[学习记录-MybatisPlus]MybatisPlus入门

MybatisPlus入门

MyBatisPlus是mybatis的增强版，官网地址https://baomidou.com/
如果学习中遇到问题可以看这篇文章
MyBatisPlus遇到的问题

1 准备好数据库文件

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user`  (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT ' ',
  `name` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin NULL DEFAULT NULL,
  `password` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE,
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES (1, 'admin', '123');
INSERT INTO `user` VALUES (2, '15717591201', '123');
INSERT INTO `user` VALUES (3, '123', '123');
INSERT INTO `user` VALUES (13, 'qwer', '123');
INSERT INTO `user` VALUES (14, '1223', '123');
INSERT INTO `user` VALUES (15, '12212', '123');
INSERT INTO `user` VALUES (16, '1232', '112');

2 创建一个springboot工程，然后添加依赖

<dependency>
    <groupId>com.baomidougroupId>
    <artifactId>mybatis-plus-boot-starterartifactId>
    <version>3.3.2version>
dependency>

<dependency>
 	<groupId>mysqlgroupId>
 	<artifactId>mysql-connector-javaartifactId>
dependency>

<dependency>
 	<groupId>org.projectlombokgroupId>
 	<artifactId>lombokartifactId>
dependency>

3 安装lombok插件

使用lombok依赖，IDEA必须要安装lombok插件

方法File -> Settings ->Plugins 搜索lombok，然后点击Install安装

4 配置文件

找到src/main/resources的application.properties

• 配置mysql数据库连接

  配置时按照自己对应的版本进行配置

  mysql5 SpringBoot2.1以下

  #mysql数据库连接
  spring.datasource.driver-class-name=com.mysql.jdbc.Driver
  spring.datasource.url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8
  spring.datasource.username=root
  spring.datasource.password=root
  

• mysql8以上（spring boot 2.1）

  $注意$：driver和url的变化

  spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
  spring.datasource.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=GMT%2B8
  spring.datasource.username=root
  spring.datasource.password=root
  

  1、这里的 url 使用了 ?serverTimezone=GMT%2B8 后缀，因为Spring Boot 2.1 集成了 8.0版本的jdbc驱动，这个版本的 jdbc 驱动需要添加这个后缀，否则运行测试用例报告如下错误：

  java.sql.SQLException: The server time zone value ‘Öйú±ê׼ʱ¼ä’ is unrecognized or represents more

  2、这里的 driver-class-name 使用了 com.mysql.cj.jdbc.Driver ，在 jdbc 8 中 建议使用这个驱动，之前的 com.mysql.jdbc.Driver 已经被废弃，否则运行测试用例的时候会有 WARN 信息

5 测试代码编写

5.1 实体类

package com.w.mpdemo.entity;

import lombok.Data;

@Data
public class User {
    private Integer id;
    private String name;
    private String password;

}

@Date就是lombk中的注解，可以自动生成get、set方法

5.2 创建Mapper接口

继承于BaseMapper类，里面有各种方法

package com.w.mpdemo.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.w.mpdemo.entity.User;
@Repository
public interface UserMapper extends BaseMapper<User> {
}

5.3 添加mapper接口的扫描

在SpringBoot启动类中添加mapper扫描注解

package com.w.mpdemo;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.w.mpdemo.mapper")
public class MpdemoApplication {

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

}

6 测试

在src\test\java\com\w\mpdemo\MpdemoApplicationTests.java

中开始测试

package com.w.mpdemo;

import com.w.mpdemo.entity.User;
import com.w.mpdemo.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
public class MpdemoApplicationTests {
    @Autowired
    private UserMapper userMapper;

    @Test
    public void findALl() {
        List<User> userList = userMapper.selectList(null);
        System.out.println(userList);
    }

}

查询结果：

2020-08-15 13:57:36.488  INFO 13244 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2020-08-15 13:57:36.676  INFO 13244 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
[User(id=1, name=admin, password=123), User(id=2, name=15717591201, password=123), User(id=3, name=123, password=123), User(id=13, name=qwer, password=123), User(id=14, name=1223, password=123), User(id=15, name=12212, password=123), User(id=16, name=1232, password=112)]

补充

1.表名问题

如果数据库的表名和实体类名不一样可以使用@TableName注解

@TableName("user")

2.MyBatisPlus日志

在配置文件中添加

#mybatis日志
mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

使用之后控制台会打印出如下日志

......
JDBC Connection [HikariProxyConnection@1023344953 wrapping com.mysql.cj.jdbc.ConnectionImpl@7c29adc8] will not be managed by Spring
==>  Preparing: SELECT id,name,password FROM user 
==> Parameters: 
<==    Columns: id, name, password
<==        Row: 1, admin, 123
<==        Row: 2, 15717591201, 123
<==        Row: 3, 123, 123
<==        Row: 13, qwer, 123
<==        Row: 14, 1223, 123
<==        Row: 15, 12212, 123
<==        Row: 16, 1232, 112
<==      Total: 7
......

3.lombok插件不生效

重启IDEA

如果还没有用找到File -> Settings -> Build,Execution,Deployment -> Compiler -> Annotation Processors

把Enable annotation processing勾选上

再重启IDEA