MyBatis-Plus ( MP for short ) is an enhancement tool for MyBatis . It only enhances and does not change on the basis of MyBatis . It is born to simplify development and improve efficiency .

vision

Our vision is to become the best partner of MyBatis , just like 1P , 2P in Contra, with friends, the efficiency is doubled.

2. Features

Non-invasive : only make enhancements without changing, introducing it will not affect existing projects, smooth as silk

Low loss : Basic CURD is automatically injected at startup, performance is basically lossless, and direct object-oriented operation

Powerful CRUD operations : built-in general mapper and general service, most CRUD operations on a single table can be realized with only a small amount of configuration, and more powerful conditional constructors to meet various usage needs
Support Lambda form invocation : Through Lambda expressions, you can easily write various query conditions, and you don't need to worry about writing wrong fields.
Supports automatic primary key generation : supports up to 4 primary key strategies (including a distributed unique ID generator - Sequence), which can be freely configured to perfectly solve the primary key problem
Support ActiveRecord mode : Support ActiveRecord form call, entity class can perform powerful CRUD operations only by inheriting Model class
Support custom global general operations : support global general method injection ( Write once, use anywhere )
Built-in code generator : Use code or Maven plugin to quickly generate Mapper , Model , Service , Controller layer code, support template engine, and more custom configurations waiting for you to use
Built-in paging plug-in : Based on MyBatis physical paging, developers do not need to care about specific operations. After configuring the plug-in, writing paging is equivalent to ordinary List query
The paging plugin supports multiple databases : MySQL, MariaDB, Oracle, DB2, H2, HSQL, SQLite, Postgre, SQLServer and other databases
Built-in performance analysis plug-in : It can output SQL statements and their execution time. It is recommended to enable this function during development and testing, which can quickly identify slow queries
Built-in global interception plug-in : provides intelligent analysis and blocking of delete and update operations on the entire table, and can also customize interception rules to prevent misoperation

3. Support database

Any database that can use MyBatis for CRUD and supports standard SQL, the specific support is as follows, if you do not see the paging part of the tutorial PR your support in the list below.

MySQL，Oracle，DB2，H2，HSQL，SQLite，PostgreSQL，SQLServer，Phoenix，Gauss ，ClickHouse，Sybase，OceanBase，Firebird，Cubrid，Goldilocks，csiidb
Dameng Database, Xugu Database, NPC Jincang Database, Nanda General (Huaku) Database, Nanda General Database, Shentong Database, Hangao Database

4. Frame structure

5. Code and document address

Official address: Redirect
Code release address:
- Github: https://github.com/baomidou/mybatis-plus
- Gitee: mybatis-plus: mybatis enhancement toolkit to simplify CRUD operations. Documentation http://baomidou.com Low-code component library http://aizuda.com
Document release address: Introduction | MyBatis-Plus

6. Introductory case

6.1. Development environment

IDE ： idea 2021.2.1

JDK：JDK8

Build tool: maven 3.6.1

MySQL version: MySQL 5.7

Spring Boot：2.6.6

MyBatis-Plus：3.5.1

6.2, create database and table

6.2.1. Create a table

USE `mybatis_plus`; 
CREATE TABLE `user` ( 
	`id` BIGINT(20) NOT NULL COMMENT '主键ID', 
	`name` VARCHAR(30) DEFAULT NULL COMMENT '姓名', 
	`age` INT(11) DEFAULT NULL COMMENT '年龄', 
	`email` VARCHAR(50) DEFAULT NULL COMMENT '邮箱', 
	PRIMARY KEY (`id`) 
) ENGINE=INNODB DEFAULT CHARSET=utf8;

6.2.2. Add data

INSERT INTO USER (id, NAME, age, email) VALUES 
(1, 'Jone', 18, '[email protected]'), 
(2, 'Jack', 20, '[email protected]'), 
(3, 'Tom', 28, '[email protected]'), 
(4, 'Sandy', 21, '[email protected]'),
(5, 'Billie', 24, '[email protected]');

6.3. Create a SpringBoot project

6.3.1. Initialization project

Use Spring Initializer to quickly initialize SpringBoot projects without checking components

6.3.2. Introducing dependencies

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.1</version>
        </dependency>
        
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

6.4, write code

6.4.1. Configure application.yml

Note:

1. Driver class driver-class-name

Spring boot 2.0 (built-in jdbc5 driver), the driver class uses: driver-class-name: com.mysql.jdbc.Driver
Spring boot 2.1 and above (built-in jdbc8 driver), driver class use: driver-class-name: com.mysql.cj.jdbc.Driver

Otherwise, there will be WARN information when running the test case

2 , the connection address url

The URL recommendations for MySQL 5.7 are as follows :

        jdbc:mysql://localhost:3306/mybatis_plus?characterEncoding=utf-8&useSSL=false

The url of MySQL 8.0 is recommended as follows (set the time zone):

        jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8&characterEncoding=utf-8&useSSL=false

Otherwise running the test case reports the following error:

        java.sql.SQLException: The server time zone value 'ÖÐ¹ú±ê×¼Ê±¼ä' is unrecognized or represents more

spring:
  # 配置数据源信息
  datasource:
    # 配置数据源类型
    type: com.zaxxer.hikari.HikariDataSource
    # 配置连接数据库的各个信息
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mybatis_plus?characterEncoding=utf-8&useSSL=false
    username: root
    password: zyj123

6.4.2. Add entity

@Data
@AllArgsConstructor
public class User {
    private long id;
    private String name;
    private Integer age;
    private String email;
}

6.4.3. Startup class (main program class)

@SpringBootApplication
@MapperScan("com.zyj.mapper") //扫描mapper接口所在的包
public class MyBatisPlusProjectApplication {

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

}

6.4.4. Add mapper interface

@Mapper
//@Repository  //将该类或接口标识为持久层组件
public interface UserMapper extends BaseMapper<User> {
}

6.4.5. Test

Note: IDEA reports an error at userMapper because the injected object cannot be found, because the class is dynamically created, but the program can be executed correctly. In order to avoid errors, you can add @Repository or @Mapper annotations to the mapper interface

@SpringBootTest
public class MyBatisPlusTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testSelectList(){
        // 通过条件构造器查询一个List集合，若没有条件，可以设置参数为null
        List<User> users = userMapper.selectList(null);
        users.forEach(System.out::println);
    }

}

Output result:

User(id=1, name=Jone, age=18, [email protected])
User(id=2, name=Jack, age=20, [email protected])
User(id=3, name=Tom, age=28, [email protected])
User(id=4, name=Sandy, age=21, [email protected])
User(id=5, name=Billie, age=24, [email protected])

6.4.6. Add log function

Configure open in application.yml

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl  #添加日志功能，StdOutImpl是mybatis-plus自带的

The log output is as follows, you can view the SQL statement:

==>  Preparing: SELECT id,name,age,email FROM user
==> Parameters: 
<==    Columns: id, name, age, email
<==        Row: 1, Jone, 18, [email protected]
<==        Row: 2, Jack, 20, [email protected]
<==        Row: 3, Tom, 28, [email protected]
<==        Row: 4, Sandy, 21, [email protected]
<==        Row: 5, Billie, 24, [email protected]
<==      Total: 5

MyBatisPlus - 1. Introduction and introductory case

1 Introduction