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wentch
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<h3><a id="welcome-to-github-pages" class="anchor" href="#" aria-hidden="true"><span class="octicon octicon-link"></span></a>Convert 快速上手</h3>
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<p> 本介绍仅以JSON为例(BSON与JSON使用方式雷同)。其操作类主要是JsonConvert，配置类主要是JsonFactory、ConvertColumn。</br></p>
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<p> JsonConvert 序列化Encode方法：</p>
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<p> JsonConvert 序列化encode方法：</p>
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<div class="highlight"><pre> <span class="kd">public</span> <span class="n">String</span> <span class="nf">convertTo</span><span class="o">(</span><span class="n">Object</span> <span class="n">value</span><span class="o">);</span>
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<span class="kd">public</span> <span class="n">ByteBuffer</span><span class="o">[]</span> <span class="nf">convertTo</span><span class="o">(</span><span class="kd">final</span> <span class="n">Charset</span> <span class="n">charset</span><span class="o">,</span> <span class="kd">final</span> <span class="n">Supplier</span><span class="o"><</span><span class="n">ByteBuffer</span><span class="o">></span> <span class="n">supplier</span><span class="o">,</span> <span class="n">Object</span> <span class="n">value</span><span class="o">);</span></pre></div>
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<p> JsonConvert 反解析Decode方法：</p>
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<p> JsonConvert 反解析decode方法：</p>
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<div class="highlight"><pre> <span class="kd">public</span> <span class="o"><</span><span class="n">T</span><span class="o">></span> <span class="n">T</span> <span class="nf">convertFrom</span><span class="o">(</span><span class="kd">final</span> <span class="n">Type</span> <span class="n">type</span><span class="o">,</span> <span class="kd">final</span> <span class="n">String</span> <span class="n">text</span><span class="o">);</span>
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<span class="kd">public</span> <span class="o"><</span><span class="n">T</span><span class="o">></span> <span class="n">T</span> <span class="nf">convertFrom</span><span class="o">(</span><span class="kd">final</span> <span class="n">Type</span> <span class="n">type</span><span class="o">,</span> <span class="kd">final</span> <span class="kt">char</span><span class="o">[]</span> <span class="n">text</span><span class="o">);</span>
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<span class="n">resp</span><span class="o">.</span><span class="na">setContentType</span><span class="o">(</span><span class="s">"text/json; charset=UTF-8"</span><span class="o">);</span>
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<span class="n">resp</span><span class="o">.</span><span class="na">getOutputStream</span><span class="o">().</span><span class="na">write</span><span class="o">(</span><span class="n">json</span><span class="o">.</span><span class="na">getBytes</span><span class="o">(</span><span class="s">"UTF-8"</span><span class="o">));</span>
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<span class="o">}</span></pre></div>
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<p> 几乎所有的JSON框架提供的接口以String作为返回结果为主，其内在都是以char[]作为JsonWriter的载体。以Gson为例，Gson拼接JSON默认使用的是StringWriter，StringWriter的扩容策略是翻倍。为了方便计算，假设一个对象转换成JSON字符串大小为了10K。Gson在转换过程中产生的临时的char[]的大小: 16 + 32 + 64 + 128 + 256 + 512 + 1K + 2K + 4K + 8K + 16K = 32K, char[]转换成最终的String结果又会产生10K的char[], 最后在response输出时又回产生10K的byte[]（方便计算不考虑双字节）,也就是说整个对象输出过程中会产生52K的临时数据。同时常见的HTTP服务器(如实现java-servlet规范的服务器)不会把底层的ByteBuffer对象池暴露给上层。所以目前所有使用其他JSON框架输出数据都会产生5倍于数据体积大小的垃圾数据。而RedKale框架的HTTP服务内置了Convert的JSON接口，避免了这么大量的垃圾数据产生。</p>
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<p> 几乎所有的JSON框架提供的接口以String作为返回结果为主，其内在都是以char[]作为JsonWriter的载体。以Gson为例，Gson拼接JSON默认使用的是StringWriter，StringWriter的扩容策略是翻倍。为了方便计算，假设一个对象转换成JSON字符串大小为了10K。Gson在转换过程中产生的临时的char[]的大小: 16 + 32 + 64 + 128 + 256 + 512 + 1K + 2K + 4K + 8K + 16K = 32K, char[]转换成最终的String结果又会产生10K的char[], 最后在response输出时又回产生10K的byte[]（方便计算不考虑双字节）,也就是说整个对象输出过程中会产生52K的临时数据。而且常见的HTTP服务器(如实现java-servlet规范的服务器)不会把底层的ByteBuffer对象池暴露给上层。所以目前所有使用其他JSON框架输出数据都会产生至少5倍于数据体积大小(其他低于1倍扩容策略的框架会产生更多)的垃圾数据。<br/>
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RedKale框架的HTTP服务内置了Convert的JSON接口，避免了这么大量的垃圾数据产生。finishJson方法将HTTP服务的ByteBuffer对象池传给Convert， 使Convert在序列化过程中直接以UTF-8编码方式输出到ByteBuffer里。</p>
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<div class="highlight"><pre> <span class="kd">protected</span> <span class="kt">void</span> <span class="nf">execute</span><span class="o">(</span><span class="n">HttpRequest</span> <span class="n">req</span><span class="o">,</span> <span class="n">HttpResponse</span> <span class="n">resp</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">IOException</span> <span class="o">{</span>
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<span class="n">resp</span><span class="o">.</span><span class="na">finishJson</span><span class="o">(</span><span class="n">record</span><span class="o">);</span>
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<span class="o">}</span></pre></div>
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