"Simple" Expression Language - arithmetic operators?

I'm using this expression in a camel route:

.when(simple("${body.updateSeq} > ${property.PrevUpdateSeq} + 1"))
    .to("direct:someError")

However it is freaking out about the + symbol.

org.apache.camel.language.simple.types.SimpleIllegalSyntaxException: Unexpected token + at location 46
${body.updateSeq} > ${property.PrevUpdateSeq} + 1
                                              *

How can I construct this expression, giving that it takes a value from the getter getUpdateSeq of the POJO on the message body and compres it to a property on the Exchange (plus 1).

The Simple Languate included in Apache Camel does not support a + operation per-se. It offers however an ++ increment operator which requires the left hand side to be a function.

The easiest solution would be to refactor the operation to a bean

public class NextValueService {
    @Handler
    public Integer nextValue(Integer value) {
        return value + 1;
    }
}

and use it in your route as follows:

.when(simple("${body.updateSeq} > ${bean:nextValueService?method=nextValue(property.PrevUpdateSeq)"}))
.to("direct:someError")

Switching simple language with f.e. JavaScript or Groovy should also help on dealing with the problem.