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<?xml version="1.0" encoding="utf-8"?>
<rss xmlns:atom="http://www.w3.org/2005/Atom" version="2.0">
<channel>
<title>JJMeg's blog</title>
<link>https://jjmeg.github.io/</link>
<description>MemE 是一个强大且可高度定制的 GoHugo 博客主题，专为个人博客设计。</description>
<generator>Hugo 0.74.3 https://gohugo.io/</generator>
<language>zh-CN</language>
<managingEditor>jjmeg.he@gmail.com (JJMeg)</managingEditor>
<webMaster>jjmeg.he@gmail.com (JJMeg)</webMaster>
<copyright>[CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/deed.zh)</copyright>
<lastBuildDate>Tue, 22 Sep 2020 23:28:26 +0800</lastBuildDate>
<atom:link rel="self" type="application/rss+xml" href="https://jjmeg.github.io/rss.xml" />
<item>
<title>2020三季度</title>
<link>https://jjmeg.github.io/posts/2020-autumn/</link>
<guid isPermaLink="true">https://jjmeg.github.io/posts/2020-autumn/</guid>
<pubDate>Tue, 22 Sep 2020 20:24:37 +0800</pubDate>
<author>jjmeg.he@gmail.com (JJMeg)</author>
<copyright>[CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/deed.zh)</copyright>
<description><![CDATA[<p><center>🕛</center></p>
<p style="text-indent:2em">2020年的第三季度，发生了很多事情，同事们相继离职，架构变动，经历二次架构变动，害，都挤在这个季度爆发了；</p>
<p style="text-indent:2em">当然，我也如愿争取到新的机会，进入新的团队，和一年前的完全不一样的技术栈，在这一个季度内，完成了0-1的重构项目，想想人还是需要压力的；</p>
<p style="text-indent:2em">回顾前一年的业务和技术，思考越来越少，近三个月，我终于体会到别人说的做业务很累，on call嘛，害，有点享受这种忙碌的状态；</p>
<p style="text-indent:2em">如愿的回到喜欢的方向，因为一年的技术上的gap，加了很多班调整适应，如愿加班，就是这个感觉吧；</p>
<p style="text-indent:2em">一整年思考缓慢，突然忙起来还有些不太适应；</p>
<p style="text-indent:2em">脾气好了嘛？- 没有</p>
<p style="text-indent:2em">做事井井有条了嘛？- 有一点吧</p>
<p style="text-indent:2em">现在最缺的就是觉了吧。</p>
<p style="text-indent:2em">2020年第四季度</p>
<p style="text-indent:2em">Enjoy it!</p>
]]></description>
<category domain="https://jjmeg.github.io/tags/%E7%A2%8E%E5%BF%B5/">碎念</category>
</item>
<item>
<title>FastJson 反序列化部分字段为 Null</title>
<link>https://jjmeg.github.io/posts/fastjson-field-null/</link>
<guid isPermaLink="true">https://jjmeg.github.io/posts/fastjson-field-null/</guid>
<pubDate>Mon, 20 Jul 2020 18:25:51 +0800</pubDate>
<author>jjmeg.he@gmail.com (JJMeg)</author>
<copyright>[CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/deed.zh)</copyright>
<description><![CDATA[
<p><center>⚠ 使用 FastJson 将 json 文件反序列化为 JavaBean 出现字段缺失 ⚠</center></p>
<h3 id="问题复现">问题复现</h3>
<p>FastJson 版本：1.2.70</p>
<div class="highlight"><div class="chroma">
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<pre class="chroma"><code class="language-xml" data-lang="xml"><span class="nt"><dependency></span>
<span class="nt"><groupId></span>com.alibaba<span class="nt"></groupId></span>
<span class="nt"><artifactId></span>fastjson<span class="nt"></artifactId></span>
<span class="nt"><version></span>1.2.70<span class="nt"></version></span>
<span class="nt"></dependency></span></code></pre></td></tr></table>
</div>
</div>
<p>json 内容</p>
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<pre class="chroma"><code class="language-json" data-lang="json"><span class="p">{</span>
<span class="nt">"properties"</span><span class="p">:</span> <span class="p">{</span>
<span class="nt">"jobName"</span><span class="p">:</span> <span class="s2">"this_is_a_test"</span><span class="p">,</span>
<span class="nt">"description"</span><span class="p">:</span> <span class="s2">"for test json"</span>
<span class="p">},</span>
<span class="nt">"task"</span><span class="p">:</span> <span class="p">[</span>
<span class="p">{</span>
<span class="nt">"name"</span><span class="p">:</span> <span class="s2">"task_1"</span><span class="p">,</span>
<span class="nt">"type"</span><span class="p">:</span> <span class="s2">"test"</span><span class="p">,</span>
<span class="nt">"className"</span><span class="p">:</span> <span class="s2">"com.jjmeg.Task"</span><span class="p">,</span>
<span class="nt">"args"</span><span class="p">:</span> <span class="p">{</span>
<span class="nt">"topic"</span><span class="p">:</span> <span class="s2">"mockTopic"</span><span class="p">,</span>
<span class="nt">"username"</span><span class="p">:</span> <span class="s2">"mockPin"</span><span class="p">,</span>
<span class="nt">"password"</span><span class="p">:</span> <span class="s2">"mockPasswd"</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="p">]</span>
<span class="p">}</span></code></pre></td></tr></table>
</div>
</div>
<p>设计的 JavaBean：</p>
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<pre class="chroma"><code class="language-Java" data-lang="Java"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Flow</span> <span class="o">{</span>
