java中VO的使用

场景:现在我们需要从数据库中查询用户列表t_user,对应的实体类如下:

import io.swagger.annotations.ApiModelProperty;public class User {    @ApiModelProperty(value = "用户id")    private String userId;    @ApiModelProperty(value = "用户名称")    private String name;    /**     * 状态参考 UserStatus     */    @ApiModelProperty(value = "用户状态  1已认证，2 认证中，3未通过认证，7未提交认证")    private Integer status;    @ApiModelProperty(value = "头像地址")    private String headPicFileName;    @ApiModelProperty(value = "手机号")    private String telephone;    /**     * 用户级别 0到期 1游客 2临时用户 3认证用户 参考health com.dachen.health.commons.vo.User     */    private Integer userLevel;    @ApiModelProperty(value = "医生信息")    private Doctor doctor;    get/setXxx()....     @Override    public boolean equals(Object o) {        if (this == o) {            return true;        }        if (o == null || getClass() != o.getClass()) {            return false;        }        User user = (User) o;        return userId != null ? userId.equals(user.userId) : user.userId == null;    }}

但是前端页面需要展示更多个关于用户的消息,如用户的角色Role,而User实体类中的信息不全,
为了返回更多的信息,有两种做法:
1.直接在user类中添加需要的信息属性
2.创建一个新类UserVO extends User,只在UserVO中添加更多属性,而且以VO结尾表示用于返回前端的数据.

如果采用第一种做法,User类可能会越来越大,也不方便后期维护,而且User类作为对数据库表的映射,添加冗余的属性
反而会破坏这种映射关系,采取第二种方法,更加清晰明确.

现在采用第二种方法,假设从数据中查出user列表:

List<User> users = userServiceImpl.findUsersByIds(userIds);//将User列表转换为UserVO列表:List<CircleUserVO> circleUserVOs=BeanUtil.copyList(users,CircleUserVO.class);//给UserVO添加角色属性wrapRole(circleUserVOs,circleId);wrapRole(List<CircleUserVO> circleUserVOs,Long circleId){    //所有角色权限    List<CircleUserVO> circleUserVOList = circleMemberRoleMapper.selectAllMemberRoleByCircleId(circleId);    for (CircleUserVO circleUserVO:circleUserVOList){        for (CircleUserVO circleUserVO1:circleUserVOs){            if(circleUserVO.getUserId().equals(circleUserVO1.getUserId())){                circleUserVO1.setRole(circleUserVO.getRole());            }        }    }}

package com.dachen.circle.model.vo;import com.dachen.circle.model.inner.User;import io.swagger.annotations.ApiModelProperty;public class CircleUserVO extends User{    @ApiModelProperty(value = "在该圈子的角色1：管理员 2：圈主（负责人）3：顾问 逗号拼接 多个角色 可同时为管理员，圈主，顾问")    private String role;    @ApiModelProperty(value = "0否 1是 永久免费")    private Integer permanentFree;    @ApiModelProperty(value = "1正常 2欠费")    private Integer arrearageStatus;    @ApiModelProperty(value = "过期时间 月数")    private Integer expirationMonth;    @ApiModelProperty(value = "医院名称")    private String hospital;    @ApiModelProperty(value = "科室")    private String departments;    @ApiModelProperty(value = "职称")    private String title;    @ApiModelProperty(value = "简介")    private String introduction;    @ApiModelProperty(value = "排序字母 A-Z Z1为#")    private String letter;   get/setXxx(); }

package com.dachen.util;import org.springframework.beans.BeanUtils;import java.util.ArrayList;import java.util.List;public class BeanUtil {     public static <T> T copy(Object poObj,final Class <T>voClass)     {         T voObj =null;         try {             voObj = voClass.newInstance();             BeanUtils.copyProperties(poObj, voObj);             return voObj;         } catch (InstantiationException | IllegalAccessException e) {             e.printStackTrace();         }         return null;     }     public static <T> List <T> copyList(List <? extends Object> poList ,final Class <T>voClass){        List<T> voList=new ArrayList<T>();        T voObj =null;        for(Object poObj:poList){            try {                voObj = voClass.newInstance();                BeanUtils.copyProperties(poObj, voObj);                voList.add(voObj);            } catch (InstantiationException | IllegalAccessException e) {                e.printStackTrace();            }            System.out.println(voObj);        }        return voList;    }}