Mybatis-Plus的一些优雅用法

Mybatis-Plus的一些优雅用法

这里写自定义目录标题

​​1、CRUD的示列:​​​​2、自动填充功能​​​​3、备注说明​​

1、CRUD的示列:

package com.chaim.mybatis.service.impl;import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;import com.baomidou.mybatisplus.core.toolkit.Wrappers;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;import com.baomidou.mybatisplus.extension.toolkit.ChainWrappers;import com.chaim.mybatis.converter.SysUserConverter;import com.chaim.mybatis.dto.SysUserDTO;import com.chaim.mybatis.entitys.SysUser;import com.chaim.mybatis.mappers.SysUserMapper;import com.chaim.mybatis.service.SysUserService;import lombok.RequiredArgsConstructor;import org.apache.commons.lang3.StringUtils;import org.springframework.stereotype.Service;/** * @author chaim * @description: 用户服务接口实现 * @date 2022/7/2 23:05 */@Service@RequiredArgsConstructorpublic class SysUserServiceImpl implements SysUserService { private final SysUserMapper sysUserMapper; private final SysUserConverter sysUserConverter; /** * ------------------ select ------------------------ * BaseMapper: 偏向一些简单的查询操作, 通常配合LambdaQueryWrapper一起使用 (推荐) * LambdaQueryWrapper: 更灵活, 适用一些判断操作, 复杂的逻辑 * ChainWrappers: 适用于一些简单的查询操作, 可以直接链式调用数据执行操作的方法 */ @Override public Object selectById(Long id) { return sysUserMapper.selectById(id); } @Override public Object selectOne(Long id) { return ChainWrappers.lambdaQueryChain(sysUserMapper) .eq(SysUser::getId, id) .select(SysUser::getUsername, SysUser::getPhone) .last("limit 1") .one(); } @Override public Object selectPage(Integer page, Integer size) { return ChainWrappers.lambdaQueryChain(sysUserMapper) .select(SysUser::getUsername, SysUser::getPhone) .page(new Page<>(page, size)); } @Override public Object selectList(String phone) { LambdaQueryWrapper queryWrapper = new LambdaQueryWrapper<>(); if (StringUtils.isNotEmpty(phone)) { queryWrapper.like(SysUser::getPhone, phone); } queryWrapper.select(SysUser::getUsername, SysUser::getPhone); return sysUserMapper.selectList(queryWrapper); } /** * ------------------ insert ------------------------ */ @Override public Object insert(SysUserDTO.InsertSysUserDTO insertSysUserDTO) { SysUser sysUser = sysUserConverter.insertUserDTOToSysUser(insertSysUserDTO); sysUser.setPassword("123456"); sysUser.setSex(1); sysUser.setState(0); sysUser.setSalt(1234); return sysUserMapper.insert(sysUser); } /** * ------------------ update ------------------------ * BaseMapper: 适用于更新多列, 以及一些复杂的逻辑 * ChainWrappers: 适用于更新少量内容, 列如状态变更 */ @Override public Object updateById(SysUserDTO.UpdateSysUserDTO updateSysUserDTO) { SysUser sysUser = sysUserConverter.updateUserDTOToSysUser(updateSysUserDTO); return sysUserMapper.updateById(sysUser); } @Override public Object update(String phone) { return ChainWrappers.lambdaUpdateChain(sysUserMapper) .set(SysUser::getPassword, "9878654") .eq(SysUser::getPhone, phone) .update(); } /** * ------------------ delete ------------------------ * BaseMapper: 适用于ID删除 * Wrappers: 适用于一些复杂的逻辑删除, 指定条件删除等 */ @Override public Object deleteById(Long id) { return sysUserMapper.deleteById(id); } @Override public Object delete(String phone) { return sysUserMapper.delete(Wrappers.lambdaQuery().eq(SysUser::getPhone, phone)); }}

2、自动填充功能

package com.chaim.mybatis.config;import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;import lombok.extern.slf4j.Slf4j;import org.apache.ibatis.reflection.MetaObject;import org.springframework.context.annotation.Configuration;import org.springframework.util.ClassUtils;import java.time.LocalDateTime;/** * @author Chaim * @date 2022/7/2 18:04 * @Description */@Configuration@Slf4jpublic class MyMetaObjectHandler implements MetaObjectHandler { /** * 模拟用户ID */ private static final Long userId = 1543166049341100034L; @Override public void insertFill(MetaObject metaObject) { log.debug("mybatis plus start insert fill ...."); LocalDateTime now = LocalDateTime.now(); fillValIfNullByName("createTime", now, metaObject, false); fillValIfNullByName("updateTime", now, metaObject, false); fillValIfNullByName("createBy", userId, metaObject, false); fillValIfNullByName("updateBy", userId, metaObject, false); } @Override public void updateFill(MetaObject metaObject) { log.debug("mybatis plus start update fill ...."); fillValIfNullByName("updateTime", LocalDateTime.now(), metaObject, true); fillValIfNullByName("updateBy", userId, metaObject, true); } /** * 填充值，先判断是否有手动设置，优先手动设置的值，例如：job必须手动设置 * * @param fieldName 属性名 * @param fieldVal 属性值 * @param metaObject MetaObject * @param isCover 是否覆盖原有值,避免更新操作手动入参 */ private static void fillValIfNullByName(String fieldName, Object fieldVal, MetaObject metaObject, boolean isCover) { // 1. 没有 get 方法 if (!metaObject.hasSetter(fieldName)) { return; } // 2. 如果用户有手动设置的值 Object userSetValue = metaObject.getValue(fieldName); if (userSetValue != null && !isCover) { return; } // 3. field 类型相同时设置 Class getterType = metaObject.getGetterType(fieldName); if (ClassUtils.isAssignableValue(getterType, fieldVal)) { metaObject.setValue(fieldName, fieldVal); } }}

3、备注说明

com.baomidou.mybatisplus.core.mapper.BaseMapper com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper com.baomidou.mybatisplus.extension.toolkit.ChainWrappers com.baomidou.mybatisplus.core.toolkit.Wrappers

我在做一些比如根据ID查询删除, 添加, 等会直接使用BaseMapper 当存在一些复杂的逻辑, 比如需要判断条件是否带入SQL时, 会使用LambdaQueryWrapper + BaseMapper 当更新部分数据, 且不复杂会使用ChainWrappers 当使用BaseMapper的方法, 需要传入一些简单的条件, 会使用Wrappers

我个人不推荐使用这种方法: sysUserMapper.update(null, Wrappers.lambdaUpdate().set(SysUser::getPassword, “9878654”).eq(SysUser::getPhone, phone));

​​示列代码:​​ https://gitee.com/xmaxm/test-code/tree/master/chaim-mybatis-plus

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