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spring boot 练手实战项目说明

码神之路网站所使用的博客，项目简单，需求明确，容易上手，非常适合做为练手级项目。

blog.mszlu.com

项目讲解说明：

  1. 提供前端工程，只需要实现后端接口即可
  2. 项目以单体架构入手，先快速开发，不考虑项目优化，降低开发负担
  3. 开发完成后，开始优化项目，提升编程思维能力
  4. 比如页面静态化，缓存，云存储，日志等
  5. docker部署上线
  6. 云服务器购买，域名购买，域名备案等

项目使用技术 ：

springboot + mybatisplus+redis+mysql

1. 工程搭建

前端的工程：

npm install
npm run build
npm run dev

1.1 新建maven工程

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.mszlu</groupId>
    <artifactId>blog-parent</artifactId>
    <version>1.0-SNAPSHOT</version>


    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.0</version>
        <relativePath/>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <!-- 排除 默认使用的logback  -->
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <!-- log4j2 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-log4j2</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>


        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.76</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
        </dependency>

        <dependency>
            <groupId>commons-collections</groupId>
            <artifactId>commons-collections</artifactId>
            <version>3.2.2</version>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.3</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <!-- https://mvnrepository.com/artifact/joda-time/joda-time -->
        <dependency>
            <groupId>joda-time</groupId>
            <artifactId>joda-time</artifactId>
            <version>2.10.10</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

1.2 配置

#server
server.port= 8888
spring.application.name=mszlu_blog
# datasource
spring.datasource.url=jdbc:mysql://localhost:3306/blog?useUnicode=true&characterEncoding=UTF-8&serverTimeZone=UTC
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

#mybatis-plus
mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl
mybatis-plus.global-config.db-config.table-prefix=ms_


package com.mszlu.blog.config;

import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
//扫包，将此包下的接口生成代理实现类，并且注册到spring容器中
@MapperScan("com.mszlu.blog.dao")
public class MybatisPlusConfig {
	//分页插件
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor(){
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor());
        return interceptor;
    }
}
package com.mszlu.blog.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebConfig  implements WebMvcConfigurer {

    @Override
    public void addCorsMappings(CorsRegistry registry) {
        //跨域配置，不可设置为*，不安全, 前后端分离项目，可能域名不一致
        //本地测试 端口不一致 也算跨域
        registry.addMapping("/**").allowedOrigins("http://localhost:8080");
    }
}

1.3 启动类

package com.mszlu.blog;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class BlogApp {

    public static void main(String[] args) {
        SpringApplication.run(BlogApp.class,args);
    }
}

2. 首页-文章列表

2.1 接口说明

接口url：/articles

请求方式：POST

请求参数：

参数名称 参数类型 说明
page int 当前页数
pageSize int 每页显示的数量

返回数据：

{
    "success": true,
    "code": 200,
    "msg": "success",
    "data": [
        {
            "id": 1,
            "title": "springboot介绍以及入门案例",
            "summary": "通过Spring Boot实现的服务，只需要依靠一个Java类，把它打包成jar，并通过`java -jar`命令就可以运行起来。\r\n\r\n这一切相较于传统Spring应用来说，已经变得非常的轻便、简单。",
            "commentCounts": 2,
            "viewCounts": 54,
            "weight": 1,
            "createDate": "2609-06-26 15:58",
            "author": "12",
            "body": null,
            "tags": [
                {
                    "id": 5,
                    "avatar": null,
                    "tagName": "444"
                },
                {
                    "id": 7,
                    "avatar": null,
                    "tagName": "22"
                },
                {
                    "id": 8,
                    "avatar": null,
                    "tagName": "11"
                }
            ],
            "categorys": null
        },
        {
            "id": 9,
            "title": "Vue.js 是什么",
            "summary": "Vue (读音 /vjuː/，类似于 view) 是一套用于构建用户界面的渐进式框架。",
            "commentCounts": 0,
            "viewCounts": 3,
            "weight": 0,
            "createDate": "2609-06-27 11:25",
            "author": "12",
            "body": null,
            "tags": [
                {
                    "id": 7,
                    "avatar": null,
                    "tagName": "22"
                }
            ],
            "categorys": null
        },
        {
            "id": 10,
            "title": "Element相关",
            "summary": "本节将介绍如何在项目中使用 Element。",
            "commentCounts": 0,
            "viewCounts": 3,
            "weight": 0,
            "createDate": "2609-06-27 11:25",
            "author": "12",
            "body": null,
            "tags": [
                {
                    "id": 5,
                    "avatar": null,
                    "tagName": "444"
                },
                {
                    "id": 6,
                    "avatar": null,
                    "tagName": "33"
                },
                {
                    "id": 7,
                    "avatar": null,
                    "tagName": "22"
                },
                {
                    "id": 8,
                    "avatar": null,
                    "tagName": "11"
                }
            ],
            "categorys": null
        }
    ]
}

