160 lines
19 KiB
HTML
160 lines
19 KiB
HTML
<!DOCTYPE html>
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<html lang="en-us">
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<head>
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<meta charset="UTF-8">
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<title>Redkale(红菜苔)--基于Java 8全新的微服务开源框架 - Redkale官网</title>
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<meta name="keywords" content="Redkale,redkale,java,微服务,架构"/>
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<meta name="description" content="Redkale(红菜苔)是基于Java 8全新的微服务开源框架"/>
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<link rel="stylesheet" type="text/css" href="stylesheets/stylesheet.css" media="screen">
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</head>
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<body>
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<section class="page-header">
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<a href="index.html" class="project-name">Redkale</a>
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<h2 class="project-tagline"></h2>
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<a href="redkale.html" class="btn">Redkale 入门</a>
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<a href="convert.html" class="btn">Convert 组件</a>
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<a href="service.html" class="btn">Service 组件</a>
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<a href="source.html" class="btn">Source 组件</a>
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<a href="net.html" class="btn">Net 组件</a>
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<a href="watch.html" class="btn">Watch 组件</a>
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<a href="plugins.html" class="btn">Redkale 插件</a>
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<a href="articles.html" class="btn">技术文章</a>
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</section>
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<section class="main-content">
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<h3>Redkale 让你重新认识Java</h3>
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<p>
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Java 已经走过了二十二个年头，依靠强大的功能、庞大的开发社区和无人能及的生态系统，成为当之无愧的业界之王。<br/>
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</p>
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<p> <b>太臃肿</b></p>
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<p>
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如今在Java界，Tomcat、Struts2、Hibernate、MyBatis、Jetty、Spring MVC/Spring Boot/Spring XXX这些框架大家都耳熟能详，似乎不懂两三个以上都不好意思说自己会Java。在一些新手眼里，Java就是Tomcat、Java就是Spring。2004年发布正式版的Spring以其轻量著称，一战成名，打败了J2EE，成为Java事实上的"标准"。然而经过十几年的发展，其生态越来越庞大，功能的增多，复杂的配置，兼容性，历史包袱，使得整个框架体系越来越臃肿，还有不计其数的衍生插件，已经不比当年J2EE轻多少了。在那个JBuilder还是主流IDE的年代，建一个Web系统还是比较简单，除了Tomcat比较大点，其他都算轻量。现在很多人建一个Web项目，需要复杂的Maven建工程，一行代码还没开始写，仅仅是导入SSH/SSM这些框架就需要好几十M，还得进行一堆SSH配置,简单的日志都需要配备log4j/snf4j。可能只是简单的管理系统，必须要搞这么复杂吗？ 如今一个1-2M的框架大家都会觉得算轻量级，MyBatis是JDBC基础上的再次封装，jar包大小近6M，但比Hibernate还是轻量些。这些只是基础框架，如果系统还需要其他功能性的框架(Lucene、Mail、Json) 会使开发包更大。同时大量的开源框架抑制了新JDK的普及，NIO出来都十五年， AIO(NIO.2)也出来六年了，如今还有很多人把NIO给贴上高性能的标签，JDK 5--Java第一个重大更新的版本在2004年发布，直到五-六年后Spring的注解方式才得到普及， Java第二个重大更新的版本JDK 8发布也有三年了，大部分人还停留在只识语法糖Lambda的层级，在JDK功能越来越强大的情况下，开发Java系统并不简化多少。相对于现在流行的NodeJs做个Web系统来说，Java就是个巨无霸。其实呢，Java无需这么复杂，真的可以很简单。
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</p>
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<p> <b>异步呢</b></p>
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<p>
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用Java开发异步系统是件很难的事情，首先Java规范中异步接口很少，Servlet 3.0虽然支持异步，也出来好几年了，但现在直接用Servlet写代码的人已经不多，而基于Servlet的Struts、Spring Boot这些框架又没把异步太当回事，基本都是实现的Servet同步方法。JDBC更是迄今为止还没有异步接口。其次开源框架以异步接口为主的凤毛麟角。 所以Java程序员在写业务代码时基本都是用同步方式，特别是最耗时的数据源操作JDBC无法异步。
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</p>
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<div class="highlight"><pre><span></span><span class="nx">http</span><span class="p">.</span><span class="nx">post</span><span class="p">(</span><span class="s">"/url"</span><span class="p">,</span> <span class="p">{</span><span class="nx">id</span><span class="o">:</span><span class="mi">10</span><span class="p">},</span> <span class="kd">function</span><span class="p">(</span><span class="nx">request</span><span class="p">,</span> <span class="nx">response</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">service</span><span class="p">.</span><span class="nx">getResource</span><span class="p">(</span><span class="nx">request</span><span class="p">,</span> <span class="kd">function</span><span class="p">(</span><span class="nx">result</span><span class="p">){</span>
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<span class="nx">response</span><span class="p">.</span><span class="nx">write</span><span class="p">(</span><span class="nx">JSON</span><span class="p">.</span><span class="nx">stringify</span><span class="p">(</span><span class="nx">result</span><span class="p">));</span>
