码神之路知识体系

1. ThreadLocal内存泄漏

实线代表强引用,虚线代表弱引用

每一个Thread维护一个ThreadLocalMap, key为使用弱引用的ThreadLocal实例，value为线程变量的副本。

强引用，使用最普遍的引用，一个对象具有强引用，不会被垃圾回收器回收。当内存空间不足，Java虚拟机宁愿抛出OutOfMemoryError错误，使程序异常终止，也不回收这种对象。

如果想取消强引用和某个对象之间的关联，可以显式地将引用赋值为null，这样可以使JVM在合适的时间就会回收该对象。

弱引用，JVM进行垃圾回收时，无论内存是否充足，都会回收被弱引用关联的对象。在java中，用java.lang.ref.WeakReference类来表示。

2. 文章详情

2.1 接口说明

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": {
        "id": 1,
        "title": "springboot介绍以及入门案例",
        "summary": "介绍",
        "commentCounts": 0,
        "viewCounts": 60,
        "weight": 0,
        "createDate": "2609-06-26 15:58",
        "author": "李四",
        "body": {
            "content": "111"
        },
        "tags": [
            {
                "id": 5,
                "tagName": "springboot"
            },
            {
                "id": 7,
                "tagName": "springmvc"
            },
            {
                "id": 8,
                "tagName": "11"
            }
        ],
        "category": {
            "id": 2,
            "avatar": "/category/back.png",
            "categoryName": "后端"
        }
    }
}

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2.2 涉及到的表

CREATE TABLE `blog`.`ms_article_body`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `content` longtext CHARACTER SET utf8 COLLATE utf8_general_ci NULL,
  `content_html` longtext CHARACTER SET utf8 COLLATE utf8_general_ci NULL,
  `article_id` bigint(0) NOT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `article_id`(`article_id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 38 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

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package com.mszlu.blog.dao.pojo;

import lombok.Data;

@Data
public class ArticleBody {

    private Long id;
    private String content;
    private String contentHtml;
    private Long articleId;
}

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CREATE TABLE `blog`.`ms_category`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `avatar` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
  `category_name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
  `description` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 6 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

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package com.mszlu.blog.dao.pojo;

import lombok.Data;

@Data
public class Category {

    private Long id;

    private String avatar;

    private String categoryName;

    private String description;
}

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2.3 Controller

  @PostMapping("view/{id}")
    public Result findArticleById(@PathVariable("id") Long id) {
        ArticleVo articleVo = articleService.findArticleById(id);

        return Result.success(articleVo);
    }

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2.4 Service

 ArticleVo findArticleById(Long id);


    @Override
    public ArticleVo findArticleById(Long id) {
        Article article = articleMapper.selectById(id);
       
        return copy(article,true,true,true,true);
    }

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package com.mszlu.blog.vo;

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 CategoryVo category;

}

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ArticleVo中的属性填充：


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

    private List<ArticleVo> copyList(List<Article> records, boolean isTag, boolean isAuthor,boolean isBody) {
        List<ArticleVo> articleVoList = new ArrayList<>();
        for (Article record : records) {
            articleVoList.add(copy(record,isTag,isAuthor,isBody,false));
        }
        return articleVoList;
    }
    private List<ArticleVo> copyList(List<Article> records, boolean isTag, boolean isAuthor,boolean isBody,boolean isCategory) {
        List<ArticleVo> articleVoList = new ArrayList<>();
        for (Article record : records) {
            articleVoList.add(copy(record,isTag,isAuthor,isBody,isCategory));
        }
        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"));
        //并不是所有的接口 都需要标签 ，作者信息
        if (isTag){
            Long articleId = article.getId();
            articleVo.setTags(tagService.findTagsByArticleId(articleId));
        }
        if (isAuthor){
            Long authorId = article.getAuthorId();
            articleVo.setAuthor(sysUserService.findUserById(authorId).getNickname());
        }
        if (isBody){
            ArticleBodyVo articleBody = findArticleBody(article.getId());
            articleVo.setBody(articleBody);
        }
        if (isCategory){
            CategoryVo categoryVo = findCategory(article.getCategoryId());
            articleVo.setCategory(categoryVo);
        }
        return articleVo;
    }