2.2 编码

2.2.1 表结构

CREATE TABLE `blog`.`ms_article`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `comment_counts` int(0) NULL DEFAULT NULL COMMENT '评论数量',
  `create_date` bigint(0) NULL DEFAULT NULL COMMENT '创建时间',
  `summary` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '简介',
  `title` varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '标题',
  `view_counts` int(0) NULL DEFAULT NULL COMMENT '浏览数量',
  `weight` int(0) NOT NULL COMMENT '是否置顶',
  `author_id` bigint(0) NULL DEFAULT NULL COMMENT '作者id',
  `body_id` bigint(0) NULL DEFAULT NULL COMMENT '内容id',
  `category_id` int(0) NULL DEFAULT NULL COMMENT '类别id',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 25 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;
CREATE TABLE `blog`.`ms_tag`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `article_id` bigint(0) NOT NULL,
  `tag_id` bigint(0) NOT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `article_id`(`article_id`) USING BTREE,
  INDEX `tag_id`(`tag_id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;
CREATE TABLE `blog`.`ms_sys_user`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `account` varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '账号',
  `admin` bit(1) NULL DEFAULT NULL COMMENT '是否管理员',
  `avatar` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '头像',
  `create_date` bigint(0) NULL DEFAULT NULL COMMENT '注册时间',
  `deleted` bit(1) NULL DEFAULT NULL COMMENT '是否删除',
  `email` varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '邮箱',
  `last_login` bigint(0) NULL DEFAULT NULL COMMENT '最后登录时间',
  `mobile_phone_number` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '手机号',
  `nickname` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '昵称',
  `password` varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '密码',
  `salt` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '加密盐',
  `status` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '状态',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 16 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;
package com.mszlu.blog.dao.pojo;

import lombok.Data;

@Data
public class Article {

    public static final int Article_TOP = 1;

    public static final int Article_Common = 0;

    private Long id;

    private String title;

    private String summary;

    private int commentCounts;

    private int viewCounts;

    /**
     * 作者id
     */
    private Long authorId;
    /**
     * 内容id
     */
    private Long bodyId;
    /**
     *类别id
     */
    private Long categoryId;

    /**
     * 置顶
     */
    private int weight = Article_Common;


    /**
     * 创建时间
     */
    private Long createDate;
}
package com.mszlu.blog.dao.pojo;

import lombok.Data;

@Data
public class SysUser {

    private Long id;

    private String account;

    private Integer admin;

    private String avatar;

    private Long createDate;

    private Integer deleted;

    private String email;

    private Long lastLogin;

    private String mobilePhoneNumber;

    private String nickname;

    private String password;

    private String salt;

    private String status;
}
package com.mszlu.blog.dao.pojo;

import lombok.Data;

@Data
public class Tag {

    private Long id;

    private String avatar;

    private String tagName;

}

2.2.2 Controller

package com.mszlu.blog.api;

import com.mszlu.blog.dao.pojo.Article;
import com.mszlu.blog.service.ArticleService;
import com.mszlu.blog.vo.Archive;
import com.mszlu.blog.vo.ArticleVo;
import com.mszlu.blog.vo.Result;
import com.mszlu.blog.vo.params.PageParams;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("articles")
public class ArticleController {

    @Autowired
    private ArticleService articleService;
	//Result是统一结果返回
    @PostMapping
    public Result articles(@RequestBody PageParams pageParams) {
        //ArticleVo 页面接收的数据
        List<ArticleVo> articles = articleService.listArticlesPage(pageParams);

        return Result.success(articles);
    }


}
package com.mszlu.blog.vo;

import com.mszlu.blog.dao.pojo.Article;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.List;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Result {

    private boolean success;

    private Integer code;

    private String msg;

    private Object data;


    public static Result success(Object data) {
        return new Result(true,200,"success",data);
    }
    public static Result fail(Integer code, String msg) {
        return new Result(false,code,msg,null);
    }
}
package com.mszlu.blog.vo;

import com.mszlu.blog.dao.pojo.ArticleBody;
import com.mszlu.blog.dao.pojo.Category;
import com.mszlu.blog.dao.pojo.SysUser;
import com.mszlu.blog.dao.pojo.Tag;
import lombok.Data;

import java.util.List;

@Data
public class ArticleVo {

    private Long id;

    private String title;

    private String summary;

    private int commentCounts;

    private int viewCounts;

    private int weight;
    /**
     * 创建时间
     */
    private String createDate;

    private String author;

    private ArticleBodyVo body;

    private List<TagVo> tags;

    private List<CategoryVo> categorys;