<span class="kd">public</span> <span class="n">Map</span><span class="o"><</span><span class="n">String</span><span class="o">,</span> <span class="n">String</span><span class="o">></span> <span class="n">properties</span><span class="o">;</span>
<span class="kd">public</span> <span class="n">List</span><span class="o"><</span><span class="n">Task</span><span class="o">></span> <span class="n">task</span><span class="o">;</span>
<span class="nd">@Override</span>
<span class="kd">public</span> <span class="n">String</span> <span class="nf">toString</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="s">"Flow{"</span> <span class="o">+</span>
<span class="s">"properties='"</span> <span class="o">+</span> <span class="n">properties</span> <span class="o">+</span> <span class="sc">'\''</span> <span class="o">+</span>
<span class="s">", task='"</span> <span class="o">+</span> <span class="n">task</span> <span class="o">+</span><span class="sc">'\''</span> <span class="o">+</span>
<span class="sc">'}'</span><span class="o">;</span>
<span class="o">}</span>
<span class="o">}</span></code></pre></td></tr></table>
</div>
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<pre class="chroma"><code class="language-java" data-lang="java"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Task</span> <span class="kd">implements</span> <span class="n">Serializable</span> <span class="o">{</span>
<span class="kd">public</span> <span class="n">String</span> <span class="n">name</span><span class="o">;</span>
<span class="kd">public</span> <span class="n">String</span> <span class="n">type</span><span class="o">;</span>
<span class="kd">public</span> <span class="n">String</span> <span class="n">className</span><span class="o">;</span>
<span class="kd">public</span> <span class="n">Map</span><span class="o"><</span><span class="n">String</span><span class="o">,</span> <span class="n">String</span><span class="o">></span> <span class="n">args</span><span class="o">;</span>
<span class="c1">// 含参构造函数、无默认构造函数
</span><span class="c1"></span> <span class="kd">public</span> <span class="nf">Task</span><span class="o">(</span><span class="n">String</span> <span class="n">name</span><span class="o">)</span> <span class="o">{</span>
<span class="k">this</span><span class="o">.</span><span class="na">name</span> <span class="o">=</span> <span class="n">name</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span><span class="o">[]</span> <span class="n">args</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">ConfigurationException</span><span class="o">,</span> <span class="n">IOException</span> <span class="o">{</span>
<span class="n">String</span> <span class="n">text</span> <span class="o">=</span> <span class="n">IOUtils</span><span class="o">.</span><span class="na">toString</span><span class="o">(</span><span class="k">new</span> <span class="n">FileInputStream</span><span class="o">(</span><span class="n">filePath</span><span class="o">),</span> <span class="n">StandardCharsets</span><span class="o">.</span><span class="na">UTF_8</span><span class="o">);</span>
<span class="n">Flow</span> <span class="n">flow</span> <span class="o">=</span> <span class="n">JSON</span><span class="o">.</span><span class="na">parseObject</span><span class="o">(</span><span class="n">text</span><span class="o">,</span> <span class="n">Flow</span><span class="o">.</span><span class="na">class</span><span class="o">);</span>
<span class="o">}</span>
<span class="o">}</span></code></pre></td></tr></table>
</div>
</div>
<p>运行结果中，Task的内容有缺失：</p>
<div class="highlight"><div class="chroma">
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<pre class="chroma"><code><span class="lnt">1
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<pre class="chroma"><code class="language-shell" data-lang="shell">Task<span class="o">{</span><span class="nv">name</span><span class="o">=</span><span class="s1">'task_1'</span>, <span class="nv">type</span><span class="o">=</span><span class="s1">'null'</span>, <span class="nv">className</span><span class="o">=</span><span class="s1">'null'</span>, <span class="nv">args</span><span class="o">=</span>null<span class="o">}</span></code></pre></td></tr></table>
</div>
</div>
<h3 id="问题原因">问题原因：</h3>
<p>FastJson 反序列过程中，使用默认的构造函数创建实例，在没有默认构造函数情况下，FastJson 使用含参的构造函数。</p>
