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From "Claus Ibsen (JIRA)" <j...@apache.org>
Subject [jira] Assigned: (CAMEL-3696) ResequenceDefinition probably should not take a List<ExpressionDefinition> for easier operation among the various DSLs (Java + XML etc) since expressions in most languages can easily do composites
Date Tue, 22 Feb 2011 08:19:38 GMT

     [ https://issues.apache.org/jira/browse/CAMEL-3696?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Claus Ibsen reassigned CAMEL-3696:
----------------------------------

    Assignee: Claus Ibsen

> ResequenceDefinition probably should not take a List<ExpressionDefinition> for
easier operation among the various DSLs (Java + XML etc) since expressions in most languages
can easily do composites
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CAMEL-3696
>                 URL: https://issues.apache.org/jira/browse/CAMEL-3696
>             Project: Camel
>          Issue Type: Improvement
>            Reporter: james strachan
>            Assignee: Claus Ibsen
>             Fix For: 2.7.0
>
>
> An expression language is usually fairly powerful & can be used to create a collection
of expressions. (e.g. in XPath: /foo + /bar). We use expressions extensively throughout Camel
and all expressions may need to be a 'composite' of different expressions which really is
just a single Expression object.
> If folks find there are times when an Expression cannot be easily created from a composite
within a language (e.g. a language that doesn't support +) then we could always have a composite
language which is a collection of expression objects - which itself is an Expression, so that
we then have consistency across the model.
> To say this another way; if one pattern takes a List<ExpressionDefinition> then
why don't they all? We might want to Resequence or Aggregate using a composite expression
etc.
> So a simpler solution is just to say that an Expression is exactly that - an arbitrary
expression (which may be implemented using a concatenation of multiple expressions) but then
from the EIP model and DSL, its simply a single Expression instance so its then easy to keep
all the DSLs in sync and the model consistent.
> In the specific case of the Resequence, the expression is simply used to create a value
which can then be used to sort messages; so its an expression returning a single object; which
sounds like a single Expression to me.

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