Selection Mediators don't carry initialization through all branches
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Key: SYNAPSE-451
URL: https://issues.apache.org/jira/browse/SYNAPSE-451
Project: Synapse
Issue Type: Bug
Components: Core
Reporter: Lucas Moten
<p>See also: JIRAs <a
href="https://issues.apache.org/jira/browse/SYNAPSE-437";>Apache
SYNAPSE-437</a>, <a href="https://wso2.org/jira/browse/ESBJAVA-422";>WSO2
ESBJAVA-422</a></p>
<p>Thus far, this mostly appears to be an issue with CalloutMediator, because
it's mediate method depends upon init() having been run to setup the
ServiceClient.</p>
<p>A FilterMediator extends AbstractListMediator, but for the else branch, uses
a ListMediator.</p>
<p>When synapse initializes inline sequences as part of SynapseConfiguration,
the init method of SequenceMediator is called. This in turn calls init of its
superclass, which is AbstractListMediator. In that class, all child mediators
that are instances of ManagedLifecycle are in turn initialized.</p>
<p>For the FilterMediator, the 'then' branch, as an AbstractListMediator being
an instance of ManagedLifecycle is initialized at startup. However, the 'else'
branch, being declared as a ListMediator, will not be. Thus, it appears as
though any mediator requiring initialization inside of the Filter else branch
will fail (NullPointerException) when it is referenced.</p>
<p>A workaround is to use named sequences wherever possible, and reference that
instead, as the 'else' branch of a FilterMediator can alternatively use an
elseKey.</p>
<p>However, this workaround appears to have limits when it comes to the
SwitchMediator. Inline sequences are handled inside of SwitchCase as an
AnonymousListMediator and like the FilterMediator, aren't initialized by top
level in/out inline target sequences. Since SwitchMediators don't have the
option of referencing a registry key for a named sequence initialized at
startup, I believe this breaks the ability to run certain child mediators that
require initialization of objects that only occur when init is called.</p>
<p>For example, this cannot work because the inline sequence is not
initialized, and thus callout isn't initialized</p>
<pre>
<switch>
<case>
<callout>...</callout>
</case>
</switch>
</pre>
<p>For filters, this cannot work because inline sequences are not
initialized</p><pre>
<filter>
<then>..</then>
<else>
<callout>
</else>
</filter>
</pre>
<p>But this can</p><pre>
<filter>
<callout>
</filter>
</pre>
<p>as can this</p><pre>
<filter>
<then>
<callout>
</then>
</filter>
</pre>
<p>and this</p><pre>
<sequence name="namedsequence">
<callout>
</sequence>
<filter>
<then>..</then>
<else sequence="namedsequence">
</filter
</pre>
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