<p>在 <code>Task</code> 类中，构造函数被重写为 <code>Task(String name)</code>，则只有 <code>name</code> 字段被赋值，同理，该示例中，只定义含三个参数的构造函数 <code>public Task(String name, String className, String type)</code> ，反序列化的 <code>Task</code> 对象的 <code>args</code> 属性为 <code>null</code>。</p>
<h3 id="解决办法">解决办法：</h3>
<p>添加无参构造函数或含所有参数的构造函数</p>
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<pre class="chroma"><code class="language-Java" data-lang="Java"><span class="c1">// 无参函数
</span><span class="c1"></span><span class="kd">public</span> <span class="nf">Task</span><span class="o">()</span> <span class="o">{</span>
<span class="o">}</span>
<span class="c1">// 含所有参数的构造函数
</span><span class="c1"></span><span class="kd">public</span> <span class="nf">Task</span><span class="o">(</span><span class="n">String</span> <span class="n">name</span><span class="o">,</span> <span class="n">String</span> <span class="n">className</span><span class="o">,</span> <span class="n">String</span> <span class="n">type</span><span class="o">,</span> <span class="n">Map</span><span class="o"><</span><span class="n">String</span><span class="o">,</span> <span class="n">String</span><span class="o">></span> <span class="n">args</span><span class="o">)</span> <span class="o">{</span>
<span class="k">this</span><span class="o">.</span><span class="na">name</span> <span class="o">=</span> <span class="n">name</span><span class="o">;</span>
<span class="k">this</span><span class="o">.</span><span class="na">args</span> <span class="o">=</span> <span class="n">args</span><span class="o">;</span>
<span class="k">this</span><span class="o">.</span><span class="na">type</span> <span class="o">=</span> <span class="n">type</span><span class="o">;</span>
<span class="k">this</span><span class="o">.</span><span class="na">className</span> <span class="o">=</span> <span class="n">className</span><span class="o">;</span>
<span class="o">}</span></code></pre></td></tr></table>
</div>
</div>
<script src="https://utteranc.es/client.js"
repo="JJMeg/jjmeg.io.comment"
issue-term="pathname"
theme="github-light"
crossorigin="anonymous"
async>
</script>
]]></description>
</item>
<item>
<title>InnoDB 与 MyISAM 区别及适用场景</title>
<link>https://jjmeg.github.io/posts/inter/mysql/innodb-myisam-scene/</link>
<guid isPermaLink="true">https://jjmeg.github.io/posts/inter/mysql/innodb-myisam-scene/</guid>
<pubDate>Thu, 28 May 2020 13:22:47 +0800</pubDate>
<author>jjmeg.he@gmail.com (JJMeg)</author>
<copyright>[CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/deed.zh)</copyright>
<description><![CDATA[
<h3 id="1-索引结构">1. 索引结构</h3>
<p>InnoDB 和 MyISAM 都使用 B+ 树作为索引结构，区别在于叶子节点：</p>
<ul>
<li>MyISAM 的叶子节点存储的是数据记录所在的地址，MyISAM 存储数据有索引文件及数据文件，先在索引文件内找到数据的地址，<strong>称为非聚集索引</strong>，再到数据文件内找到具体的文件记录</li>
<li>InnoDB索引文件就是数据文件，主索引树的叶子节点存储的是行数据的数据页，页内存储了完整的行数据记录，<strong>称为聚集索引</strong>，辅助索引树叶子节点存储主键值</li>
</ul>
<h3 id="2-事务-锁处理及外键支持的区别">2. 事务、锁处理及外键支持的区别</h3>
<table>
<thead>
<tr>
<th></th>
<th align="center">InnoDB</th>
<th align="center">MyISAM</th>
</tr>
</thead>
<tbody>
<tr>
<td>事务处理</td>
<td align="center">事务安全</td>
<td align="center">非事务安全</td>
</tr>
<tr>
<td>锁级别</td>
<td align="center">行锁和表锁</td>
<td align="center">表锁</td>
</tr>
<tr>
<td>外键支持</td>
<td align="center">支持</td>
<td align="center">不支持</td>
</tr>
</tbody>
</table>
<h3 id="3-查询效率">3. 查询效率</h3>
<table>
<thead>
<tr>
<th align="center">InnoDB</th>
<th align="center">MyISAM</th>
</tr>
</thead>
<tbody>
<tr>
<td align="center">慢</td>
<td align="center">快</td>
</tr>
</tbody>
</table>
<p>原因：</p>
<ul>
<li>InnoDB要加载数据页到缓存内，MyISAM只缓存索引块，MyISAM较少的磁盘io</li>
<li>InnoDB映射到数据页、到行，MyISAM记录文件的offset，定位比InnoDB快</li>
<li>InnoDB需要维护版本并发控制</li>
</ul>
<h3 id="4-适用场景">4. 适用场景</h3>
<table>
<thead>
<tr>
<th align="center">InnoDB</th>
<th align="center">MyISAM</th>
</tr>
</thead>
<tbody>
<tr>
<td align="center">多读多写</td>
<td align="center">多读少写</td>
</tr>
<tr>
<td align="center">有事务</td>
<td align="center">无事务</td>
</tr>
<tr>
<td align="center">高并发</td>
<td align="center">非高并发</td>
</tr>
</tbody>
</table>
]]></description>
<category domain="https://jjmeg.github.io/tags/%E6%95%B0%E6%8D%AE%E5%BA%93/">数据库</category>
<category domain="https://jjmeg.github.io/tags/mysql/">MySQL</category>
<category domain="https://jjmeg.github.io/tags/myisam/">MyISAM</category>
</item>
<item>
<title>Kafka客户端--Go版本</title>
<link>https://jjmeg.github.io/posts/kafka-golang-client/</link>
<guid isPermaLink="true">https://jjmeg.github.io/posts/kafka-golang-client/</guid>
<pubDate>Wed, 06 May 2020 20:56:46 +0800</pubDate>
<author>jjmeg.he@gmail.com (JJMeg)</author>
