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class="content index posts-expand"><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/85682d75/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/85682d75/" class="post-title-link" itemprop="url">Redis数据结构</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2020-04-28 10:44:01" itemprop="dateCreated datePublished" datetime="2020-04-28T10:44:01+08:00">2020-04-28</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/Redis/" itemprop="url" rel="index"><span itemprop="name">Redis</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/85682d75/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/85682d75/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>1.2k</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>1 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><h2 id="Redis数据类型简介"><a href="#Redis数据类型简介" class="headerlink" title="Redis数据类型简介"></a>Redis数据类型简介</h2><blockquote><p><a href="https://redis.io/topics/data-types-intro" target="_blank" rel="noopener">Introduction to Redis data types</a></p></blockquote><h3 id="Redis支持的所有数据结构列表"><a href="#Redis支持的所有数据结构列表" class="headerlink" title="Redis支持的所有数据结构列表"></a>Redis支持的所有数据结构列表</h3><ul><li><a href="https://redis.io/topics/data-types-intro#redis-strings" target="_blank" rel="noopener">String</a>: 字符串；</li><li><a href="https://redis.io/topics/data-types-intro#redis-lists" target="_blank" rel="noopener">List</a>: 根据插入顺序排序的字符串元素集合，基本上是一个双向链表；</li><li><a href="https://redis.io/topics/data-types-intro#redis-sets" target="_blank" rel="noopener">Set</a>: 不重复且无序的字符串元素的集合；</li><li><a href="https://redis.io/topics/data-types-intro#redis-sorted-sets" target="_blank" rel="noopener">SortedSet</a>: 排序集，类似于<code>Set</code>，但每个字符串元素都与一个浮点数（称为<code>score</code>）相关联，元素总是按<code>score</code>排序，因此与<code>Set</code>不同，可以检索一系列元素（例如，您可能会问：给我前10个，或后10个）；</li><li><a href="https://redis.io/topics/data-types-intro#redis-hashes" target="_blank" rel="noopener">Hash</a>: 是由与值关联的字段组成的映射，key 和 value 都是字符串；</li><li><a href="https://redis.io/topics/data-types-intro#bitmaps" target="_blank" rel="noopener">Bitmap(Bit array)</a>: 通过特殊的命令，你可以将 String 值当作一系列 bits 处理：可以设置和清除单独的 bits，数出所有设为 1 的 bits 的数量，找到最前的被设为 1 或 0 的 bit，等等</li><li><a href="https://redis.io/topics/data-types-intro#hyperloglogs" target="_blank" rel="noopener">HyperLogLog</a>: 用于估计<code>Set</code>中元素数量的的的概率数据结构;</li><li><a href="https://redis.io/topics/streams-intro" target="_blank" rel="noopener">Stream (Redis 5.0+)</a>: 一种更抽象的日志数据类型：就像一个日志文件一样，总是以仅追加的方式操作，Redis的stream就是一种append only的数据类型。</li></ul><p><strong>Redis key 的大小最大为 512MB</strong></p><div class="post-button"> <a class="btn" href="/posts/85682d75/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/8baae715/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/8baae715/" class="post-title-link" itemprop="url">深入分析Synchronized原理</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2020-03-14 17:11:35" itemprop="dateCreated datePublished" datetime="2020-03-14T17:11:35+08:00">2020-03-14</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/Java%E5%9F%BA%E7%A1%80/" itemprop="url" rel="index"><span itemprop="name">Java基础</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/8baae715/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/8baae715/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>14k</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>13 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><p>记得开始学习Java的时候，一遇到多线程情况就使用synchronized，相对于当时的我们来说synchronized是这么的神奇而又强大，那个时候我们赋予它一个名字“同步”，也成为了我们解决多线程情况的百试不爽的良药。但是，随着学习的进行我们知道在JDK1.5之前synchronized是一个重量级锁，相对于j.u.c.Lock，它会显得那么笨重，以至于我们认为它不是那么的高效而慢慢摒弃它。<br>不过，随着Javs SE 1.6对synchronized进行的各种优化后，synchronized并不会显得那么重了。下面来一起探索synchronized的基本使用、实现机制、Java是如何对它进行了优化、锁优化机制、锁的存储结构等升级过程。</p><h2 id="1-基本使用"><a href="#1-基本使用" class="headerlink" title="1 基本使用"></a>1 基本使用</h2><p>Synchronized是Java中解决并发问题的一种最常用的方法，也是最简单的一种方法。