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Cyclic dependencies
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reply from <a href="http://community.jboss.org/people/alesj">Ales Justin</a> in <i>JBoss Microcontainer</i> - <a href="http://community.jboss.org/message/558337#558337">View the full discussion</a>
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<div class="jive-rendered-content"><blockquote class="jive-quote">>From what I've read, MC can do cyclic injections, but can't do cyclic dependencies (<depends>) , true?</blockquote><p>Injection is also just a dependency.<br/>We can do whatever you can do programatically.<br/>It's the different states that make this happen.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>e.g. if A depends on B and B depends on A, both at ctor, then of course it's impossible to solve this</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>class A {<br/>   A(B b) {}<br/>}</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>class B {<br/>   B(A a) {}<br/>}</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>but if you set the A into B via setter (which gets populated at different state), then it would work.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>class B {<br/>   B() {}</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>  void setA(A a) {}<br/>}</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>The same goes for <demand> which can take the state at which you depend on target,<br/>while you can also declare target's state.</p><p><span>* </span><a class="jive-link-external-small" href="http://anonsvn.jboss.org/repos/jbossas/projects/kernel/trunk/kernel/src/main/java/org/jboss/beans/metadata/plugins/AbstractDemandMetaData.java" target="_blank">http://anonsvn.jboss.org/repos/jbossas/projects/kernel/trunk/kernel/src/main/java/org/jboss/beans/metadata/plugins/AbstractDemandMetaData.java</a></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><depends> is slightly different, as it has this states already "hardcoded" -- same functionality as you're used from old JMX kernel.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><blockquote class="jive-quote">I just started with MC so I am not yet too aware of what terms like Installed mean from the MC POV.<br/></blockquote><p>MC state machine works on top of linear states:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><pre class="jive-pre"><code class="jive-code jive-java">   <font color="navy"><b>public</b></font> AbstractController()
   <font color="navy">{</font>
      addState(ControllerState.NOT_INSTALLED, <font color="navy"><b>null</b></font>);
      addState(ControllerState.PRE_INSTALL, <font color="navy"><b>null</b></font>);
      addState(ControllerState.DESCRIBED, <font color="navy"><b>null</b></font>);
      addState(ControllerState.INSTANTIATED, <font color="navy"><b>null</b></font>);
      addState(ControllerState.CONFIGURED, <font color="navy"><b>null</b></font>);
      addState(ControllerState.CREATE, <font color="navy"><b>null</b></font>);
      addState(ControllerState.START, <font color="navy"><b>null</b></font>);
      addState(ControllerState.INSTALLED, <font color="navy"><b>null</b></font>);
</code></pre><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>While you can dynamically add new states -- see DeployersImpl.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><blockquote class="jive-quote">Could you pls point me to some good material explaining this issue, and perhaps the types of relations in MC?</blockquote><p><span>* </span><a class="jive-link-external-small" href="http://anonsvn.jboss.org/repos/jbossas/projects/presentations/trunk/microcontainer/" target="_blank">http://anonsvn.jboss.org/repos/jbossas/projects/presentations/trunk/microcontainer/</a></p><p><span>* </span><a class="jive-link-external-small" href="http://java.dzone.com/articles/a-look-inside-jboss-microconta-0" target="_blank">http://java.dzone.com/articles/a-look-inside-jboss-microconta-0</a></p></div>
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<p style="margin: 0;">Reply to this message by <a href="http://community.jboss.org/message/558337#558337">going to Community</a></p>
<p style="margin: 0;">Start a new discussion in JBoss Microcontainer at <a href="http://community.jboss.org/choose-container!input.jspa?contentType=1&containerType=14&container=2114">Community</a></p>
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