}

2.2.3 Service

package com.mszlu.blog.service;

import com.mszlu.blog.vo.Archive;
import com.mszlu.blog.vo.ArticleVo;
import com.mszlu.blog.vo.params.PageParams;

import java.util.List;

public interface ArticleService {

    List<ArticleVo> listArticlesPage(PageParams pageParams);

}
package com.mszlu.blog.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.mszlu.blog.dao.ArticleMapper;
import com.mszlu.blog.dao.SysUserMapper;
import com.mszlu.blog.dao.pojo.Article;
import com.mszlu.blog.dao.pojo.SysUser;
import com.mszlu.blog.dao.pojo.Tag;
import com.mszlu.blog.service.ArticleService;
import com.mszlu.blog.service.SysUserService;
import com.mszlu.blog.service.TagsService;
import com.mszlu.blog.vo.ArticleBodyVo;
import com.mszlu.blog.vo.ArticleVo;
import com.mszlu.blog.vo.TagVo;
import com.mszlu.blog.vo.params.PageParams;
import org.joda.time.DateTime;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

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

@Service
public class ArticleServiceImpl implements ArticleService {
    @Autowired
    private ArticleMapper articleMapper;
   @Autowired
   private SysUserService sysUserService;
    @Autowired
    private TagsService tagsService;

    public ArticleVo copy(Article article,boolean isAuthor,boolean isBody,boolean isTags){
        ArticleVo articleVo = new ArticleVo();
        BeanUtils.copyProperties(article, articleVo);
        if (isAuthor) {
            SysUser sysUser = sysUserService.findSysUserById(article.getAuthorId());
            articleVo.setAuthor(sysUser.getNickname());
        }
        articleVo.setCreateDate(new DateTime(article.getCreateDate()).toString("yyyy-MM-dd HH:mm"));
        if (isTags){
           List<TagVo> tags = tagsService.findTagsByArticleId(article.getId());
           articleVo.setTags(tags);
        }
        return articleVo;
    }

    private List<ArticleVo> copyList(List<Article> records,boolean isAuthor,boolean isBody,boolean isTags) {
        List<ArticleVo> articleVoList = new ArrayList<>();
        for (Article article : records) {
            ArticleVo articleVo = copy(article,isAuthor,isBody,isTags);
            articleVoList.add(articleVo);
        }
        return articleVoList;
    }


    @Override
    public List<ArticleVo> listArticlesPage(PageParams pageParams) {
        QueryWrapper<Article> queryWrapper = new QueryWrapper<>();
        Page<Article> page = new Page<>(pageParams.getPage(),pageParams.getPageSize());
        Page<Article> articlePage = articleMapper.selectPage(page, queryWrapper);
        List<ArticleVo> articleVoList = copyList(articlePage.getRecords(),true,false,true);
        return articleVoList;
    }


}
package com.mszlu.blog.service;

import com.mszlu.blog.dao.pojo.SysUser;

public interface UserService {

    SysUser findUserById(Long userId);
}
package com.mszlu.blog.service.impl;

import com.mszlu.blog.dao.SysUserMapper;
import com.mszlu.blog.dao.pojo.SysUser;
import com.mszlu.blog.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private SysUserMapper sysUserMapper;

    @Override
    public SysUser findUserById(Long userId) {
        SysUser sysUser = sysUserMapper.selectById(userId);
        if (sysUser == null) {
            sysUser = new SysUser();
            sysUser.setNickname("码神之路");
        }
        return sysUser;
    }
}
package com.mszlu.blog.service;

import com.mszlu.blog.dao.pojo.Tag;
import com.mszlu.blog.vo.TagVo;

import java.util.List;

public interface TagsService {


    List<TagVo> findTagsByArticleId(Long id);
}
package com.mszlu.blog.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.mszlu.blog.dao.TagMapper;
import com.mszlu.blog.dao.pojo.Tag;
import com.mszlu.blog.service.TagsService;
import com.mszlu.blog.vo.TagVo;
import org.apache.commons.collections.CollectionUtils;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

@Service
public class TagsServiceImpl implements TagsService {
    @Autowired
    private TagMapper tagMapper;

    public TagVo copy(Tag tag){
        TagVo tagVo = new TagVo();
        BeanUtils.copyProperties(tag,tagVo);
        return tagVo;
    }
    public List<TagVo> copyList(List<Tag> tagList){
        List<TagVo> tagVoList = new ArrayList<>();
        for (Tag tag : tagList) {
            tagVoList.add(copy(tag));
        }
        return tagVoList;
    }

    @Override
    public List<TagVo> findTagsByArticleId(Long id) {
        List<Tag> tags = tagMapper.findTagsByArticleId(id);
        return copyList(tags);
    }
}