Synchronized的作用主要有三个：</p><blockquote><ol><li>原子性：确保线程互斥的访问同步代码；</li><li>可见性：保证共享变量的修改能够及时可见，其实是通过Java内存模型中的 “<strong>对一个变量unlock操作之前，必须要同步到主内存中；如果对一个变量进行lock操作，则将会清空工作内存中此变量的值，在执行引擎使用此变量前，需要重新从主内存中load操作或assign操作初始化变量值</strong>” 来保证的；</li><li>有序性：有效解决重排序问题，即 “一个unlock操作先行发生(happen-before)于后面对同一个锁的lock操作”；</li></ol></blockquote><p>从语法上讲，Synchronized可以把任何一个非null对象作为”锁”，在HotSpot JVM实现中，<strong>锁有个专门的名字：对象监视器（Object Monitor）</strong>。<br>Synchronized总共有三种用法：</p><div class="post-button"> <a class="btn" href="/posts/8baae715/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/cd7a25a4/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/cd7a25a4/" class="post-title-link" itemprop="url">Java7和Java8中的ConcurrentHashMap原理解析</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2020-02-20 11:33:32" itemprop="dateCreated datePublished" datetime="2020-02-20T11:33:32+08:00">2020-02-20</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90/" itemprop="url" rel="index"><span itemprop="name">源码分析</span></a></span> ， <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90/Java/" itemprop="url" rel="index"><span itemprop="name">Java</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/cd7a25a4/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/cd7a25a4/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>24k</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>22 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><h2 id="1-Java7中ConcurrentHashMap"><a href="#1-Java7中ConcurrentHashMap" class="headerlink" title="1. Java7中ConcurrentHashMap"></a>1. Java7中ConcurrentHashMap</h2><p>ConcurrentHashMap 和 HashMap 思路是差不多的，但是因为它支持并发操作，所以要复杂一些。<br>整个 ConcurrentHashMap 由一个个 Segment 组成，Segment 代表”部分“或”一段“的意思，所以很多地方都会将其描述为<strong>分段锁</strong>。注意，行文中，我很多地方用了<strong>“槽”</strong>来代表一个 segment。<br>简单理解就是，ConcurrentHashMap 是一个 Segment 数组，Segment 通过继承 ReentrantLock 来进行加锁，所以每次需要加锁的操作锁住的是一个 segment，这样只要保证每个 Segment 是线程安全的，也就实现了全局的线程安全。</p><p><img data-src="/images/pasted-61.png" alt="upload successful"></p><p><strong>concurrencyLevel</strong>：并行级别、并发数、Segment 数，怎么翻译不重要，理解它。默认是 16，也就是说 ConcurrentHashMap 有 16 个 Segments，所以理论上，这个时候，最多可以同时支持 16 个线程并发写，只要它们的操作分别分布在不同的 Segment 上。这个值可以在初始化的时候设置为其他值，但是一旦初始化以后，它是不可以扩容的。<br>再具体到每个 Segment 内部，其实每个 Segment 很像之前介绍的 HashMap，不过它要保证线程安全，所以处理起来要麻烦些。</p><h3 id="1-1-初始化"><a href="#1-1-初始化" class="headerlink" title="1.1. 初始化"></a>1.1. 初始化</h3><div class="post-button"> <a class="btn" href="/posts/cd7a25a4/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/9cb319e/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/9cb319e/" class="post-title-link" itemprop="url">Java7和Java8中的HashMap原理解析</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2020-02-20 11:05:11" itemprop="dateCreated datePublished" datetime="2020-02-20T11:05:11+08:00">2020-02-20</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90/" itemprop="url" rel="index"><span itemprop="name">源码分析</span></a></span> ， <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90/Java/" itemprop="url" rel="index"><span itemprop="name">Java</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/9cb319e/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/9cb319e/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>11k</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>10 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><p>HashMap可能是面试的时候必问的题目了，面试官为什么都偏爱拿这个问应聘者？因为HashMap它的设计结构和原理比较有意思，它既可以考初学者对Java集合的了解又可以深度的发现应聘者的数据结构功底。<br>阅读前提：本文分析的是源码，所以至少读者要熟悉它们的接口使用，同时，对于并发，读者至少要知道CAS、ReentrantLock、Unsafe操作这几个基本的知识，文中不会对这些知识进行介绍。Java8用到了红黑树，不过本文不会进行展开，感兴趣的读者请自行查找相关资料。</p><h2 id="1-Java7中HashMap"><a href="#1-Java7中HashMap" class="headerlink" title="1. Java7中HashMap"></a>1. Java7中HashMap</h2><p>HashMap是最简单的，一来我们非常熟悉，二来就是它不支持并发操作，所以源码也非常简单。<br>首先，我们用下面这张图来介绍HashMap的结构。</p><p><img data-src="/images/pasted-63.png" alt="upload successful"></p><p>大方向上，HashMap 里面是一个数组，然后数组中每个元素是一个单向链表。为什么是这种的结构，这涉及到数据结构方面的知识了。