This commit is contained in:
Redkale
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<h3>Redkale 让你重新认识Java</h3>
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<p>
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长期以来，Hibernate和Mybatis一直是大家使用最多的持久层开发框架。针对这两种框架网络上是各种比较，各种讨论优缺点。其实这两个框架(算上前身ibatis)都是2002年左右发布, 迄今已有15载已笨重不堪，一个mybatis.jar包大小6M左右，Hibernate更是巨大，毫无轻巧灵活可言，提供简化SQL操作的同时带来了复杂繁琐的配置和高学习门槛。而Redkale的Source组件非常轻量级，通过十多个<span style="color: #2041B4;">interface</span>、<span style="color: #2041B4;">enum</span>和十多个<span style="color: #2041B4;">class</span>完成常见的DB操作功能。<br/>
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Source组件在接口设计上参考了JPA接口，为了降低学习成本，部分注解仍沿用javax.persistence中的类，以多个注解结合一个主操作类 <a href="http://redkale.org/javadoc/org/redkale/source/DataSource.html" target="_blank">DataSource</a> 的方式提供API。在没有IDE自动生成代码的插件支持的情况下Redkale提供了一个Demo代码<a href="https://github.com/redkale/redkale-demo/blob/master/src/org/redkale/demo/base/AutoClassCreator.java" target="_blank"> AutoClassCreator</a> 能很方便的将数据库表生成Entity类。
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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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。<br/>
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Source组件在接口设计上参考了JPA接口，为了降低学习成本，部分注解仍沿用javax.persistence中的类，以多个注解结合一个主操作类 <a href="http://redkale.org/javadoc/org/redkale/source/DataSource.html" target="_blank">DataSource</a> 的方式提供API。在没有IDE自动生成代码的插件支持的情况下Redkale提供了一个Demo代码<a href="https://github.com/redkale/redkale-demo/blob/master/src/org/redkale/demo/base/AutoClassCreator.java" target="_blank"> AutoClassCreator</a> 能很方便的将数据库表生成Entity类。
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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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<div class="highlight"><pre><span class="n">Constructor</span><span class="o"><</span><span class="n">T</span><span class="o">></span> <span class="n">constructor0</span> <span class="o">=</span> <span class="kc">null</span><span class="o">;</span>
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<span class="k">for</span> <span class="o">(</span><span class="n">Constructor</span> <span class="n">c</span> <span class="o">:</span> <span class="n">clazz</span><span class="o">.</span><span class="na">getConstructors</span><span class="o">())</span> <span class="o">{</span> <span class="c1">//优先找public 的构造函数</span>
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<span class="k">if</span> <span class="o">(</span><span class="n">c</span><span class="o">.</span><span class="na">getParameterCount</span><span class="o">()</span> <span class="o">==</span> <span class="mi">0</span><span class="o">)</span> <span class="o">{</span>
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<span class="n">constructor0</span> <span class="o">=</span> <span class="n">c</span><span class="o">;</span>
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<span class="k">break</span><span class="o">;</span>
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<a href="articles.html"></a>
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<span class="o">}</span>
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<span class="o">}</span>
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<span class="k">if</span> <span class="o">(</span><span class="n">constructor0</span> <span class="o">==</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span><span class="c1">//其次找非private带ConstructorProperties的构造函数</span>
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<span class="k">for</span> <span class="o">(</span><span class="n">Constructor</span> <span class="n">c</span> <span class="o">:</span> <span class="n">clazz</span><span class="o">.</span><span class="na">getDeclaredConstructors</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">Modifier</span><span class="o">.</span><span class="na">isPrivate</span><span class="o">(</span><span class="n">c</span><span class="o">.</span><span class="na">getModifiers</span><span class="o">()))</span> <span class="k">continue</span><span class="o">;</span>
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<span class="k">if</span> <span class="o">(</span><span class="n">c</span><span class="o">.</span><span class="na">getAnnotation</span><span class="o">(</span><span class="n">ConstructorProperties</span><span class="o">.</span><span class="na">class</span><span class="o">)</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span>
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<span class="n">constructor0</span> <span class="o">=</span> <span class="n">c</span><span class="o">;</span>
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<span class="k">break</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="k">if</span> <span class="o">(</span><span class="n">constructor0</span> <span class="o">==</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span><span class="c1">//再次找非private且带-parameters编译项的构造函数 java 8以上才支持</span>
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<span class="k">for</span> <span class="o">(</span><span class="n">Constructor</span> <span class="n">c</span> <span class="o">:</span> <span class="n">clazz</span><span class="o">.</span><span class="na">getDeclaredConstructors</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">Modifier</span><span class="o">.</span><span class="na">isPrivate</span><span class="o">(</span><span class="n">c</span><span class="o">.</span><span class="na">getModifiers</span><span class="o">()))</span> <span class="k">continue</span><span class="o">;</span>
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<span class="n">Parameter</span><span class="o">[]</span> <span class="n">params</span> <span class="o">=</span> <span class="n">c</span><span class="o">.</span><span class="na">getParameters</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="na">length</span> <span class="o">==</span> <span class="mi">0</span><span class="o">)</span> <span class="k">continue</span><span class="o">;</span>
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<span class="kt">boolean</span> <span class="n">flag</span> <span class="o">=</span> <span class="kc">true</span><span class="o">;</span>
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<span class="k">for</span> <span class="o">(</span><span class="n">Parameter</span> <span class="n">param</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">try</span> <span class="o">{</span>
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<span class="n">clazz</span><span class="o">.</span><span class="na">getDeclaredField</span><span class="o">(</span><span class="n">param</span><span class="o">.</span><span class="na">getName</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">Exception</span> <span class="n">e</span><span class="o">)</span> <span class="o">{</span>
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<span class="n">flag</span> <span class="o">=</span> <span class="kc">false</span><span class="o">;</span>
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<span class="k">break</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="k">if</span> <span class="o">(</span><span class="n">flag</span><span class="o">)</span> <span class="o">{</span>
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<span class="n">constructor0</span> <span class="o">=</span> <span class="n">c</span><span class="o">;</span>
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<span class="k">break</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="k">if</span> <span class="o">(</span><span class="n">constructor0</span> <span class="o">==</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span><span class="c1">//最后找非private的空构造函数</span>
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<span class="k">for</span> <span class="o">(</span><span class="n">Constructor</span> <span class="n">c</span> <span class="o">:</span> <span class="n">clazz</span><span class="o">.</span><span class="na">getDeclaredConstructors</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">Modifier</span><span class="o">.</span><span class="na">isPrivate</span><span class="o">(</span><span class="n">c</span><span class="o">.</span><span class="na">getModifiers</span><span class="o">()))</span> <span class="k">continue</span><span class="o">;</span>
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<span class="k">if</span> <span class="o">(</span><span class="n">c</span><span class="o">.</span><span class="na">getParameterCount</span><span class="o">()</span> <span class="o">==</span> <span class="mi">0</span><span class="o">)</span> <span class="o">{</span>
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<span class="n">constructor0</span> <span class="o">=</span> <span class="n">c</span><span class="o">;</span>
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<span class="k">break</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></pre></div>
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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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@@ -159,7 +137,7 @@
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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_creator.html</a>
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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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</p>
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<footer class="site-footer">
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