<copyright>[CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/deed.zh)</copyright>
<description><![CDATA[
<p><center>「 Kafka 」</center>
分布式消息平台，用Scala实现，本项目使用Go语言实现简单的消息生产和消费。</p>
<h3 id="kafka-客户端-golang-版">Kafka 客户端 Golang 版</h3>
<table>
<thead>
<tr>
<th>project</th>
<th>feature</th>
<th>weakness</th>
</tr>
</thead>
<tbody>
<tr>
<td><a href="https://shopify.github.io/sarama">Shopify/sarama</a></td>
<td>最受欢迎</td>
<td>集群式消费难实现，不支持Context</td>
</tr>
<tr>
<td><a href="https://github.com/bsm/sarama-cluster">bsm/sarama-cluster</a></td>
<td>基于sarama补充集群式消费</td>
<td>不支持Context</td>
</tr>
<tr>
<td><a href="https://github.com/confluentinc/confluent-kafka-go">confluentinc/confluent-kafka-go</a></td>
<td></td>
<td>依赖C语言库，不支持Context</td>
</tr>
<tr>
<td><a href="https://github.com/lovoo/goka">lovoo/goka</a></td>
<td>依赖于sarama</td>
<td>不支持Context</td>
</tr>
<tr>
<td><a href="https://github.com/segmentio/kafka-go">segmentio/kafka-go</a></td>
<td>同时支持集群模式，易与软件交互</td>
<td>未正式发布，支持Context</td>
</tr>
</tbody>
</table>
<hr />
<p>下面将基于 <a href="https://github.com/Shopify/sarama" target="_blank">Shopify/sarama</a> 实现简单的消费者及生产者。</p>
<h3 id="基本数据结构">基本数据结构</h3>
<ul>
<li><p>Reporter
生产者：包含一个Producer及一个logger用于日志记录</p></li>
<li><p>Subscriber
消费者：包含一个Consumer及logger
具体实现</p></li>
</ul>
<h3 id="生产者">生产者</h3>
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<td class="lntd">
<pre class="chroma"><code class="language-Go" data-lang="Go"><span class="kn">package</span> <span class="nx">reporter</span>
<span class="kn">import</span> <span class="p">(</span>
<span class="s">"github.com/Shopify/sarama"</span>
<span class="s">"github.com/sirupsen/logrus"</span>
<span class="s">"../error_const"</span>
<span class="p">)</span>
<span class="c1">// kafka server 端配置
</span><span class="c1"></span><span class="kd">type</span> <span class="nx">KafkaCfg</span> <span class="kd">struct</span> <span class="p">{</span>
<span class="nx">Host</span> <span class="kt">string</span> <span class="s">`json:"host"`</span>
<span class="nx">Topic</span> <span class="kt">string</span> <span class="s">`json:"topic"`</span>
<span class="p">}</span>
<span class="c1">// 消息生产者数据结构
</span><span class="c1"></span><span class="kd">type</span> <span class="nx">Reporter</span> <span class="kd">struct</span> <span class="p">{</span>
<span class="nx">Producer</span> <span class="nx">sarama</span><span class="p">.</span><span class="nx">SyncProducer</span>
<span class="nx">logger</span> <span class="o">*</span><span class="nx">logrus</span><span class="p">.</span><span class="nx">Logger</span>
<span class="p">}</span>
<span class="c1">// 构造函数
</span><span class="c1"></span><span class="kd">func</span> <span class="nf">NewReporter</span><span class="p">(</span><span class="nx">cfg</span> <span class="o">*</span><span class="nx">KafkaCfg</span><span class="p">,</span> <span class="nx">log</span> <span class="o">*</span><span class="nx">logrus</span><span class="p">.</span><span class="nx">Logger</span><span class="p">)</span> <span class="o">*</span><span class="nx">Reporter</span> <span class="p">{</span>
<span class="nx">reporter</span> <span class="o">:=</span> <span class="o">&</span><span class="nx">Reporter</span><span class="p">{</span>
<span class="nx">logger</span><span class="p">:</span> <span class="nx">log</span><span class="p">,</span>
<span class="p">}</span>
<span class="nx">reporter</span><span class="p">.</span><span class="nf">setProducer</span><span class="p">(</span><span class="nx">cfg</span><span class="p">)</span>
<span class="k">return</span> <span class="nx">reporter</span>
<span class="p">}</span>
<span class="kd">func</span> <span class="p">(</span><span class="nx">reporter</span> <span class="o">*</span><span class="nx">Reporter</span><span class="p">)</span> <span class="nf">setProducer</span><span class="p">(</span><span class="nx">cfg</span> <span class="o">*</span><span class="nx">KafkaCfg</span><span class="p">)</span> <span class="p">{</span>
<span class="kd">var</span> <span class="nx">broker</span> <span class="p">=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="nx">cfg</span><span class="p">.</span><span class="nx">Host</span><span class="p">}</span>
<span class="nx">config</span> <span class="o">:=</span> <span class="nx">sarama</span><span class="p">.</span><span class="nf">NewConfig</span><span class="p">()</span>
<span class="nx">config</span><span class="p">.</span><span class="nx">Producer</span><span class="p">.</span><span class="nx">Return</span><span class="p">.</span><span class="nx">Successes</span> <span class="p">=</span> <span class="kc">true</span>
