mybatis-plus

VO包

当我们给前台传数据的时候，可能不想要将所有的数据项都传给前台，这时候需要使用VO映射类来封装我们的 数据

domain/vo/实体类名字

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package com.nuyoah.domain.vo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * 当我们返回给前端数据的时候，并不是想要将数据库中的所有数据项都展示出来
 * 这时候我们可以使用vo封装我们想要给前台展示的数据
 */

@Data
@NoArgsConstructor
@AllArgsConstructor
public class HotArticleVo {
    private Long id;
    private String title;
    private Long viewCount;
}

实体对象转换成VO对象

service/impl/service对象

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package com.nuyoah.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.fasterxml.jackson.databind.util.BeanUtil;
import com.nuyoah.domain.ResponseResult;
import com.nuyoah.domain.entity.Article;
import com.nuyoah.domain.vo.HotArticleVo;
import com.nuyoah.mapper.ArticleMapper;
import com.nuyoah.service.ArticleService;

import org.springframework.beans.BeanUtils;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.List;

/**
 * 文章表(Article)表服务实现类
 *
 * @author makejava
 * @since 2024-03-07 21:07:55
 */
@Service
public class ArticleServiceImpl extends ServiceImpl<ArticleMapper, Article> implements ArticleService {
    
    @Override
    public ResponseResult hostArticleList() {
        // 构建查询对象
        LambdaQueryWrapper<Article> lambdaQueryWrapper = new LambdaQueryWrapper<>();
        // 构建查询参数
        // 正式文章
        lambdaQueryWrapper.eq(Article::getStatus, 0);
        // 按照浏览量排序
        lambdaQueryWrapper.orderByAsc(Article::getViewCount);
        // 最多展示10条
        Page<Article> page = new Page<>(1, 10);
        page(page, lambdaQueryWrapper);

        List<Article> articles = page.getRecords();
        // 将查到的数据进行封装，分装成Vo数据类型
        // bean拷贝
        List<HotArticleVo> hotArticleVos = new ArrayList<>();
        for (Article article : articles) {
            HotArticleVo vo = new HotArticleVo();
            BeanUtils.copyProperties(article, vo);
            hotArticleVos.add(vo);
        }
        return ResponseResult.okResult(hotArticleVos);
    }

}


封装工具类将Bean转换成VO的代码封装一下

utils

返回前台状态和对象

我们可以封装一个类来给前台返回对象，例如状态信息，文字信息，数据信息

enums/AppHttpCodeEnum.java前台状态码

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package com.nuyoah.enums;

public enum AppHttpCodeEnum {
    // 成功
    SUCCESS(200,"操作成功"),
    // 登录
    NEED_LOGIN(401,"需要登录后操作"),
    NO_OPERATOR_AUTH(403,"无权限操作"),
    SYSTEM_ERROR(500,"出现错误"),
    USERNAME_EXIST(501,"用户名已存在"),
    PHONENUMBER_EXIST(502,"手机号已存在"), EMAIL_EXIST(503, "邮箱已存在"),
    REQUIRE_USERNAME(504, "必需填写用户名"),
    LOGIN_ERROR(505,"用户名或密码错误");
    int code;
    String msg;

    AppHttpCodeEnum(int code, String errorMessage){
        this.code = code;
        this.msg = errorMessage;
    }

    public int getCode() {
        return code;
    }

    public String getMsg() {
        return msg;
    }
}

domain/ResponseResult返回对象

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package com.nuyoah.domain;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.nuyoah.enums.AppHttpCodeEnum;
import java.io.Serializable;

/**
 * @author 35238
 * @date 2023/7/19 0019 12:49
 */
//统一响应格式。实体类，或者这个类严格来说叫响应体
@JsonInclude(JsonInclude.Include.NON_NULL)
public class ResponseResult<T> implements Serializable {
    private Integer code;
    private String msg;
    private T data;

    public ResponseResult() {
        this.code = AppHttpCodeEnum.SUCCESS.getCode();
        this.msg = AppHttpCodeEnum.SUCCESS.getMsg();
    }

    public ResponseResult(Integer code, T data) {
        this.code = code;
        this.data = data;
    }

    public ResponseResult(Integer code, String msg, T data) {
        this.code = code;
        this.msg = msg;
        this.data = data;
    }

