Apache Camel: how store variable for later use

Question

while 'playing around' with Camel using Spring DSL, I came across the following problem. Suppose the expected message flow looks like this:

client sends HTTP POST message with XML body to CAMEL
CAMEL proxies HTTP POST message towards server, with the URI slightly adapted using info from the received XML body (eg: use XPATH to filter out a certain parameter)
after CAMEL has received a reply, CAMEL sends HTTP PUT message towards server, using parameters out of the XML body received in 1

So something like:

<route>
   <from uri="...">
   <to uri="...">
   <to uri="...">
 </route>

Question: how do I store the parameters in Spring DSL in step 1, so that I can use them later in step 3 ?

So, I would like to extract XML parameters out of the XML body of the message received in step 1 and put them into variables, which I then later on can use to compose the message to be sent in step 3.

For extracting the parameters, I was thinking of using XPATH. That looks ok, but I just don't see how to put the output of the XPATH into a variable and then use that variable later on ... (syntax ??)

Note: as you can see, my development knowledge is rather limited ... sorry for that. But it would still be great if someone could help with this :).

score 26 · Accepted Answer · answered Feb 08 '12 at 16:15

26

you can set store data in the Exchange properties or message headers like this...

.setHeader("ID", XPathBuilder.xpath("/order/@id", String.class))
.setProperty("ID", XPathBuilder.xpath("/order/@id", String.class))

and then retrieve them in a bean/processor from the Exchange like this...

String propId = (String) exchange.getProperty("ID");
String headerId = (String) exchange.getIn().getHeader("ID");                        }

answered Feb 08 '12 at 16:15

Ben ODay

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2

Thanks already for the reply. However, any chance to get the same code but for Spring DSL (XML notation) ? Cheers. – opstalj Feb 09 '12 at 09:24
1

In the meanwhile, I re-coded with Java DSL and it works nicely. Thanks once more. I do have 1 more question: what is the difference between using setHeader and setProperty ? – opstalj Feb 10 '12 at 07:25
4

Read this chapter to learn about the Camel concepts, and you will know whats the difference between properties and headers: http://manning.com/ibsen/chapter1sample.pdf – Claus Ibsen Feb 10 '12 at 09:07
Thanks. That chapter explains it well :). – opstalj Feb 15 '12 at 12:17
`setProperty` does not take three arguments. – swade Apr 26 '17 at 15:14
.log("access in route using ${exchangeProperty.ID}") – Gerry Oct 28 '21 at 22:25

score 10 · Answer 2 · edited Oct 24 '17 at 14:28

I leave you some examples:

<setHeader headerName="token">
    <constant>someValue</constant>
</setHeader>

<setHeader headerName="userName">
    <simple>${properties:userName}</simple>  //from config
</setHeader>

<setProperty propertyName="bodyBkp">
    <simple>${in.body}</simple>
</setProperty>

<setProperty propertyName="orderNumber">
    <xpath resultType="String">//item[1]/orderNumber/text()</xpath>
</setProperty>

Getter

${exchangeProperty[orderNumber]}

${in.headers.token}

Documentation

Check the simple expression language: http://camel.apache.org/simple.html

Sometimes looking at the test cases of Camel can be helpful as well, in particular for Spring DSL:

Apache Camel: how store variable for later use

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