<span class="c1">// new 一个Producer
</span><span class="c1"></span> <span class="nx">producer</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">sarama</span><span class="p">.</span><span class="nf">NewSyncProducer</span><span class="p">(</span><span class="nx">broker</span><span class="p">,</span> <span class="nx">config</span><span class="p">)</span>
<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nx">reporter</span><span class="p">.</span><span class="nx">logger</span><span class="p">.</span><span class="nf">Errorf</span><span class="p">(</span><span class="nx">error_const</span><span class="p">.</span><span class="nx">InitProducerError</span><span class="p">,</span> <span class="nx">err</span><span class="p">)</span>
<span class="p">}</span>
<span class="nx">reporter</span><span class="p">.</span><span class="nx">Producer</span> <span class="p">=</span> <span class="nx">producer</span>
<span class="p">}</span>
<span class="kd">func</span> <span class="p">(</span><span class="nx">reporter</span> <span class="o">*</span><span class="nx">Reporter</span><span class="p">)</span> <span class="nf">DoReport</span><span class="p">(</span><span class="nx">topic</span> <span class="kt">string</span><span class="p">,</span> <span class="nx">msg</span> <span class="p">[]</span><span class="kt">byte</span><span class="p">)</span> <span class="p">{</span>
<span class="nx">reporter</span><span class="p">.</span><span class="nf">do</span><span class="p">(</span><span class="nx">topic</span><span class="p">,</span> <span class="nx">msg</span><span class="p">)</span>
<span class="p">}</span>
<span class="kd">func</span> <span class="p">(</span><span class="nx">reporter</span> <span class="o">*</span><span class="nx">Reporter</span><span class="p">)</span> <span class="nf">do</span><span class="p">(</span><span class="nx">topic</span> <span class="kt">string</span><span class="p">,</span> <span class="nx">msg</span> <span class="p">[]</span><span class="kt">byte</span><span class="p">)</span> <span class="p">{</span>
<span class="nx">kafkaMsg</span> <span class="o">:=</span> <span class="nf">generateProducerMessage</span><span class="p">(</span><span class="nx">topic</span><span class="p">,</span> <span class="nx">msg</span><span class="p">)</span>
<span class="nx">_</span><span class="p">,</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">reporter</span><span class="p">.</span><span class="nx">Producer</span><span class="p">.</span><span class="nf">SendMessage</span><span class="p">(</span><span class="nx">kafkaMsg</span><span class="p">)</span>
<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nx">reporter</span><span class="p">.</span><span class="nx">logger</span><span class="p">.</span><span class="nf">Errorf</span><span class="p">(</span><span class="nx">error_const</span><span class="p">.</span><span class="nx">ReportKafkaMsgError</span><span class="p">,</span> <span class="nx">err</span><span class="p">,</span> <span class="nb">string</span><span class="p">(</span><span class="nx">msg</span><span class="p">))</span>
<span class="p">}</span>
<span class="nx">reporter</span><span class="p">.</span><span class="nx">logger</span><span class="p">.</span><span class="nf">Infof</span><span class="p">(</span><span class="nx">error_const</span><span class="p">.</span><span class="nx">ReportKafkaMsgSuccess</span><span class="p">,</span> <span class="nb">string</span><span class="p">(</span><span class="nx">msg</span><span class="p">))</span>
<span class="p">}</span>
<span class="kd">func</span> <span class="nf">generateProducerMessage</span><span class="p">(</span><span class="nx">topic</span> <span class="kt">string</span><span class="p">,</span> <span class="nx">message</span> <span class="p">[]</span><span class="kt">byte</span><span class="p">)</span> <span class="o">*</span><span class="nx">sarama</span><span class="p">.</span><span class="nx">ProducerMessage</span> <span class="p">{</span>
<span class="k">return</span> <span class="o">&</span><span class="nx">sarama</span><span class="p">.</span><span class="nx">ProducerMessage</span><span class="p">{</span>
<span class="nx">Topic</span><span class="p">:</span> <span class="nx">topic</span><span class="p">,</span>
<span class="nx">Partition</span><span class="p">:</span> <span class="o">-</span><span class="mi">1</span><span class="p">,</span>