2.2.4 Dao

package com.mszlu.blog.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mszlu.blog.dao.pojo.Article;
import com.mszlu.blog.vo.ArticleVo;

import java.util.List;

public interface ArticleMapper extends BaseMapper<Article> {
	
}
package com.mszlu.blog.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mszlu.blog.dao.pojo.Tag;

import java.util.List;

public interface TagMapper extends BaseMapper<Tag> {

    List<Tag> findTagsByArticleId(Long articleId);
}
package com.mszlu.blog.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mszlu.blog.dao.pojo.SysUser;

public interface SysUserMapper extends BaseMapper<SysUser> {
}
<?xml version="1.0" encoding="UTF-8" ?>
<!--MyBatis配置文件-->
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.mszlu.blog.dao.TagMapper">

    <sql id="all">
        id,avatar,tag_name as tagName
    </sql>

    <select id="findTagsByArticleId" parameterType="long" resultType="com.mszlu.blog.dao.pojo.Tag">
        select <include refid="all" />  from ms_tag
        <where>
            id in
            (select tag_id from ms_article_tag where article_id = #{articleId})
        </where>
    </select>
</mapper>

2.2.5 测试

3. 首页-最热标签

3.1 接口说明

接口url：/tags/hot

请求方式：GET

请求参数：无

返回数据：

{
    "success": true,
    "code": 200,
    "msg": "success",
    "data": [
        {
            "id":1,
            "tagName":"4444"
        }
    ]
}

3.2 编码

3.2.1 Controller

package com.mszlu.blog.api;

import com.mszlu.blog.service.ArticleService;
import com.mszlu.blog.service.TagsService;
import com.mszlu.blog.vo.Archive;
import com.mszlu.blog.vo.ArticleVo;
import com.mszlu.blog.vo.Result;
import com.mszlu.blog.vo.TagVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("tags")
public class TagsController {

    @Autowired
    private TagsService tagsService;

    @GetMapping("/hot")
    public Result listHotTags() {
        int limit = 6;
        List<TagVo> tagVoList = tagsService.hot(limit);
        return Result.success(tagVoList);
    }

}
package com.mszlu.blog.vo;

import lombok.Data;

@Data
public class TagVo {

    private Long id;

    private String tagName;
}

3.2.2 Service

package com.mszlu.blog.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.mszlu.blog.dao.TagMapper;
import com.mszlu.blog.dao.pojo.Tag;
import com.mszlu.blog.service.TagsService;
import com.mszlu.blog.vo.TagVo;
import org.apache.commons.collections.CollectionUtils;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

@Service
public class TagsServiceImpl implements TagsService {
    @Autowired
    private TagMapper tagMapper;

    public TagVo copy(Tag tag){
        TagVo tagVo = new TagVo();
        BeanUtils.copyProperties(tag,tagVo);
        return tagVo;
    }
    public List<TagVo> copyList(List<Tag> tagList){
        List<TagVo> tagVoList = new ArrayList<>();
        for (Tag tag : tagList) {
            tagVoList.add(copy(tag));
        }
        return tagVoList;
    }
    @Override
    public List<TagVo> hot(int limit) {

        List<Long> hotsTagIds = tagMapper.findHotsTagIds(limit);
        if (CollectionUtils.isEmpty(hotsTagIds)){
            return Collections.emptyList();
        }
        List<Tag> tagList = tagMapper.findTagsByTagIds(hotsTagIds);
        return copyList(tagList);
    }

}
package com.mszlu.blog.service;

import com.mszlu.blog.vo.TagVo;

import java.util.List;

public interface TagsService {

    List<TagVo> hot(int limit);

}

3.2.3 Dao

package com.mszlu.blog.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mszlu.blog.dao.pojo.Tag;

import java.util.List;

public interface TagMapper extends BaseMapper<Tag> {

    List<Tag> findTagsByTagIds(List<Long> tagIds);

    List<Long> findHotsTagIds(int limit);
}
<?xml version="1.0" encoding="UTF-8" ?>
<!--MyBatis配置文件-->
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.mszlu.blog.dao.TagMapper">

    <sql id="all">
        id,avatar,tag_name as tagName
    </sql>
    <select id="findTagsByTagIds" parameterType="list" resultType="com.mszlu.blog.dao.pojo.Tag">
        select <include refid="all" />  from ms_tag where id in
        <foreach collection="tagIds" item="tagId" separator="," open="(" close=")">
            #{tagId}
        </foreach>
    </select>
    <select id="findHotsTagIds" parameterType="int" resultType="long">
        select tag_id from ms_article_tag at group by tag_id order by count(1) desc limit #{size}
    </select>

</mapper>

3.2.4 测试