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https://issues.apache.org/jira/browse/TUSCANY-2239?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12590785#action_12590785
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Greg Dritschler commented on TUSCANY-2239:
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I have attached a new patch for CompositeWireBuilderImpl.
> Support for mutually-exclusive intents
> --------------------------------------
>
> Key: TUSCANY-2239
> URL: https://issues.apache.org/jira/browse/TUSCANY-2239
> Project: Tuscany
> Issue Type: New Feature
> Components: Java SCA Core Runtime
> Reporter: Greg Dritschler
> Assignee: Venkatakrishnan
> Attachments: tuscany-2239-CompositeWireBuilder.patch,
> tuscany-2239.patch
>
>
> The SCA Policy specification does not provide a means to define intents which
> are mutually exclusive. This is a noticeable omission when considering the
> intents in the SCA Transaction specification which are mutually exclusive by
> nature (managedTransaction vs. noManagedTransaction, propagatesTransaction
> vs. suspendsTransaction). There is a need to be able to define intents
> which are mutually exclusive and for the exclusion to be checked by the SCA
> runtime to avoid the error of specifying exclusive intents on a single
> artifact. In addition, there should be rules defined for the handling of
> mutually exclusive intents which are attached at different levels of a
> composite or a hierarchy of composites.
> I have attached a patch to provide the capability to define mutually
> exclusive intents. This is achieved using a new @excludes attribute on the
> <intent/> element in definitions.xml. For example:
> <intent name="propagatesTransaction" constrains="implementation"
> excludes="suspendsTransaction"/>
> @excludes is a list of intents which are mutually-exclusive with the named
> intent. In order to be effective, a reciprocal definition needs to be made
> as shown below.
> <intent name="suspendsTransaction" constrains="implementation"
> excludes="propagatesTransaction"/>
> The patch makes no assumptions about the relationship of qualified intents to
> the base intent. Therefore exclusive relationships between qualified intents
> need to be spelled out.
> <intent name="noManagedTransaction" constrains="implementation"
> excludes="managedTransaction managedTransaction.global
> managedTransaction.local"/>
> A key part of the patch is that there now are two types of intent inheritance
> with respect to exclusive intents. There is a "default" inheritance between
> certain hierarchical elements within a composite. For example consider this
> snippet from a composite:
> <component name="C1" requires="propagatesTransaction">
> <reference name="r1"/>
> <reference name="r2"/>
> <reference name="r3" requires="suspendsTransaction"/>
> </component>
> In this case the first two references inherit the default intent
> "propagatesTransaction" from the component element. However the third
> reference does not inherit it because it specifies an exclusive intent
> "suspendsTransaction" which overrides the component-level default.
> The second type of inheritance is used when inheriting intents from an
> implementation (e.g. introspected Java code, or an implementation composite).
> In this case the intents of the implementation cannot be overridden.
> Consider this example:
> <component name="D1">
> <implementation.composite name="CZ1"/>
> <reference name="r1" requires="suspendsTransaction"/>
> </component>
> Let's assume CZ1 contains the component C1 shown earlier and that it promotes
> the component reference C1/r1 as r1. C1/r1 has the intent
> "propagatesTransaction". This intent is considered a requirement of the
> implementation and it cannot be overridden by the using composite. Therefore
> D1 is in error.
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