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<span class="nx">response</span><span class="p">.</span><span class="nx">end</span><span class="p">();</span>
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<span class="p">});</span>
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<span class="p">});</span>
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<span class="kd">var</span> <span class="nx">mysql</span> <span class="o">=</span> <span class="nx">require</span><span class="p">(</span><span class="s">'mysql'</span><span class="p">);</span>
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<span class="kd">var</span> <span class="nx">pool</span> <span class="o">=</span> <span class="nx">mysql</span><span class="p">.</span><span class="nx">createPool</span><span class="p">(</span><span class="nx">config</span><span class="p">);</span>
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<span class="nx">pool</span><span class="p">.</span><span class="nx">getConnection</span><span class="p">(</span><span class="kd">function</span><span class="p">(</span><span class="nx">err</span><span class="p">,</span> <span class="nx">connection</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">connection</span><span class="p">.</span><span class="nx">query</span><span class="p">(</span> <span class="s">'SELECT * FROM table'</span><span class="p">,</span> <span class="kd">function</span><span class="p">(</span><span class="nx">err</span><span class="p">,</span> <span class="nx">rows</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">connection</span><span class="p">.</span><span class="nx">end</span><span class="p">();</span>
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<span class="p">});</span>
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<span class="p">});</span>
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</pre></div>
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<p>
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而在NodeJs里，IO操作都是异步的。这也是为什么有的用Nodejs做的系统比Java还快。Java在语言上和(NIO/NIO.2)框架的性能优势弥补不了同步的副作用。
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</p>
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<p> <b>新设计</b></p>
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<p>
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Redkale 一个全新设计的Java异步微服务框架。集HTTP、WebSocket、REST、JSON、RPC、DB操作、依赖注入等功能于一身，其jar包大小仅790K，且不依赖任何第三方包。
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</p>
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<p>
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从以上代码可以看出，根据优先级选择Constructor，为了减少学习成本，Creator直接重用了java.beans.ConstructorProperties注解，又因ConstructorProperties只能标记在Constructor上，因此定义一个Creator.ConstructorParameters注解，用于标记在Creator的create方法上。
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</p>
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<div class="highlight"><pre><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Record</span> <span class="o">{</span>
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<span class="kd">private</span> <span class="kd">final</span> <span class="kt">int</span> <span class="n">id</span><span class="o">;</span>
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<span class="kd">private</span> <span class="n">String</span> <span class="n">name</span><span class="o">;</span>
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<span class="nd">@ConstructorProperties</span><span class="o">({</span><span class="s">"id"</span><span class="o">,</span> <span class="s">"name"</span><span class="o">})</span>
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<span class="n">Record</span><span class="o">(</span><span class="kt">int</span> <span class="n">id</span><span class="o">,</span> <span class="n">String</span> <span class="n">name</span><span class="o">)</span> <span class="o">{</span>
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<span class="k">this</span><span class="o">.</span><span class="na">id</span> <span class="o">=</span> <span class="n">id</span><span class="o">;</span>
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<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>
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<span class="o">}</span>
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<span class="kd">public</span> <span class="kt">int</span> <span class="nf">getId</span><span class="o">()</span> <span class="o">{</span>
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<span class="k">return</span> <span class="n">id</span><span class="o">;</span>
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<span class="o">}</span>
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<span class="kd">public</span> <span class="n">String</span> <span class="nf">getName</span><span class="o">()</span> <span class="o">{</span>