<span class="nx">Value</span><span class="p">:</span> <span class="nx">sarama</span><span class="p">.</span><span class="nf">StringEncoder</span><span class="p">(</span><span class="nx">message</span><span class="p">),</span>
<span class="p">}</span>
<span class="p">}</span></code></pre></td></tr></table>
</div>
</div>
<h3 id="消费者">消费者</h3>
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<td class="lntd">
<pre class="chroma"><code class="language-Go" data-lang="Go"><span class="kn">package</span> <span class="nx">subscriber</span>
<span class="kn">import</span> <span class="p">(</span>
<span class="s">"github.com/Shopify/sarama"</span>
<span class="s">"github.com/sirupsen/logrus"</span>
<span class="s">"../error_const"</span>
<span class="s">"../reporter"</span>
<span class="p">)</span>
<span class="kd">type</span> <span class="nx">Subscriber</span> <span class="kd">struct</span> <span class="p">{</span>
<span class="nx">Consumer</span> <span class="nx">sarama</span><span class="p">.</span><span class="nx">Consumer</span>
<span class="nx">logger</span> <span class="o">*</span><span class="nx">logrus</span><span class="p">.</span><span class="nx">Logger</span>
<span class="p">}</span>
<span class="kd">func</span> <span class="nf">NewSubscriber</span><span class="p">(</span><span class="nx">cfg</span> <span class="o">*</span><span class="nx">reporter</span><span class="p">.</span><span class="nx">KafkaCfg</span><span class="p">,</span> <span class="nx">log</span> <span class="o">*</span><span class="nx">logrus</span><span class="p">.</span><span class="nx">Logger</span><span class="p">)</span> <span class="o">*</span><span class="nx">Subscriber</span> <span class="p">{</span>
<span class="nx">subscriber</span> <span class="o">:=</span> <span class="o">&</span><span class="nx">Subscriber</span><span class="p">{</span>
<span class="nx">logger</span><span class="p">:</span> <span class="nx">log</span><span class="p">,</span>
<span class="p">}</span>
<span class="nx">subscriber</span><span class="p">.</span><span class="nf">setConsumer</span><span class="p">(</span><span class="nx">cfg</span><span class="p">)</span>
<span class="k">return</span> <span class="nx">subscriber</span>
<span class="p">}</span>
<span class="kd">func</span> <span class="p">(</span><span class="nx">subscriber</span> <span class="o">*</span><span class="nx">Subscriber</span><span class="p">)</span> <span class="nf">setConsumer</span><span class="p">(</span><span class="nx">cfg</span> <span class="o">*</span><span class="nx">reporter</span><span class="p">.</span><span class="nx">KafkaCfg</span><span class="p">)</span> <span class="p">{</span>
<span class="nx">consumer</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">sarama</span><span class="p">.</span><span class="nf">NewConsumer</span><span class="p">([]</span><span class="kt">string</span><span class="p">{</span><span class="nx">cfg</span><span class="p">.</span><span class="nx">Host</span><span class="p">},</span> <span class="kc">nil</span><span class="p">)</span>
<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="p">}</span>
<span class="nx">subscriber</span><span class="p">.</span><span class="nx">Consumer</span> <span class="p">=</span> <span class="nx">consumer</span>
<span class="p">}</span>
<span class="kd">func</span> <span class="p">(</span><span class="nx">subscriber</span> <span class="o">*</span><span class="nx">Subscriber</span><span class="p">)</span> <span class="nf">Consume</span><span class="p">(</span><span class="nx">topic</span> <span class="kt">string</span><span class="p">,</span> <span class="nx">ch</span> <span class="kd">chan</span> <span class="kt">string</span><span class="p">)</span> <span class="p">{</span>
<span class="k">defer</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span>
<span class="k">if</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">subscriber</span><span class="p">.</span><span class="nx">Consumer</span><span class="p">.</span><span class="nf">Close</span><span class="p">();</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nx">subscriber</span><span class="p">.</span><span class="nx">logger</span><span class="p">.</span><span class="nf">Errorf</span><span class="p">(</span><span class="nx">error_const</span><span class="p">.</span><span class="nx">SubcriberCloseConsumerError</span><span class="p">,</span> <span class="nx">err</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}()</span>
<span class="c1">// 获取所有 partition
