title: Aries Blueprint in Karaf - Can a blueprint reference an external properties file
body: <p>I am using an ActiveMQ blueprint to setup a JMS Connection Pool. 
  I also use Camel to service some functionality.  </p>
  
  <p>I use the <code>org.apache.camel.spring.spi.BridgePropertyPlaceholderConfigurer</code> to allow the use of an external properties file in setting up the <code>camel-context</code> file.  </p>
  
  <p>Is there a similar type functionality using blueprints?  </p>
  
  <p>So basically, I want to replace ${server.address} with a property I get from a property file in the configuration below:</p>
  
  <pre><code>&lt;blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
          xmlns:cm="http://aries.apache.org/blueprint/xmlns/blueprint-cm/v1.0.0"
          xmlns:ext="http://aries.apache.org/blueprint/xmlns/blueprint-ext/v1.0.0"
          xmlns:amq="http://activemq.apache.org/schema/core"&gt;
  
          &lt;bean id="activemqConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory"&gt;
               &lt;property name="brokerURL"
                         value="nio://${server.address}" /&gt;
          &lt;/bean&gt;
  
          &lt;bean id="pooledConnectionFactory" class="org.apache.activemq.pool.PooledConnectionFactory"&gt;
               &lt;property name="maxConnections" value="8" /&gt;
               &lt;property name="connectionFactory" ref="activemqConnectionFactory" /&gt;
          &lt;/bean&gt;
  
          &lt;bean id="jmsConfig" class="org.apache.camel.component.jms.JmsConfiguration"&gt;
               &lt;property name="connectionFactory" ref="pooledConnectionFactory" /&gt;
               &lt;property name="concurrentConsumers" value="5" /&gt;
          &lt;/bean&gt;
  
          &lt;bean id="resourceManager" class="org.apache.activemq.pool.ActiveMQResourceManager"
               init-method="recoverResource"&gt;
               &lt;property name="transactionManager" ref="transactionManager" /&gt;
               &lt;property name="connectionFactory" ref="activemqConnectionFactory" /&gt;
               &lt;property name="resourceName" value="activemq.localhost" /&gt;
          &lt;/bean&gt;
  
          &lt;bean id="xaConnectionFactory" class="org.apache.activemq.ActiveMQXAConnectionFactory"&gt;
               &lt;argument value="nio://${server.address}" /&gt;
          &lt;/bean&gt;
  
          &lt;bean id="connectionFactory" class="org.fusesource.jms.pool.JcaPooledConnectionFactory"
               init-method="start" destroy-method="stop"&gt;
               &lt;property name="connectionFactory" ref="pooledConnectionFactory" /&gt;
               &lt;property name="name" value="activemq" /&gt;
          &lt;/bean&gt;
  
          &lt;reference id="transactionManager" interface="javax.transaction.TransactionManager" /&gt;
  
          &lt;service ref="pooledConnectionFactory" interface="javax.jms.ConnectionFactory"&gt;
                  &lt;service-properties&gt;
                          &lt;entry key="name" value="localhost" /&gt;
                  &lt;/service-properties&gt;
          &lt;/service&gt; 
  &lt;/blueprint&gt;
  </code></pre>