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<span class="k">return</span> <span class="n">name</span><span class="o">;</span>
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<span class="o">}</span>
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<span class="kd">public</span> <span class="kt">void</span> <span class="nf">setName</span><span class="o">(</span><span class="n">String</span> <span class="n">name</span><span class="o">)</span> <span class="o">{</span>
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<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>
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<span class="o">}</span>
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<span class="o">}</span>
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<span class="na"><b>Record.class通过ASM自动构建与Record同package的Creator类如下:</b></span>
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<span class="kd">public</span> <span class="kd">final</span> <span class="kd">class</span> <span class="nc">Record_DynCreator</span> <span class="kd">implements</span> <span class="n">Creator</span><span class="o"><</span><span class="n">Record</span><span class="o">></span> <span class="o">{</span>
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<span class="nd">@Override</span>
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<span class="nd">@Creator.ConstructorParameters</span><span class="o">({</span><span class="s">"id"</span><span class="o">,</span> <span class="s">"name"</span><span class="o">})</span>
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<span class="kd">public</span> <span class="n">Record</span> <span class="nf">create</span><span class="o">(</span><span class="n">Object</span><span class="o">...</span> <span class="n">params</span><span class="o">)</span> <span class="o">{</span>
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<span class="k">if</span> <span class="o">(</span><span class="n">params</span><span class="o">[</span><span class="mi">0</span><span class="o">]</span> <span class="o">==</span> <span class="kc">null</span><span class="o">)</span> <span class="n">params</span><span class="o">[</span><span class="mi">0</span><span class="o">]</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span>
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<span class="k">return</span> <span class="k">new</span> <span class="nf">Record</span><span class="o">((</span><span class="n">Integer</span><span class="o">)</span> <span class="n">params</span><span class="o">[</span><span class="mi">0</span><span class="o">],</span> <span class="o">(</span><span class="n">String</span><span class="o">)</span> <span class="n">params</span><span class="o">[</span><span class="mi">1</span><span class="o">]);</span>
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<span class="o">}</span>
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<span class="o">}</span></pre></div>
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<p>
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如上代码，若构造参数是primitive类，而Creator.create传入的参数可能是null，因此需要给null的primitive对象赋予默认值0。细心的人可能发现了Record的构造函数并不是public的，虽然Record_DynCreator与Record在同一package，但由于两者不是同一个ClassLoader，故不能直接new Record。Redkale曲线救国，通过URLClassLoader的私有方法在Record.class的ClassLoader加载Record_DynCreator。
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</p>
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<div class="highlight"><pre><span class="k">if</span> <span class="o">(</span><span class="n">loader</span> <span class="k">instanceof</span> <span class="n">URLClassLoader</span> <span class="o">&&</span> <span class="o">!</span><span class="n">Modifier</span><span class="o">.</span><span class="na">isPublic</span><span class="o">(</span><span class="n">constructor</span><span class="o">.</span><span class="na">getModifiers</span><span class="o">()))</span> <span class="o">{</span>
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<span class="k">try</span> <span class="o">{</span>
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<span class="kd">final</span> <span class="n">URLClassLoader</span> <span class="n">urlLoader</span> <span class="o">=</span> <span class="o">(</span><span class="n">URLClassLoader</span><span class="o">)</span> <span class="n">loader</span><span class="o">;</span>
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<span class="kd">final</span> <span class="n">URL</span> <span class="n">url</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">URL</span><span class="o">(</span><span class="s">"memclass"</span><span class="o">,</span> <span class="s">"localhost"</span><span class="o">,</span> <span class="o">-</span><span class="mi">1</span><span class="o">,</span> <span class="s">"/"</span> <span class="o">+</span> <span class="n">newDynName</span><span class="o">.</span><span class="na">replace</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="s">"/"</span><span class="o">,</span> <span class="k">new</span> <span class="nf">URLStreamHandler</span><span class="o">()</span> <span class="o">{</span>
