一.练习
Service
package com.itheima.mp.service;import com.baomidou.mybatisplus.extension.service.IService;
import com.itheima.mp.domain.po.User;
import com.itheima.mp.domain.vo.AddressVO;
import com.itheima.mp.domain.vo.UserVO;import java.util.List;public interface IUserService extends IService<User> {void updateBalance(Long id, Integer money);List<User> queryList(String name, Integer status, Integer minBalance, Integer maxBalance);UserVO getByIdWithAddress(Long id);List<UserVO> getUsersAndAddresses(List<Long> ids);}
Impl
package com.itheima.mp.service.Impl;import cn.hutool.core.bean.BeanUtil;
import cn.hutool.core.collection.CollUtil;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.baomidou.mybatisplus.extension.toolkit.Db;
import com.itheima.mp.domain.po.Address;
import com.itheima.mp.domain.po.User;
import com.itheima.mp.domain.vo.AddressVO;
import com.itheima.mp.domain.vo.UserVO;
import com.itheima.mp.mapper.UserMapper;
import com.itheima.mp.service.IUserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;// 要先继承，再实现接口
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements IUserService {@Overridepublic void updateBalance(Long id, Integer money) {// 1.根据id查询用户User user = getById(id);// 2.查询用户状态是否正常if (user.getStatus() != 1) {throw new RuntimeException("用户状态异常");}// 3.查询用户余额是否充足if (user.getBalance() < money) {throw new RuntimeException("用户余额不足");}// 4.更新用户余额，如果扣减后余额为0，则将用户status修改为冻结状态
// baseMapper.deductionBalanceById(id, money);int remainBalance = user.getBalance() - money;lambdaUpdate().set(User::getBalance, remainBalance).set(remainBalance == 0, User::getStatus, 2).eq(User::getId, id).eq(User::getBalance,user.getBalance()) // 避免并发问题，如果有多个线程同时扣减，可能会导致多扣。如果扣减后余额与获取的余额不一致，证明上一个线程已经扣减了余额，则不更新用户，返回结果为0.update(); // 必须加update()，要不不会执行。上面是构建，构建完之后，需要执行}@Overridepublic List<User> queryList(String name, Integer status, Integer minBalance, Integer maxBalance) {return lambdaQuery().like(name!= null,User::getUsername, name).eq(status != null,User::getStatus, status).gt(minBalance != null,User::getBalance, minBalance).lt(maxBalance != null,User::getBalance, maxBalance).list();}/*** 根据id查询用户及其收货地址* @param id* @return*/@Overridepublic UserVO getByIdWithAddress(Long id) {// 1.首先根据id查询出用户信息User user = getById(id);if (user == null || user.getStatus() == 2) {throw new RuntimeException("用户状态异常");}// 2.将User对象转换成UserVO对象UserVO userVO = BeanUtil.copyProperties(user, UserVO.class);// 3.接着根据id查询出用户的收货地址List<Address> addresses = Db.lambdaQuery(Address.class).eq(Address::getUserId, id).list();if (CollUtil.isNotEmpty( addresses)) {// 4.将收货地址列表转换成AddressVO对象// 5.将AddressVO对象设置到UserVO对象中userVO.setAddresses(BeanUtil.copyToList(addresses, AddressVO.class));}return userVO;}/*** 根据id批量查询用户及其收货地址* @param ids* @return*/@Overridepublic List<UserVO> getUsersAndAddresses(List<Long> ids) {// 1.根据ids批量查询用户信息List<User> users = listByIds(ids);if (CollUtil.isEmpty(users)) {throw new RuntimeException("用户不存在");}// 2.设置userVOS列表List<UserVO> userVOS = new ArrayList<>(users.size());// 3.获取当前用户的id(因为传过来的ids中的id可能没有对应的用户)List<Long> userIds = users.stream().map(User::getId).collect(Collectors.toList());// 4.根据用户id批量查询用户收货地址List<Address> addresses = Db.lambdaQuery(Address.class).in(Address::getUserId, userIds).list();// 5.将用户的收货地址转为VO对象List<AddressVO> addressVOS = BeanUtil.copyToList(addresses, AddressVO.class);// 6.如果addressVOS不为空，那么将addressVOS按照用户id进行分组Map<Long, List<AddressVO>> addressVOMap = new HashMap<>(0);if (CollUtil.isNotEmpty(addressVOS)) {addressVOMap = addressVOS.stream().collect(Collectors.groupingBy(AddressVO::getUserId));}// 7.按照用户id进行分组for (User user : users) {UserVO userVO = BeanUtil.copyProperties(user, UserVO.class);userVO.setAddresses(addressVOMap.get(user.getId()));userVOS.add(userVO);}return userVOS;}}
查询成功：
