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The Loop allows for processing a message a number of times, possibly in a different way for each iteration. Useful mostly during testing.
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Notice by default the loop uses the same exchange throughout the looping. So the result from the previous iteration will be used for the next (eg Pipes
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and Filters). From Camel 2.8 onwards you can enable copy mode instead. See the options table for more details.
Options
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Name | Default Value | Description |
---|---|---|
|
| Camel 2.8: Whether or not copy mode is used. If |
doWhile | Camel 2.17: Enables the while loop that loops until the predicate evaluates to false or null. |
Exchange properties
For each iteration two properties are set on the Exchange
. Processors can rely on these properties to process the Message in different ways.
Property | Description |
---|---|
| Total number of loops. This is not available if running the loop in while loop mode. |
| Index of the current iteration (0 based) |
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Pass loop count as an argument
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Use expression to determine loop count
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Use expression to determine loop count
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Using the Spring XML Extensions
Pass loop count as an argument
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Use expression to determine loop count
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For further examples of this pattern in use you could look at one of the junit test case
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Now suppose we send a message to "direct:start" endpoint containing the letter A.
The output of processing this route will be that, each "mock:loop" endpoint will receive "AB" as message.
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However if we do not enable copy mode then "mock:loop" will receive "AB", "ABB", "ABBB", etc. messages.
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The equivalent example in XML DSL in copy mode is as follows:
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Using while mode
Available as of Camel 2.17
The loop can act like a while loop that loops until the expression evaluates to false or null.
For example the route below loops while the length of the message body is 5 or less characters. Notice that the DSL uses loopDoWhile.
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And the same example in XML:
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Notice in XML that the while loop is turned on using the doWhile attribute.
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