</p><div class="post-button"> <a class="btn" href="/posts/9cb319e/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/3a646236/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/3a646236/" class="post-title-link" itemprop="url">调研|5种分布式事务解决方案优缺点对比</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2020-02-19 17:33:03" itemprop="dateCreated datePublished" datetime="2020-02-19T17:33:03+08:00">2020-02-19</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E6%8A%80%E6%9C%AF%E8%A7%A3%E5%86%B3%E6%96%B9%E6%A1%88/" itemprop="url" rel="index"><span itemprop="name">技术解决方案</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/3a646236/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/3a646236/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>5.3k</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>5 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><h2 id="背景"><a href="#背景" class="headerlink" title="背景"></a>背景</h2><p>分布式事务是企业集成中的一个技术难点，也是每一个分布式系统架构中都会涉及到的一个东西，特别是在微服务架构中，几乎可以说是无法避免。</p><h3 id="ACID"><a href="#ACID" class="headerlink" title="ACID"></a>ACID</h3><p>指数据库事务正确执行的四个基本要素：</p><ul><li><strong>原子性（Atomicity）</strong></li><li><strong>一致性（Consistency）</strong></li><li><strong>隔离性（Isolation）</strong></li><li><strong>持久性（Durability）</strong></li></ul><div class="post-button"> <a class="btn" href="/posts/3a646236/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/96e108be/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/96e108be/" class="post-title-link" itemprop="url">常用的分布式事务解决方案</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2020-02-19 17:11:30" itemprop="dateCreated datePublished" datetime="2020-02-19T17:11:30+08:00">2020-02-19</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E6%8A%80%E6%9C%AF%E8%A7%A3%E5%86%B3%E6%96%B9%E6%A1%88/" itemprop="url" rel="index"><span itemprop="name">技术解决方案</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/96e108be/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/96e108be/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>13k</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>12 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><blockquote><p>众所周知，数据库能实现<strong>本地事务</strong>，也就是在<strong>同一个数据库中</strong>，你可以允许一组操作要么全都正确执行，要么全都不执行。这里特别强调了<strong>本地事务</strong>，也就是目前的数据库只能支持同一个数据库中的事务。但现在的系统往往采用微服务架构，业务系统拥有独立的数据库，因此就出现了跨多个数据库的事务需求，这种事务即为“分布式事务”。那么在目前数据库不支持跨库事务的情况下，我们应该如何实现分布式事务呢？本文首先会为大家梳理分布式事务的基本概念和理论基础，然后介绍几种目前常用的分布式事务解决方案。废话不多说，那就开始吧～</p></blockquote><h2 id="什么是事务"><a href="#什么是事务" class="headerlink" title="什么是事务?"></a>什么是事务?</h2><p>事务由一组操作构成，我们希望这组操作能够全部正确执行，如果这一组操作中的任意一个步骤发生错误，那么就需要回滚之前已经完成的操作。也就是同一个事务中的所有操作，要么全都正确执行，要么全都不要执行。</p><h2 id="事务的四大特性-ACID"><a href="#事务的四大特性-ACID" class="headerlink" title="事务的四大特性 ACID"></a>事务的四大特性 ACID</h2><p>说到事务，就不得不提一下事务著名的四大特性。</p><div class="post-button"> <a class="btn" href="/posts/96e108be/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/a4427452/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/a4427452/" class="post-title-link" itemprop="url">一文告诉你Spring是如何利用"三级缓存"巧妙解决Bean的循环依赖问题的</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2020-02-19 14:43:09" itemprop="dateCreated datePublished" datetime="2020-02-19T14:43:09+08:00">2020-02-19</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90/" itemprop="url" rel="index"><span itemprop="name">源码分析</span></a></span> ， <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90/Spring/" itemprop="url" rel="index"><span itemprop="name">Spring</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/a4427452/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/a4427452/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>26k</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>24 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><h2 id="前言"><a href="#前言" class="headerlink" title="前言"></a>前言</h2><p><strong>循环依赖：就是N个类循环(嵌套)引用</strong>。通俗的讲就是N个Bean互相引用对方，最终形成<code>闭环</code>。用一副经典的图示可以表示成这样（A、B、C都代表对象，虚线代表引用关系）：<br><img data-src="/images/pasted-50.png" alt="upload successful"></p><blockquote><p>注意：其实可以N=1，也就是极限情况的循环依赖：<code>自己依赖自己</code><br>另需注意：这里指的循环引用不是方法之间的循环调用，<strong>而是对象的相互依赖关系</strong>。