springboot基础——公共字段填充

1.背景

在项目中增加和更改数据时，会有一些通用的字段入ctime、utime、更新人等，这些字段的写入和更新逻辑几乎完全相同，在各service中重复写会造成代码冗余

employee.setCreateTime(LocalDateTime.now());
employee.setUpdateTime(LocalDateTime.now());

//获得当前登录用户的id
Long empId = (Long) request.getSession().getAttribute("employee");

employee.setCreateUser(empId);
employee.setUpdateUser(empId);

employeeService.save(employee);

为了缩减写数据时的这种重复代码，我们可以使用mybatisPlus提供的自动填充功能。

2.实现方法

a.使用mybatisPlus，引入jar包

<dependency>
      <groupId>com.baomidougroupId>
      <artifactId>mybatis-plus-boot-starterartifactId>
      <version>3.4.2version>
dependency>

b.在需要自动填充的entity类中添加@TableField注解

package com.itheima.reggie.entity;

import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.annotation.TableField;
import lombok.Data;
import java.io.Serializable;
import java.time.LocalDateTime;

/**
 * 员工实体
 */
@Data
public class Employee implements Serializable {

    private static final long serialVersionUID = 1L;

    private Long id;

    private String username;

    private String name;

    private String password;

    private String phone;

    private String sex;

    private String idNumber;

    private Integer status;

    //写入时自动填充
    @TableField(fill=FieldFill.INSERT)
    private LocalDateTime createTime;
    
    //写入或更新时自动填充 
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private LocalDateTime updateTime;

    @TableField(fill = FieldFill.INSERT)
    private Long createUser;

    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Long updateUser;

}

c.在MetaObjectHandler接口实现类中定义填充的值

package com.itheima.reggie.common;

import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.stereotype.Component;
import java.time.LocalDateTime;

/**
 * 自定义元数据对象处理器
 */
@Component
@Slf4j
public class MyMetaObjecthandler implements MetaObjectHandler {
    /**
     * 插入操作，自动填充
     * @param metaObject
     */
    @Override
    public void insertFill(MetaObject metaObject) {
        log.info("公共字段自动填充[insert]...");
        log.info(metaObject.toString());
        metaObject.setValue("createTime", LocalDateTime.now());
        metaObject.setValue("updateTime",LocalDateTime.now());
        metaObject.setValue("createUser", Long.valueOf(1));
        metaObject.setValue("updateUser",Long.valueOf(1));
//        metaObject.setValue("createUser", BaseContext.getCurrentId());
//        metaObject.setValue("updateUser",BaseContext.getCurrentId());
    }

    /**
     * 更新操作，自动填充
     * @param metaObject
     */
    @Override
    public void updateFill(MetaObject metaObject) {
        log.info("公共字段自动填充[update]...");
        log.info(metaObject.toString());

        long id = Thread.currentThread().getId();
        log.info("线程id为：{}",id);

        metaObject.setValue("updateTime",LocalDateTime.now());
        metaObject.setValue("updateUser","nome");
//        metaObject.setValue("updateUser",BaseContext.getCurrentId());
    }
}

3.进阶——使用ThreadLocal填充当前用户登录的用户id等

git地址
https://github.com/nome1024/reggie_take_out/tree/feature/threadlocaltest