Mybatis-Plus
1.快速入门地址：安装 | MyBatis-Plus (baomidou.com)
2.创建数据库mybatis-plus
CREATE TABLE user
(
id BIGINT(20) NOT NULL COMMENT "主键ID",
name VARCHAR(30) NULL DEFAULT NULL COMMENT "姓名",
age INT(11) NULL DEFAULT NULL COMMENT "年龄",
email VARCHAR(50) NULL DEFAULT NULL COMMENT "邮箱",
PRIMARY KEY (id)
);
INSERT INTO user (id, name, age, email) VALUES (1, "Jone", 18, "test1@baomidou.com"), (2, "Jack", 20, "test2@baomidou.com"), (3, "Tom", 28, "test3@baomidou.com"), (4, "Sandy", 21, "test4@baomidou.com"), (5, "Billie", 24, "test5@baomidou.com");
以上数据的运行均在cmd命令运行
3.创建springboot项目，配置yml文件
spring:
datasource:
username: root
password: 123456
url: jdbc:mysql://localhost:3306/mybatis_plus?userSSL=false&Unicode=true&CharacterEncoding=utf-8&serverTimezone=GMT%2B8
driver-class-name: com.mysql.cj.jdbc.Driver
4.导入依赖
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.5.2</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.sxau</groupId>
<artifactId>mybatis_plus</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>mybatis_plus</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- mysql-connector-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<!-- mybatis-plus-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.4.0</version>
</dependency>
<!-- lombok-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
5.创建pojo包，新建User实体类
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
//主键自增配合 数据库主键自增使用
@TableId(type = IdType.AUTO)
private Long id;
private String name;
private int age;
private String email;
}
6.创建mapper包，新建UserMapper实体类
package com.sxau.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.sxau.pojo.User;
import org.springframework.stereotype.Repository;
@Repository
public interface Usermapper extends BaseMapper<User> {
//所有CRUD操作已经完成
//不需要一大堆的。xml配置文件
}
7.在主启动类中加上Mapperscan注解扫描mapper映射文件
@MapperScan("com.sxau.mapper")
8.查询所有数据测试类
package com.sxau.mybatis_plus;
import com.baomidou.mybatisplus.annotation.IdType;
import com.sxau.mapper.Usermapper;
import com.sxau.pojo.User;
import org.junit.jupiter.api.Test;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import java.util.List;
@MapperScan("com.sxau.mapper")
@SpringBootTest
class MybatisPlusApplicationTests {
@Autowired
Usermapper usermapper;
@Test
void contextLoads() {
List<User> users = usermapper.selectList(null);
users.forEach(System.out::println);
}
}
遇到这种情况，直接解决
9.开启mybatis-plus日志配置文件
#mybatis-plus日志配置文件
mybatis-plus:
configuration:
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
10.主键生成策略
默认 ID_WORKER 全局唯一id 对应数据库中的主键(uuid.自增id.雪花算法.redis.zookeeper)
分布式系统唯一id生成:https://www.cnblogs.com/haoxinyue/p/5208136.html
雪花算法
