你应该知道的这些Mybatis-Plus使用技巧(小结)

SELECT * FROM user_info WHERE 1=1 AND age = 20

QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("age", 20);
List<UserInfo> list = userInfoMapper.selectList(queryWrapper );

QueryWrapper<UserInfo> queryWrapper = new QueryWrapper<>();
queryWrapper.lambda().eq(UserInfo::getAge, 20);
List<UserInfo> list = userInfoMapper.selectList(queryWrapper );

LambdaQueryWrapper<UserInfo> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.eq(UserInfo::getAge, 20);
List<UserInfo> list = userInfoMapper.selectList(queryWrapper );

// 条件查询
LambdaQueryWrapper<UserInfo> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.eq(UserInfo::getAge, 20);
// 分页对象
Page<UserInfo> queryPage = new Page<>(page, limit);
// 分页查询
IPage<UserInfo> iPage = userInfoMapper.selectPage(queryPage , queryWrapper);
// 数据总数
Long total = iPage.getTotal();
// 用户数据
List<UserInfo> list = iPage.getRecords();

SELECT
 a.*,
 b.`name` AS sex_text 
FROM
 user_info a
 LEFT JOIN user_sex b ON ( a.sex = b.id ) 
WHERE
 1 = 1 
 AND a.age > 20

import com.zyxx.entity.UserInfo;
import lombok.Data;

@Data
public class UserInfoVO extends UserInfo {

  // 性别
  private String sexText;
}

IPage<UserInfoVO> list(Page<UserInfoVO> page, @Param(Constants.WRAPPER) Wrapper<UserInfoVO> queryWrapper);

<select id="list" resultType="com.zyxx.vo.UserInfoVO">
  SELECT
 a.*,
 b.`name` AS sex_text 
 FROM
 user_info a
 LEFT JOIN user_sex b ON ( a.sex = b.id ) 
  ${ew.customSqlSegment}
</select>

// 条件查询
LambdaQueryWrapper<UserInfoVO> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.eq(UserInfo::getAge, 20);
// 分页对象
Page<UserInfoVO> queryPage = new Page<>(page, limit);
// 分页查询
IPage<UserInfoVO> iPage = userInfoMapper.list(queryPage , queryWrapper);
// 数据总数
Long total = iPage.getTotal();
// 用户数据
List<UserInfoVO> list = iPage.getRecords();

SELECT
 a.* 
FROM
 user_info a 
WHERE
 1 = 1 
 AND a.id <> 1 
 AND ( a.`name` = 'jack' OR a.phone = '13888888888' )

LambdaQueryWrapper<UserInfo> queryWrapper = new LambdaQueryWrapper<>();
// AND a.id <> 1 
queryWrapper.ne(UserInfo::getId, "1");
// AND ( a.`name` = 'jack' OR a.phone = '13888888888' )
queryWrapper.and(i -> i.eq(UserInfo::getName, "jack").or().eq(UserInfo::getPhone, "13888888888"));
// 查询结果
List<UserInfo> list = userInfoMapper.selectList(queryWrapper);

SELECT
 a.* 
FROM
 user_info a 
WHERE
 1 = 1 
 AND a.id <> 1 
 AND ( (a.`name` = 'jack' AND a.category = 1) OR (a.phone = '13888888888' OR a.category = 2) )

LambdaQueryWrapper<UserInfo> queryWrapper = new LambdaQueryWrapper<>();
// AND a.id <> 1 
queryWrapper.ne(UserInfo::getId, "1");
// AND ( (a.`name` = 'jack' AND a.category = 1) OR (a.phone = '13888888888' OR a.category = 2) )
queryWrapper.and(i -> (i.and(j -> j.eq(UserInfo::getName, "jack").eq(UserInfo::getCategory, 1))).or(j -> j.eq(UserInfo::getPhone, "13888888888").eq(UserInfo::getCategory, 2)));
// 查询结果
List<UserInfo> list = userInfoMapper.selectList(queryWrapper);

@ApiModelProperty(value = "删除状态（0--未删除1--已删除）")
@TableField("del_flag")
@TableLogic
private Integer delFlag;

@ApiModelProperty(value = "删除状态（0--未删除1--已删除）")
@TableField("del_flag")
@TableLogic(value = "1", delval = "0")
private Integer delFlag;

# mybatis配置
mybatis-plus:
 # 全局配置
 global-config:
  db-config:
   # 逻辑删除全局字段 (默认无 设置会自动扫描实体字段)
   logic-delete-field: delFlag
   # 逻辑删除全局值（默认 1、表示已删除）
   logic-delete-value: 1
   # 逻辑未删除全局值（默认 0、表示未删除）
   logic-not-delete-value: 0

AND del_flag = 0

UPDATE user_info set del_flag = 1 where id = #{id}

SELECT
 id,
 `name`,
 phone 
FROM
 user_info 
WHERE
 1 = 1 
 AND age = 20

LambdaQueryWrapper<UserInfo> queryWrapper = new LambdaQueryWrapper<>();
// 只查询 id，name，phone
queryWrapper.select(UserInfo::getId, UserInfo::getName, UserInfo::getPhone);
// 查询条件为：age = 20
queryWrapper.eq(UserInfo::getAge, 20);
List<UserInfo> list = userInfoMapper.selectList(queryWrapper );

UserInfo userInfo = userInfoService.getById(id);

LambdaQueryWrapper<UserInfo> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.eq(UserInfo::getOpenId, openId);
UserInfo userInfo = userInfoService.getOne(queryWrapper);

LambdaQueryWrapper<UserInfo> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.eq(UserInfo::getOpenId, openId);
UserInfo userInfo = userInfoService.getOne(queryWrapper, false);

@Override
public T getOne(Wrapper<T> queryWrapper, boolean throwEx) {
  if (throwEx) {
    return baseMapper.selectOne(queryWrapper);
  }
  return SqlHelper.getObject(log, baseMapper.selectList(queryWrapper));
}

/**
* 从list中取第一条数据返回对应List中泛型的单个结果
*
* @param list ignore
* @param <E> ignore
* @return ignore
*/
public static <E> E getObject(Log log, List<E> list) {
  if (CollectionUtils.isNotEmpty(list)) {
    int size = list.size();
    if (size > 1) {
      log.warn(String.format("Warn: execute Method There are %s results.", size));
    }
    return list.get(0);
  }
  return null;
}