• mybatis-plus依赖导入

<dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.2</version>
        </dependency>

倡议应用3.3.0后的版本。
导入mybatis-plus就不必导入mybatis了，抵触！

• 连贯数据库

spring.datasource.username=root
spring.datasource.password=19981204
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl//配置默认日志

• 设置主键自增

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    @TableId(type = IdType.AUTO)
    private Long id;
    private String name;
    private Integer age;
    private String email;
   
}

应用注解 @TableId(type=IdType.AUTO),同时将数据库中的id字段设置为自增即可。

• 编写配置类来进行主动注入工夫（继承元数据类并重写它的insertFill和updateFill办法）
  应用注解@TableFiled(fill=FieldFill.INSERT)

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    @TableId(type = IdType.AUTO)
    private Long id;
    private String name;
    private Integer age;
    private String email;
    @TableField(fill = FieldFill.INSERT)
    private LocalDateTime createTime;
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private LocalDateTime updateTime;
}

package com.ls.handler;

        import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
        import org.apache.ibatis.reflection.MetaObject;
        import org.springframework.stereotype.Component;

        import java.time.LocalDateTime;

/**
 * @author dell
 */
@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
    @Override
    public void insertFill(MetaObject metaObject) {
        this.strictInsertFill(metaObject,"createTime", LocalDateTime.class,LocalDateTime.now());
        this.strictUpdateFill(metaObject,"updateTime",LocalDateTime.class,LocalDateTime.now());

    }

    @Override
    public void updateFill(MetaObject metaObject) {
        this.strictUpdateFill(metaObject,"updateTime",LocalDateTime.class,LocalDateTime.now());
    }
}