    public ResponseResult(Integer code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    public static ResponseResult errorResult(int code, String msg) {
        ResponseResult result = new ResponseResult();
        return result.error(code, msg);
    }
    public static ResponseResult okResult() {
        ResponseResult result = new ResponseResult();
        return result;
    }
    public static ResponseResult okResult(int code, String msg) {
        ResponseResult result = new ResponseResult();
        return result.ok(code, null, msg);
    }

    public static ResponseResult okResult(Object data) {
        ResponseResult result = setAppHttpCodeEnum(AppHttpCodeEnum.SUCCESS, AppHttpCodeEnum.SUCCESS.getMsg());
        if(data!=null) {
            result.setData(data);
        }
        return result;
    }

    public static ResponseResult errorResult(AppHttpCodeEnum enums){
        return setAppHttpCodeEnum(enums,enums.getMsg());
    }

    public static ResponseResult errorResult(AppHttpCodeEnum enums, String msg){
        return setAppHttpCodeEnum(enums,msg);
    }

    public static ResponseResult setAppHttpCodeEnum(AppHttpCodeEnum enums){
        return okResult(enums.getCode(),enums.getMsg());
    }

    private static ResponseResult setAppHttpCodeEnum(AppHttpCodeEnum enums, String msg){
        return okResult(enums.getCode(),msg);
    }

    public ResponseResult<?> error(Integer code, String msg) {
        this.code = code;
        this.msg = msg;
        return this;
    }

    public ResponseResult<?> ok(Integer code, T data) {
        this.code = code;
        this.data = data;
        return this;
    }

    public ResponseResult<?> ok(Integer code, T data, String msg) {
        this.code = code;
        this.data = data;
        this.msg = msg;
        return this;
    }

    public ResponseResult<?> ok(T data) {
        this.data = data;
        return this;
    }

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }

}

返回对象

service

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package com.nuyoah.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.fasterxml.jackson.databind.util.BeanUtil;
import com.nuyoah.domain.ResponseResult;
import com.nuyoah.domain.entity.Article;
import com.nuyoah.domain.vo.HotArticleVo;
import com.nuyoah.mapper.ArticleMapper;
import com.nuyoah.service.ArticleService;

import org.springframework.beans.BeanUtils;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.List;

/**
 * 文章表(Article)表服务实现类
 *
 * @author makejava
 * @since 2024-03-07 21:07:55
 */
@Service
public class ArticleServiceImpl extends ServiceImpl<ArticleMapper, Article> implements ArticleService {
    
    @Override
    public ResponseResult hostArticleList() {
        // 构建查询对象
        LambdaQueryWrapper<Article> lambdaQueryWrapper = new LambdaQueryWrapper<>();
        // 构建查询参数
        // 正式文章
        lambdaQueryWrapper.eq(Article::getStatus, 0);
        // 按照浏览量排序
        lambdaQueryWrapper.orderByAsc(Article::getViewCount);
        // 最多展示10条
        Page<Article> page = new Page<>(1, 10);
        page(page, lambdaQueryWrapper);

        List<Article> articles = page.getRecords();
        // 将查到的数据进行封装，分装成Vo数据类型
        // bean拷贝
        List<HotArticleVo> hotArticleVos = new ArrayList<>();
        for (Article article : articles) {
            HotArticleVo vo = new HotArticleVo();
            BeanUtils.copyProperties(article, vo);
            hotArticleVos.add(vo);
        }
     	// 封装返回信息   
        return ResponseResult.okResult(hotArticleVos);
    }

}

常量类

当我们数据库中有数字表示状态信息的时候，在JAVA里面需要封装一个常量类，这样在修改状态字符的时候，只需要修改常量类中的数字即可

constants/SystemConstants

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package com.nuyoah.constants;

public class SystemConstants {
    /**
     * 文章是草稿
     */
    public static final int ARTICLE_STATUS_DRAFT = 1;

    /**
     * 文章是正常分布状态
     */
    public static final int ARTICLE_STATUS_NORMAL = 0;
}

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@Service
public class ArticleServiceImpl extends ServiceImpl<ArticleMapper, Article> implements ArticleService {
    
    @Override
    public ResponseResult hostArticleList() {
        
        LambdaQueryWrapper<Article> lambdaQueryWrapper = new LambdaQueryWrapper<>();
        // 将status数字转换为常量
        lambdaQueryWrapper.eq(Article::getStatus, SystemConstans.ARTICLE_STATUS_DRAFT);
       
    }

}