</span><span class="c1"></span> <span class="nx">partitionList</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">subscriber</span><span class="p">.</span><span class="nx">Consumer</span><span class="p">.</span><span class="nf">Partitions</span><span class="p">(</span><span class="nx">topic</span><span class="p">)</span>
<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nx">subscriber</span><span class="p">.</span><span class="nx">logger</span><span class="p">.</span><span class="nf">Errorf</span><span class="p">(</span><span class="nx">error_const</span><span class="p">.</span><span class="nx">SubScriberGetPartitionsError</span><span class="p">,</span> <span class="nx">err</span><span class="p">,</span> <span class="nx">topic</span><span class="p">)</span>
<span class="p">}</span>
<span class="c1">// 遍历所有 partition 获取最新 offset 上的消息
</span><span class="c1"></span> <span class="k">for</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">partition</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">partitionList</span> <span class="p">{</span>
<span class="nx">pc</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">subscriber</span><span class="p">.</span><span class="nx">Consumer</span><span class="p">.</span><span class="nf">ConsumePartition</span><span class="p">(</span><span class="nx">topic</span><span class="p">,</span> <span class="nx">partition</span><span class="p">,</span> <span class="nx">sarama</span><span class="p">.</span><span class="nx">OffsetNewest</span><span class="p">)</span>
<span class="c1">// 启动一个 goroutine 用于持续监听消息
</span><span class="c1"></span> <span class="k">go</span> <span class="kd">func</span><span class="p">(</span><span class="nx">pc</span> <span class="nx">sarama</span><span class="p">.</span><span class="nx">PartitionConsumer</span><span class="p">)</span> <span class="p">{</span>
<span class="k">for</span> <span class="nx">message</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">pc</span><span class="p">.</span><span class="nf">Messages</span><span class="p">()</span> <span class="p">{</span>
<span class="nx">subscriber</span><span class="p">.</span><span class="nx">logger</span><span class="p">.</span><span class="nf">Infof</span><span class="p">(</span><span class="nf">messageReceived</span><span class="p">(</span><span class="nx">message</span><span class="p">))</span>
<span class="nx">ch</span> <span class="o"><-</span> <span class="nf">messageReceived</span><span class="p">(</span><span class="nx">message</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}(</span><span class="nx">pc</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="kd">func</span> <span class="nf">messageReceived</span><span class="p">(</span><span class="nx">message</span> <span class="o">*</span><span class="nx">sarama</span><span class="p">.</span><span class="nx">ConsumerMessage</span><span class="p">)</span> <span class="kt">string</span> <span class="p">{</span>
<span class="k">return</span> <span class="nb">string</span><span class="p">(</span><span class="nx">message</span><span class="p">.</span><span class="nx">Value</span><span class="p">)</span>
<span class="p">}</span></code></pre></td></tr></table>
</div>
</div>
<h3 id="main">main</h3>
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<pre class="chroma"><code class="language-Go" data-lang="Go"><span class="kn">package</span> <span class="nx">main</span>
<span class="kn">import</span> <span class="p">(</span>
<span class="s">"encoding/json"</span>
<span class="s">"fmt"</span>
<span class="s">"os"</span>
<span class="s">"github.com/sirupsen/logrus"</span>
<span class="s">"./reporter"</span>
<span class="s">"./subscriber"</span>
<span class="p">)</span>
<span class="kd">var</span> <span class="p">(</span>
<span class="nx">config</span> <span class="p">=</span> <span class="s">`{
</span><span class="s"> "host": "localhost:9092",
</span><span class="s"> "topic": "kafka_test"
</span><span class="s"> }`</span>
<span class="p">)</span>
<span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
<span class="kd">var</span> <span class="nx">cfg</span> <span class="nx">reporter</span><span class="p">.</span><span class="nx">KafkaCfg</span>
<span class="nx">json</span><span class="p">.</span><span class="nf">Unmarshal</span><span class="p">([]</span><span class="nb">byte</span><span class="p">(</span><span class="nx">config</span><span class="p">),</span> <span class="o">&</span><span class="nx">cfg</span><span class="p">)</span>