    @Autowired
    private CategoryService categoryService;

    private CategoryVo findCategory(Long categoryId) {
        return categoryService.findCategoryById(categoryId);
    }

    @Autowired
    private ArticleBodyMapper articleBodyMapper;

    private ArticleBodyVo findArticleBody(Long articleId) {
        LambdaQueryWrapper<ArticleBody> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(ArticleBody::getArticleId,articleId);
        ArticleBody articleBody = articleBodyMapper.selectOne(queryWrapper);
        ArticleBodyVo articleBodyVo = new ArticleBodyVo();
        articleBodyVo.setContent(articleBody.getContent());
        return articleBodyVo;
    }

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package com.mszlu.blog.vo;

import lombok.Data;

@Data
public class CategoryVo {

    private Long id;

    private String avatar;

    private String categoryName;
}

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package com.mszlu.blog.vo;

import lombok.Data;

@Data
public class ArticleBodyVo {

    private String content;
}

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package com.mszlu.blog.service;

import com.mszlu.blog.vo.CategoryVo;


public interface CategoryService {

    CategoryVo findCategoryById(Long id);
}

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package com.mszlu.blog.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.mszlu.blog.dao.mapper.CategoryMapper;
import com.mszlu.blog.dao.pojo.Category;
import com.mszlu.blog.service.CategoryService;
import com.mszlu.blog.vo.CategoryVo;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;


@Service
public class CategoryServiceImpl implements CategoryService {
    @Autowired
    private CategoryMapper categoryMapper;

    @Override
    public CategoryVo findCategoryById(Long id){
        Category category = categoryMapper.selectById(id);
        CategoryVo categoryVo = new CategoryVo();
        BeanUtils.copyProperties(category,categoryVo);
        return categoryVo;
    }
}

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package com.mszlu.blog.dao.mapper;

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

public interface ArticleBodyMapper extends BaseMapper<ArticleBody> {
}

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package com.mszlu.blog.dao.mapper;

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

public interface CategoryMapper extends BaseMapper<Category> {
}

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2.5 测试

3. 使用线程池更新阅读次数

3.1 线程池配置

package com.mszlu.blog.config;

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;

@Configuration
@EnableAsync
public class ThreadPoolConfig {

    @Bean("taskExecutor")
    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("码神之路博客项目");
        // 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;
    }
}

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3.1 使用

package com.mszlu.blog.service;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.mszlu.blog.dao.mapper.ArticleMapper;
import com.mszlu.blog.dao.pojo.Article;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;

@Component
public class ThreadService {


    @Async("taskExecutor")
    public void updateViewCount(ArticleMapper articleMapper,Article article){

        Article articleUpdate = new Article();
        articleUpdate.setViewCounts(article.getViewCounts() + 1);
        LambdaQueryWrapper<Article> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(Article::getId,article.getId());
        queryWrapper.eq(Article::getViewCounts,article.getViewCounts());
        articleMapper.update(articleUpdate,queryWrapper);
        try {
            //睡眠5秒 证明不会影响主线程的使用
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

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    @Autowired
    private ThreadService threadService;

    @Override
    public ArticleVo findArticleById(Long id) {
        Article article = articleMapper.selectById(id);
        threadService.updateViewCount(articleMapper,article);
        return copy(article,true,true,true,true);
    }

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3.3 测试

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

# 1. ThreadLocal内存泄漏

# 2. 文章详情

# 2.1 接口说明

# 2.2 涉及到的表

# 2.3 Controller

# 2.4 Service

# 2.5 测试

# 3. 使用线程池 更新阅读次数

# 3.1 线程池配置

# 3.1 使用

# 3.3 测试

1. ThreadLocal内存泄漏

2. 文章详情

2.1 接口说明

2.2 涉及到的表

2.3 Controller

2.4 Service

2.5 测试

3. 使用线程池更新阅读次数

3.1 线程池配置

3.1 使用

3.3 测试