（方法之间循环调用若有出口也是能够正常work的）</p></blockquote><p>可以设想一下这个场景：如果在日常开发中我们用new对象的方式，若构造函数之间发生这种<strong>循环依赖</strong>的话，程序会在运行时一直循环调用<strong>最终导致内存溢出</strong>，示例代码如下：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Main</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> System.out.println(<span class="keyword">new</span> A());</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">A</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="title">A</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">new</span> B();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">B</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="title">B</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">new</span> A();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><div class="post-button"> <a class="btn" href="/posts/a4427452/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/36f079e3/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/36f079e3/" class="post-title-link" itemprop="url">Java线上CPU占用过高问题排查思路</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2019-10-31 17:09:00" itemprop="dateCreated datePublished" datetime="2019-10-31T17:09:00+08:00">2019-10-31</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E9%97%AE%E9%A2%98%E6%8E%92%E6%9F%A5/" itemprop="url" rel="index"><span itemprop="name">问题排查</span></a></span> ， <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/%E9%97%AE%E9%A2%98%E6%8E%92%E6%9F%A5/Java/" itemprop="url" rel="index"><span itemprop="name">Java</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/36f079e3/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/36f079e3/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>2.1k</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>2 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><h4 id="一、根据-Java-进程-ID，用-ps-或-top-命令查询出-CPU-占用率高的线程"><a href="#一、根据-Java-进程-ID，用-ps-或-top-命令查询出-CPU-占用率高的线程" class="headerlink" title="一、根据 Java 进程 ID，用 ps 或 top 命令查询出 CPU 占用率高的线程"></a>一、根据 Java 进程 ID，用 <code>ps</code> 或 <code>top</code> 命令查询出 CPU 占用率高的线程</h4><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">ps -mp <pid> -o THREAD,tid,time | sort -rn | more // (sort -rn 已数值的方式进行逆序排列)</span><br><span class="line">// 或top -Hp <pid></span><br><span class="line">top - 08:31:16 up 30 min, 0 users, load average: 0.75, 0.59, 0.35</span><br><span class="line">Threads: 11 total, 1 running, 10 sleeping, 0 stopped, 0 zombie</span><br><span class="line"><span class="meta">%</span><span class="bash">Cpu(s): 3.5 us, 0.6 sy, 0.0 ni, 95.9 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st</span></span><br><span class="line">KiB Mem: 2046460 total, 1924856 used, 121604 free, 14396 buffers</span><br><span class="line">KiB Swap: 1048572 total, 0 used, 1048572 free. 1192532 cached Mem</span><br><span class="line"></span><br><span class="line"> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND</span><br><span class="line"> 10 root 20 0 2557160 289824 15872 R 79.3 14.2 0:41.49 java</span><br><span class="line"> 11 root 20 0 2557160 289824 15872 S 13.2 14.2 0:06.78 java</span><br></pre></td></tr></table></figure><h4 id="二、转换线程-ID-为-16-进制"><a href="#二、转换线程-ID-为-16-进制" class="headerlink" title="二、转换线程 ID 为 16 进制"></a>二、转换线程 ID 为 16 进制</h4><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">printf "%x\n" <tid></span><br><span class="line">// printf "%x\n" 10</span><br><span class="line">// a</span><br></pre></td></tr></table></figure><h4 id="三、利用-JDK-提供的工具-jstack-打印导出线程信息"><a href="#三、利用-JDK-提供的工具-jstack-打印导出线程信息" class="headerlink" title="三、利用 JDK 提供的工具 jstack 打印导出线程信息"></a>三、利用 JDK 提供的工具 <code>jstack</code> 打印导出线程信息</h4><div class="post-button"> <a class="btn" href="/posts/36f079e3/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/5ec24585/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/5ec24585/" class="post-title-link" itemprop="url">Spring Boot添加admin监控</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2017-08-17 22:46:57" itemprop="dateCreated datePublished" datetime="2017-08-17T22:46:57+08:00">2017-08-17</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/Spring/" itemprop="url" rel="index"><span itemprop="name">Spring</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/5ec24585/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/5ec24585/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>2.2k</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>2 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><h2 id="什么是Spring-Boot-Admin？"