<span class="nx">log</span> <span class="o">:=</span> <span class="o">&</span><span class="nx">logrus</span><span class="p">.</span><span class="nx">Logger</span><span class="p">{</span><span class="nx">Out</span><span class="p">:</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">}</span>
<span class="c1">//reporter
</span><span class="c1"></span> <span class="nx">producer</span> <span class="o">:=</span> <span class="nx">reporter</span><span class="p">.</span><span class="nf">NewReporter</span><span class="p">(</span><span class="o">&</span><span class="nx">cfg</span><span class="p">,</span> <span class="nx">log</span><span class="p">)</span>
<span class="c1">//subscriber
</span><span class="c1"></span> <span class="nx">consumer</span> <span class="o">:=</span> <span class="nx">subscriber</span><span class="p">.</span><span class="nf">NewSubscriber</span><span class="p">(</span><span class="o">&</span><span class="nx">cfg</span><span class="p">,</span> <span class="nx">log</span><span class="p">)</span>
<span class="nx">message</span> <span class="o">:=</span> <span class="s">"Hello Kafka World."</span>
<span class="nx">ch</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">string</span><span class="p">)</span>
<span class="nx">consumer</span><span class="p">.</span><span class="nf">Consume</span><span class="p">(</span><span class="nx">cfg</span><span class="p">.</span><span class="nx">Topic</span><span class="p">,</span> <span class="nx">ch</span><span class="p">)</span>
<span class="nx">producer</span><span class="p">.</span><span class="nf">DoReport</span><span class="p">(</span><span class="nx">cfg</span><span class="p">.</span><span class="nx">Topic</span><span class="p">,</span> <span class="p">[]</span><span class="nb">byte</span><span class="p">(</span><span class="nx">message</span><span class="p">))</span>
<span class="k">select</span> <span class="p">{</span>
<span class="k">case</span> <span class="nx">msg</span> <span class="o">:=</span> <span class="o"><-</span><span class="nx">ch</span><span class="p">:</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"Got msg: "</span><span class="p">,</span> <span class="nx">msg</span><span class="p">)</span>
<span class="k">break</span>
<span class="p">}</span>
<span class="p">}</span></code></pre></td></tr></table>
</div>
</div>
<h3 id="其他">其他</h3>
<p>为避免漏消费消息，可指定 group，Kafka 确保每个 partition 只能同一个 group 中的同一个 consumer 消费，若要重复消费，更换 group。</p>
<p>项目代码：<a href="https://github.com/JJMeg/Kafka-with-golang/" target="_blank">kafka-client-golang</a>，项目结构：</p>
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<pre class="chroma"><code class="language-shell" data-lang="shell">.
├── README.md
├── error_const
│ └── error_const.go
├── main.go
├── reporter
│ └── report.go
└── subscriber
└── subscribe.go</code></pre></td></tr></table>
</div>
</div>
<p><center>👏欢迎评论👏</center></p>
<script src="https://utteranc.es/client.js"
repo="JJMeg/jjmeg.io.comment"
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]]></description>
<category domain="https://jjmeg.github.io/tags/kafka/">kafka</category>
<category domain="https://jjmeg.github.io/tags/golang/">golang</category>
</item>
<item>
<title>Golang系列教程--JSON解析</title>
<link>https://jjmeg.github.io/posts/golang-json/</link>
<guid isPermaLink="true">https://jjmeg.github.io/posts/golang-json/</guid>
<pubDate>Wed, 06 May 2020 14:32:31 +0800</pubDate>
<author>jjmeg.he@gmail.com (JJMeg)</author>
<copyright>[CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/deed.zh)</copyright>
<description><![CDATA[
<p><center>「 <a href="https://golang.org/pkg/encoding/json/">json</a> 」</center>
<center>
提供了 JSON 与 Go 变量之间的序列化与反序列化。
</center></p>
<h1 id="本文内容">📜本文内容</h1>
<ul>
<li>📚 <a href="#JSON序列化">JSON序列化</a></li>
<li>📚 <a href="#tag及使用技巧">tag及使用技巧</a>
<ul>
<li>📖 <a href="#1-省略空字段-omitempty">1. 省略空字段 omitempty</a></li>
<li>📖 <a href="2-忽略特定字段" target="_blank">2. -忽略特定字段</a></li>
<li>📖 <a href="#3-json字段类型转换">3. json字段类型转换</a></li>
<li>📖 <a href="#4-临时添加新字段">4. 临时添加新字段</a></li>
<li>📖 <a href="#5-多结构体组合成">5. 多结构体组合成</a></li>
<li>📖 <a href="#6-对时间类型的序列化">6. 对时间类型的序列化</a></li>
</ul></li>
</ul>
<p></br></p>
<ul>
<li>📚 <a href="#JSON反序列化">JSON反序列化</a></li>
<li>📚 <a href="#JSON反序列化的常用技巧">JSON反序列化的常用技巧</a>
<ul>
<li>📖 <a href="#拆分成多个结构体">拆分成多个结构体</a></li>
</ul></li>
<li>📚 <a href="#JSON与私有属性">JSON与私有属性</a></li>
</ul>
<hr />
<h3 id="json序列化">JSON序列化</h3>
<blockquote>
<p>func Marshal(v interface{}) ([]byte, error)</p>
<p>func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error)</p>
</blockquote>
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