如何让SpEL将两个数字相加

Question

I want to compute my port number inside application.properties like this:

server.port=#{ 1 + ${myapp.web.server.port.ssl} }
myapp.web.server.port.ssl=8300

But when I start my Spring Boot app all I get is an execption.

org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type java.lang.String to type java.lang.Integer]

The Mathematical Operators section of the reference guide suggests that it should work, but it doesn't.

Inside Spring it gets as far as calling:

GenericConversionService.convert("#{ 1 + 8300 }", java.lang.String, java.lang.Integer)

But there is no logic in there for recognising it's SpEL. It's like it's not recognising it's SpEL at all. However if I change the expression to #{ n1 + ${myapp.web.server.port.ssl} } then I get the following exception, showing that it is being evaluated as SpEL:

SpelEvaluationException: EL1008E:(pos 0): Property or field 'n1' cannot be found on object of type 'org.springframework.beans.factory.config.BeanExpressionContext' - maybe not public?

How can I make SpEL add one to the value of another property?

Update:

I found a similar question so I tried a similar approach:

server.port=#{T(java.lang.Integer).parseInt('${fire.web.server.port.ssl}') + 1}

But that still doesn't work. For some reason it's not treating it as an SpEL expression. But is does treat it as a SpEL expression if there is a syntax error!

Answer 1

You can do that only from config, but not from properties:

<bean class="...">
   <property name="port" value="#{1 + ${myapp.web.server.port.ssl}}"/>
</bean>

Answer 2

I think the problem is that ${myapp.web.server.port.ssl} is evaluated as String , try something like this

#{1 + new Integer(props['myapp.web.server.port.ssl'])}

where props is the bean holding your properties.