><a href="#什么是Spring-Boot-Admin？" class="headerlink" title="什么是Spring Boot Admin？"></a>什么是Spring Boot Admin？</h2><p>Spring Boot Admin是一个用于管理和监控Spring Boot应用程序的Web应用程序。应用程序通过我们的Spring Boot Admin Client（通过HTTP）注册，或者使用Spring Cloud（例如Eureka, Consul）进行注册。</p><h2 id="入门"><a href="#入门" class="headerlink" title="入门"></a>入门</h2><h3 id="设置Admin-Server服务"><a href="#设置Admin-Server服务" class="headerlink" title="设置Admin Server服务"></a>设置Admin Server服务</h3><ul><li>添加<code>Spring Boot Admin Server starter</code>依赖:</li></ul><div class="post-button"> <a class="btn" href="/posts/5ec24585/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><article itemscope itemtype="http://schema.org/Article" class="post-block" lang="zh-CN"><link itemprop="mainEntityOfPage" href="http://zhangfei.men/posts/69b13214/"><span hidden itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="image" content="https://avatars2.githubusercontent.com/u/16345433?s=40&v=4"><meta itemprop="name" content="Zhang Fei"><meta itemprop="description" content="胡编一通，乱写一气"></span><span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="Zhangfei's Blog"></span><header class="post-header"><h2 class="post-title" itemprop="name headline"> <a href="/posts/69b13214/" class="post-title-link" itemprop="url">Spring Retry</a></h2><div class="post-meta"><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-calendar"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建时间：2017-08-14 23:50:34" itemprop="dateCreated datePublished" datetime="2017-08-14T23:50:34+08:00">2017-08-14</time></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-folder"></i></span> <span class="post-meta-item-text">分类于</span> <span itemprop="about" itemscope itemtype="http://schema.org/Thing"><a href="/categories/Spring/" itemprop="url" rel="index"><span itemprop="name">Spring</span></a></span></span><span class="post-meta-item"><span class="post-meta-item-icon"><i class="far fa-comment"></i></span> <span class="post-meta-item-text">Valine：</span><a title="valine" href="/posts/69b13214/#valine-comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/posts/69b13214/" itemprop="commentCount"></span></a></span><br><span class="post-meta-item" title="本文字数"><span class="post-meta-item-icon"><i class="far fa-file-word"></i></span> <span class="post-meta-item-text">本文字数：</span> <span>999</span></span><span class="post-meta-item" title="阅读时长"><span class="post-meta-item-icon"><i class="far fa-clock"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span>1 分钟</span></span></div></header><div class="post-body" itemprop="articleBody"><h2 id="使用场景"><a href="#使用场景" class="headerlink" title="使用场景"></a>使用场景</h2><p>在实际工作中,重处理是一个非常常见的场景,比如:发送消息失败,调用远程服务失败,争抢锁失败,等等,这些错误可能是因为网络波动造成的,等待过后重处理就能成功.通常来说,会用try/catch,while循环之类的语法来进行重处理,但是这样的做法缺乏统一性,并且不是很方便,要多写很多代码.然而spring-retry却可以通过注解,在不入侵原有业务逻辑代码的方式下,优雅的实现重处理功能.</p><h2 id="Maven-Dependencies"><a href="#Maven-Dependencies" class="headerlink" title="Maven Dependencies"></a>Maven Dependencies</h2><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>org.springframework.retry<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>spring-retry<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>1.2.5.RELEASE<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure><h2 id="如何启用"><a href="#如何启用" class="headerlink" title="如何启用"></a>如何启用</h2><div class="post-button"> <a class="btn" href="/posts/69b13214/#more" rel="contents">阅读全文 »</a></div></div><footer class="post-footer"><div class="post-eof"></div></footer></article><nav class="pagination"> <span class="page-number current">1</span><a class="page-number" href="/page/2/">2</a><span class="space">…</span><a class="page-number" href="/page/4/">4</a><a class="extend next" 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