列表查询记录
List<T> selectBatchIds(Collection<? extends Serializable> idList);

// 查询所有记录
List<T> selectAll();

// 根据条件查询记录数量
int selectCount(@Param("queryWrapper") QueryWrapper<T> queryWrapper);

// 根据条件查询单条记录
T selectOne(@Param("queryWrapper") QueryWrapper<T> queryWrapper);

// 根据条件查询多条记录
List<T> selectList(@Param("queryWrapper") QueryWrapper<T> queryWrapper);

It should be noted that these methods are generic methods, where the type parameter T represents the entity class. If annotations are used in your entity class @TableIdto identify the primary key, MyBatis Plus will automatically set the primary key value according to the primary key generation strategy when calling the above CRUD operation method.

In addition to the basic CRUD operation methods, BaseMapperit also provides some other useful methods, such as batch insert or update records, pagination query, etc., which will be discussed later

Use mybatis-plus in springboot