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<title> 愚钝的故事 — Grails 中服务懒加载
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<meta name="description" content="现象 前两天在Grails中使用guava的EventBus做消息分发时发现我得一个Subscrib死活没有被调用。很时费解！ 我代码的结构如下: class HandlerAServices { def eventBus @PostConstruct def init(){ eventBus.register(this) } @Subscribe def someEventHandler(SomeEvent event){ } } class HandlerBServices { def eventBus @PostConstruct def init(){ eventBus.register(this) } @Subscribe def someEventHandler(SomeEvent event){ } } 最后当有SomeEvent这个的事件发出时 发现HandlerBServices 中得someEventHandler 方法被调用，HandlerAServices 中的someEventHandler完全没有执行。 同样的代码，同样的配置啊。怎么会这么邪乎呢！ 排查原因 因为grails中对service的初始化在默认情况下采用懒加载的方式。加入一个服务没有被其他的内容如controller，service， domain class等等引用。那么这个服务将不会在已启动的时候就被初始化 ...">
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<a href="/grails-zhong-fu-wu-lan-jia-zai.html" title="Permalink to Grails 中服务懒加载">Grails 中服务懒加载</a>
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<a class="text-muted" href="/grails-zhong-fu-wu-lan-jia-zai.html" title="2015-06-10T17:39:00+08:00">Wed 10 June 2015</a>
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<a href="./category/grails.html">Grails</a>
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<a href="/tag/Gorm.html">Gorm</a>, <a href="/tag/Grails.html">Grails</a> </li>
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By <a href="./author/jet-geng.html">Jet Geng</a>
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<h2>现象</h2>
<p>前两天在Grails中使用guava的EventBus做消息分发时发现我得一个Subscrib死活没有被调用。很时费解！</p>
<p>我代码的结构如下:</p>
<div class="highlight"><pre><span></span><span class="kd">class</span> <span class="nc">HandlerAServices</span> <span class="o">{</span>
<span class="kt">def</span> <span class="n">eventBus</span>
<span class="nd">@PostConstruct</span>
<span class="kt">def</span> <span class="nf">init</span><span class="o">(){</span>
<span class="n">eventBus</span><span class="o">.</span><span class="na">register</span><span class="o">(</span><span class="k">this</span><span class="o">)</span>
<span class="o">}</span>
<span class="nd">@Subscribe</span>
<span class="kt">def</span> <span class="nf">someEventHandler</span><span class="o">(</span><span class="n">SomeEvent</span> <span class="n">event</span><span class="o">){</span>
<span class="o">}</span>
<span class="o">}</span>
<span class="kd">class</span> <span class="nc">HandlerBServices</span> <span class="o">{</span>
<span class="kt">def</span> <span class="n">eventBus</span>
<span class="nd">@PostConstruct</span>
<span class="kt">def</span> <span class="nf">init</span><span class="o">(){</span>
<span class="n">eventBus</span><span class="o">.</span><span class="na">register</span><span class="o">(</span><span class="k">this</span><span class="o">)</span>
<span class="o">}</span>
<span class="nd">@Subscribe</span>
<span class="kt">def</span> <span class="nf">someEventHandler</span><span class="o">(</span><span class="n">SomeEvent</span> <span class="n">event</span><span class="o">){</span>
<span class="o">}</span>
<span class="o">}</span>
</pre></div>
<p>最后当有SomeEvent这个的事件发出时 发现HandlerBServices 中得someEventHandler 方法被调用，HandlerAServices 中的someEventHandler完全没有执行。 同样的代码，同样的配置啊。怎么会这么邪乎呢！</p>
</div>
<div class="section" id="id2">
<h2>排查原因</h2>
<p>因为grails中对service的初始化在默认情况下采用懒加载的方式。加入一个服务没有被其他的内容如controller，service， domain class等等引用。那么这个服务将不会在已启动的时候就被初始化。
我们的HandlerAServices 中 someEventHandler 没有被执行的原因就是这个HandlerAServices 没有被其他内容直接使用，导致这个HandlerAServices这个bean没有被创建。所以他就没有被调用了。</p>
<p>为了解决这个问题要做的东西很少，只是告诉grails，我们不要懒加载的方式。修改代码如下：</p>
<div class="highlight"><pre><span></span><span class="kd">class</span> <span class="nc">HandlerAServices</span> <span class="o">{</span>
<span class="kd">static</span> <span class="n">lazyInit</span> <span class="o">=</span> <span class="kc">false</span> <span class="c1">//申明不需要懒加载</span>
<span class="o">}</span>
</pre></div>
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<div class="section" id="id3">
<h2>参考资料</h2>
<ol class="arabic simple">
<li><a class="reference external" href="http://grails.1312388.n4.nabble.com/Is-it-possible-to-avoid-lazy-services-initialization-td4646285.html">http://grails.1312388.n4.nabble.com/Is-it-possible-to-avoid-lazy-services-initialization-td4646285.html</a></li>
<li><a class="reference external" href="http://stackoverflow.com/questions/14832002/postconstruct-fails-silently-on-a-grails-service">http://stackoverflow.com/questions/14832002/postconstruct-fails-silently-on-a-grails-service</a></li>
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