How to change a property value inside a Apache Camel Route? - groovy

Question

In a property file a variable test has been defined:
test=OLD_VALUE
In the following Spring-DSL definition a camel route is defined. Properties are loaded via PropertiesComponent.
<bean id="properties" class="org.apache.camel.component.properties.PropertiesComponent">
<property name="cache" value="false"/>
<property name="location" value="classpath:res.properties"/>
</bean>
<camelContext id="ctx" xmlns="http://camel.apache.org/schema/spring">
<route id="toParamRoute">
<from uri="servlet:myParam"/>
HERE I WOULD LIKE TO SET THE
VARIABLE TEST WITH A NEW VALUE,
SUCH THAT THE FOLLOWING LOG MESSAGE
WILL PRINT THE NEW VALUE,
E.G: test=NEW_VALUE
<log message="{{test}}"/>
</route>
</camelContext>
I tried different approach using groovy, language script expression, external spring bean but without success. Is there a way to set and change the value of a variable loaded at startup?
What is the best way to do it?
Anyone can help me? I did not find any similar question on stackoverflow! The problem I am facing and the solution I am looking for is a basic building-block to build a WEB UI management console to change some behavior of routes on the fly. To simplify the flow I can say that after propertyPlaceholder has loaded a property file then via a UI web page the default parameters of routes can be changed, and only after the route can be started.

Answer 1

Properties evaluated with syntax {{property}} are resolved only once during context initialization. If you need to reflect runtime changes, use Simple language
Example:
<bean id="myProperties" class="java.util.Properties"/>
<bean id="properties" class="org.apache.camel.component.properties.PropertiesComponent">
<property name="cache" value="false"/>
<property name="location" value="classpath:res.properties"/>
<property name="overrideProperties" ref="myProperties" />
</bean>
<camelContext id="ctx" xmlns="http://camel.apache.org/schema/spring">
<route id="toParamRoute">
<from uri="timer://foo"/>
<log message="About to change property test from value ${properties:test} to value ${exchangeProperty.CamelTimerCounter}. Initial value was {{test}}"/>
<bean ref="myProperties" method="setProperty(test, ${exchangeProperty.CamelTimerCounter})" />
<log message="New value is ${properties:test}"/>
</route>
</camelContext>