MybatisPlus-14.扩展机制-DB静态应用-练习

一.练习

• 根据id批量查询用户，并查询出用户对应的所有地址

  @GetMapping("/{id}")
  @ApiOperation("根据id查询用户及其收货地址")
  public UserVO getUserById(@ApiParam("用户id") @PathVariable("id") Long id) {
  return userService.getByIdWithAddress(id);
  }

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 {
void updateBalance(Long id, Integer money);
List queryList(String name, Integer status, Integer minBalance, Integer maxBalance);
UserVO getByIdWithAddress(Long id);
List getUsersAndAddresses(List 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 implements IUserService {
@Override
public 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()  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
*/
@Override
public 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 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
*/
@Override
public List getUsersAndAddresses(List ids) {
// 1.根据ids批量查询用户信息
List users = listByIds(ids);
if (CollUtil.isEmpty(users)) {
throw new RuntimeException("用户不存在");
}
// 2.设置userVOS列表
List 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 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 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 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> 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：