5.文章详情、使用线程池，更新阅读次数

文章详情：

接口url：/articles/view/{id}

请求方式：POST

请求参数：

参数名称	参数类型	说明
id	long	文章id（路径参数）

返回数据：

{
    "success": true,
    "code": 200,
    "msg": "success",
    "data": "token"
}

ArticleController:

package com.example.blog.controller;

import com.example.blog.service.ArticleService;
import com.example.blog.vo.Result;
import com.example.blog.vo.params.PageParams;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

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

    @Autowired
    private ArticleService articleService;
    

    
    @PostMapping("/view/{id}")
    public Result findArticleById(@PathVariable("id") Long articleId)
    {
        return articleService.findArticleById(articleId);
    }
}

ArticleServiceImpl:

package com.example.blog.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.blog.dao.mapper.ArticleBodyMapper;
import com.example.blog.dao.mapper.ArticleMapper;
import com.example.blog.dao.mapper.CategoryMapper;
import com.example.blog.dos.Archives;
import com.example.blog.entity.Article;
import com.example.blog.entity.ArticleBody;
import com.example.blog.entity.Category;
import com.example.blog.service.ArticleService;
import com.example.blog.service.CategoryService;
import com.example.blog.service.SysUserService;
import com.example.blog.service.TagService;
import com.example.blog.vo.ArticleBodyVo;
import com.example.blog.vo.ArticleVo;
import com.example.blog.vo.CategoryVo;
import com.example.blog.vo.Result;
import com.example.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.sql.Date;
import java.util.ArrayList;
import java.util.List;

@Service
public class ArticleServiceImpl implements ArticleService
{

    @Autowired
    private ArticleMapper articleMapper;

    @Autowired
    private TagService tagService;

    @Autowired
    private SysUserService sysUserService;

    @Autowired
    private ArticleBodyMapper articleBodyMapper;

    @Autowired
    private CategoryService categoryService;
    
    @Override
    public Result listArticle(PageParams pageParams)
    {
        Page page = new Page<>(pageParams.getPage(), pageParams.getPageSize());
        LambdaQueryWrapper queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.orderByDesc(Article::getWeight);
        queryWrapper.orderByDesc(Article::getCreateDate);
        Page articlePage = articleMapper.selectPage(page, queryWrapper);
        List records = articlePage.getRecords();
        List articleVoList = copyList(records,true,true);
        return Result.success(articleVoList);
    }

    
    private List copyList(List records,boolean isTag,boolean isAuthor)
    {
        ArrayList articleVoList = new ArrayList<>();
        for(Article record:records)
        {
            articleVoList.add(copy(record,isTag,isAuthor,false,false));
        }
        return articleVoList;
    }


    
    private ArticleVo copy(Article article,boolean isTag,boolean isAuthor,boolean isBody,boolean isCategory)
    {
        ArticleVo articleVo = new ArticleVo();
        BeanUtils.copyProperties(article,articleVo);
        articleVo.setCreateDate(new DateTime(article.getCreateDate()).toString("yyyy-MM-dd HH:mm"));
        
        if(isTag)
        {
            Long articleId = article.getId();
            articleVo.setTags(tagService.findTagsById(articleId));
        }
        if(isAuthor)
        {
            Long authorId = article.getAuthorId();
            articleVo.setAuthor(sysUserService.findUserById(authorId).getNickname());
        }
        if(isBody)
        {
            Long bodyId = article.getBodyId();
            articleVo.setBody(findArticleBodyById(bodyId));
        }
        if(isCategory)
        {
            Long categoryId = article.getCategoryId();
            articleVo.setCategory(categoryService.findCategoryById(categoryId));
        }
        return articleVo;
    }

    
    private ArticleBodyVo findArticleBodyById(Long bodyId)
    {
        ArticleBody articleBody = articleBodyMapper.selectById(bodyId);
        ArticleBodyVo articleBodyVo = new ArticleBodyVo();
        articleBodyVo.setContent(articleBody.getContent());
        return articleBodyVo;
    }


    
    @Override
    public Result findArticleById(Long articleId)
    {
        
        Article article = articleMapper.selectById(articleId);

        ArticleVo articleVo = copy(article, true, true,true,true);
        return Result.success(articleVo);
    }
}

这里有一点复杂，理一下逻辑

1.把ArticleVo对应的ArticleBodyVo 和category注释去掉，也就是现在需要使用这两个成员(文章详情和文章分类)，并添加对应的Vo类

1.1ArticleVo：

package com.example.blog.vo;


import com.example.blog.entity.Tag;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import lombok.Data;
import java.util.List;

