Spring Integration Java DSL - Http Outbound Gateway uri variable Expression

Question

I have a Http Outbound Gateway where I want to set a uri variable with a value from a Message header. I can see that this can be done like so:

            .handle(Http
                    .outboundGateway(serviceUri, restTemplate)
                    .uriVariable("var", expression)
                    .httpMethod(HttpMethod.POST)

The expression is of type org.springframework.expression.Expression. How do I create such an Expression object for say a JmsHeaders.CORRELATION_ID value? I can't find any examples anywhere. I know that the String SPEL would be "headers['correlationId']" but I don't know how to turn that into an Expression object?

I am using spring-integration-java-dsl:1.1.0.RELEASE.

Community · Accepted Answer · 2017-05-23 12:03:56Z

1

See this answer to a similar question.

Note that JmsHeaders.CORRELATION_ID is actually jms_correlationId. It's safer to use the constant...

PARSER.parseExpression("headers['" + JmsHeaders.CORRELATION_ID + "']");

edited May 23, 2017 at 12:03

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answered Nov 11, 2015 at 13:41

Gary Russell

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3 Comments

Going Bananas Over a year ago

Thanks for that Gary. Yes, I am using the constant in JmsHeaders. In the end I had created the expression as a literal (new LiteralExpression("headers['" + JmsHeaders.CORRELATION_ID + "']")) which I assume is also valid?

Gary Russell Over a year ago

No; that is not correct; a LiteralExpression is an, err, literal - i.e. it will set the variable to the exact literal in the constructor. LiteralExpressions are not evaluated, getValue() simply returns the value passed into the constructor. You need to parse the expression so it is evaluated at runtime.

Going Bananas Over a year ago

Ah, ok. I'll use the expression as you have provided then Gary.

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