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From "Lucas Moten (JIRA)" <j...@apache.org>
Subject [jira] Updated: (SYNAPSE-451) Selection Mediators don't carry initialization through all branches
Date Wed, 17 Sep 2008 14:13:44 GMT

     [ https://issues.apache.org/jira/browse/SYNAPSE-451?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lucas Moten updated SYNAPSE-451:
--------------------------------

    Description: 
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>

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.

A FilterMediator extends AbstractListMediator, but for the else branch, uses a ListMediator.

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.

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.

The workaround is to use named sequences wherever possible, and reference that instead, as
the 'else' branch of a FilterMediator can alternatively use an elseKey.

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.

For example, this cannot work because the inline sequence is not initialized
<switch>
  <case>
    <callout>...</callout>
  </case>
</switch>

For filters, this cannot work because inline sequences are not initialized
<filter>
  <then>..</then>
  <else>
    <callout>
  </else>
</filter>

But this can
<filter>
  <callout>
</filter>

as can this
<filter>
  <then>
    <callout>
  </then>
</filter>

and this
<sequence name="namedsequence">
  <callout>
</sequence>
<filter>
  <then>..</then>
  <else sequence="namedsequence">
</filter>

  was:
<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>


> Selection Mediators don't carry initialization through all branches
> -------------------------------------------------------------------
>
>                 Key: SYNAPSE-451
>                 URL: https://issues.apache.org/jira/browse/SYNAPSE-451
>             Project: Synapse
>          Issue Type: Bug
>          Components: Core
>            Reporter: Lucas Moten
>
> 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>
> 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.
> A FilterMediator extends AbstractListMediator, but for the else branch, uses a ListMediator.
> 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.
> 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.
> The workaround is to use named sequences wherever possible, and reference that instead,
as the 'else' branch of a FilterMediator can alternatively use an elseKey.
> 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.
> For example, this cannot work because the inline sequence is not initialized
> <switch>
>   <case>
>     <callout>...</callout>
>   </case>
> </switch>
> For filters, this cannot work because inline sequences are not initialized
> <filter>
>   <then>..</then>
>   <else>
>     <callout>
>   </else>
> </filter>
> But this can
> <filter>
>   <callout>
> </filter>
> as can this
> <filter>
>   <then>
>     <callout>
>   </then>
> </filter>
> and this
> <sequence name="namedsequence">
>   <callout>
> </sequence>
> <filter>
>   <then>..</then>
>   <else sequence="namedsequence">
> </filter>

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