@Data
public class ArticleVo {

    @JsonSerialize(using = ToStringSerializer.class)
    private Long id;

    private String title;

    private String summary;

    private int commentCounts;

    private int viewCounts;

    private int weight;
    
    private String createDate;

    private String author;

    private ArticleBodyVo body;

    private List tags;

    private CategoryVo category;

}

1.2 ArticleBodyVo

package com.example.blog.vo;

import lombok.Data;

@Data
public class ArticleBodyVo
{
    private String content;
}

1.3 CategoryVo

package com.example.blog.vo;

import lombok.Data;

@Data
public class CategoryVo
{
    private Long id;

    private String avatar;

    private String categoryName;
}

2.根据articleId查询文章article，获取对应的bodyId和categoryId

3.根据bodyId 和categoryId 去关联查询对应的文章详情和文章标签

ArticleServiceImpl：

    
    private ArticleBodyVo findArticleBodyById(Long bodyId)
    {
        ArticleBody articleBody = articleBodyMapper.selectById(bodyId);
        ArticleBodyVo articleBodyVo = new ArticleBodyVo();
        articleBodyVo.setContent(articleBody.getContent());
        return articleBodyVo;
    }

CategoryServiceImpl：

package com.example.blog.service.impl;

import com.example.blog.dao.mapper.CategoryMapper;
import com.example.blog.entity.Category;
import com.example.blog.service.CategoryService;
import com.example.blog.vo.CategoryVo;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class CategoryServiceImpl implements CategoryService
{

    @Autowired
    private CategoryMapper categoryMapper;

    @Override
    public CategoryVo findCategoryById(Long categoryId)
    {
        Category category = categoryMapper.selectById(categoryId);
        return copy(category);
    }

    private CategoryVo copy(Category category)
    {
        CategoryVo categoryVo = new CategoryVo();
        BeanUtils.copyProperties(category,categoryVo);
        return categoryVo;
    }
}

4.将查到的文章详情和文章标签注入到articleVo中

ArticleVo articleVo = copy(article, true, true,true,true);

    
    private ArticleVo copy(Article article,boolean isTag,boolean isAuthor,boolean isBody,boolean isCategory)
    {
        ArticleVo articleVo = new ArticleVo();
        BeanUtils.copyProperties(article,articleVo);
        
        articleVo.setCreateDate(new DateTime(article.getCreateDate()).toString("yyyy-MM-dd HH:mm"));
        
        if(isTag)
        {
            Long articleId = article.getId();
            articleVo.setTags(tagService.findTagsById(articleId));
        }
        if(isAuthor)
        {
            Long authorId = article.getAuthorId();
            articleVo.setAuthor(sysUserService.findUserById(authorId).getNickname());
        }
        if(isBody)
        {
            Long bodyId = article.getBodyId();
            articleVo.setBody(findArticleBodyById(bodyId));
        }
        if(isCategory)
        {
            Long categoryId = article.getCategoryId();
            articleVo.setCategory(categoryService.findCategoryById(categoryId));
        }
        return articleVo;
    }

5.重点！！

==> Preparing:

SELECT id,title,summary,comment_counts,view_counts,author_id,body_id,category_id,weight,create_date FROM ms_article WHERe id=?
==> Parameters: 1405564731300831200(Long)
<== Total: 0

发现：前端传入的值1405564731300831200丢失了两位精度，所以前端传入的articleId，后端通过该id找不到对应的article!!!

原因：由于前端传入的articleId丢失了精度，java中long数据能表示的范围比js中number大,在跟前端交互时，这样也就意味着部分数值在js中存不下(变成不准确的值)。

解决方案：ArticleVo 中的id字段使用fastjson的ToStringSerializer注解，让系统序列化时，保留相关精度。

package com.example.blog.vo;


import com.example.blog.entity.Tag;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import lombok.Data;
import java.util.List;

@Data
public class ArticleVo {

    @JsonSerialize(using = ToStringSerializer.class)
    private Long id;

    private String title;

    private String summary;

    private int commentCounts;

    private int viewCounts;

    private int weight;
    
    private String createDate;

    private String author;

    private ArticleBodyVo body;

    private List tags;

    private CategoryVo category;

}

这里阅读数应该随着点击增加，所以需要使用线程池，更新阅读次数

查看完该文章之后，本应该直接返回数据，这个时候做了一个更新操作，更新时加写锁，阻塞其他的读操作，性能就会比较低。

更新肯定会增加此次接口的耗时，如果更新一旦除了问题，不能影响查看文章的操作。

这时可以增加线程池，把更新操作扔到线程池中去执行，这样就和主线程不相关了。

创建一个线程池：

package com.example.blog.cofig;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;

