How do I load a Camel Property into a Bean?

Question

I have been reading the following page on Camel properties: http://camel.apache.org/using-propertyplaceholder.html and also reading the book "Camel In Action".

I found Chapter 6 of "Camel In Action" very helpful in defining Camel properties, and I can load the following three properties from my config.properties:

config.timeout=10000
config.numSamples=1000
config.defaultViz=a

When I run my Java code I'm able to see the following three values inside my camel route in my applicationContext.xml, as shown in the thread#0 messages below:

14669 [Camel (HelloWorldContext) thread #0 - timer://hello.world.request.timer] INFO  route1  - printing values read from config.properties file
14669 [Camel (HelloWorldContext) thread #0 - timer://hello.world.request.timer] INFO  route1  - config.timeout= 10000
14669 [Camel (HelloWorldContext) thread #0 - timer://hello.world.request.timer] INFO  route1  - config.numSamples= 1000
14670 [Camel (HelloWorldContext) thread #0 - timer://hello.world.request.timer] INFO  route1  - config.defaultViz= a

However, when I try to pass the variable {{config.defaultViz}} to a String called defaultViz in my SensorGenerator Java class, and print that string I get "{{config.defaultViz}}" on the console instead of the value contained within {{config.defaultViz}}.

In other words, here's what I see on the screen:

Returning List
defaultViz= {{config.defaultViz}}

But I really want to see this on the screen:

Returning List
defaultViz=a

So what am I doing wrong in my applicationContext.xml?

UPDATED: The issue was that I needed to add a Bridge between Spring and Camel as outlined in the link I referenced above.

Here's my UPDATED applicationContext.xml with the bridge:

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"     xmlns:camel="http://camel.apache.org/schema/spring"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:util="http://www.springframework.org/schema/util"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans     http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/util     http://www.springframework.org/schema/util/spring-util-3.0.xsd
        http://camel.apache.org/schema/spring     http://camel.apache.org/schema/spring/camel-spring.xsd
        http://www.springframework.org/schema/context     http://www.springframework.org/schema/context/spring-context.xsd">

    <bean
            class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" />
    <context:component-scan base-package="com.data.world2" />
    <context:annotation-config />

    <camel:camelContext id="HelloWorldContext">

<!--        Add Jackson library to render Java Map into JSON -->
        <camel:dataFormats>
          <camel:json id="jack" library="Jackson"/>
        </camel:dataFormats>

        <camel:route>
            <!-- sends a request to the hello world JMS queue every 10 seconds -->
            <camel:from
                uri="timer://hello.world.request.timer?fixedRate=true&amp;period={{config.timeout}}" />
            <camel:to uri="log:hello.world.request?level=INFO&amp;showAll=true" />
            <camel:bean ref="helloWorld" />

            <!-- now print out the map in JSON format -->
            <camel:marshal ref ="jack"/>
            <camel:convertBodyTo type="java.lang.String" />
            <camel:log message="${body}"/> 

            <!-- print out values read from config.properties file -->
            <camel:log message="printing values read from config.properties file"/>
            <camel:log message="config.timeout= {{config.timeout}}"/> 
            <camel:log message="config.numSamples= {{config.numSamples}}"/>
            <camel:log message="config.defaultViz= {{config.defaultViz}}"/>

            <!-- now log the message -->
            <camel:to uri="log:hello.world.response?level=INFO&amp;showAll=true" />

        </camel:route>

    </camel:camelContext>

<!-- creates a java.util.Properties instance with values loaded from the supplied location -->
<util:properties id="sensorProperties" location="classpath:/sensor.properties"/>

    <!--  pass in sensor.properties and defaultViz from config.properties -->
    <bean class="com.data.world2.SensorGenerator">
        <property name="sourceProperties" ref="sensorProperties" />
        <property name="defaultViz" value="${config.defaultViz}"/>
    </bean>

<!-- declare a Spring bean to use the Camel Properties component in Spring XML -->
    <bean id="properties"
          class="org.apache.camel.component.properties.PropertiesComponent">
        <property name="location" value="classpath:config.properties"/>
    </bean>
<!-- bridge spring property placeholder with Camel -->
<!-- you must NOT use the <context:property-placeholder at the same time, only this bridge bean -->
    <bean id="bridgePropertyPlaceholder" class="org.apache.camel.spring.spi.BridgePropertyPlaceholderConfigurer">
      <property name="location" value="classpath:config.properties"/>
    </bean>

</beans>

I found this question that is similar but not quite the same: Injecting property into bean

Answer 1

The {{}} notation just works inside the routes (ie inside the XML camel contexts). To use it in the bean I think you need to define the property placeholder bridge that camel provides but in your bean use the ${} notation. The explanation of how to use that bridge is in the link you have provided.