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<span class="nd">@Override</span>
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<span class="kd">protected</span> <span class="n">URLConnection</span> <span class="nf">openConnection</span><span class="o">(</span><span class="n">URL</span> <span class="n">u</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="k">return</span> <span class="k">new</span> <span class="nf">URLConnection</span><span class="o">(</span><span class="n">u</span><span class="o">)</span> <span class="o">{</span>
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<span class="nd">@Override</span>
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<span class="kd">public</span> <span class="kt">void</span> <span class="nf">connect</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="o">}</span>
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<span class="nd">@Override</span>
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<span class="kd">public</span> <span class="n">InputStream</span> <span class="nf">getInputStream</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="k">return</span> <span class="k">new</span> <span class="nf">ByteArrayInputStream</span><span class="o">(</span><span class="n">bytes</span><span class="o">);</span>
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<span class="o">}</span>
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<span class="o">};</span>
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<span class="o">}</span>
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<span class="o">});</span>
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<span class="n">Method</span> <span class="n">addURLMethod</span> <span class="o">=</span> <span class="n">URLClassLoader</span><span class="o">.</span><span class="na">class</span><span class="o">.</span><span class="na">getDeclaredMethod</span><span class="o">(</span><span class="s">"addURL"</span><span class="o">,</span> <span class="n">URL</span><span class="o">.</span><span class="na">class</span><span class="o">);</span>
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<span class="n">addURLMethod</span><span class="o">.</span><span class="na">setAccessible</span><span class="o">(</span><span class="kc">true</span><span class="o">);</span>
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<span class="n">addURLMethod</span><span class="o">.</span><span class="na">invoke</span><span class="o">(</span><span class="n">urlLoader</span><span class="o">,</span> <span class="n">url</span><span class="o">);</span>
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<span class="n">resultClazz</span> <span class="o">=</span> <span class="n">urlLoader</span><span class="o">.</span><span class="na">loadClass</span><span class="o">(</span><span class="n">newDynName</span><span class="o">.</span><span class="na">replace</span><span class="o">(</span><span class="sc">'/'</span><span class="o">,</span> <span class="sc">'.'</span><span class="o">));</span>
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<span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="n">Throwable</span> <span class="n">t</span><span class="o">)</span> <span class="o">{</span> <span class="c1">//异常无需理会， 使用下一种loader方式</span>
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<span class="n">t</span><span class="o">.</span><span class="na">printStackTrace</span><span class="o">();</span>
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<span class="o">}</span>
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<span class="o">}</span></pre></div>
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<p>
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如上代码，构建一个虚拟协议的URL来实现加载，若Record.class的ClassLoader不是URLClassLoader导致resultClazz为null则会抛出异常。
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</p>
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<p>
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Creator是一个典型通过ASM构建一个简单功能地动态类，同类型还有 <a href="https://redkale.org/javadoc/org/redkale/util/Attribute.html" target="_blank">org.redkale.util.Attribute</a>、<a href="https://redkale.org/javadoc/org/redkale/util/Reproduce.html" target="_blank">org.redkale.util.Reproduce</a>。
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</p>
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<br/>
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<p>
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转载请注明出处：<a href="https://redkale.org/article_regain.html" target="_blank">https://redkale.org/article_regain.html</a>
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<span class="site-footer-owner"> 欢迎加入Redkale QQ群: 527523235</span>
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