@Configuration
@EnableAsync //开启多线程
public class ThreadPoolConfig
{
    @Bean("taskExcutor")
    public Executor asyncServiceExecutor()
    {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        // 设置核心线程数
        executor.setCorePoolSize(5);
        // 设置最大线程数
        executor.setMaxPoolSize(20);
        //配置队列大小
        executor.setQueueCapacity(Integer.MAX_VALUE);
        // 设置线程活跃时间（秒）
        executor.setKeepAliveSeconds(60);
        // 设置默认线程名称
        executor.setThreadNamePrefix("博客");
        // 等待所有任务结束后再关闭线程池
        executor.setWaitForTasksToCompleteonShutdown(true);
        //执行初始化
        executor.initialize();
        return executor;
    }
}

ArticleServiceImpl中的显示文章详情的方法findArticleById中，添加一个线程池，用于增加阅读量

    @Autowired
    private ThreadService threadService;
    @Override
    public Result findArticleById(Long articleId)
    {
        
        Article article = articleMapper.selectById(articleId);
        ArticleVo articleVo = copy(article, true, true,true,true);
        //查看完该文章之后，本应该直接返回数据，这个时候做了一个更新操作，更新时加写锁，阻塞其他的读操作，性能就会比较低
        //更新肯定会增加此次接口的耗时，如果更新一旦除了问题，不能影响 查看文章的操作
        //这时可以增加线程池，把更新操作扔到线程池中去执行，这样就和主线程不相关了
        threadService.updateArticleViewCount(articleMapper,article);
        return Result.success(articleVo);
    }

ThreadService：

package com.example.blog.service;

import com.baomidou.mybatisplus.core.conditions.update.LambdaUpdateWrapper;
import com.example.blog.dao.mapper.ArticleMapper;
import com.example.blog.entity.Article;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;

@Component
public class ThreadService
{
    //期望此次操作在线程池执行 不会影响原有的主线程
    @Async("taskExcutor")//将该任务丢到线程池中
    public void updateArticleViewCount(ArticleMapper articleMapper, Article article)
    {
        int viewCounts = article.getViewCounts();

        Article articleUpdate = new Article();
        articleUpdate.setViewCounts(viewCounts+1);
        LambdaUpdateWrapper updateWrapper = new LambdaUpdateWrapper<>();
        updateWrapper.eq(Article::getId,article.getId());
        //设置一个 为了在多线程的环境下 线程安全
        //乐观锁的一个思想 如果操作的时候发现阅读数与期望的阅读数不一致，修改失败
        updateWrapper.eq(Article::getViewCounts,viewCounts);

        articleMapper.update(articleUpdate,updateWrapper);
        try {
            //睡眠 ThredService中的方法 5秒，不会影响主线程的使用，即文章详情会很快的显示出来，不受影响
            Thread.sleep(5000);
            System.out.println("更新完成了~~~");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

这里有一个Bug

由于article类中的commentCounts，viewCounts，weight 字段为int

package com.example.blog.entity;

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;

    
    private Long authorId;
    
    private Long bodyId;
    
    private Long categoryId;

    
    private int weight = Article_Common;


    
    private Long createDate;
}

发现：会造成更新阅读次数的时候，将commentCounts，viewCounts，weight 字段设为初始值0,也就是这条语句

articleMapper.update(articleUpdate,updateWrapper);

原因：在更新阅读次数的时候，只要该成员值不为null，mybatisPlus都会把该成员赋值进去更新，也就是把commentCounts，viewCounts，weight这三个int类型的赋值进去

解决：如果设置为integer，该成员值就为null，就不会被更新

总结：需要把与数据库对应字段的成员设置为integer，而不是int类型

修改：

package com.example.blog.entity;

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 Integer commentCounts;

    private Integer viewCounts;

    
    private Long authorId;
    
    private Long bodyId;
    
    private Long categoryId;

    
    private Integer weight;


    
    private Long createDate;
}

以及对应vo

package com.example.blog.vo;


import com.example.blog.entity.Tag;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import lombok.Data;
import java.util.List;

@Data
public class ArticleVo {

    @JsonSerialize(using = ToStringSerializer.class)
    private Long id;

    private String title;

    private String summary;

    private Integer commentCounts;

    private Integer viewCounts;

    private Integer weight;
    
    private String createDate;

    private String author;

    private ArticleBodyVo body;

    private List tags;

    private CategoryVo category;

}

5.文章详情、使用线程池，更新阅读次数

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